Influence of Cu~(2+) sustained loads on bio-nitrification of activated sludge

The inhibition on microbial nitrification by heavy metal is a common problem in many wastewater treatment plants. In this work,the effects of different Cu2 +concentrations on microbial nitrification efficiency,microbial nitrifying activity and distribution of Cu in sludge solution were investigated through sustained load tests in sequencing batch reactors(SBRs). The results show that the inhibition effects of Cu2 +on the ammonia nitrogen removal became significant with the loading concentration of Cu2 +and running cycle. The inhibition effect of Cu2 +on ammonia-oxidizing bacteria was greater than that on nitrite-oxidizing bacteria. When the accumulation amount of Cu inside and outside the sludge was up to(14. 0 ± 1. 0) mg·g- 1,the ammonia nitrogen removal rate dropped to 26. 5% ± 4. 0%. In the inhibition period,nitrite-oxidizing bacteria could partly or entirely adapt to the presence of Cu2 + in 10 and 20 mg·L- 1Cu2 +systems. After a period of recovery,the activities of nitrifying bacteria and nitrification efficiency could partly or entirely recover. Cu was mainly accumulated inside or outside the cells of activated sludge. The adsorbed Cu was hard to be released from activated sludge. The nitrification inhibition rate was negative correlated to the concentration of soluble Cu.