| A series of studies on channel catfish pond effluent characteristics and treatment options were conducted at the Auburn University Fisheries Research Station (FRU), Auburn, Alabama in 2000 and 2001. In the first year, the size distribution of particles in storm overflow from catfish ponds and the settling rates for these particles were determined. The benefits of sedimentation and dirt-bag filtration for treating effluents also were studied. In the second year, information on concentrations of total, organic and inorganic suspended particles in channel catfish pond waters was obtained, and the relationship between suspended solids concentration and turbidity was estimated. The effectiveness of coagulants to treat catfish pond effluents was also determined in the second year.; In the first year, findings from serial filtration showed that a small reduction in concentrations of most water quality variables of interest occurred when samples passed a 41 μm filter. The settling time to remove 21% of mineral particles was 0.18 hours, while 5.09 hours would be necessary to settle 21% of organic particles.; In the sedimentation study, differences (P < 0.05) were observed in the water quality variables for both surface and bottom pond effluents between the settling ponds used for each effluent type over a 72-hour settling interval. However, the effectiveness of sedimentation was much greater for the bottom effluents released during pond draining because this effluent contained a high concentration of coarse mineral particles.; In the second year, 46% of 141 pond samples exceeded the usual limit for total suspended solids in typical National Pollution Discharge Elimination System permits. Most samples contained less than 50 mg/L inorganic suspended solids. The particulate organic matter comprised, on average, 43.5% of the total suspended solids. Inorganic suspended solids accounted for a little over half of the total suspended solids. Average turbidity also exceeded the typical limit for this variable specified in effluent permits, making it an important issue in relation to aquaculture pond effluents.; Application of aluminum sulfate (alum) with agricultural limestone was more effective as a coagulant aid in sedimentation basins than was calcium sulfate (gypsum), ferric chloride, and ferric chloride with non-ionic polymer treatments. Nevertheless, the high cost of alum and the lack of space for settling basin at most Alabama catfish farms do not favor its use. (Abstract shortened by UMI.)... |
