Preliminary Studies Characterizing Wastewater From the Intensive Culture of Channel Catfish and Nitrification in Laboratory Scale Submerged Filters
A study was conducted to determine the pollutional load generated by catfish cultured under a salinity range of 1000 to 9000 mg/l TDS and to evaluate the effect of high salinity on the process of biological nitrification in laboratory scale submerged filters. Water quality parameters that were monitored included: COD, BOD5, PO4-P, Organic-P, NH3-N, NO3-N, Organic-N, SS, and VSS. A respirometer study also was performed to determine the influence of high salinity on the exertion of nitrogenous BOD. The results of the wastewater characterization study demonstrated that increasing the salinity from 1000-3000 mg/l TDS stimulated nutrient production, while increasing the salinity from 3000 to 9000 mg/l TDS decreased the nutrient production rates. Catfish nutrient production rates under saline conditions were approximately 57 percent less than those reported in the literature for catfish cultured in fresh water systems. A salinity level of 3000 to 5000 mg/l TDS was found to optimize nitrification while a TDS level of 5000 to 9000 mg/l was found to inhibit nitrification in a submerged upflow filter. A specific ion(s) in the saline water was not identified as the sources(s) of inhibition to nitrification. Hydraulic loading rates of 18.9 to 37.9 m/day were found to be acceptable operating rates for the nitrification filter. At a hydraulic loading rate of 18.9 m/day a recycle ratio of 1.0 was found to optimize nitrification while increasing the recycle ratio to 3.0 did not improve filter performance. The results of the respirometer study verified that a salinity range of 3000 to 5000 mg/l TDS was optimum for nitrification under high salinity conditions.