CONSTRUCTED WETLANDS FOR TREATMENT OF CHANNEL CATFISH POND EFFLUENTS

Water from a production pond for channel catfish (Ictalurus punctatus) in Hale County, Alabama, was passed through a constructed wetland con sisting of two cells, one planted with California bulrush (Scirpus cal ifornicus) and giant cutgrass (Zizaniopsis miliacea) and one planted w ith Halifax maidencane (Panicum hemitomon). The removal of potential p ollutants from water Bowing through the wetland was determined for 1-, 2-, 3-, and 4-d hydraulic residence times (HRTs), with hydraulic load ing rates of 77-91 L/m(2) of wetland per day. Concentrations of potent ial pollutants were much lower in effluent from the wetland than in in fluent from the channel catfish ponds. The following reductions in con centrations were recorded: total ammonia nitrogen, 1-81%; nitrite-nitr ogen, 43-98%; nitrate-nitrogen, 51-75%; total Kjeldahl nitrogen, 45-61 %; total phosphorus, 59-84%; biochemical oxygen demand, 37-67%; suspen ded solids, 75-87%; volatile suspended solids, 68-91%; and settleable solids, 57-100%. Overall performance of the wetland was best when oper ated with a 4-d HRT in the vegetative season, but good removal of pote ntial pollutants was achieved for shorter HRTs and when vegetation was dormant.