EROSION CONTROL AND REMOVAL OF SUSPENDED SOIL PARTICLES IN 
PONDS: EVALUATION OF GEOFABRIC LINERS AND CHEMICAL COAGULANTS 
 
by 
 
Puttitorn Saengrungruang 
 
 
 
 
A dissertation submitted to the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
requirements for the Degree of 
Doctor of Philosophy  
 
Auburn, Alabama 
August 4, 2012 
 
 
 
 
Keywords: erosion control, suspended soil particles removal, catfish pond, lined pond, geofabric, 
chemical coagulants  
 
 
Copyright 2012 by Puttitorn Saengrungruang 
 
 
Approved by 
 
Claude E. Boyd, Chair, Professor of Fisheries and Allied Aquacultures 
John W. Odom, Associate Professor of Agronomy and Soils 
Yolanda J. Brady, Professor of Fisheries and Allied Aquacultures 
Philip L. Chaney, Associate Professor of Geology and Geography 
ii 
 
 
 
 
 
 
 
Abstract 
 
 
In an experiment conducted at the E. W. Shell Fisheries Center, Auburn, Alabama, three 
ponds each were lined with a permeable geotextile with 0.090-mm opening sizes, a permeable 
geotextile with 0.355-mm opening sizes, or served as unlined, controls.  During the 2-yr study, 
geotextile liners did not tear or decay. This prevented erosion of the bottom of the ponds stocked 
with a high density of channel catfish and aerated nightly.  The liners tended to float up in the 
water column; the liner with smaller opening sizes floated in all three ponds, while the other liner 
floated in only one pond.  Fish production, survival, and feed conversion ratio did not differ (P > 
0.05) among the control and lined ponds or between liner types.  Water quality variables often 
differed between lined ponds and control ponds.  The greatest difference was higher 
phytoplankton abundance in the lined ponds?especially in ponds lined with the less permeable 
geotextile ? than in the control.  This difference was attributed to differences in phosphorus 
uptake by bottom soils related to the liners and their permeability.  However, in spite of more 
phytoplankton growth in lined ponds, the control ponds tended to have higher turbidity because 
of erosion of bottoms by aeration. 
 To investigate phosphorus uptake rate by soil through the geotextiles, six kinds of 
geotextile liners with apparent opening sizes ranging from 0.090 mm to 0.84 mm were installed 
in separate soil from water in aquaria.  Water was treated with 0.75 mg/L of phosphorus from 
monopotassium phosphate.  Phosphorus concentration did not decline in aquaria without soil, 
and all liners reduced the amount of phosphorus removed by the soil.  Phosphorus removal by 
iii 
 
soil did not differ among liners with opening size < 0.200, but these liners interfered less with 
soil phosphorus uptake than did the liner with 0.090-mm opening size.  Final phosphorus 
concentrations were 0.089 mg/L in the unlined aquaria with soil, 0.397 mg/L for the liner with 
0.090-mm openings, and 0.157 to 0.202 mg/L for the liners with larger openings. 
 Geotextiles can reduce erosion resulting in less turbidity in water. However, fine particles 
settle very slowly and may remain suspended almost indefinitely restricting light penetration in 
the water column and reducing primary productivity. Particles of three soils ? each containing a 
different type of clay ? settled at different rates.  Nevertheless, particles tended to settle faster as 
concentration of total dissolved solids (TDS) increased in diluted seawater. In freshwater, total 
hardness concentration increased as TDS concentration rose.  
Several chemical coagulants were tested for their ability to remove suspended soil 
particles.  Potassium and sodium chloride were comparatively ineffective for turbidity removal.  
Calcium sulfate was more effective than magnesium sulfate in removing turbidity.  Aluminum 
chloride and sulfate tended to perform better than ferrous sulfate and ferric chloride.   
Although there were some differences in effectiveness of coagulants among the types of 
soils, calcium sulfate (gypsum), aluminum sulfate (alum), and aluminum chloride appear to have 
the greatest potential for use in ponds.  Aluminum compounds neutralize alkalinity and cause a 
decrease in pH.  Treatment rates (mg/L) for aluminum sulfate and aluminum chloride should not 
exceed the total alkalinity (mg/L as CaCO3) to avoid low pH.  Knowledge of conductivity, total 
alkalinity, total hardness, and type of clay mineral suspended in water can be useful in selecting a 
suitable coagulant.  
 
iv 
 
 
 
 
 
 
 
Acknowledgements 
 
 
 I would like to thank Dr. Claude E. Boyd for his support, advice and the opportunity to 
let me have the great experience to study at Auburn University as his student. I would like to 
thank all of my committee members and the outside reader for their time and comment. 
Appreciation is extended to June Burns, Mrs. Pornpimon Boyd, William Trimble, and the 
Segrest family for their encouragement and support. I would like to thank the faculty and staff of 
the Department of Fisheries and Allied Aquacultures and all teachers who have taught me from 
the beginning of my education until now. I would also like to give special thanks to my 
supervisors and colleagues at my work place in Rajabhat Suan Dusit University. I want to thank  
my old friends and new friends during the time spent in Auburn for their help and friendship. I 
also extend my gratitude to my gorgeous parents, brothers, husband, and family.    
 
 
 
 
 
 
 
 
 
v 
 
 
 
 
 
 
 
Table of Contents 
 
 
Abstract  ........................................................................................................................................ ii 
Acknowledgments ....................................................................................................................... iv 
List of Tables  ............................................................................................................................. vii 
List of Illustrations  .................................................................................................................... viii 
I.  INTRODUCTION . ............................................................................................................. 1 
II.  REVIEW OF LITERATURE  ............................................................................................. 4 
III.  EVALUATION OF TWO, POROUS, GEOTEXTILE LINERS FOR EROSION 
CONTROL IN SMALL AQUACULTURE PONDS  ....................................................... 24 
  
 Abstract   ............................................................................................................................ 24 
 Introduction   ...................................................................................................................... 25 
 Materials and Method   ...................................................................................................... 26 
 Results and Discussion   .................................................................................................... 29 
 Literature Cited   ................................................................................................................ 38 
IV.  PHOSPHORUS REMOVAL BY SOIL SEPARATED FROM WATER BY 
PERMEABLE, GEOTEXTILES  ...................................................................................... 58 
 
 Abstract   ............................................................................................................................ 58 
 Introduction   ...................................................................................................................... 59 
 Materials and Method   ...................................................................................................... 59 
 Results and Discussion   .................................................................................................... 60 
 Literature Cited   ................................................................................................................ 62 
vi 
 
V.  EFFECTS OF WATER QUALITY AND CHEMICAL COAGULANTS ON 
SEDIMENTATION OF SUSPENDED SOIL PARTICLES FROM WATER  ................ 66 
 
 Abstract   ............................................................................................................................ 66 
 Introduction   ...................................................................................................................... 67 
 Materials and Method   ...................................................................................................... 68 
 Results and Discussion   .................................................................................................... 71 
 Literature Cited   ................................................................................................................ 80 
VI.  Conclusions  ....................................................................................................................... 92 
 Literature Cited   ................................................................................................................ 96 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
vii 
 
 
 
 
 
 
 
List of Tables 
III. 1. Characteristics of the two, geotextile liner materials as reported by manufacturers ... 41 
III. 2. Correlation coefficients for relationships of turbidity, total suspended solids, and 
chlorophyll a for pooled data from geotextile-lined and control ponds...................................... 42 
 
III. 3. Grand means for 2008 and 2009 in control ponds and ponds lined with one of two 
permeable, geotextiles................................................................................................................. 43 
 
III. 4. Fish production data for 2008 and 2009 in control ponds and ponds lined with one of 
two permeable, geotextiles .......................................................................................................... 45 
 
IV. 1. Characteristics of six, geotextile materials .................................................................. 63 
 
IV. 2. Mean concentrations and standard deviations (SD) for soluble reactive phosphorus 
concentrations (mg/L) after 18 days in aquaria (n = 3) with soil separated from water by different 
types of geotextiles as compared to controls .............................................................................. 64 
 
V. 1. Total alkalinity (TA), total hardness (TH), and total dissolved solids (TDS) 
concentrations and pH in freshwater samples used in sedimentation rate trials ......................... 82 
 
V. 2. Properties of soils used as sources of suspended solids in sedimentation trials .......... 83 
 
V. 3. Effectiveness of low concentrations of aluminum sulfate and aluminum chloride for 
turbidity removal ......................................................................................................................... 84 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
viii 
 
 
 
 
 
 
 
List of Illustrations 
 
 
III. 1. Concrete retaining wall in earthen ponds at the Auburn University E.W. Shell Fisheries 
Center, Auburn, Alabama  .......................................................................................................... 46 
 
III. 2. Geotextile material used to line ponds at the Auburn University E. W. Shell Fisheries 
Center, Auburn, Alabama ........................................................................................................... 47 
 
III. 3. Sketch (not to scale) of attachment of geotextile liners to bottoms of earthen ponds  48 
 
 
III. 4. Sketch (not to scale) showing the method of securing geotextile liners to concrete 
retaining walls in ponds  ............................................................................................................. 49 
 
III. 5. Photographs showing ponds lined with the black, style 307 geotextile (upper) and the 
gray, Style 3801 G geotextile (lower)  ........................................................................................ 50 
 
III. 6. Photographs of a pond in which the gray liner floated ................................................ 51 
 
III. 7. Photographs of an unlined pond bottom following fish harvest (upper) and of a lined 
pond following fish harvest and removal of the liner ................................................................. 52 
  
III. 8. Mean values for pH, water temperature, and concentrations of total alkalinity and total 
hardness in ponds lined with two types of geotextile liners and in unlined, control ponds........ 53 
 
III. 9. Mean values for concentrations of dissolved oxygen (DO) and 5-d biochemical oxygen 
demand (BOD5) in pond lined with two types of geotextile liners and in unlined, control ponds
 ?????? ????????????????????????????.?5 4 
 
III. 10. Mean values for concentrations of total ammonia nitrogen (TAN), Nitrate (NO3-N), 
Nitrite (NO2-N), and total nitrogen in pond lined with two types of geotextile liners and in 
unlined, control ponds ................................................................................................................. 55 
 
III. 11. Mean values for concentrations of soluble reactive phosphorus and total phosphorus in 
pond lined with two types of geotextile liners and in unlined, control ponds ............................ 56 
 
III. 12. Mean values for concentrations of turbidity, total suspended solids, and chlorophyll a in 
pond lined with two types of geotextile liners and in unlined, control ponds ............................ 57 
 
ix 
 
IV. 1. Mean concentration of soluble reactive phosphorus over and 18-d period in aquaria (n = 
3) with soil separated from water by difference type of geotextiles as compared to controls .... 65 
 
V. 1. Changes in turbidity over time in cylinders containing water and suspended particles of 
three, different soils: CP soil, West Gulf Coastal Plain; BP Soil, Blackland Prarie; PP soil, 
Piedmont Plateau ........................................................................................................................ 85 
 
V. 2. Changes in turbidity in cylinders containing waters of different salinity (diluted 
seawater) and suspended particles of three, different soils: CP soil, West Gulf Coastal Plain; BP 
soil, Blackland Prarie; PP soil, Piedmont Plateau....................................................................... 86 
 
V. 3. Change in turbidity in cylinders containing freshwater of three compositions and 
suspended particles of three, different soils: CP soil, West Gulf Coastal Plain; BP soil, Blackland 
Prarie; PP soil, Piedmont Plateau................................................................................................ 87 
 
V. 4. Results of preliminary tests of nine, potential, chemical coagulants for moving turbidity 
from water. Each test was conducted in water containing particles of three, different soils: CP 
soil, West Gulf Coastal Plain; BP soil ? Blackland Prarie; PP soil ? Piedmont Plateau.  ....... 88 
 
V. 5. Effectiveness of different coagulants in removing turbidity from water. Each test was 
conducted in water containing particles of three, different soils: CP soil ? West Gulf Coastal 
Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. ..................................................... 89 
 
V. 6. Effectiveness of different concentration of six, chemical, coagulants on pH. Each test 
was conducted in water containing particles of three, different soils: CP soil, West Gulf Coastal 
Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. ..................................................... 90 
 
V. 7. Effectiveness of different concentration of six, chemical, coagulants on conductivity. 
Each test was conducted in water containing particles of three, different soils: CP soil, West Gulf 
Coastal Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. ........................................ 91 
 
 
 
 
 
1 
 
 
 
 
 
 
 
I. Introduction 
 
 
 Erosion of pond embankments is a ubiquitous and troublesome occurrence in aquaculture 
(Boyd 1995).  Erosion degrades pond embankments, but soil particles suspended in water create 
turbidity that can limit phytoplankton productivity and availability of natural food organisms for 
aquacultural species.  Moreover, suspended soil particles often settle in deeper areas of ponds to 
make ponds shallower and to create soft sediment that can interfere with various management 
procedures (Steeby et al. 2001).  There have been some estimates of rates of sediment 
accumulation in ponds.  Munsiri et al. (1995) found that in small, aquaculture research ponds 
(0.04 to 0.1 ha) ranging from 2 to 52 yr in age, the average rate of sediment accumulation was 
about 1 cm/yr.  Sedimentation rates in 233 aquaculture ponds from nine countries ranged from 
0.5 to 3.7 cm/yr and averaged 1.44 cm/yr (Boyd et al. 2010).  Steeby et al. (2004) found that 
sedimentation rate in ponds in Mississippi ranged from 12.5 cm during the first year to 1.3 cm/yr 
in 16 to 21 yr-old ponds. Thus, sedimentation decreased as ponds aged. 
 Erosion of pond embankments can be minimized by designing side slopes of 
embankments in accordance with soil properties and establishing grass cover.  Also, aerators 
should be installed in deeper water in a manner that avoids impingement of aerator-induced 
currents on embankments (Boyd et al. 2003).  Erosion-prone areas of embankments should be 
lined with stone (rip-rap) or other material capable of lessening erosion.  Nevertheless, 
traditional erosion control measures do not stop erosion of pond earthwork; they just lessen the 
rate of soil loss. 
2 
 
 Several common aquaculture species also cause considerable disturbance of pond 
bottoms by stirring sediment in search of benthic food organisms and by making depressions or 
burrows during spawning activities.  Occasionally, wild aquatic animal species may enter ponds 
and create burrows in pond bottoms. 
 One way to completely stop erosion of pond earthwork would be to cover pond bottoms 
and embankments with a plastic liner.  Liners are frequently used in certain types of highly-
intensive aquaculture ? especially in heterotrophic, floc systems for pond culture of marine 
shrimp (Avnimelech 2012).  Several research stations also have used liners to reduce seepage in 
ponds.  However, liners that have previously been used in aquaculture were not porous and 
prevented contact of water with bottom soils.  Phosphorus is strongly adsorbed from water by 
bottom soil (Masuda and Boyd 1994), and it will accumulate in ponds with impermeable liners 
causing dense unstable phytoplankton blooms (Leonard 1995).  Where liners have been used to 
prevent seepage, a layer of soil usually is placed over pond bottoms increasing the already high 
price of lining ponds (Daniels and Boyd 1989; Leonard 1995). 
 Geotextile technology is expanding rapidly as new applications are found for these 
products.  Some geotextiles are porous and less expensive than the thick, non-porous, plastic 
liners occasionally used in aquaculture.  Permeable liners might allow exchange of dissolved 
substances ? particularly phosphorus ? between bottom soil and water, and because of their 
lower cost, porous geotextiles might have application for erosion control in ponds and especially 
in small ponds on research stations and hatcheries. 
 Turbidity in pond water also can originate from suspended solids in source water, and in 
some cases, ponds remain turbid even after all sources of turbidity have been eliminated.  This 
results because clay particles settle slowly from water ? some may remain in suspension 
3 
 
permanently.  Therefore, methods for clearing turbid water in ponds are needed.  Chemical 
coagulations are probably the best choice for lined ponds, but relatively little research has been 
conducted on the relative effectiveness of different coagulants and of the influence of basic water 
quality on turbidity removal by coagulants. 
 The purpose of the present study was to evaluate porous, geotextile liners as potential 
pond lining material and to determine the relative effectiveness of common chemical coagulants 
in clearing turbidity from water. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4 
 
 
 
 
 
 
 
II. Literature Review 
 
 
Erosion in aquaculture ponds 
 
 Erosion is a natural process by which earthen material is removed from a land or 
earthwork surface and transported, usually by water, to another area away from the original 
location.  Erosion is caused by strong wind, heavy rains, snow or ice, wave action, and activities 
of animals such as livestock, burrowing animals, and humans (Brady 1990).  In aquaculture 
ponds, erosion occurs mainly on the side slopes of embankments.  Soil material is eroded from 
embankments by strong waves, rainfall, and aerator-generated water currents.  Embankments 
should be constructed with proper side slopes and thoroughly compacted at optimum moisture 
content for compaction (McCarthy 1998; Yoo and Boyd 1994).  The above water portions of 
embankments should be lined with vegetation, rocks, or synthetic liners to minimize erosion.  
Erosion control will avoid high concentration of suspended solids and turbidity and reduces the 
cost of maintaining pond earthwork (Egna and Boyd 1997).  It also reduces the rate of sediment 
accumulation in ponds. 
 In Alabama, erosion is an important issue at catfish farms.  Hence, when the Alabama 
Catfish Producers, Auburn University, Alabama Department of Environmental Management 
(ADEM), and the United States Department of Agriculture Natural Resources Conservation 
Service (USDA NRCS) collaborated to develop Best Management Practices for channel catfish 
5 
 
farming in Alabama, techniques for erosion control were included in the BMPs (Boyd et al. 
2003). 
 
Water quality in fish ponds 
 
 Water quality in fish ponds includes physical, chemical, and biological factors that affect 
the suitability of the water for fish production (Hepher and Pruginin 1981).  Wherever 
aquaculture takes place, water quality should be measured. If water quality is not optimum for 
survival, reproduction, and growth of fish or other aquaculture species, water quality 
management should be applied.  Although there are many water quality variables, only a few of 
them play an important role in aquaculture.  Nevertheless, these variables need to be measured, 
because a pond that has ?good? water quality has more production and a greater survival rate 
than a pond that has ?poor? water quality (Boyd and Tucker 1998). 
 
Temperature 
 
 Temperature affects chemical and biological processes.  The rate of chemical reactions 
and biological processes roughly doubles for every 10oC increase in temperature (Williams and 
Williams 1964).  Thus, aquatic organisms will use two times as much oxygen at 30oC as they 
will use at 20oC.  Moreover, chemical reactions in pond waters and sediment will occur twice as 
fast at 30oC as at 20oC.  Thus, the dissolved oxygen requirement for aquatic organisms is more 
critical in warm water than in cooler water (Boyd and Tucker 1998).  Water temperature also 
6 
 
influences management procedures.  For example, in cooler water fertilizer dissolves slower and 
herbicides act slower.  
 In ponds and other water bodies, heat enters at the surfaces, and the surface water heats 
faster than deeper water.  This can lead to thermal stratification of water bodies with warmer 
water at the surface and cooler water at the bottom (Wetzel 2001).  Thermal stratification usually 
can be prevented in aquaculture ponds by avoiding water more than 2 m deep and by using 
mechanical aeration (Boyd and Tucker 1998). 
 In intensive aquaculture systems, deterioration of water quality can stress fish or other 
culture species making them more susceptible to diseases and parasites (Boyd and Tucker 1998).  
Disease outbreaks are especially likely if fish are stressed at a time when the environment is 
optimal for pathogens to reproduce.  Temperature can play an important role in aquatic 
organisms, because temperatures may be either below or above the thermal limit affecting to the 
fish?s immunity (Watt 2001).  Channel catfish Ictalurus punctatus held at temperatures of 15, 20, 
25, 30oC had different immune and hematological responses after being vaccinated with live 
theronts of Ichthyophtihrius multifillis (ich).  Vaccinated catfish held at 20oC temperatures before 
being challenged with ich responded by having more red blood cells, white blood cells, 
thrombocytes, and monocytes.  Tilapia held at a temperature of 15oC gave bad results for 
survival and no sign of anti-ich antibodies following vaccination (Martins et al. 2008). 
 
pH 
 
 The pH expresses the degree of acidic or basic conditions in water.  The pH in freshwater 
ponds usually will be between 6 and 9, and in a given pond, pH can fluctuate daily by one or two 
7 
 
units because of differences in the photosynthesis rate relative to the respiration rate (Boyd and 
Tucker 1998).  Carbon dioxide reacts in water to produce acidity (Wetzel 2001) as shown in the 
equation below: 
 
CO2 + H2O = HCO3- + H+ 
 
From the equation, it can be seen that if CO2 in water increases, H+ will increase, and pH will 
decrease.  On the other hand, if CO2 in water decreases, H+ will decrease, and pH will increase.  
Hence, in daytime, phytoplankton in the water column will lose CO2 as plants use it in 
photosynthesis, and pH will increase.  At night, phytoplankton no longer use CO2, and organisms 
release CO2 by respiration decreasing pH in the water column (Wetzel 2001). 
 The fingerlings of channel catfish and hybrid catfish (female channel catfish ? male blue 
catfish I. furcatus) are sensitive to sudden changes in pH, but they become more tolerant to pH as 
they age and grow larger.  A recent study of pH tolerance in channel catfish versus hybrid catfish 
at three states of growth:  sac fry, swim-up fry, and fingerlings found that channel catfish sac fry 
were less tolerant than hybrid catfish to low rate changes of pH:  24-h LC10 (0.13 and 0.38 pH 
unit increase, respectively), and 24-h LC50 (0.36 and 0.48 pH unit increase, respectively).  
Conversely at a higher rate change of pH increase (0.62 pH unit), channel catfish were more 
tolerant than hybrid catfish.   
For swim-up fry, the hybrid catfish were less tolerant of pH increase (24-h LC50 = 0.83 
pH unit) than channel catfish (24-h LC50 = 1.28 pH unit.). However, fingerling channel catfish 
were less tolerant of pH increase (24-h LC50 = 1.33 pH unit) than were hybrid catfish (24-h 
8 
 
LC50 = 1.54 pH unit.  However, the relationship between fish survival and pH levels reveals that 
catfish are less sensitive to consistently high pH than to abrupt pH change (Mischke 2012). 
 
Suspended solids and turbidity 
 
 Turbidity in a water column results from suspended solids that block the light from 
penetrating into the water.  There are three kinds of suspended solids (Wetzel 2001; Boyd and 
Tucker 1998) that can affect the level of turbidity in the water body. 
 
? Phytoplankton, zooplankton, and bacterial blooms:  algal blooms or eutrophication occur 
from additions of nutrients to water in fertilizer, organism waste, and pollution.  This 
phenomenon can raise the pH up to 10 or more.  Dense phytoplankton blooms also can 
lead to fish kills from oxygen depletion.  Some algal species produce toxins which can 
harm aquatic animals. 
 
? Suspended organic and humic acids:  These substances reduce light penetration and some 
may even inhibit phytoplankton growth through toxic effects.  Although organic 
substances stain water (tea or coffee color), they seldom cause dissolved oxygen 
depletion. 
 
? Suspension of silt and clay particles:  Colloidal clay particles resulting from erosion on 
watersheds or within ponds may remain suspended in water for a long time.  They reduce 
photosynthesis, but clay turbidity usually is not toxic. 
9 
 
All sources of turbidity scatter and block sunlight, preventing its penetration into the 
water column.  Thus, it has a negative effect on growth of phytoplankton and aquatic weeds 
which are the primary producers in water bodies.  Freshwater organisms can tolerate more 
turbidity than brackishwater organisms, and seawater organisms are the least tolerant to turbidity. 
Most channel catfish Ictalurus punctatus are produced mainly in the southeastern United 
States.  They are raised in earthen ponds.  In catfish ponds, phytoplankton will absorb and reduce 
NH3-N concentrations from the water column (Hargreaves 1998).  Blue-green algae or 
cyanobacteria commonly dominate the phytoplankton communities in eutrophic water bodies.  
They are able to control cell buoyancy by collapsing and reforming intracellular gas vesicles 
making them float to the water surface.  This gives blue-green algae a competitive advantage 
over other kinds of phytoplankton for light (Paerl and Tucker 1995).  Some species of 
cyanobacteria are unwanted because of odorous compounds that can affect the quality of fish 
flesh (Rimando and Schraeder 2003). 
 
Total alkalinity and total hardness 
 
Total alkalinity is the total concentration of titratable bases in water expressed as the 
concentration of equivalent calcium carbonate (CaCO3) in milligrams per liter (Boyd and Tucker 
1998). The bases in water include hydroxide, ammonia, borate, phosphate, silicate, bicarbonate, 
and carbonate, but bicarbonate and carbonate contribute most of the alkalinity to natural water 
(Wetzel 2001).  Water with a pH above 4.5 contains alkalinity, and water contains carbon 
dioxide up to pH 8.3.  Because carbon dioxide causes acidity, a water has acidity up to pH 8.3.  
Waters between pH 4.5 and 8.3 ? because they contain both bicarbonate and carbon dioxide ? 
10 
 
contain both acidity and alkalinity.  Waters below pH 4.5 are said to contain mineral acidity, 
because carbon dioxide usually cannot depress pH below 4.5.  Water above pH 8.3 does not 
contain acidity.  There the concept of alkalinity and acidity in water is a little different from the 
traditional manner of calling water of pH 7 neutral, water below pH 7 acidic, and water above 
pH 7 alkaline (Boyd et al. 2011).  
 Total hardness is expressed as the concentration of all divalent cations expressed in 
milligrams per liter of calcium carbonate.  Calcium and magnesium dominate the divalent 
cations in almost all pond waters.  Copatti et al. (2011) found that raising water hardness can 
improve the growth rate of silver catfish Rhamdia quelen juveniles in acidic or alkaline water.  
Conversely, hardness did not affect growth of silver catfish at neutral pH. Investigation found 
that the highest concentrations of water hardness reduced silver catfish growth in acidic water as 
well as in water of pH 9.0.  Silver catfish juveniles held under acidic conditions (pH 5.5) in soft 
water (30-60 mg/L CaCO3) water for 30 days had significantly reduced growth rate when 
compared with those kept at pH 7.0 and the same level of hardness. 
 
Phosphorus 
 
 Phosphorus is a key nutrient stimulating phytoplankton production in ponds.  Thus, as 
feeding rates increase, phytoplankton abundance increases.  Phytoplankton blooms in fish pond 
often contain a high frequency of blue-green algae that can cause off-flavor in fish flesh (Paerl 
and Tucker 1995), and species of algae that can be toxic to fish may sometimes occur (English 
et. al. 1993; Snyder et. al. 2002; Zimba et. al. 2001).  In addition, low dissolved oxygen 
concentration ? especially at night ? may be a problem in ponds with dense plankton blooms 
11 
 
(Boyd and Tucker 1998).  The main natural control of phosphorus concentrations in ponds is 
uptake by the bottom soil (Boyd 1995).  Bottom soil adsorbs phosphorus, and once bound in the 
soil, it is sparingly soluble.  Thus, ponds with impermeable liners that are not covered with soil 
can accumulate large amounts of phosphorus in their waters.  The blooms become very dense in 
such ponds, and die-offs often occur.  When the dead cells decompose, the phosphorus contained 
in them is released back into the water triggering another phytoplankton bloom, and the cycle 
repeats itself (Hopkins et al. 1993; Krom et al. 1989; Neori et al. 1989). 
 
Nitrogen 
 
 Nitrogen can enter ponds from the air in N2 form and some of this form can be fixed in 
organic compounds by certain species of blue-green algae and bacteria (Wetzel 2001).  Some 
nitrogen can enter ponds in rain in the form of nitrate, and many forms of nitrogen may enter 
ponds via the water supply.  Inorganic nitrogen may enter ponds in fertilizers and organic 
nitrogen or enter in manure or feed.  A high rate of nitrogen recycling occurs in pond ecosystems 
when organic matter from dead blue-green algae and bacteria and other sources decompose.  In 
aquaculture ponds, feeds can result in a high level of nitrogen in water.  Ammonia enters the 
pond from metabolic wastes of the culture species and from decomposition of uneaten feed and 
feces.  Hence, an important concern in intensive aquaculture is excessive concentration of 
ammonia (Boyd and Tucker 1998). 
 Nitrogen is recycled from dead plankton cells in ponds with impermeable liners as 
described for phosphorus above.  However, soil is not a major control on nitrogen concentrations 
in ponds.  Ammonia is lost from ponds by diffusion, and nitrate is denitrified to nitrogen gas by 
12 
 
certain bacteria (Boyd and Tucker 1998).  These processes can occur in a pond lined with an 
impermeable liner not covered with soil.  However, in such ponds, there may not be an anaerobic 
zone that occurs in bottom soil.  Denitrification possibly does not progress as rapidly in a pond 
with an impermeable liner as in an earthen-bottomed pond. 
 
Liners in aquaculture ponds 
 
 There are two major kinds of materials that can be used to line ponds ? a permeable 
geotextile liner that can let water and nutrients in the water body flow to them and impermeable 
plastic sheets that allow neither water nor nutrients to pass through.  Impermeable liners have 
been used exclusively in aquaculture ponds.  Unless soil is placed over impermeable liners, 
phosphorus concentration will increase in the water.  This can lead to phytoplankton blooms that 
tend to increase to high density, crash, increase to high density again, etc. (Krom et. al. 1989; 
Barkoh 1996; Neori et. al. 1989) Thus, water quality is not stable in ponds that have 
impermeable liners without soil on top of them.   
The possibility of using permeable liners in ponds should be investigated, because they 
might not interfere with phosphorus removal from water by bottom soil, lessening the problem 
with unstable phytoplankton blooms that occur in ponds with permeable liners.  Impermeable 
pond liners are excellent for preventing erosion ? especially if soil is not placed on top of them 
(Funge-Smith and Briggs 1998).  Permeable liners likely could also be effective in avoiding 
erosion. 
 A basic problem for pond management is excessive macrophyte growth in ponds and 
embankments.  Too much macrophytic biomass in a pond is undesirable; excessive vegetation 
13 
 
can interfere with the use of ponds for recreation.  In aquaculture ponds, macrophytes interfere 
with feeding and other management activities.  After macrophytes die, they decompose, 
releasing nutrients back into the water.  This cycle of growth, death, and decaying of aquatic 
plants results in overabundant pond vegetation which affects oxygen levels causing stress and 
mortality of fish.  Bottom liners can be used to control rooted macrophytes in the pond, because 
they cover the soil and do not allow rooted plants access to the bottom.  Of course, macrophytic 
algae that do not have roots, and floating, higher plants such as water hyacinths Eicchornia 
crassipes that do not root in the soil can grow in lined ponds.  Permeable liners also would likely 
prevent the growth of rooted aquatic vegetation.   
 A polypropylene liner (DuPont Typar 3201 and 3301) was used to control macrophytes 
over the bottom of a lake.  In summer time, the regrowth was counted in order to compare to a 
control area.  Regrowth of macrophytes was slight in lined ponds ? macrophyte biomass was at 
least 100 times greater in the controls.  Even though the liner material was permeable to gases, it 
did not float or form a ?balloon? problem (Cooke and Gorman 1980). 
Geotextile fabric, a porous woven polyethylene material, is used for construction site 
erosion control (Rickson 2006). It is also used for improving drainage and enhancing 
reinforcement of marginally stable slopes (Vishnudas et al. 2003), and it can be used as covers 
for anaerobic odor control (Miner et al 2003). Double layers of geotextile bags filled with a 
variety of materials have been used to decrease bridge abutment scouring (Korkut et al. 2007) 
and for beach erosion reduction (Elko and Mann 2007; Oh and Shin, 2006; Allan and Komar 
2004). Moreover, hydraulically loaded geotextile bags are used to dewater dredge slurry (Shin et 
al. 2002) dairy and swine lagoon waste (Worley et al. 2008; Baker et al. 2002), and sewage 
sludge in decentralize sites (Wett et al. 2005). 
14 
 
 The major use of geotextiles in aquaculture has been to dewater (remove solids) effluent 
from intensive production facilities such as backwash water from indoor facilities (Sharrer et al. 
2009) and intensive biofloc systems (Danaher et al. 2011). I did not find references to use of 
porous geotextiles for avoiding erosion in production ponds.   
 
Catfish pond management 
 
  Feed is applied to catfish ponds in order to increase fish production beyond that possible 
in fertilized ponds.  Almost all feed applied will be consumed by fish, and feed conversion ratios 
of 1.5 to 2.0 are possible (Bosworth et al. 2004; Dunham et al. 2008; Jiang et al. 2008; Green and 
Rawles 2010; Kumar and Engle 2010; Li et al. 2012).  Growth rates of hybrid catfish were found 
to be 29.3% more than those of channel catfish (Green and Rawles 2010).   
Aerators are used in catfish ponds to oxidize organic wastes from feeding and provide 
dissolved oxygen for the respiration of fish and other organisms (Boyd and Tucker 1998).  
Aeration allows production to be increased two to four times above that possible in un-aerated 
ponds.  However, aerators generate strong water currents that contribute to erosion of pond 
embankments and bottoms.   
 Aquaculture facilities discharge nutrients, organic matter, and suspended solids when 
they overflow or are drained.  Thus, the U.S. Environmental Protection Agency has made an 
effluent rule for US aquaculture (USOFF 2004).  However, this rule does not apply to catfish 
ponds unless they discharge more than 30 days per year. 
Pond draining effluents have high concentrations of total suspended solids.  Songsawang 
and Boyd (2012) reported that settling basins can remove coarse, suspended soil particles from 
15 
 
aquaculture pond effluents, but settling basins are not able to settle particles smaller than 10-5 m 
(Ozbay and Boyd 2003, 2004). 
 
16 
 
Literature Cited 
 
 
Allan, J.C., P.D. Komar. 2004. Environmentally compatible cobble berm and artificial dune for 
shore protection. Shore Beach 72(1), 9-18. 
Avnimelech, Y.  2012.  Biofloc Technology ? a Practical Handbook, 2nd edition.  The World 
Aquaculture Society, Baton Rouge, Louisiana, USA. 
Baker, K.B., J. P. Chastian, R.B. Dodd. 2002. Treatment of lagoon sludge and liquid animal 
manure utilizing geotextile filtration. In: ASAE Annual International Meeting, Chicago, 
IL. 
Barkoh, A. 1996. Effects of Three Fertilization Treatments on Water Quality, Zooplankton, and 
Striped Bass Fingerling Production in Plastic-Lined Ponds. Aerican Fisheries Society. 58: 
237-247. 
Bosworth, B. G., W. R. Wolters, J. L. Silva, R. S. Chamul, and S. Park. 2004. Comparison of 
production, meat yield, and meat quality traits of NWAC103 Line Channel catfish, Norris 
Line Channel Catfish, and female Channel catfish ? male Blue catfish F1 hybrids. North 
American Journal of Aquaculture 66:177?183. 
Boyd, C. E.  1995.  Bottom Soils, Sediment, and Pond Aquaculture.  Chapman and Hall, New 
York, New York, USA. 
Boyd, C.E. and C.S. Tucker. 1998. Pond Aquaculture Water Quality Management. Kluwer 
Academic Publishers, Boston, Massachusetts. 700 p. 
17 
 
Boyd, C.E., C.S. Tucker, and R. Viriyatum. 2011. Interpretation of pH, acidity and alkalinity in 
aquaculture and fisheries. North American Journal of Aquaculture 73(4):403-408. 
Boyd, C. E., C. W. Wood, P. Chaney, and J. F. Queiroz.  2010.  Role of aquaculture pond 
sediments in sequestration of annual global carbon emissions.  Environmental Pollution 
158:2,537-2,540. 
Boyd, C. E., J. F. Queiroz, G. N. Whitis, R. Hulcher, P. Oakes, J. Carlisle, D. Odom, Jr., M. 
Nelson, and W. G. Hemstreet.  2003.  Best management practices for channel catfish for 
Alabama.  Special Report 1, Alabama Catfish Producers, Montgomery, Alabama, USA. 
Brady, N.C., 1990. The Nature and Properties of Soils. 10th edition. Macmillan, New York, 621 p. 
Cooke, G.D. and M.E. Gorman. 1980. Effectiveness of Dupont TYPAR sheeting in controlling 
macrophyte regrowth after overwinter drawdown. Water Resources Bulletin. American 
Water Resources Association. 2: 353-355. 
Copatti, CE, De Oliveira Garcia L, Da Cunha MA, Baldisserotto B, Kochhann D. 2011. 
Interaction of water hardness and pH on growth of silver catfish, Rhamdia quelen, 
juveniles. Journal of the World Aquaculture Society 42: 580-585. 
Danaher J.J., C.S. Richard, and E.R. Rakocy. 2011. Evaluation of two textiles with or without 
polymer addition for dewatering effluent from an intensive biofloc production system. 
Journal of the World Aquaculture Society 42 (1): 66-72  
Daniels, H. V. and C. E. Boyd.  1989.  Chemical budgets for polyethylene-lined brackishwater 
ponds.  Journal of the World Aquaculture Society 20:53-60. 
18 
 
Dunham, R. A., G. M. Umali, R. Beam, A. H. Kristanto, and M. Trask. 2008. Comparison of 
production traits of NWAC103 channel catfish, NWAC103 channel catfish ? blue catfish 
hybrids, Kansas Select 21 channel catfish, and blue catfish grown at commercial densities 
and exposed to natural bacterial epizootics. North American Journal of Aquaculture 
70:98?106. 
Egna, H.S. and C.E. Boyd (editors). 1997. Dynamics of Pond Aquaculture. CRC Press, Boca 
Raton, Florida. 437 p. 
Elko, N.A., D.W. Mann. 2007. Implementation of geotextile T-groins in Pinellas County, 
Florida. Shore Beach 75(2), 2-10 
English, W.R., T.E. Schwedler, and L. A. Dyck. 1993. Aphanizomenon flos-aquae, a toxic Blue-
Green Alga in Commercial Channel Catfish, Ictalurus punctatus, ponds: A Case History. 
Journal of Applied Aquaculture 3:195-209. 
Funge-Smith, SJ and M.R.P. Briggs. 1998. Nutrient budgets in intensive shrimp ponds: 
Implications for sustainability. Aquaculture 164:117-133. 
Green, B.W., and S. D. Rawles. 2010. Comparative growth and yield of Channel Catfish and 
Channel ? Blue Hybrid catfish fed a full or restricted ration. Aquaculture Research 
41:e109?e119. 
Hargreaves, J.A. 1998. Nitrogen Biochemistry of Aquaculture Ponds. Aquaculture. 166: 181-212 
Hepher, B and Y. Pruginin. 1981. Commercial fish farming: with special reference to fish culture 
in Israel: Wiley. New York. USA. 262p. 
19 
 
Hopkins, J.S., R.D. Hamilton II, P.A. Sandifer, C.L. Browdy, and A.D. Stokes. 1993. Effect of 
water exchange rate on production, water quality, effluent characteristics and Nitrogen 
budgets of intensive shrimp ponds. Journal of The World Aquaculture Society. 
24(3):304-312. 
Jiang, M., W. H. Daniels, H. J. Pine, and J. A. Chappell. 2008. Production and processing trait 
comparisons of Channel catfish, Blue catfish, and their hybrids grown in earthen ponds. 
Journal of the World Aquaculture Society 39:736?745. 
Korkut, R., E.J. Martinez, R. Morales, R. Ettema, B. Barkdoll. 2007. Geobag performance as 
scour countermeasure for bridge abutments. J. Hydrual. Eng. 133 (4), 431-439 
Krom M, J. Erez, C. Porter, and S.Ellner. 1989. Phytoplankton nutrient uptake dynamics in 
earthen marine fishponds under winter and summer conditions. Aquaculture 76: 237-253. 
Kumar, G., and C. Engle. 2010. Relative production performance and cost of food fish 
production from fingerlings of channel-blue F1 hybrids, Ictalurus punctatus?Ictalurus 
furcatus, and NWAC-103 channel catfish, I. punctatus. Journal of the World Aquaculture 
Society 41:545?554. 
Leonard, S. E.  1995.  Water quality factors influencing striped bass (Morone saxatilis) 
production in lined ponds.  Ph.D. dissertation, Auburn University, Auburn, Alabama, 
USA. 
Li, M.H., E.H. Robinson, D.F. Oberle, and P.M. Lucas. 2012. Effects of Feeding Rate and 
Frequency on Production Characteristics of Pond-Raised Hybrid Catfish. North American 
Journal of Aquaculture 74: 142-147. 
20 
 
Martins, M.L., JLP. Mouri?o, GV. Amaral, FN. Vieira, G. Dotta, Jatoba AMB, et al. 2008. 
Haematological changes in Nile tilapia experimentally infected with Enterococcus 
sp. Braz J Biol. 68(3):657-661. 
Masuda, K. and C. E. Boyd.  1994.  Phosphorus fractions in soil and water of aquaculture ponds 
built on clayey, Ultisols at Auburn, Alabama.  Journal of the World Aquaculture Society 
25:379-395. 
McCarthy, D. 1998. Essentials of Soil Mechanics and Foundations - Basic Geotechnics. 5th 
Edition. Prentice-Hall. Upper Saddle River, New Jersey. USA. 730 p. 
Miner, J.R., F.J. Humenik, J.M. Rice, D.M.C. Rashash, C.M. Williams, W. Robarge, D.B. 
Harris, R. Sheffield. 2003. Evaluation of a permeable, 5 cm thick polyethylene foam 
lagoon cover. Trans. ASAE 46 (5), 1421-1426. 
Mischke, C.C. and N. Chatakondi 2012. Effects of abrupt pH increases on survival of different 
ages of young catfish. North American Journal of Aquaculture. 74:160-163. 
Munsiri, P., C. E. Boyd, and B. F. Hajek.  1995.  Physical and chemical characteristics of bottom 
soil profiles in ponds at Auburn, Alabama, USA, and a proposed method for describing 
pond soil horizons.  Journal of the World Aquaculture Society 26:346-377. 
Neori, A., M. Krom, I. Cohen, and H. Gordin, 1989. Water quality conditions and particulate 
chlorophyll a of new intensive seawater fishponds in Eilat, Israel: daily and diel 
variations. Aquaculture 80: 63-78. 
21 
 
Oh, Y.I., and E.C. Shin. 2006. Using submerged geotextile tubes in the protection of the E. 
Korean shore. Coast Eng. 53(11), 879-895 
Ozbay, G. and C.E. Boyd. 2003. Particle size fractions in pond effluents. World Aquaculture 
34(4): 56-59. 
Ozbay, G. and C.E. Boyd. 2004. Treatment of Channel catfish pond effluents in sedimentation 
basins. World Aquaculture 35(3): 10-13. 
Paerl, H.W. and C. S. Tucker. 1995. Ecology of blue-Green algae in aquaculture ponds. Journal 
of the World Aquaculture Society 26: 109-131. 
Rickson, R.J., 2006. Controlling sediment at source: an evaluation of erosion control geotextiles. 
Earth Surf. Proc. Land. 31(5), 550-560 
Rimando, A.M. and K.K. Schrader. 2003. Off-Flavors in Aquaculture. American Chemical 
Society. Washington, DC. USA. 268 p.  
Sharrer, M.J., R. Kata, and S. Steven. 2009. Evaluation of geotextile filtration appling coagulant 
and flocculant amendments for apuaculture biosolids dewatering and phosphorus 
removal. Aquacultural Enginerring. 40(2009) 1-10. 
Shin, E.C., K.S. Ahn, Y.I. Oh, and B.M. Das. 2002. Construction and monitoring of geotubes. In: 
Proceedings of the International Offshore and Polar Engineering Conference, vol. 12. pp. 
469-473 
Snyder, G., A. Goodwin, and D. Freeman. 2002. Evidence that channel catfish, Ictalurus 
punctatus (Rafinesque), mortality is not linked to ingestion of the hepatotoxin 
microcystin?LR. Journal of Fish Diseases 25: 275-285. 
22 
 
Soongsawang S. and Boyd CE. 2012. Effects of effluents from a fisheries research station on 
stream water quality. North American Journal of Aquaculture 74: 73-79. 
Steeby, J. A., J. A. Hargreaves, C. S. Tucker, and S. Kingsbury.  2004.  Accumulation, organic 
carbon and dry matter concentration of sediment in commercial channel catfish ponds.  
Aquacultural Engineering 30:115-126. 
Steeby, J. A., S. Kingsbury, and J. Hargreaves.  2001.  Sediment accumulation in channel catfish 
production ponds.  Global Aquaculture Advocate 4(3):54-56. 
USOFR (U.S. Office of the Federal Register). 2004. Effluent limitations guidelines and new 
source performance standards for the concentrated aquatic animal production point 
source category: final rule. Federal Register 69:162(23 August 2004):51892?51930. 
Vishnudas, S., H.H.G. Savenije, P. Van der Zaag, K.R. Anil, and K. Balan, 2006. The protective 
and attractive covering of a vegetated embankment using coir geotextiles. Hydrol. Earth 
Syst. Sci. 10(4), 565-574 
Watts M., BL. Munday, and CM. Burke. 2001. Immune responses of teleost fish. Australian 
Veterinary Journal 79(8):570-574. 
Wett, B., M. Demattio, and W. Becker, 2005. Parameter investigation for decentralized 
dewatering and solar thermic drying of sludge. Water Sci. Technol. 41(10), 65-73. 
Wetzel R.G. 2001. Limnology Lake and River Ecosystems. 3rd Edition. Academic Press. New 
York, New York. USA. 1006 p. 
Williams, V.R. and H.B. Williams 1964. Basic Physical Chemistry for The Life Sciences. 2nd 
Edition. W.H. Freeman and Company, San Francisco, California. USA. 524 p. 
23 
 
Worley, J.W., T.M. Bass, and P.F. Vendrell. 2008. Use of geotextile tubes with chemical 
amendments to dewater dairy lagoon solids. Bioresour. Technol. 91, 4451-4459. 
Yoo, K.H. and C.E. Boyd. 1994. Hydrology and Water Supply for Aquaculture. Chapman and 
Hall, New York, New York. 483 p. 
Zimba, P., L. Khoo, P. Gaunt, S. Brittain, and W. Carmichael. 2001. Confirmation of catfish, 
Ictalurus punctatus (Rafinesque), mortality from Microcystis toxins. Journal of Fish 
Diseases 24: 41-47. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
24 
 
 
 
 
 
 
 
III. Evaluation of Two, Porous, Geotextile Liners for Erosion Control 
in Small Aquaculture Ponds 
 
 
Abstract 
 
 
 In an experiment conducted at the E. W. Shell Fisheries Center, Auburn, Alabama, three 
ponds each were lined with a permeable geotextile with 0.090-mm opening sizes, a permeable 
geotextile with 0.355-mm opening sizes, or served as unlined, controls.  During the 2-yr study, 
geotextile liners did not tear or decay, they prevented erosion of the bottom of the ponds stocked 
with a high density of channel catfish and aerated nightly.  The liners did tend to float up in the 
water column; the liner with smaller opening sizes floated in all three ponds, while the other liner 
floated in only one pond.  Fish production, survival, and feed conversion ratio did not differ (P > 
0.05) among the control and lined ponds or between liner types.  Water quality variables often 
differed between lined ponds and control ponds.  The greatest difference was greater 
phytoplankton growth in the lined ponds especially in ponds lined with the less permeable 
geotextile ? than in the control.  This difference was attributed to differences in phosphorus 
uptake by bottom soils related to the liners and their permeability.  However, in spite of more 
phytoplankton growth in lined ponds, the control ponds tended to have higher turbidity because 
of erosion of bottoms by aeration. 
 
25 
 
Introduction 
 
 Erosion of pond embankments is a ubiquitous and troublesome occurrence in aquaculture 
(Boyd 1995).  Erosion degrades pond embankments, but soil particles suspended in water create 
turbidity that can limit phytoplankton productivity and availability of natural food organisms for 
aquacultural species.  Moreover, suspended soil particles often settle in deeper areas of ponds to 
make ponds shallower and to create soft sediment that can interfere with various management 
procedures (Steeby et al. 2001, 2004).  There have been some estimates of rates of sedimentation 
in ponds.  Munsiri et al. (1995) found that in small, aquaculture research ponds (0.04 to 0.1 ha) 
ranging from 2 to 52 yr in age sediment accumulation averaged about 1 cm/yr.  Sedimentation 
rates in 233 aquaculture ponds from nine countries ranged from 0.5 to 3.7 cm/yr and averaged 
1.44 cm/yr (Boyd et al. 2010).  Steeby et al. (2004) found that sedimentation decreased as large, 
commercial catfish ponds (? 8 ha) aged:  annual sediment accumulation was 12.5 cm in 1-yr-old 
ponds, but only 1.3 cm in 16 to 21 yr-old ponds. 
 Erosion of pond embankments can be minimized by designing side slopes of 
embankments in accordance with soil properties and establishing grass cover.  Aerators should 
be installed in deeper water in a manner that avoids impingement of aerator-induced currents on 
embankments (Boyd et al. 2003).  Erosion prone areas of embankments should be lined with 
stone (rip-rap) or other material capable of lessening erosion.  Nevertheless, traditional control 
measures do not stop erosion of pond earthwork; they just lessen the rate of soil loss. 
 Several common aquaculture species also cause considerable disturbance of pond 
bottoms by stirring sediment in search of benthic food organisms and by making depressions or 
26 
 
burrows during spawning activities (Boyd 1995).  Occasionally, wild aquatic animal species may 
enter ponds and create burrows in pond bottoms. 
 Erosion of pond bottoms can be stopped by lining bottoms and side-slopes of 
embankments with a plastic liner.  Liners are frequently used in certain types of highly-intensive 
aquaculture ? especially in heterotrophic, floc systems for pond culture of marine shrimp 
(Avnimelech 2009).  Several research stations also have used liners to reduce seepage in ponds 
(Daniels and Boyd 1989).  Liners that have previously been used in aquaculture were not porous 
and prevented contact between pond water and bottom soils.  Phosphorus is strongly adsorbed 
from water by bottom soil (Masuda and Boyd 1994), and it will accumulate in waters of ponds 
with impermeable liners causing dense unstable phytoplankton blooms (Krom et al. 1989; 
Leonard 1995; Neori et al. 1989).  Where liners have been used to prevent seepage, a layer of 
soil usually is placed over pond bottoms. This increases the already high price of lining ponds 
(Daniels and Boyd 1989; Hopkins et al. 1993; Leonard 1995). 
 Geotextile technology is expanding rapidly as new applications are found for these 
products.  Some geotextiles are porous and less expensive than the thick, non-porous, plastic 
liners occasionally used in aquaculture.  Permeable liners might allow exchange of dissolved 
substances ? particularly phosphorus ? between bottom soil and water, and because of their 
lower cost, porous geotextiles might have wide application for erosion control in ponds. 
  
Materials and Methods 
 
 Ponds used in this study are located on the E. W. Shell Fisheries Center, 2101 North 
College Street, Auburn, Alabama.  Ponds are embankment-type water bodies built on the 
27 
 
Piedmont Plateau; soils in the area are Typic, Kandiudults (clayey, kaolinitic, and thermic) 
(McNutt 1981).  When filled to tops of standing overflow pipes, ponds are 28.3 m long ? 14.1 m 
wide (? 400 m2 surface area).  Maximum depth was about 1.5 m with an average around 1.0 m 
following initial construction (1969 to 1971).  A concrete retaining wall (15 cm wide) was 
installed to a depth of about 1 m around the inside of each pond (Fig. 1) to prevent bank erosion 
and to assure that water depth was not less than 50 cm when ponds were full in normal use.  
Ponds gradually filled over the years, and in 2004, a renovation project was initiated to remove 
sediment from the central areas, and the entire bottoms were graded (Yuvanatemiya and Boyd 
2006). 
 In March 2008, nine ponds for which renovation had been completed in fall 2007 were 
selected for this study.  Three ponds were lined with a black, porous, polypropylene geotextile 
(Style 307) manufactured by Belton Industries, Belton, SC, USA (Fig. 2).  Three ponds were 
lined with a gray, porous, polypropylene geotextile (Style 3801 G) produced by Typar 
Geotextiles, Old Hickory, TN, USA (Fig. 2).  Physical characteristics of the two geotextile 
materials are provided (Table 1).  For brevity, liners will be referred to as black and gray liners.  
Three ponds were not fitted with liners and served as controls. 
 Bottoms of the ponds were further smoothed by hand raking.  The 3-m-wide sheets of 
geotextile were sewed together with nylon thread at pond sites using a hand-held sewing device.  
A 25-cm deep by 25-cm wide ditch was excavated at a distance of 50 cm behind the concrete 
retaining wall.  Liners were installed over pond bottoms and sides, and the geotextile fabric liner 
was made wide enough to line the ditch and extend 1 m beyond.  The ditch was backfilled with 
soil to secure edges of the liner (Fig. 3).  Steel pins (61 cm long ? 1.27 cm diameter) that had one 
end sharpened to a point and a 5-cm diameter washer were welded on the other end.  Each pin 
28 
 
was forced through a 15 cm ? 0.5 cm thick plastic tile.  The washer kept the tile in place, and the 
tile prevented the washer from tearing through the liner.  Ninety-eight pins were inserted through 
the liner on a 2 m ? 2 m grid over the pond bottom.  A 4-cm wide ? 1-mm thick aluminum strip 
was attached over the liner around the inside top of the entire concrete wall.  The attachment was 
made by inserting 5-cm long ? 0.63-cm diameter screws through the metal and liner into the 
concrete wall.  In addition, a 1.2-m long ? 0.63-cm diameter steel pin was shaped to provide a 
rectangular bracket; the long side of the pin was inserted through the liner and into the 
embankment on the outside of the concrete wall, the rectangular part of the pin fitted over the top 
of the retaining wall and extended downward 50 cm over the liner (Fig. 4).  Brackets were 
installed at 2-m intervals around the pond.  Photographs (Fig. 5) show bottoms of lined ponds 
before filling with water. 
 Each pond was stocked on 5 June 2008 with 400 fingerling hybrid catfish (? Ictalurus 
punctatus ? ? I. furcatus) weighing an average of 52.1 g/fish.  Fish were fed a floating, pelleted, 
commercial feed (32% crude protein) at an estimated 3% of body weight per day.  A 0.5-hp 
vertical pump aerator was placed in each pond and operated when low nighttime dissolved 
oxygen concentration was anticipated.  Ponds were completely drained on 11 November 2008, 
and fish were counted and weighed.   
Fish smaller than marketable size were placed in a holding tank and returned to ponds on 
14 November.  On 3 December, additional fish similar in size to fish returned to ponds on 14 
November were stocked to provide a total of 400 fish/pond.  Fish added to ponds had an average 
individual weight of 302 g.  Ponds were managed in 2009 according to procedures used in 2008.  
Ponds were completely drained on 14 October 2009, and all fish harvested and weighed. 
29 
 
 Between 15 June to 1 December 2008 and 6 February to 14 October 2009, dissolved 
oxygen concentrations and water temperatures were measured weekly between 0600 and 0700 h 
at a depth of 10 cm using a polarographic dissolved oxygen meter with thermistor.  Water 
samples were dipped from the pond surface following dissolved oxygen measurement.  These 
samples were transported to the laboratory and water quality analyses immediately initiated 
using standard protocol (Eaton et al. 2005) for the following variables:  pH (glass electrode); 
turbidity (laboratory turbidimeter); total suspended solids (glass fiber filtration and gravimetry); 
total alkalinity (titration with 0.02 N H2SO4 to pH 5.1); total hardness (titration with 0.01 M 
ethylenediaminetetraacetic acid to erichrome black-T endpoint); BOD (standard, 5-d test); total 
ammonia nitrogen (phenate method); nitrite-nitrogen (diazotization procedure); soluble reactive 
phosphorus (ascorbic acid method).  Nitrate-nitrogen was determined by the szechrome reagent 
(4-phenylamino-benzenesulfonic acid) method (van Rijn 1993).  Unfiltered water samples were 
digested in an alkaline persulfate solution to convert all phosphorus and nitrogen to phosphate 
and nitrate, respectively.  Phosphate and nitrate concentrations were determined by ascorbic acid 
procedure and ultraviolet spectrophotometric screening technique, respectively (Eaton et al. 
2005; Gross et al. 1999). 
 
Results and Discussion 
 
The gray liner pulled free from the bottom and floated upward in the water column in all 
ponds, and the black liner floated up in one pond (Fig. 6).  Fifty concrete blocks (40 cm ? 20 cm 
? 20 cm) were placed over the liner, and this alleviated, but did not prevent completely, the 
floating liner problem.  Concrete blocks were left in ponds during the second year of the study. 
30 
 
 Because liners tended to float, it was decided by the manager of the E. W. Shell Fisheries 
Center that they were unacceptable, and they were removed after fish harvest in 2009.  
Nevertheless, liners were quite effective in maintaining the original shape of pond bottoms (Fig. 
7).  Unlined ponds exhibited considerable bottom erosion and sediment accumulation in deeper 
portions.  Bottom of the lined ponds showed no alteration of bottom shape.  Moreover, liners did 
not tear or develop holes because of fabric decay; they were completely intact after 2 yr.  Of 
course, the liners were not left in ponds long enough to allow comment on manufacturers? 
estimates of service life (Table 1). 
 Results of weekly water analyses are given (Figs. 8-12).  Values for water quality 
variables differed considerably among replicate ponds, but averages of variables for individual 
dates often were similar.  Thus, standard error bars were not plotted with means because the 
many overlaps would have made them impossible to distinguish.  Some trends in concentrations 
of water variables among treatments and control were noted. 
 Water temperature ranged from 20.7 to 30.9 C in 2008 and from 10.0 to 33.9 C in 2009.  
The greater water temperature range in 2009 resulted because measurements were initiated in 
February rather than in June as in 2008.  However, there were no differences in water 
temperature among control and treatments (Fig 8).  Thus, the dark color of liners did not increase 
heat absorption in lined ponds. 
Average pH of pond waters usually was above 7.5, and, values higher than 9.0 were 
observed (Fig. 8).  Higher pH values corresponded to periods with clear weather and abundant 
phytoplankton, while dips in pH ? most notable in mid May 2008 and early September 2009 ? 
were related to extended periods of cloudy weather.  Differences in pH did not result from the 
presence of liners. 
31 
 
Total alkalinity and total hardness concentrations tended to be greater in lined ponds than 
in control ponds in 2008 (Fig. 8).  In 2009, lined ponds had slightly greater total alkalinity, but 
hardness was about the same as in control ponds.  Greater total hardness and total alkalinity in 
ponds in 2008 as compared to 2009 deserves comment.  In 2008, ponds that were used as 
controls ? but not the ponds that were lined ? were treated with agricultural limestone before the 
decision was made to conduct this study.  Agricultural limestone treatment increased total 
hardness and total alkalinity concentrations in control ponds.  Because lined ponds were not 
treated with agricultural limestone, concrete blocks placed in lined ponds likely caused increased 
total alkalinity and total hardness.   
Concrete blocks consist of about 2 parts aggregate (sand, gravel, crushed stone, etc.) and 
1 part concrete.  Concrete contains Portland cement that consists of tricalcium silicate, dicalcium 
silicate, tricalcium aluminate, tetracalcium aluminoferrite, and gypsum.  When mixed with water, 
the tricalcium silicate in Portland cement reacts to form a solid mass with the other ingredients 
(Taylor 1997).  The basic reaction is: 
 
2Ca3SiO5 + 7H2O ? 3(CaO) ? Z(SiO2) ? 4(H2O)(gel) + 3Ca(OH)2 
 
 Components of concrete are slightly soluble and can increase calcium (total hardness) in 
water, and calcium hydroxide can react with carbon dioxide to produce bicarbonate (total 
alkalinity). 
Ponds were drained in December 2008, and refilled with water of relatively-low total 
alkalinity and total hardness.  Agricultural limestone was not applied after refilling.  Draining of 
control ponds and refilling caused lower total alkalinity and total hardness relative to 2008 in 
32 
 
control ponds.  Solubility of calcium-containing, alkaline substances in concrete blocks probably 
occurred most rapidly in 2008, and the already weathered blocks contributed less to total 
alkalinity and total hardness in 2009. 
 During 2008, there was little difference in dissolved oxygen concentration among control 
and treatment ponds (Fig. 9).  Only once did average dissolved oxygen concentration fall below 
6 mg/L.  Dissolved oxygen concentrations also were typically above 6 mg/L in 2009, but in late 
winter and early spring, dissolved oxygen concentration tended to be greater in lined ponds than 
in control ponds.  Dissolved oxygen concentrations never fell to concentrations considered 
dangerous to fish (Boyd and Tucker 1998; Torrans 2008), because aerators were operated often 
at night during periods when water temperature was above 25 C. 
 All three combined nitrogen fractions (total ammonia nitrogen, nitrite-nitrogen, and 
nitrate-nitrogen) were unexpectedly low in concentration during 2008 (Fig. 10).  Analytical 
procedures were checked for accuracy and found to be reliable.  The likely reason for low total 
ammonia nitrogen concentration was relatively-low fish standing crops.  Daily feed input was 
rather low in response to small fish biomass, and phytoplankton were able to absorb most of the 
ammonia nitrogen resulting from decomposition of uneaten feed, fish feces, and metabolic waste 
of fish (Tucker et al. 1994).  Without appreciable total ammonia nitrogen in water, nitrification 
occurred at low rates and nitrate-nitrogen concentrations also remained low.  There also was less 
opportunity for nitrite-nitrogen being produced as an intermediate in nitrification or from 
reduction of nitrate in anaerobic zones (Boyd and Tucker 1998; Hargreaves 1998). 
 Total nitrogen increased during the 2008 growing season.  Most of the total nitrogen 
probably was contained in phytoplankton cells.  Although average total nitrogen concentration 
33 
 
did not exceed 3 mg/L (Fig. 10), it tended to be slightly greater ? especially in September and 
October ? in lined ponds than in control ponds. 
 In 2009, total ammonia- and nitrate-nitrogen concentrations were fairly low until late 
spring, but they increased greatly during late summer and fall in response to large daily feed 
inputs when fish biomass was high.  There were no clear differences among control and lined 
ponds for total ammonia nitrogen concentration (Fig. 10).  However, other than for two spikes of 
nitrate-nitrogen in ponds with gray liners, control ponds had the highest nitrate-nitrogen 
concentrations from June onward.  Nitrite concentration tended to be much greater in control 
ponds than in lined ponds in 2009.  Less nitrite-nitrogen in lined ponds may have resulted 
because organic matter was captured on liners and was prevented from entering anaerobic zones 
of sediment as it did in unlined ponds.  Nitrate is reduced to nitrite in anaerobic sediment by 
denitrifying bacteria and stirred into the water column by aerators as described by Hollerman and 
Boyd (1980).  Aerator-generated water currents likely provided plenty of dissolved oxygen in 
water at the liner surface preventing anaerobic conditions.  Nevertheless, nitrite concentrations in 
unlined, control ponds did not reach levels reported to be harmful to channel catfish (Boyd and 
Tucker 1998). 
 In 2009, total nitrogen concentrations increased to much higher levels than in 2008 in 
response to greater feed input (Fig. 10).  Lined ponds tended to have higher total nitrogen 
concentrations than found in control ponds, but there was no difference between gray and black 
liners with respect to this variable. 
 Soluble reactive phosphorus concentrations fluctuated considerably among sampling 
dates during both years (Fig. 11).  There were a few periods during both years when soluble 
reactive phosphorus concentration in lined ponds were elevated above those in control ponds.  
34 
 
Total phosphorus concentrations were low and similar among control and treated ponds in 2008 
(Fig. 11).  Concentrations of total phosphorus were greater in 2009 in all ponds, and in late 
summer and fall, total phosphorus concentrations were markedly greater in lined ponds.  Most of 
the total phosphorus in water was probably contained in living phytoplankton cells or in their 
particulate remains (Masuda and Boyd 1994). 
 Turbidity tended to be higher during August and September 2008 in ponds with the gray 
liner, and ponds with the black liner and control ponds were similar in turbidity (Fig. 12). 
Throughout most of the growing season in 2009, control ponds had much greater turbidity than 
ponds with either liner.  Total dissolved solids concentrations varied more among ponds of the 
same treatment and among treatments than did turbidity (Fig. 12).  But, on many sampling dates 
in 2008, total dissolved solids concentrations were as high or higher in ponds with the gray liner 
than in other ponds ? the same can be said for control ponds in 2009. 
 Chlorophyll a concentrations (Fig. 12) also varied greatly among treatments and among 
ponds within treatments, but in general, chlorophyll a concentration was consistently higher in 
lined ponds ? especially in 2009. 
 Higher turbidity and total dissolved solids concentrations in control ponds in 2009 as 
compared to 2008 are likely related to several factors.  Ponds were newly renovated; sediment 
was removed and bottoms reshaped and compacted.  Fish were not stocked until 5 June in 2008, 
and the fingerlings were small.  Aeration was not necessary for several weeks, and bottoms were 
not disturbed greatly by fish activity and aerator-generated water currents.  It is likely that 
turbidity in both lined ponds and control ponds resulted primarily from plankton rather than 
suspended soil particles.  After harvest in 2008, ponds were restocked with relatively large fish 
in November and December.  Thus, in 2009, fish standing crop was much higher than in 2008 at 
35 
 
the beginning of the grow-out period, and aeration was needed more frequently.  Fish activity 
and aerator-generated water currents likely caused much erosion of bottoms of unlined ponds 
resulting in suspension of soil particles.  Low chlorophyll a concentrations in unlined ponds 
supports this hypothesis; low chlorophyll a concentration would be expected because of light 
limitation imposed by turbidity from suspended soil particles.  However, when all data were 
considered, there was a high correlation between turbidity and total suspended solids both years 
(Table 2), but chlorophyll a concentration was not correlated with either of these two variables. 
 The 5-d biochemical oxygen demand (BOD) tended to be elevated in lined ponds as 
compared to control ponds during both years (Fig. 9).  High BOD concentration in lined ponds in 
early 2009 cannot be explained, because chlorophyll a, turbidity, and total suspended solids were 
not elevated at this time.  There is no reason to believe that there was a high concentration of 
dissolved organic matter in ponds at this time, and we assume there was an analytical error.  
However, BOD concentrations in lined ponds were within the range typically found in 
commercial channel catfish ponds (Boyd and Gross 1999). 
 Grand means for water quality data from 2008 and 2009 were computed (Table 3).  A 
few differences were found among grand means.  The pH averaged higher in ponds with the gray 
liner than in controls or ponds with black liners in 2009.  Dissolved oxygen concentration was 
greater in lined ponds than in control ponds both years.  In 2008, total nitrogen concentration did 
not differ among lined ponds and control ponds.  In 2009, ponds with both liners had a higher 
mean concentration (P < 0.05) of total nitrogen than did unlined ponds.  Total phosphorus did 
not differ among control and treatments in 2008 (P > 0.05), but in 2009 when fish biomass was 
greater, the two lined-pond treatments had higher concentrations of this variable than control 
ponds (P < 0.05).  Ponds with the gray liner also had greater phosphorus concentration than 
36 
 
ponds with the black liner (P < 0.05).  This most likely is the result of the gray liner being more 
porous than the black liner.  However, in spite of total phosphorus being elevated in the lined 
ponds, there were no differences among control and treatments with respect to soluble reactive 
phosphorus (P > 0.05).  This probably was caused by rapid uptake of soluble phosphorus by 
phytoplankton 
 Turbidity was greater in ponds with the gray liner in 2008 than it was in the other ponds.  
However, in 2009, turbidity was highest in the lined ponds.  This probably resulted from 
suspension of soil particles by the aerators.  Chlorophyll a concentration was greater in ponds 
with the gray liner than in control ponds in 2008 (P < 0.05), but there was no difference in 
chlorophyll a concentration between ponds with the two types of liners.   In 2009, unlined, 
control ponds were very low in chlorophyll a concentration as compared to 2008 (Table 3), and 
ponds with both types of liners had more chlorophyll a than was found in control ponds.   
Nevertheless, there was no difference in chlorophyll a concentrations between ponds with the 
two types of liners in 2009. 
 The BOD was greater in lined ponds than in control ponds both years, but the gray liner 
and black liner ponds did not differ in BOD.  The greater BOD in lined ponds likely was related 
to higher phytoplankton abundance in these ponds, because much of the BOD in channel catfish 
ponds results from plankton respiration (Boyd and Gross 1999). 
 Fish production data (Table 4) show that good survival of fish was achieved in all ponds, 
and net production was equivalent to 2,492 to 2,555 kg/ha in the abbreviated 2008 grow-out 
period.  In 2009, production ranged from 3,108 to 3,605 kg/ha ? levels commiserate with the 
stocking density (Boyd and Tucker 1998).  There were no differences in survival and production 
among controls and lined ponds (P > 0.05). 
37 
 
 In conclusion, permeable geotextile liners prevented erosion in ponds, and fish survival 
and production were typical of that realized in unlined ponds.  However, permeable liners did not 
seem to allow normal uptake of phosphorus by bottom soil, because total phosphorus and 
chlorophyll a concentrations tended to be elevated in lined ponds as compared to control ponds.  
Unfortunately, it was not economically possible to have three ponds with impermeable liners for 
comparison with permeable liners.  Geotextiles of larger apparent opening size than present in 
the liners of this study are available.  Future research probably should focus on more permeable 
geotextiles. 
  
38 
 
Literature Cited 
 
 
Avnimelech, Y.  2012.  Biofloc Technology ? A Handbook, 2nd edition.  The World Aquaculture 
Society, Baton Rouge, Louisiana, USA. 
Boyd, C. E.  1995.  Bottom Soils, Sediment, and Pond Aquaculture.  Chapman and Hall, New 
York, New York, USA. 
Boyd, C. E. and A. Gross.  1999.  Biochemical oxygen demand in channel catfish Ictalurus 
punctatus pond waters.  Journal of the World Aquaculture Society 30:349-356. 
Boyd, C. E. and C. S. Tucker.  1998.  Pond Aquaculture Water Quality Management.  Kluwer 
Academic Publishers, Boston, Massachusetts, USA. 
Boyd, C. E., C. W. Wood, P. Chaney, and J. F. Queiroz.  2010.  Role of aquaculture pond 
sediments in sequestration of annual global carbon emissions.  Environmental Pollution 
158:2,537-2,540. 
Boyd, C. E., J. F. Queiroz, G. N. Whitis, R. Hulcher, P. Oakes, J. Carlisle, D. Odom, Jr., M. 
Nelson, and W. G. Hemstreet.  2003.  Best management practices for channel catfish for 
Alabama.  Special Report 1, Alabama Catfish Producers, Montgomery, Alabama, USA. 
Daniels, H. V. and C. E. Boyd.  1989.  Chemical budgets for polyethylene-lined brackishwater 
ponds.  Journal of the World Aquaculture Society 20:53-60. 
Eaton, A. D., L. S. Clesceri, E. W. Rice, and A. E. Greenberg.  2005.  Standard Methods for the 
Examination of Water and Wastewater, 21st edition.  American Public Health 
Association, Washington, DC, USA. 
Gross, A. and C. E. Boyd.  1998.  A digestion procedure for the simultaneous determination of 
total nitrogen and total phosphorus in pond water.  Journal of the World Aquaculture 
Society 29:300-303. 
39 
 
Hargreaves, J. A.  1998.  Nitrogen biogeochemistry of aquaculture ponds.  Aquaculture 166:181-
212. 
Hollerman, W. D. and C. E. Boyd.  1980.  Nightly aeration to increase production of channel 
catfish.  Transactions of the American Fisheries Society 109:446-452. 
Hopkins, J. S., R. O. Hamilton II, P. A. Sandifer, C. L. Browdy, and A. D. Stokes.  1993.  Effects 
of water exchange rate on production, water quality, effluent characteristics, and nutrient 
budgets of intensive shrimp ponds.  Journal of the World Aquaculture Society 24:304-
320. 
Krom, M. D., J. Erez, C. B. Porter, and S. Ellner.  1989.  Phytoplankton nutrient uptake 
dynamics in earthen marine fishponds under winter and summer conditions.  Aquaculture 
76:237-253. 
Leonard, S. E.  1995.  Water quality factors influencing striped bass (Morone saxatilis) 
production in lined ponds.  Ph.D. dissertation, Auburn University, Auburn, Alabama, 
USA. 
Masuda, K. and C. E. Boyd.  1994.  Phosphorus fractions in soil and water of aquaculture ponds 
built on clayey, Ultisols at Auburn, Alabama.  Journal of the World Aquaculture Society 
25:379-395. 
Neori, A., M. D. Krom, I. Cohen, and H. Gordin.  1989.  Water quality conditions and particulate 
chlorophyll a of new intensive seawater fishponds in Eilat, Israel:  daily and diel 
variations.  Aquaculture 80:63-78. 
Steeby, J. A., S. Kingsbury, and J. Hargreaves.  2001.  Sediment accumulation in channel catfish 
production ponds.  Global Aquaculture Advocate 4(3):54-56. 
40 
 
Steeby, J. A., J. A. Hargreaves, C. S. Tucker, and S. Kingsbury.  2004.  Accumulation, organic 
carbon and dry matter concentration of sediment in commercial channel catfish ponds.  
Aquacultural Engineering 30:115-126. 
Taylor, H. F. W.  1997.  Cement Chemistry, 2nd edition.  Academic Press, London, UK. 
Torrans, E. L.  2008.  Production responses of channel catfish to minimum daily dissolved 
oxygen concentrations in earthen ponds.  North American Journal of Aquaculture 50:371-
381. 
Tucker, C. S., S. W. Lloyd, and R. L. Busch.  1984.  Relationships between phytoplankton 
periodicity and the concentrations of total and un-ionized ammonia in channel catfish 
ponds.  Hydrobiologia 111:75-79. 
van Rijin, J.  1993.  Methods to evaluate water quality in aquaculture.  Faculty of Aquaculture, 
The Hebrew University of Jerusalem, Rehovot, Israel. 
  
41 
 
Table 1.  Characteristics of the two, geotextile liner materials as reported by manufacturers. 
 
Variable 
Belton Industries  
Style 307 
Typar Geotextile  
Style 3801 G 
Composition of fabric Polypropylene Polypropylene 
Type Woven fiber Woven fiber 
Color Black Gray 
Weight (g/m2) 105.2 272 
Specific gravity 0.93 0.91 
Apparent opening size (mm) 0.355 0.090 
Water flow rate (L/min/m2) 509 328 
 
 
  
42 
 
Table 2.  Correlation coefficients for relationships of turbidity, total suspended solids, and 
chlorophyll a for pooled data from geotextile-lined and control ponds. 
Variables Pearsons Correlation Coefficient 
Turbidity versus total suspended solids  
      2008    0.600** 
      2009    0.482** 
Turbidity versus chlorophyll a  
      2008 0.008 
      2009 0.001 
Total suspended solids versus chlorophyll a  
      2008 0.013 
      2009 0.005 
**Significant at P < 0.01.  
 
 
 
  
43 
 
Table 3.  Grand means for 2008 and 2009 in control ponds and ponds lined with one of two 
permeable, geotextiles. 
 Year  Year  Year 
Liner 2008 2009  2008 2009  2008 2009 
  
pH 
 Water temperature 
 (oC) 
 Total alkalinity  
(mg/L) 
None (control) 8.24 a 8.24 a  27.08 a 26.45 a  64.16 a 42.46 a 
Black 8.26 a 8.26 a  26.93 a 26.67 a  76.03 a 38.05 a 
Gray 8.67 a 8.67 b  26.77 a 26.57 a  71.85 a 42.68 a 
         
 Total hardness 
(mg/L) 
 Dissolved oxygen 
(mg/L) 
 Total ammonia 
nitrogen (mg/L) 
None (control) 51.8 a 31.9 a  7.75 a 8.18 a  0.12 a 0.30 a 
Black 63.7 ab 29.5 a  8.15 b 9.82 b  0.14 a 0.24 a 
Gray 71.9 b 37.6 a  8.36 b 9.34 b  0.14 a 0.18 a 
         
 Nitrate-nitrogen 
(mg/L) 
 Nitrite-nitrogen 
(mg/L) 
 Total nitrogen 
(mg/L) 
None (control) 0.0 a 0.4 a  0.01 a 0.11 a  0.44 a 1.40 a 
Black 0.0 a 0.09 a  0.0 a 0.01 b  0.58 ab 2.11 b 
Gray 0.0 a 0.16 a  0.0 a 0.01 b  0.73 b 2.17 b 
         
      
44 
 
Soluble reactive 
phosphorus 
(mg/L) 
Total phosphorus 
(mg/L) 
Turbidity 
(NTU) 
None (control) 0.03 a 0.06 a  0.15 a 0.46 a  26.72 a 109.28 a 
Black 0.04 a 0.07 a  0.10 a 0.61 b  19.72 a 47.64 b 
Gray 0.04 a 0.06 a  0.13 a 1.00 c  41.56 b 52.88 b 
         
 Chlorophyll a 
(?g/L) 
 5-d biochemical 
oxygen demand (mg/L) 
  
None (control) 225 a 54 a  3.06 a 4.48 a    
Black 387 ab 391 b  5.68 b 7.03 b    
Gray 510 b 453 b  6.08 b 7.00 b    
*Means indicated by the same letter did not differ at P < 0.05 as determined by Duncan?s 
multiple range test ? vertical comparisons only. 
 
  
45 
 
Table 4.  Fish production data for 2008 and 2009 in control ponds and ponds lined with one of 
two permeable, geotextiles. 
 2008  2009 
 
Variable 
 
Control 
Black 
liner 
Gray 
liner 
  
Control 
Black 
liner 
Gray 
liner 
Number stocked 400 400 400  400 400 400 
Stocking weight (kg/fish) 0.052 0.052 0.052  0.302 0.287 0.306 
Stocking weight (kg/pond) 20.8 20.8 20.8  120.8 114.8 122.4 
Harvest weight (kg/pond) 120.5 123.0 122.7  245.1 259.0 266.0 
Net production (kg/pond) 99.7 102.2 101.9  124.3 144.2 143.6 
Survival (%) 93.6 90.8 90.2  79.8 88.2 76.3 
Feed applied (kg/pond) 151.36 151.36 151.36  198.88 198.88 198.88 
Feed conversion ratio 1.52 1.48 1.48  1.60 1.38 1.38 
 
  
46 
 
 
Figure 1. Concrete retaining wall in earthen ponds at the Auburn University E. W. Shell 
Fisheries Center, Auburn, Alabama. 
 
 
 
 
 
47 
 
 
Figure 2. Geotextile material used to line ponds at the Auburn University E.W. Shell Fisheries 
Center, Auburn, Alabama: Left ? Style 307, (Bolton Industries); Right ? Style 3801G (Typar 
Geotextiles). 
 
 
 
 
 
48 
 
 
Figure 3. Sketch (not to scale) of attachment of geotextile liners to bottoms of earthen ponds. 
 
 
 
 
 
 
 
 
 
 
49 
 
 
Figure 4. Sketch (not to scale) showing the method of securing geotextile liners to concrete 
retaining walls in ponds. 
 
 
 
 
 
 
 
 
50 
 
 
Figure  5. Photographs showing ponds lined with the black, Style 307 geotextile (upper) and the 
gray, style 3801G geotextile (lower). 
 
 
 
 
 
 
51 
 
 
Figure 6. Photograph of a pond in which the gray liner floated 
 
 
 
 
 
 
52 
 
 
Figure 7. Photographs of an unlined pond bottom following fish harvest (upper) and of a lined 
pond following fish harvest and removal of the liner. 
 
 
 
 
 
 
53 
 
Figure 8. Mean values for pH, water temperature, and concentrations of total alkalinity and 
total hardness in ponds lined with two types of geotextile liners and in unlined, control ponds. 
 
54 
 
Figure 9. Mean values for concentrations of dissolved oxygen (DO) and 5-d biochemical 
oxygen demand (BOD5) in pond lined with two types of geotextile liners and in unlined, control 
ponds. 
 
 
 
 
 
 
 
 
55 
 
Figure 10. Mean values for concentrations of total ammonia nitrogen (TAN), Nitrate (NO3-N), 
Nitrite (NO2-N), and total nitrogen in pond lined with two types of geotextile liners and in 
unlined, control ponds. 
 
 
56 
 
Figure 11. Mean values for concentrations of soluble reactive phosphorus and total phosphorus 
in pond lined with two types of geotextile liners and in unlined, control ponds. 
 
 
 
 
 
 
 
 
 
57 
 
Figure 12. Mean values for concentrations of turbidity, total suspended solids, and chlorophyll a 
in pond lined with two types of geotextile liners and in unlined, control ponds. 
 
 
 
 
 
 
 
 
 
 
 
 
58 
 
 
 
 
 
 
 
IV. Phosphorus Removal by Soil Separated from Water 
by Permeable, Geotextiles 
 
 
Abstract 
 
 
Six, geotextile liners with apparent opening sizes ranging from 0.090 mm to 0.84 mm 
were used to separate soil from water in aquaria.  Water was treated with 0.75 mg/L of 
phosphorus from monopotassium phosphate. Phosphorus concentration did not decline in aquaria 
without soil, and all liners reduced the amount of phosphorus removed by the soil.  Phosphorus 
removal by soil did not differ among liners with opening size < 0.200, but these liners interfered 
less with soil phosphorus uptake than did the liner with 0.090 mm opening size.  Final 
phosphorus concentrations were 0.089 mg/L in the unlined aquaria with soil, 0.397 mg/L for the 
liner with 0.090-mm opening, and 0.157 to 0.202 mg/L for the liners with larger openings. 
 
 
  
59 
 
Introduction 
 
 
 The study of water quality and fish production in ponds lined with permeable, geotextiles 
revealed that these liners prevent erosion of pond earthwork by waves, aerator-generated water 
currents, and bioturbation (Boyd 1995).  Although fish survival and production were as good in 
the ponds lined with geotextiles as in the control ponds, the liners had a tendency to float, and 
they interfered with the uptake of phosphorus by bottom soil.  Phosphorus concentration and the 
abundance of phytoplankton were greater in the lined ponds than in the control ponds. 
 The two geotextiles used in the previous experiment had a relatively small apparent pore 
sizes ? 0.090 and 0.355 mm.  Therefore, a laboratory study was conducted to determine if 
geotextiles with larger, apparent pore sizes would allow greater uptake of phosphorus by bottom 
soil. 
 
Materials and Methods 
 
 Samples of six, geofabrics were obtained from Fiberweb, Old Hickory, Tennessee (Table 
1).  A sample of soil was obtained from the B horizon of the soil profile exposed by a road cut on 
the E. W. Shell Fisheries Center at Auburn, Alabama.  This area is in the Alabama Piedmont 
Plateau and the soil material was a Typic, Kandiudult (clayey, kalonitic, and thermic) (McNutt 
1981).      
 A 5-cm layer of the soil was placed in the bottom of each of 21 aquaria (20-L).  Three 
liners were made from each geofabric.  The material was cut and sewed to make liners of the 
same dimensions as the insides of the aquaria.  The liners were placed in aquaria ? their bottoms 
on top of the soil ? preventing direct contact of water with soil.  Three aquaria with soil did not 
60 
 
receive liners, and three more aquaria were not supplied with either soil or liners.  Aquaria were 
filled with 18-L of tap water and monopotassium phosphorus (KH2PO4) applied to provide 0.75 
mg/L of soluble orthophosphate.  An air stone was placed 10 cm above the bottom in each 
aquarium, and air from an air pump was gently introduced to effect continuous water circulation.  
The aquaria were held in a dark room at 23 to 26oC.  A 50-mL water sample was collected from 
each aquarium after 1, 2, 3, 4, 6, 8, 10, 14, and 18 days.  These samples were analyzed for 
soluble reactive phosphorus by the ascorbic acid method (Eaton et al. 2005). 
 
Results and Discussion 
 
 The phosphorus concentration remained fairly constant in aquaria without soil, but it 
declined rapidly in aquaria with soil, reaching a concentration of about 0.1 mg/L after 18 days 
(Fig. 1).  The phosphorus concentration in aquaria that contained the Typar 3801 geotextile liner 
? the one used to line ponds for the experiment described in earlier ? declined to an average 
concentration of 0.397 mg/L after 18 days (Fig. 1).  In aquaria lined with the other Typar 
geotextiles, phosphorus concentration declined much faster than in those lined with Typar 3801 
geotextile.  After 18 d, phosphorus concentrations averaged 0.157 to 0.202 mg/L ? lower than for 
the Typar 3801 geotextile, but higher than the control (Table 2). 
 The Typar 3801 geotextile has the smallest apparent opening size and water flow rate 
(Table 1) ? 0.090 mm and 328 L/min/m2, respectively.  Thus, the low permeability of this fabric 
likely was the reason that phosphorus concentration was greater in aquaria lined with it than in 
aquaria lined with more permeable fabrics.  Nevertheless, in spite of the wide range in apparent 
61 
 
opening sizes (0.200 to 0.840 mm) and water flow rates (2,050 to 9,635 L/min/m2) in the other 
geotextile materials, there were no differences in phosphorus concentration after 18 d (Table 2). 
 The trapezoidal tear strength and puncture strength of the geotextiles decrease rapidly 
with increasing permeability (Table 1).  Thus, for use in ponds, it would be desirable to select 
one of the materials with apparent opening sizes of 0.2 to 0.3 mm.  These three geotextiles would 
be stronger than the two geotextiles with larger apparent opening sizes (Table 1). In the 
phosphorus uptake study, phosphorus loss from the water was as great for these three geotextiles 
as for the two with larger apparent opening sizes. 
 The results of this small effort suggest that it might be fruitful to repeat the pond lining 
study presented earlier using a geotextile of greater apparent opening size.  Such a fabric should 
interfere less than a finer fabric with normal uptake of phosphorus by bottom soils.  The coarse-
weave geotextile might also have less tendency to float. 
 
 
 
 
 
 
 
 
 
 
 
62 
 
Literature Cited 
 
 
Boyd, C. E.  1995.  Bottom Soils, Sediment, and Pond Aquaculture.  Chapman and Hall, New 
York, New York, USA. 
Eaton, A. D., L. S. Clesceri, E. W. Rice, and A. E. Greenberg.  2005.  Standard Methods for the 
Examination of Water and Wastewater, 21st edition.  American Public Health 
Association, Washington, DC, USA. 
McNutt, R. B.  1981.  Soil Survey of Lee County, Alabama.  USDA Soil Conservation Service, 
U.S. Government Printing Office, Washington, DC, USA. 
 
 
 
 
 
 
  
63 
 
 
Table 1.  Characteristics of six, geotextile materials. 
 Apparent opening 
size (mm) 
Water flow rate 
(L/min/m2) 
Trapezoidal tear 
strength (N) 
Puncture 
strength (N) 
Typar 3801 0.090 328 425 415 
Typar 3501 0.200 2,050 270 250 
Typar 3401 0.212 2,460 270 180 
Typar 3301 0.300 3,895 155 110 
Typar 3201 0.590 7,790 110 80 
Typar 3151 0.840 9,635 70 45 
 
 
 
 
 
  
64 
 
Table 2.  Mean concentrations and standard deviations (SD) for soluble reactive 
phosphorus concentrations (mg/L) after 18 days in aquaria (n = 3) with soil separated from 
water by different types of geotextiles as compared to controls. 
Treatment Mean ? SD* 
Control (no soil) 0.737 ? 0.020  a 
Control (soil, no liner) 0.089 ? 0.020  b 
Typar 3801 geotextile liner 0.397 ? 0.066  c 
Typar 3501 geotextile liner 0.202 ? 0.019  c 
Typar 3401 geotextile liner 0.157 ? 0.020  c 
Typar 3301 geotextile liner 0.163 ? 0.013  c 
Typar 3201 geotextile liner 0.159 ? 0.015  c 
Typar 3151 geotextile liner 0.179 ? 0.013  c 
*Means indicated by the same letter did not differ at P = 0.05 by Duncan?s multiple range 
test. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
65 
 
Figure. 1. Mean concentration of soluble reactive phosphorus over a period of 18 days in 
aquaria (n = 3) with soil separated from water by differenct type of geotextiles as compared to 
controls. 
 
 
 
 
 
 
 
 
 
 
 
66 
 
 
 
 
 
 
 
V. Effects of Water Quality and Chemical Coagulants on Sedimentation of 
Suspended Soil Particles from Water 
 
 
Abstract 
 
 Particles of three soils ? each containing a different type of clay ? settled at different 
rates.  Nevertheless, particles tended to settle faster as concentration of total dissolved solids 
(TDS) increased in diluted seawater and in freshwater in which total hardness concentration 
increased as TDS concentration rose.  Several chemical coagulants were tested for their ability to 
remove suspended soil particles.  Potassium and sodium chloride were comparatively ineffective 
for turbidity removal.  Calcium sulfate was more effective than magnesium sulfate.  Aluminum 
chloride and sulfate tended to perform better than ferrous sulfate and ferric chloride.  Although 
there were some differences in effectiveness of coagulants among the types of soils, calcium 
sulfate (gypsum), aluminum sulfate (alum), and aluminum chloride appear to have the greatest 
potential for use in ponds.  Aluminum compounds neutralize alkalinity and cause a decrease in 
pH.  Treatment rates (mg/L) for aluminum sulfate and aluminum chloride should not exceed the 
total alkalinity (mg/L as CaCO3) to avoid low pH.  Knowledge of conductivity, total alkalinity, 
total hardness, and type of clay mineral suspended in water can be useful in selecting a suitable 
coagulant.  
67 
 
Introduction 
 
 
 Turbidity from suspended soil particles resulting from external erosion on watersheds or 
internal erosion of earthwork by wave action, bioturbation, and aerator-generated water currents 
is a common problem in ponds used for sportfishing or commercial production of aquaculture 
species (Boyd 1995).  Reduction in erosion will lessen the concentration of suspended particles 
to the water column of ponds, but fine soil particles ? especially colloidal ones ? may remain 
suspended indefinitely.  The two most common recommendations for clearing turbidity from 
ponds are to apply organic matter such as barnyard manure and cut grass or to treat ponds with 
calcium sulfate.  However, neither of these procedures has been highly successful, because 
application rates usually are not great enough (Boyd 1995).  Aluminum sulfate ? the coagulant 
frequently used to remove turbidity from drinking water ? was shown to be highly effective in 
clearing pond water of turbidity (Boyd 1979; Boyd and Tucker 1998). 
 The mechanism responsible for mutual repulsion of colloidal clay particles and the 
process that causes these particles to coagulate are complex (Stumm and Morgan 1996).  A 
highly-simplified explanation is that a negatively-charged layer around particles causes them to 
repel each other, but introduction of positively-charged cations in surrounding water will 
neutralize the negatively-charged layer allowing the particles to coagulate and the resulting floc 
will be massive enough to settle (Boyd 1995).  It is well known that the greater the charge on 
cations, the better they function in removing colloidal clay particles from water (Sawyer et al. 
2003) ? the reason that aluminum sulfate is widely used for removing turbidity from potable 
water. 
 More information is needed on the effectiveness of various salts that could be used in 
aquaculture to remove turbidity from water.  It would be particularly useful if a substitute for 
68 
 
alum could be found.  Because alum has a highly acidic reaction in water, the doses necessary to 
remove turbidity from some low-alkalinity waters can cause an excessive reduction in pH (Boyd 
and Tucker 1998).  Therefore, a laboratory study was conducted to determine the effect of basic 
water quality characteristics on the sedimentation rate of soil particles, to evaluate several 
possible chemicals as coagulants, and to consider effects of coagulants on water quality. 
 
Materials and Methods 
 
 Clayey soil from each of three locations for use in this study were obtained from the B-
horizon of soil profiles.  A sample of West Gulf Coastal Plain soil was taken from the catchment 
of Lake Rodemacher, the cooling water reservoir for the Cleco Corporation electricity generating 
plant near Boyce, Louisiana.  This soil was selected because it was responsible for a persistent 
turbidity problem that developed in the reservoir following a logging operation and associated 
erosion on the catchment (C. E. Boyd, Auburn University, unpublished data).   
A sample of soil from the Piedmont Plateau was collected from a road cut at the Alabama 
Agricultural Experiment Station near Auburn, Alabama.  Ponds built in this physiographic area 
typically have persistent turbidity problems following erosion on watersheds (Boyd 1979).   
hA sample of Blackland Prairie soil was excavated from a field beside an inland shrimp 
farm located near Forkland, Alabama.  Ponds in this area may become turbid following erosion 
on watersheds, but turbidity usually subsides after a few days.  Soils will be referred to as BP 
(Blackland Prairie), CP (West Gulf Coastal Plain), and PP (Piedmont Plateau) soils. 
 The pH of soil samples was measured in a 1:1 mixture of pulverized soil and distilled 
water by aid of a glass electrode (Thunjai et al. 2001).  Particle-size analysis was done by a 
69 
 
simplified, hydrometric method (Weber 1977; Boyd and Tucker 1992).  Organic carbon was 
determined by the Walkley-Black, sulfuric acid-potassium dichromate oxidation procedure 
(Nelson and Sommers 1982).  Cation exchange capacity was measured by the ammonium acetate 
method (Jackson 1958; Rhoades 1982). 
Waters of several compositions were used in sedimentation trials.  These included 
Auburn, Alabama, municipal tap water diluted 1:1 with distilled water.  The diluted tap water 
contained 38 to 40 mg/L total alkalinity, 32 to 36 mg/L total hardness, and 70 to 80 mg/L total 
dissolved solids (TDS).  Waters containing different concentrations of total alkalinity, total 
hardness, and TDS (Table 1) were prepared by adding different amounts of sodium bicarbonate 
(NaHCO3), calcium sulfate (CaSO4?2H2O), magnesium chloride (MgCl2?6H2O), sodium chloride 
(NaCl), and potassium sulfate (K2SO4) to diluted tap water.  Sodium bicarbonate provided 
alkalinity and calcium sulfate and magnesium chloride were sources of hardness.  The other 
compounds were added to adjust TDS concentration.  These solutions included alkalinity ? 
hardness, alkalinity > hardness, and alkalinity < hardness ? the usual situations encountered in 
natural waters (Boyd 2000).   
Waters of widely different salinities were obtained by diluting seawater (28.9 ppt 
salinity) obtained from the Gulf of Mexico at the Auburn University Shellfish Laboratory, 
Dauphin Island, Alabama with tap water.  Aliquots containing 0.5, 1.0, 2.5, 10, 15, 20, and 25 
ppt salinity ? as measured with a refractometer ? were prepared. 
 Sedimentation trials were conducted in soil test cylinders (35 cm tall ? 6 cm diameter) 
placed on a laboratory bench at temperature of 23 to 26 C.  Cylinders were filled with 990 mL of 
test water.  Soil (20 g) to be used in a sedimentation trial was placed in 300 mL of tap water in a 
500-mL beaker.  The mixture was vigorously stirred with a wide-bladed spatula to separate and 
70 
 
suspend soil particles, and the beaker was held on a magnetic stirrer to assure uniform dispersion 
of suspended particles.  A 10-mL portion of turbid water from the beaker was removed (without 
stopping the stirrer) using a pipet with a wide-bore tip and transferred to each soil test cylinder.  
If chemical coagulants were used in a trial, appropriate quantities of each chemical were 
weighed, transferred to soil test cylinders, and the chemical thoroughly mixed with the water 
using a 60-cm long ? 1.25-cm diameter dowel pin. 
 At the beginning of each trial, the content of each cylinder was stirred thoroughly with 
the dowel pin, and a 20-mL sample was removed from a depth of 10 cm using a pipet with a 
wide-bore tip.  Turbidity of the sample was measured with a Orbeco-Hellige Model 965-10 A 
Direct Reading Turbidimeter (Orbeco Analytical Systems, Inc, New Jersey, USA), and the 
sample was returned to the cylinder.  Additional samples were taken from 10-cm depth using a 
pipet with a wide-bore tip for turbidity measurement after 1, 2, 3, 4, 5, 8, 12, and 24 h, but the 
content of the test cylinder was not stirred before samples were removed.  At the end of a trial, 
pH and specific conductance were measured using an Orion 3 Star pH Meter (Thermo Scientific, 
Singapore) and an Orion 3 Star Conductivity Meter (Thermo Scientific, Singapore), respectively. 
 The following concentrations of several chemical coagulants were tested initially:  
sodium chloride, 271 mg/L; potassium chloride (KCl), 346 mg/L; calcium chloride 
(CaCl2?2H2O), 339 mg/L; calcium sulfate, 400 mg/L; magnesium sulfate (MgSO4?7H2O), 559 
mg/L; ferrous sulfate (FeSO4?7H2O), 100 mg/L; ferric chloride (FeCl3?6H2O), 64.9 mg/L; 
aluminum chloride (AlCl3?6H2O), 57.9 mg/L; aluminum sulfate [Al2(SO4)3?18H2O], 80 mg/L.  
These concentrations equated to 4.62 meq/L of sodium, potassium, calcium, and magnesium and 
to 0.72 meq/L of iron and aluminum.  Based on results of preliminary trials, chemicals were 
71 
 
selected for further investigation of the relationship between concentration and degree of 
turbidity removal. 
 
Results and Discussion 
 
Water Quality and Sedimentation Rate 
 
 The CP and PP soils were acidic, but the BP soil was basic (Table 2).  All soils were low 
in organic matter concentration.  The PP and BP soils each contained more than 50% clay, and 
CECs were 4.6 and 50.2 meq/100 g, respectively.  The difference in CEC resulted from the type 
of clay mineral in soils.  Soils in Lee County Alabama typically contain kaolinite (McNutt 1981), 
and those in the Blackland Prairie region of Alabama usually contain smectite (Dixon and Nash 
1968).  Typical CECs for pure kaolinite and smectite are 1 to 10 meq/100 g and 80 to 120 
meq/100 g, respectively (Goldberg et al. 2000).  The size of the soil sample from the West Gulf 
Coastal Plain in Louisiana proved inadequate to allow analyses of particle-size distribution and 
CEC, and it was not possible to obtain an additional quantity of this soil.  However, the sample 
had a very high clay content as obvious from feel and from the amount of the material that 
remained suspended in water when a small amount mixed with water was allowed to stand 
overnight.  Dr. Joey Shaw of the Department of Agronomy and Soils at Auburn University 
thought that the clay in the CP soil likely consisted mainly of vermiculite.  This clay mineral has 
a very high CEC ? typically 120 to 150 meq/100 g (Goldberg et al. 2000).  Thus, the CP soil 
likely had a CEC value greater than that of the BP soil. 
72 
 
 Soils each resulted in a different turbidity when introduced into diluted tap water in soil 
test cylinders (Fig. 1).  In the trial depicted in Fig. 1, initial turbidity ranged from 156 
nephelometer turbidity units (NTU) for the CP soil to 405 NTU for the BP soil.  In addition to 
variation in initial turbidity among test cylinders with different soils, there also were variations in 
initial turbidity within test cylinders receiving the same soil.  The average initial turbidities were 
as follows:  BP soil ? mean = 286 ? 100 NTU, range = 182 to 540 NTU; CP soil ? mean = 177? 
43 NTU, range = 109 to 252 NTU; PP soil ? mean = 381 ? 86 NTU, range = 216 to 547 NTU.  
This variation was between trials; all cylinders for a given trial were filled from the same soil-
water mixture and had equal turbidities.  In order to facilitate evaluation and presentation of data, 
the percentage of initial turbidity remaining at each sampling time was estimated as follows: 
 
Turbidity remaining at a given time (%) = (100) Turbidity at that time (NTU) 
                                                                                                   Initial turbidity (NTU) 
 
 
 It also can be seen from Fig. 1 that sedimentation of particles of the three soils in diluted 
tap water occurred at different rates.  Turbidity quickly declined by about 50% with the BP soil 
in about 8 h, and an even greater decline was observed after 8 h with the PP soil.  However, 
turbidity declined little in diluted tap water containing the CP soil.  After 8 h, sedimentation rate 
became quite slow for all soils.  Soils differed in particle-size distribution (Table 2), and in 
sedimentation trials (Fig. 1), most particles that settled quickly were likely sand or silt size.  The 
rather stable turbidity during trials in cylinders containing the CP soil probably resulted from the 
soil being mostly clay.  Residual turbidity after 24 h was much greater for the CP and BP soils 
than for the PP soil.  This probably is the result of clay fractions of these two soils having a high 
CEC and a great degree of mutual repulsion among particles.  
73 
 
 Increasing salinity in test water had a marked influence on sedimentation of particles ? 
especially for the CP soil (Fig. 2).  Turbidity remaining after 4 h decreased from about 80% at 
0.075 ppt salinity to about 35% at 0.5 ppt salinity and about 15% at 2.5 ppt salinity for the CP 
soil.  Although the trial included salinities up to 25 ppt, data presentation was limited to 10 ppt, 
because there was no difference in sedimentation rate at greater salinities.  Because 
sedimentation continued slowly after 8 h, it was decided to present only 24-h data in describing 
most trials. 
 Freshwater is considered to contain no more than 1,000 mg/L TDS (Boyd 2000), and 
salinity and TDS usually have almost equal concentrations.  Thus, increasing the degree of 
mineralization of freshwater should favor sedimentation.  However, the salinity trial (Fig. 2) was 
conducted in diluted seawater.  Such water is high in concentration of all major ions (Brown et 
al. 1989), and it has a much greater total hardness than total alkalinity ? the undiluted sample 
used in this study contained 6,495 mg/L total hardness but only 121.3 mg/L total alkalinity. 
 For the CP soil in water of similar alkalinity and hardness (TA = TH), the percentage of 
turbidity remaining after 12 h (Fig. 3) was greater for water with low TDS concentration (75 
mg/L) than at greater TDS (369 and 663 mg/L).  Turbidity remaining tended to be greater in the 
water with moderate TDS concentration for several hours; but, after 24 h, there was much less 
difference between the two waters.  Moreover, at this time, loss of turbidity was much greater for 
both 369 and 663 mg/L TDS than for 75 mg/L TDS.  When trials with the CP soil were 
conducted in water of low total alkalinity but high total hardness (TA < TH), but at the same 
TDS concentrations used for the trial with (TA = TH), turbidity removal in the two higher 
salinity water was much greater than in diluted tap water (75 mg/L TDS).  There was, however, 
no appreciable difference in turbidity removal related to time between sedimentation trials 
74 
 
conducted in waters of 369 and 663 mg/L TDS.  When total hardness concentration was 38 mg/L 
(75 mg/L TDS) and alkalinity increased to 138 mg/L (369 mg/L TDS) and 238 mg/L (663 mg/L 
TDS), there was no apparent increase in turbidity decline in the more highly-mineralized waters 
(Fig. 3). 
 A similar pattern with respect to relationships of alkalinity, hardness, and TDS 
concentrations to sedimentation rate was observed for the BP soils, but particles of the BP soil 
settled faster than those of the CP soil (Fig. 3).  Turbidity loss was fairly great for the BP soil 
even in diluted tap water.  The PP soil particles settled fairly well in all three types of water (Fig. 
3).  It should be noted that salinity concentrations in waters used in trials depicted in Fig. 3 were 
the same as TDS concentration.  In natural waters, salinity also is usually about the same 
concentration as TDS (Boyd 2000). 
 Results of sedimentation trials depicted in Figs. 2 and 3 reveal interesting information 
about sedimentation of soil particles.  They settle very quickly in highly-diluted seawater ? even 
at 0.5 ppt salinity; particles of all three soils had almost completely settled within 24 h.  This 
does not necessarily imply, however, that as total dissolved solids concentration increases, soil 
particles will settle more quickly from freshwater.  Freshwater can vary considerably in 
composition; waters of the same salinity may differ in concentrations of ions responsible for 
alkalinity and hardness:  (1) a large part of TDS concentration in many waters results from the 
anion bicarbonate and the divalent cations calcium and magnesium ? sources of alkalinity and 
hardness, respectively; (2) a large part of the TDS in a second type of water is contributed by 
bicarbonate and monovalent cations sodium and potassium (this water has distinctly greater 
alkalinity than hardness); (3) in a third type of water, much of the TDS is from calcium and 
75 
 
magnesium ions that are associated with the anions chloride and sulfate (hardness is considerably 
greater than alkalinity).   
Sedimentation rate results for the CP soil revealed that water must increase in calcium 
and magnesium concentration as TDS concentration increases if a positive relationship between 
TDS concentration and settling rate is to occur.  The results for the BP soil tend to show the same 
trend as the CP soil, but the PP soil particles settled rather quickly in all three types of water.  
Thus, all soil particles cannot be expected to settle at the same rate at a particular TDS 
concentration or in a specific type of freshwater. 
 
Coagulants for Turbidity Removal 
 
 Results of preliminary trials of chemical coagulants (Fig. 4) revealed that calcium 
chloride, calcium sulfate, magnesium sulfate, ferrous sulfate, aluminum sulfate, and aluminum 
chloride provided the best overall removal of soil particles.  Although sodium chloride, 
potassium chloride, and ferric chloride were removed from further consideration because of 
lower, overall efficiency in particle removal, in some cases these compounds actually did as well 
or better than one or more of the compounds selected for further investigation ? especially for the 
PP soil. 
 Calcium sulfate ? often called gypsum ? was quite effective in precipitating suspended 
particles of the CP and BP soils ? 40 mg/L of this compound removed over 90% of turbidity 
(Fig. 5).  It was less effective for removing turbidity caused by the PP soil; a concentration of 
120 mg/L removed only about 50% of turbidity.  Gypsum has been widely recommended for 
removing turbidity from farm ponds (Boyd and Tucker 1998).  It is a safe compound to handle, 
76 
 
and it does not cause a change in pH (Fig. 6).  The increase in specific conductance resulting 
from gypsum (Fig. 7) is from calcium and sulfate ions.  These ions will not be removed from 
water bodies quickly by chemical reactions, and calcium will remain to provide protection 
against turbidity until flushed from ponds in overflow after rainfall events. 
 Calcium chloride was quite similar to calcium sulfate in removing soil particles (Fig. 5) ? 
an observation that is not surprising as results in Fig. 3 show that divalent cations rather than 
associated anions are responsible for accelerating sedimentation of soil particles.  However, 
calcium chloride is less commonly available and more expensive than calcium sulfate ? 
especially agricultural gypsum. 
 Magnesium sulfate was of similar effectiveness as calcium sulfate for removing BP and 
PP soil particles.  However, it is surprising and not clear why magnesium sulfate was less 
effective than calcium sulfate in removing turbidity when the source of particles was the CP soil 
(Fig. 5).  Magnesium sulfate and calcium sulfate had similar effects on pH and conductivity 
(Figs. 6 and 7). 
 Ferrous sulfate caused a marked reduction in turbidity at 20 mg/l for all soils, but at 
higher concentrations turbidity removal was less (Fig. 5).  There was a decrease in pH ? although 
not particularly large in comparison to that observed for aluminum compounds ? with increasing 
concentrations of ferrous sulfate (Fig. 6).  This probably was the result of hydrolysis of ferrous 
iron (Boyd 2000): 
 
Fe2+ + H2O = Fe(OH)+ + H+. 
 
77 
 
Sawyer et al. (2003) warned that turbidity removal by aluminum sulfate commonly used 
for clearing turbidity from water for municipal water supply will be ineffective in low alkalinity 
waters, and they recommended liming before application of aluminum sulfate in such waters.  
The increase in conductivity per concentration unit was greater for ferrous sulfate than for 
calcium and magnesium compounds (Fig. 7).  This observation also is not surprising, because of 
the decline in pH ? increase in hydrogen ion.  The equivalent conductance of hydrogen ion is 
349.8 mho?cm2/eq while those of calcium, magnesium, and other cations are less than 75 
mho?cm2/eq (Laxen 1977).  However, hydrogen ion is not very effective as a coagulant for 
colloidal soil particles. 
 Aluminum sulfate and aluminum chloride were highly effective in removing turbidity 
when used at 10 mg/L.  There was a tendency of less turbidity removal when these compounds 
were used at greater concentrations.  This resulted because both compounds caused a marked 
decline in pH when used at concentrations above 10 mg/L (Fig. 6).  The source of acidity from 
aluminum sulfate and aluminum chloride is hydrolysis of aluminum ion (Boyd 2000) as follows: 
 
Al3+ + H2O = Al(OH)3 + 3H+ 
 
Hydrogen ion neutralizes alkalinity causing a decline in pH: 
 
HCO3- + H+ = H2O + CO2. 
 
Alkalinity concentration is expressed in milligrams per liter of equivalent calcium carbonate ? at 
least in the United States.  The following stoichiometric relationship exists for alum: 
78 
 
 
Al2(SO4)3?18H2O = 2Al3+ = 6H+ = 3CaCO3. 
 
Thus, 1 mg/L of alum (m.w. = 666.42) would theoretically neutralize 0.45 mg/l CaCO3 (m.w. = 
100) or total alkalinity.  Using this approach, the neutralization of total alkalinity (CaCO3) by 
aluminum chloride (m.w. = 241.43) and ferrous chloride (m.w. = 270.32) would be 0.62 mg/L 
and 0.55 mg/L, respectively.  Thus, an alkalinity reduction of 0.45 to 0.62 mg/L per each 1 mg/L 
of the coagulating agents would occur.  Excessively low pH could be avoided by never applying 
a concentration of one of these three coagulating agents that exceeds the total alkalinity.  Liming 
before using these three coagulating agents also could avoid a low pH. 
 Further testing of lower concentrations of aluminum sulfate revealed that concentrations 
of 5 mg/L or less of this chemical would not reduce turbidity below 60% of the initial 
concentration after 24 h when the sources of turbidity were PP or BP soils (Table 3).  However, 2 
mg/L of aluminum sulfate removed nearly 95% of turbidity when CP soil was the source of 
turbidity. 
 Aluminum chloride at 5 mg/L reduced turbidity to 50% of initial concentration for the PP 
soil in 24 h (Table 3).  However, 5 mg/L of this chemical reduced turbidity by BP soil to 14.7% 
of the initial value, and 4 mg/L reduced turbidity caused by CP soil to 1.2% of the starting 
concentration. 
 
Conclusions 
 
79 
 
 This study suggests that particles of some soils ? possibly those with high cation 
exchange capacities ? may be expected to cause more persistent turbidity than others.  
Nevertheless, the findings clearly reveal that the tendency of fine particles of the three soils to 
remain suspended in marine or estuarine water decreases with greater TDS concentration 
(salinity).  The same also may be said for freshwater provided total hardness concentration 
increases as TDS concentration rises.  Freshwaters most likely to develop persistent turbidity 
following input of suspended clay particles are those with low total hardness concentration. 
 The findings also revealed that calcium sulfate is effective at 20 to 40 mg/L in removing 
suspended clay particles of soil with a high CEC ? soils CP and BP, but it was not effective for 
removing particles of the low CEC, PP soil.  Aluminum sulfate and aluminum chloride 
concentrations 5 mg/L or less lead to effective removal of suspended particles of CP soil, but 
about 10 mg/L was necessary for similar removal of particles of the other two soils.  
 Considering the variability in turbidity resulting from different clay minerals and water 
chemistries, and the differences in response to coagulating suspended clay particles by the 
chemical coagulants, water should be analyzed for conductivity, total hardness, and total 
alkalinity before deciding upon a coagulant.  The type of clay causing the turbidity also could 
help choose the coagulant.  Finally, it would be desirable to conduct a trial with the selected 
coagulant to determine the optimum treatment concentration. 
  
80 
 
Literature Cited 
 
 
Boyd, C. E.  1979.  Aluminum sulfate (alum) for precipitating clay turbidity from fish ponds.  
Transactions of the American Fisheries Society 108:307-313. 
Boyd, C. E.  1995.  Bottom Soils, Sediment, and Pond Aquaculture.  Chapman and Hall, New 
York, New York, USA. 
Boyd, C. E.  2000.  Water Quality, an Introduction.  Kluwer Academic Publishers, Boston, 
Massachusetts, USA. 
Boyd, C. E. and C. S. Tucker.  1992.  Water Quality and Pond Soil Analyses for Aquacutlure.  
Alabama Agricultural Experiment Station, Auburn University, Auburn, Alabama, USA. 
Boyd, C. E. and C. S. Tucker.  1998.  Pond Aquaculture Water Quality Management.  Kluwer 
Academic Publishers, Boston, Massachusetts, USA. 
Brown, J., A. Collins, D. Park, J. Phillips, D. Rothery, and J. Wright.  1989.  Seawater:  Its 
Composition, Properties, and Behaviour.  Pergamon Press, New York, New York, USA. 
Dixon, J. B. and V. E. Nash.  1968.  Chemical, mineralogical and engineering properties of 
Alabama and Mississippi Blackbelt soils.  Alabama and Mississippi Agricultural 
Experiment Stations and United States Department of Agriculture Soil Conservation 
Service, Southern Cooperative Series Number 130, Auburn University, Auburn, 
Alabama, USA. 
Goldberg, S., I. Lebron, and D. L. Squarez.  2000.  Soil colloidal behavior.  Pages B195-B240 in 
M. E. Summer, editor.  Handbook of Soil Science.  CRC Press, Boca Raton, Florida, 
USA. 
Jackson, M. L.  1958.  Soil Chemical Analysis.  Prentice-Hall Inc., Englewood Cliffs, New 
Jersey, USA. 
81 
 
Laxen, D. P. H.  1977.  A specific conductance method for quality control in water analysis.  
Water Research 11:91-94. 
McNutt, R. B.  1981.  Soil Survey of Lee County, Alabama.  USDA Soil Conservation Service, 
U. S. Government Printing Office, Washington, DC, USA. 
Nelson, D. W. and L. E. Sommers.  1982.  Total carbon, organic carbon, and organic matter.  
Pages 539-579 in A. L. Page, R. H. Miller, and D. R. Keeney (editors).  Methods of Soil 
Analysis, Part 2. Chemical and Microbiological Properties.  American Society of 
Agronomy, Madison, Wisconsin, USA. 
Rhoades, J. D.  1982.  Cation exchange capacity.  Pages 149-158 in A. L. Page, R. H. Miller, and 
D. R. Keeney (editors).  Methods of Soil Analysis, Part 2. Chemical and Microbiological 
Properties.  American Society of Agronomy, Madison, Wisconsin, USA. 
Sawyer, C. N., P. L. McCarty, and G. F. Parkin.  2003.  Chemistry for Environmental 
Engineering and Science, 3rd edition.  McGraw Hill, New York, New York, USA. 
Stumm, W. and J. J. Morgan.  1996.  Aquatic Chemistry, 3rd edition.  John Wiley & Sons, Inc., 
New York, New York, USA. 
Thunjai, T., C. E. Boyd, and K. Dube.  2001.  Pond soil pH measurement.  Journal of the World 
Aquaculture Society 32:141-152. 
Weber, J. B.  1977.  Soil properties, herbicide sorption and model soil systems.  Pages 59-62 in 
B. Truelove (editor).  Research Methods in Weed Science, 2nd edition.  Southern Weed 
Science Society, Auburn, Alabama, USA. 
 
  
82 
 
Table 1.  Total alkalinity (TA), total hardness (TH), and total dissolved solids (TDS) 
concentrations and pH in freshwater samples used in sedimentation rate trials. 
Alkalinity to        TDS Concentration (mg/L)  
hardness        level TA TH TDS pH 
TA ? TH       Low 38 36 75 7.25 
       Medium 138 136 369 8.05 
       High 238 236 663 8.40 
TA > TH       Medium 138 36 369 8.01 
       High 238 36 663 8.45 
TA < TH       Medium 38 136 369 7.09 
       High 38 236 663 7.27 
 
 
  
83 
 
Table 2.  Properties of soils used as sources of suspended solids in sedimentation trials. 
 Soila 
Property  PP  BP CP 
pH 5.00 7.44 4.16 
Organic carbon (%) 0.63 1.92 0.20 
Sand (%) 23.3 5.0 -- 
Silt (%) 24.3 26.0 -- 
Clay (%) 52.4 69.0 -- 
Cation exchange capacity  
   (meq/100 g) 
 
4.6 
 
50.2 
 
-- 
aPP = Piedmont Plateau; BP = Blackland Prairie; CP = West Gulf Coastal Plain. 
  
84 
 
Table 3.  Effectiveness of low concentrations of aluminum sulfate and aluminum chloride 
for turbidity removal. 
Concentration Soil used to create turbidity 
(mg/L) PP BP CP 
Aluminum sulfate 
0 100.0 100.0 100.0 
1 100.0   90.9   14.9 
2  77.8   81.8    5.4 
3  77.8   81.8    3.6 
4  66.7   81.8    3.0 
5  66.7   63.6    3.0 
Aluminum chloride 
0 100.0 100.0 100.0 
1   61.1   73.5   23.6 
2   61.1   52.9    5.9 
3   61.1   47.0    2.4 
4   50.0   26.4    1.2 
5  50.0   14.7    1.2 
aPP = Piedmont Plateau; BP = Blackland Prairie; CP = West Gulf Coastal Plain. 
 
 
 
  
85 
 
Figure 1. Changes in turbidity over time in cylinders containing water and suspended particles 
of three, different soils: CP soil, West Gulf Coastal Plain; BP Soil, Blackland Prarie; PP soil, 
Piedmont Plateau. 
 
 
 
 
 
 
 
0
100
200
300
400
500
0 4 8 12 16 20 24
Turbi
dity
 (N
TU
) 
Time (hr) 
BP soil
CP soil
PP soil
86 
 
Figure 2. Changes in turbidity in cylinders containing waters of different salinity (diluted 
seawater) and suspended particles of three, different soils: CP soil, West Gulf Coastal Plain; BP 
soil, Blackland Prarie; PP soil, Piedmont Plateau. 
 
 
 
0
50
100
0 4 8 12 16 20 24Turbidi
ty 
rem
aining 
(%
) 
Hour 
0 ppt of Salinity 
0
50
100
0 4 8 12 16 20 24
Hour 
0.5 ppt of Salinity 
LA
BB
ST
0
50
100
0 4 8 12 16 20 24Turbidi
ty 
rem
aining 
(%
) 
Hour 
1 ppt of Salinity 
0
50
100
0 4 8 12 16 20 24
Hour 
2.5 ppt of Salinity 
LA
BB
ST
0
50
100
0 4 8 12 16 20 24T
urbi
dit
y rem
aini
ng 
(%)
 
Hour 
5 ppt of Salinity 
0
50
100
0 4 8 12 16 20 24
Hour 
10 ppt of Salinity 
LA
BB
ST
CP 
BP 
PP 
CP 
BP 
PP 
 
CP 
BP 
PP 
87 
 
Figure 3. Change in turbidity in cylinders containing freshwater of three compositions and 
suspended particles of three, different soils: CP soil, West Gulf Coastal Plain; BP soil, Blackland 
Prarie; PP soil, Piedmont Plateau. 
 
CP 
 
BP 
 
PP 
 
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
0
50
100
0 4 8 12 16 20 24
TA<TH 
TA=TH TA<TH TA>TH 
TA=TH TA<TH TA>TH 
TA=TH TA>TH 
 
88 
 
Figure 4. Results of preliminary tests of nine, potential, chemical coagulants for moving 
turbidity from water. Each test was conducted in water containing particles of three, different 
soils: CP soil, West Gulf Coastal Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. 
 
 
 
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Figure 5. Effectiveness of different coagulants in removing turbidity from water. Each test was 
conducted in water containing particles of three, different soils: CP soil, West Gulf Coastal Plain; 
BP soil, Blackland Prarie; PP soil, Piedmont Plateau. 
 
 
 
 
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Figure 6. Effectiveness of different concentration of six, chemical, coagulants on pH. Each test 
was conducted in water containing particles of three, different soils: CP soil, West Gulf Coastal 
Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. 
 
 
 
 
 
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Figure 7. Effectiveness of different concentration of six, chemical, coagulants on conductivity. 
Each test was conducted in water containing particles of three, different soils: CP soil, West Gulf 
Coastal Plain; BP soil, Blackland Prarie; PP soil, Piedmont Plateau. 
 
 
 
 
 
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VI. Conclusions 
 
 
 Erosion control in production ponds is important to maintain the integrity of the 
earthwork and avoid excessive sediment accumulation in the bottom of ponds. Control of erosion 
on watersheds and embankments can decrease the input of solids to ponds, reduce turbidity, and 
reduce concentrations of suspended solids in effluents (Boyd 2003). The three experiments in 
this study were designed to identify solutions to erosion and associated problems in aquaculture 
ponds.  
 
Evaluation of two, porous, geofabric liners for erosion control in small aquaculture ponds 
 
Three ponds each were lined with a permeable geotextile with 0.090-mm opening sizes, a 
permeable geotextile with 0.355-mm opening sizes, or served as unlined, controls.  During the 2-
yr study, geotextile liners did not tear or decay. This prevented erosion of the bottom of the 
ponds stocked with a high density of channel catfish and aerated nightly.  The liners tended to 
float up in the water column; the liner with smaller opening sizes floated in all three ponds, while 
the other liner floated in only one pond.  Fish production, survival, and feed conversion ratio did 
not differ (P > 0.05) among the control and lined ponds or between liner types.   
Water quality variables often differed between lined ponds and control ponds.  The 
greatest difference was higher phytoplankton abundance in the lined ponds?especially in ponds 
lined with the less permeable geotextile ? than in the control.  This difference was attributed to 
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differences in phosphorus uptake by bottom soils related to the liners and their permeability.  
However, in spite of more phytoplankton growth in lined ponds, the control ponds tended to 
have higher turbidity because of erosion of bottoms by aeration. 
 
Phosphorus removal by soil separated from water by permeable, geotextiles 
 
 Six kinds of geotextile liners with apparent opening sizes ranging from 0.090 mm to 0.84 
mm were installed in separate soil from water in aquaria.  Water was treated with 0.75 mg/L of 
phosphorus from monopotassium phosphate.  Phosphorus concentration did not decline in 
aquaria without soil, and all liners reduced the amount of phosphorus removed by the soil.  
Phosphorus removal from soil did not differ among liners with opening size < 0.200, but these 
liners interfered less with soil phosphorus uptake than did the liner with 0.090-mm opening size.  
Final phosphorus concentrations were 0.089 mg/L in the unlined aquaria with soil, 0.397 mg/L 
for the liner with 0.090-mm openings, and 0.157 to 0.202 mg/L for the liners with larger 
openings. 
 
Effects of water quality and chemical coagulants on sedimentation of suspended soil 
particles from water 
 
 Particles of three soils ? each containing a different type of clay ? settled at different 
rates.  Nevertheless, particles tended to settle faster as concentration of total dissolved solids 
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(TDS) increased in diluted seawater and in freshwater in which total hardness concentration 
increased as TDS concentration rose.  Several chemical coagulants were tested for their ability to 
remove suspended soil particles.  Potassium and sodium chloride were comparatively ineffective 
for turbidity removal.  Calcium sulfate was more effective than magnesium sulfate.  Aluminum 
chloride and sulfate tended to perform better than ferrous sulfate and ferric chloride.  Although 
there were some differences in effectiveness of coagulants among the types of soils, calcium 
sulfate (gypsum), aluminum sulfate (alum), and aluminum chloride appear to have the greatest 
potential for use in ponds.  Aluminum compounds neutralize alkalinity and cause a decrease in 
pH.  Treatment rates (mg/L) for aluminum sulfate and aluminum chloride should not exceed the 
total alkalinity (mg/L as CaCO3) to avoid low pH.  Knowledge of conductivity, total alkalinity, 
total hardness, and type of clay mineral suspended in water can be useful in selecting a suitable 
coagulant.  
 
Future studies 
 
For the future, studies of geotextile should investigate the exchange rate of nutrients 
between the soil and water with more porous geotextiles, because the lined-pond study involved 
geotextiles with relatively fine mesh size, but larger size may have different effects. Moreover, 
the durability of the fabric should be carefully studied, and ways of preventing the fabric from 
floating most be devised. 
The economics of the use of geotextiles also must be considered. In research ponds, 
economics may not be the major concern, provided the techniques stabilize earthwork. Erosion 
control in ponds could save on maintenance and also provide a more controlled environment in 
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which to investigate aquaculture issues. However, in commercial production the geofabric liners 
would have to be cost effective. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Literature Cited 
 
Boy, C.E. 2003. Guidelines for aquaculture effluent management at the farm-level. Aquaculture. 
226: 101? 112.