Design of water reuse facilities for warm water fish culture

Abstract

Design criteria for warm water fish culture utilizing a reuse system were developed. Standard municipal waste treatment methods were used to the maximum extent possible. A trickling filter preceded and followed by settling basins were adequate for nitrification. Primary settling basins should have a detention time of 25-30 minutes, an overflow rate less than 100 m³/m²-d and a depth of at least 1.3m. Solids flushed from the fish tanks required a detention time between 20 and 25 minutes, an overflow rate less than I60 m³/m²-d and a depth of at least 1.3 m for 80 percent removal of suspended solids. Trickling filters were recommended due to simplicity of operation. Minimum depth should be 6 feet with a hydraulic loading rate between 7.5 and 30 m³ /m²-d. Ammonia nitrogen loading rates should not exceed 20 x 10⁻⁵ kg/m²-d. Settling of the trickling filter effluent requiring a detention time of 20 minutes was adequate with an overflow rate of 175 m³/m²-d and a depth of at least 1.8m for 80 percent removal of suspended solids. Fish loading rates of 50 kg/m³ with turnover times of 0.5 hours resulted in acceptable growth, survival and food conversion rates. Possible implications for tranference of experimental results to other water quality conditions are discussed.