| Aquaculture is the cultivation and harvesting of aquatic organisms in marine or freshwater. The industry continues to grow at a rapid rate, places great demands on water resources and produces large quantities of wastewater which can contribute to significant environmental degradation. Hydroponics is the cultivation of plants in nutrient enriched water with or without the mechanical support of a medium such as sand or gravel. The primary aim of this study was to evaluate the feasibility of integrating an aquaculture operation with a plant production system. Three terrestrial crops (wheat, barley and oats) and three aquatic macrophytes (water hyacinth, water lettuce and parrot's feather) were evaluated for their ability to remove nutrients from aquaculture wastewater and for their suitability as a component in fish feed. The objectives of this study were: (a) to evaluate the quality of wastewater from a recirculating aquaculture system stocked with Arctic charr (Salvelinus alpinus), (b) to evaluate the effects of surface sterilization on seed germination percentage, (c) to evaluate the effects of seed quantity and wastewater application rate on crop height and yield of the three agricultural crops, (d) to evaluate the effects of hydraulic retention time on the yield of the three aquatic macrophytes, (e) to evaluate the ability of the agricultural crops and the aquatic macrophytes to reduce the pollution load of the wastewater as measured by TS, COD, NH4+-N, NO2--N, NO3--N, PO 43+-P, and pH, (f) to evaluate the suitability of recycling the treated wastewater for fish culture and (g) to evaluate the suitability of using the wastewater grown plants as a component of fish feed as determined by their nutritive value (energy, carbohydrates, crude protein, crude fat, crude fiber, Ca, Cl, Mg, P, K, Na, S, B, Cu, Fe, Mn, Mo, Se and Zn).; The quality of water from a recirculating aquaculture facility stocked with Arctic charr in terms of TS, COD, NH4+-N, NO 2--N, NO3--N, PO4 3+-P and pH was 827 +/- 28, 157.97 +/- 9.32, 2.08 +/- 0.5, 1.27 +/- 0.09, 21.64 +/- 0.60 mg/L and 7.00 +/- 0.13, respectively. Wheat produced the highest yield (64 t/ha) at a seed quantity of 300 g/tray followed by barley (59 t/ha) and oats (42 t/ha). Increasing the wastewater application rate from 690 to 1380 mL/compartment/day increased the barley yield from 59 to 83 t/ha. Increasing the wastewater application rate from 1000 to 2000 mL/compartment/day increased the yield from 5.1 to 8.9 t/ha, from 1.7 to 3.0 t/ha and from 1.2 to 2.9 t/ha for water hyacinth, water lettuce and parrot's feather, respectively. The TS, COD, NW-N, NO2--N, NO3--N, and PO43+-P removal efficiencies of the hydroponics system ranged from 21 to 56%, from 48 to 90%, from 60 to 81%, from 50 to 98%, from 35 to 82% and from 65 to 95%, respectively. The final pH of the effluents ranged from 6.65 to 7.43 and from 8.20 to 8.49 for the terrestrial and aquatic plants, respectively. Waters suitable for reuse in aquaculture were not produced. On a nutritional basis, the terrestrial plants were more suitable for inclusion in fish feed than the aquatic plants. The three terrestrial crops met the energy, fat, Ca, Mg, P, Na, S and Mn dietary requirements of aquatic animals, exceeded the carbohydrate, crude fiber, Cl, K, Cu, Fe, Se and Zn requirements of fish and shellfish and did not contain sufficient amounts of protein to meet the dietary requirements of fish and shellfish. On the basis of growth performance, yield, effluent water quality and nutrition, barley at a seed quantity of 300 g/tray and a wastewater application rate of 1380 mL/compartment/day was recommended for use in the hydroponics system. |
