[Influencing factors of high-concentration lead removal using the phosphorus-accumulating sludge]

Phosphorus-accumulating activated sludge was used to remove lead [rho(Cu2+) = 150.0 mg x L(-1)] in wastewater in this experiment. The efficiency ratio and stability of Pb removal were studied at different dissolved oxygen concentration and different initial pH. The result showed that under anaerobic condition and pH 6, the Ph removal efficiency ratio increased with time elapsing, the value reached 99.8% after 32 days. Lead in form of organic and sulfide-bound lead and residual lead in residual sludge accounted for 41.8% and 52.6%, respectively, and the lead in the sludge showed a good stability. While under aerobic condition, the lead removal efficiency ratio increased with the increase of pH within the first 2 hours, the values reached 99.9%, 96.9% and 30.3% at pH 6, pH 4 and pH 2, respectively. In contrast, the residual lead was 3 072.3, 4 726.8 and 2 359.1 mg x kg(-1) under aerobic condition after 32 days, accounting for 41.8%, 65.8% and 88.8% of total lead in the sludge. Taking the lead removal efficiency ratio and lead stability into account, aerobic condition at pH 4 is the best for removing lead with phosphorus-accumulating sludge in theory.