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 consisting of two cells, one planted with California bulrush (Scirpus californicus) and giant cutgrass (Zizaniopsis miliacea) and one planted with Halifax maidencane (Panicum hemitomon). The removal of potential pollutants from water Bowing through the wetland was determined for 1-, 2-, 3-, and 4-d hydraulic residence times (HRTs), with hydraulic loading rates of 77-91 L/m(2) of wetland per day. Concentrations of potential pollutants were much lower in effluent from the wetland than in influent from the channel catfish ponds. The following reductions in concentrations were recorded: total ammonia nitrogen, 1-81%; nitrite-nitrogen, 43-98%; nitrate-nitrogen, 51-75%; total Kjeldahl nitrogen, 45-61%; total phosphorus, 59-84%; biochemical oxygen demand, 37-67%; suspended solids, 75-87%; volatile suspended solids, 68-91%; and settleable solids, 57-100%. Overall performance of the wetland was best when operated with a 4-d HRT in the vegetative season, but good removal of potential pollutants was achieved for shorter HRTs and when vegetation was dormant.