Water quality improvements of wastewater from confined animal feeding operations after advanced treatment.

摘要

Current trends of animal production concentration and new regulations promote the need for environmentally safe alternatives to land application of liquid manure. These technologies must be able to substantially remove nutrients, heavy metals, and emissions of ammonia and odors and disinfect the effluent. A new treatment system was tested full-scale in a 4360-swine farm in North Carolina to demonstrate environmentally superior technology (EST) that could replace traditional anaerobic lagoon treatment. The system combined liquid-solids separation with nitrogen and phosphorus removal processes. Water quality was monitored at three sites: (i) the treatment plant as the raw manure liquid was depurated in the various processes, (ii) the converted lagoon as it was being cleaned up with the treated effluent, and (iii) an adjacent traditional anaerobic lagoon. The treatment plant removed 98% of total suspended solids (TSS), 76% of total solids (TS), 100% of 5-d biochemical oxygen demand (BOD₅), 98% of total Kjeldahl nitrogen (TKN) and NH₄-N, 95% of total phosphorus (TP), 99% of Zn, and 99% of Cu. The quality of the liquid in the converted lagoon improved rapidly as cleaner effluent from the plant replaced anaerobic lagoon liquid. The converted lagoon liquid became aerobic (dissolved oxygen, 6.95 mg L-1; Eh, 342 mv) with the following mean reductions in the second year of the conversion: 73% of TSS, 40% of TS, 77% of BOD₅, 85% of TKN, 92% of NH₄-N, 38% of TP, 37% of Zn, and 39% of Cu. These findings overall showed that EST can have significant positive impacts on the environment and on the livestock industries.