WATER QUALITY MANAGEMENT IN WASTE-TREATMENT SECTIONS OF SPLIT POND AQUACULTURE

The original split-pond concept involved no water quality management in the waste-treatment section of the system. Dissolved oxygen concentrations commonly fall to near 0 mg/L each night during the summer. Cycles of daily aerobic conditions and nightly anaerobic conditions are thought to be keys to efficient waste nitrogen processing, which is a distinguishing characteristic of split-pond systems. This study focuses on the possible benefits of using mechanical aeration in the waste-treatment section of the split-pond culture system.

Work was conducted on a commercial catfish farm in west Alabama. The farm currently has eight split-ponds, each with a fish-holding section of about 8,000 m². Two, 10-hp floating, electric paddlewheel aerators were placed in the waste treatment section of each of four ponds; while four ponds - the controls - had un-aerated waste treatment cells. Water samples were collected biweekly at the inflow and outflow of the waste-treatment cells; once the water became cooler in the fall and winter, the samples were collected monthly. These samples were analyzed for Secchi disk visibility, pH, chemical oxygen demand (soluble and total), total ammonia nitrogen, nitrite, nitrate, total nitrogen, total phosphorus, and chlorophyll a. Other parameters measured less frequently: biological demand, soluble total nitrogen, soluble total phosphorus, and acidification. Dissolved oxygen concentrations were monitored by an automated system that was installed and is operated by the farmer. For the data collected, there was no significant difference for only variables between the control ponds and the aerated waste-cell ponds. Further research is required before recommendations and impacts can be addressed.