Abstract
AbstractPiggery wastewater is characterized by its high ammonium concentration and low COD/nitrogen ratio. The indiscriminate discharge of untreated piggery wastewater from scattered household pig farms has posed a potential risk of surface water pollution in rural areas of southern China. In this study, an anoxic/oxic (A/O) process with elastic fillers tightly packed in each tank was investigated for piggery wastewater treatment. Two anoxic tanks and two aerobic tanks were used in series and the hydraulic retention time of each was 24 h. Dissolved oxygen concentration in the aerobic tanks was intentionally controlled at below 2 mg L–1 for the implementation of nitritation. After sludge acclimation, three recycle ratios from 100 to 300% were tested. More than 90% of organic matter was removed from raw piggery wastewater despite recycle ratio values. However, the NH4+-N concentrations in the effluent slightly increased from 30 to 65 mg L–1 as the recycle ratio increased. Higher recycle ratio benefited the ...
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