Ozonation of Coking Wastewater Effluent to Remove Disinfection By-Product Precursors Using an O3 Fluidized Bed Reactor

Abstract

Various types of dissolved organic matter (DOM) exist in the effluent of coking wastewater treatment plants. These can become precursors for disinfection by-products (DBPs) during chlorination in downstream drinking water treatment plants, representing a significant threat to the water supply. In this study, an O3 fluidized bed reactor (FBR) process is proposed to stabilize and reduce the number of precursors of haloacetonitriles (HANs) and trihalomethanes (THMs) in coking wastewater effluent. It was found that higher O3 concentrations resulted in lower amounts of precursors. Analysis of dissolved organic carbon (DOC) and total organic carbon (TOC), as well as three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy, showed that O3 preferentially decomposed DOM containing unsaturated and aromatic components. Ozonation also changed the species of organic compounds in the effluent. Furthermore, nitrogenous organic compounds such as nitrogen-containing heterocyclic compounds and nitrile were quickly oxidized. Amines were first increased then decreased, while the olefin and phenol, which contain unsaturated functional groups, were also selectively oxidized by ozonation. Organic acids and alkanes were formed during ozonation; however, these intermediate compounds showed relatively low formation potential for HANs and THMs. Therefore, the precursors can be mineralized or converted to organic compounds, which are less likely to form disinfection by-products. These results indicate that the ozonation treatment of coking wastewater effluent can effectively minimize disinfection by-product formation potential (DBPFP), reducing risks to the downstream water supply.