[Effect of Ozonation on Microorganism in the Biological Activated Carbon and Disinfection By-Products in the Effluent].

This study was carried out in the ozone (O) and biological activated carbon (BAC) section of a drinking water plant to investigate the effects of O on microbial and effluent disinfection by-products (DBPs) in BAC during drinking water treatment. The water quality, dissolved organic matter (DOM) characteristics, microbial activity, and DBPs formation at different O concentrations were analyzed. Results showed that the effect of O on microorganisms is mainly that it increased the utilization efficiency of DOM. However, excessive O increased the amount of organic matter such as protein and microbial metabolites (SMPs) in the effluent. When the O concentration increased from 0 mg·L to 2.0 mg·L, the survival rate of microorganisms in the BAC decreased from 95.10% to 62.60%. However, since O transforms organic matter into a biodegradable substance, we found that microbial activity increased by 62.52% and that the biofiltration of the BAC was enhanced. When the O concentration was further increased to 4.0 mg·L, the microbial survival rate decreased to 49.9% and the protein and SMPs produced by the microorganisms increased. This resulted in an increased formation of carbon-containing DBPs (C-DBPs) and nitrogen-containing DBPs (N-DBPs) by 41.93% and 7.18%, respectively. In summary, an appropriate dosage of O was beneficial for removing DOM by O-BAC, but we found that an excessive O concentration caused the formation of new DBPs precursors.