The effect of heavy metals on the activated sludge process and its microbial community analysis using 16S ribosomal DNA

The effect of heavy metal shock loading on biological treatment systems was studied by traditional methods and molecular biological techniques. Two kinds of SBR (sequence batch reactor) operation units, unacclimated and acclimated activated sludge systems, were studied. The addition of special nutrients and powdered activated carbon (PAC) to stimulate heavy metal uptake and recovery were studied. The kinetic constants could be used to describe the effect of the inhibition of substance utilization. The results showed that heavy metal shock loading had a greater effect on the unacclimated activated sludge system than on the acclimated one. The special nutrients greatly enhanced the uptake of copper, and the PAC improved sludge settling and decreased the turbidity of the effluent. The variation of dominant species and the diversity of the bacterial community were analysed using 16S ribosomal DNA. Compared with the slight change of dominant species during acclimation by copper, there was a great change in the acclimated system shocked by a high concentration of copper. The results confirmed that the acclimation could improve the resistance of microorganisms to heavy metal toxicity.