Usage Of Aquaculture Wastewater Produced in A Recirculating Aquaculture System as A Medium for Lettuce (Lactuca sativa Var Longifolia) Production

A recirculating aquaculture system was designed, consisted of a fish tank ( 110 L x 84 W x 100 D em), three hydroponic troughs (110 L x 30 W x 5 D em) and a water pump with the capabilty of pumping 30 liters of water per minute for circulation of water through the system. Hydroponic troughs were installed over the fish tank with in a distance of 20 ern. Each fish tank was filled with a volume of640 liters of water and then 75 juveniles (20 ± 0.02g) of red tilapia were introduced in each tank to be reared for a 3-week period. The fish were fed a floating pellet feed, containing 24% protein, twice a day at 09.00 and 18.00. The mean amount of supplementary feed was 2025g in each fish tank during the experimental period. The fish attained mean individual weight of 44.73 ± 0.35g at harvest time and the remaining wastewater or residual in each system was used as a medium to supply nutrient needs of 42 one-week old lettuce seedlings in a culture system. Lettuce seedlings were cultivated for a 5-week period . The yield in lettuce was 2017±197g at the end of the experiment.
The concentration of nutrients in water were determined after the harvest of fish as well as the lettuce seedlings. On average, lettuce seedlings could intake 3.20, 73.76 , 7.97, 3.48, 5.01, 4.72, 1.48, 8.98, and 0.28 % of feed's Fe, Mn, Zn, Cu, Ca, Mg, P, Nand K, respectively. Results in this study indicated that aquaculture wastewater can be used as a suitable nutrient supplying solution for lettuce culture in a NFT(Nutrient Film Technique) system