Reduction of excess sludge by physical-chemical solubilization and recirculation into the anoxic tank of the anoxic-oxic biological process

摘要

Sludge pretreatment methods including, thermal treatment, surfactants and sodium hypochloride, and high-pressure homogenizer, were found effective for sludge solubilization. Using these methods, sludge solids were reduced by 20～30%. French press method was more effective than others for solubilization and recycle in term of short reaction time and no generation of toxic compounds. A/O process with sludge solubilization using French press and recycle into the anoxic tank reduced sludge production from 2,114 mg/day to 546 mg/day. Nitrogen produced from sludge solubilization was effectively reduced to 20～30 mg/L and further decreased to 10～20 mg/L by adding methanol. Sludge recycle showed no negative effects on SCOD removal and pH value, but the increase of phosphorus concentration in the effluent should be monitored.