Phytoremediation of Aquaculture Effluent Using Integrated Aquaculture Production Systems

Abstract

A series of experiments were conducted to determine how vegetable seedlings, herbs and bedding plants responded to the solid or liquid component in discharged aquaculture effluent collected from a freshwater, recirculating aquaculture system producing Nile tilapia (Oreochromis niloticus). First, petunia (Petunia×hybrida ‘Celebrity’) growth response was evaluated to partial replacement of a commercial potting mix with different amounts of dewatered aquaculture effluent (AE) and watered with municipal water or a 20N-4.4P-16.6K water soluble, fertilizer at 250 mg∙L-1 nitrogen. Petunia growth response in substrates with <25% AE was generally better with the addition of fertilizer; however, the water source had no effect on petunia growth paramters when grown in ≥25% AE. Next, tomato (Solanum lycopersicum), cv. Bolseno, seedling growth responses were evaluated when a commercial potting mix was amended with differing amounts (0 to 75%) of AE (v/v) and fertigated with a 20N-4.4P-16.6K water soluble, fertilizer at 100 mg∙L-1 nitrogen. Growth parameters decreased when AE was ≥25% container volume due to sub-optimal physical and chemical properties of the substrate, but AE could amend the commercial potting mix at quantities ≤15% for production of greenhouse-grown tomato seedlings. Also, tomato seedling growth response was evaluated when a commercial potting mix was amended (v/v) with 0, 5 or 10% AE and watered with municipal water or a 20N-4.4P-16.6K water soluble, fertilizer at 100 mg∙L-1 nitrogen. Tomato plant growth parameters improved in 0% and 5% AE substrates when provided 100 mg∙L-1 nitrogen, twice weekly, compared to municipal water, only. However, water source did not affect final growth parameters for plants grown in 10% AE indicating AE could partially replace the commercial potting mix and had sufficient nutrients for plant growth. In addition, basil (Ocimum basilicum), cilantro (Coriandrum sativum), parsley (Petroselinum crispum), and savory (Satureja hortensis) growth responses were evaluated when fertigated with a water soluble, fertilizer at 100 mg∙L-1 nitrogen or geotextile bag leachate. In general, water source did not affect plant growth parameters indicating geotextile leachate had sufficient nutrients for culinary herb production. A final experiment evaluated marigold (Tagetes patula ‘Jamie Primrose’) and petunia, cv. Dreams Burgundy, growth response to different nutrient solutions: 1) 100 mg∙L-1 nitrogen; 2) 200 mg∙L-1 nitrogen; and 3) Geotextile leachate. Marigold watered with geotextile leachate had similar growth response compared to plants watered with 100 mg∙L-1 nitrogen, but growth parameters decreased compared to marigold watered with 200 mg∙L-1 nitrogen. Petunia watered with geotextile leachate had decreased growth parameters compared to plants watered with either 100 mg∙L-1 nitrogen or 200 mg∙L-1 nitrogen. The geotextile leachate dissolved nutrient concentration has potential for plant production, but the high pH (8.2) may have limited marigold and petunia growth. Aquaculture effluent treated with geotextile technology demonstrated potential for plant production, but a negative plant growth response was observed as proportions of AE increased due to a decrease in the physical and chemical qualities of substrates. Furthermore, chemical properties of geotextile leachate would require additional management strategies to ensure plant growth responds positively to the leachate.