Removal of soluble microbial products as the precursors of disinfection by-products in drinking water supplies

Abstract

Water pollution worsens the problem of disinfection by-products (DBPs) in drinking water supply. Biodegradation of wastewater organics produces soluble microbial products (SMPs), which can be important DBP precursors. In this laboratory study, a number of enhanced water treatment methods for DBP control, including enhanced coagulation, ozonation, and activated carbon adsorption, were evaluated for their effectiveness in treating SMP-containing water for the DBP reduction purpose. The results show that enhanced coagulation with alum could remove SMPs only marginally and decrease the DBP formation potential (DBPFP) of the water by less than 20%. Although ozone could cause destruction of SMPs in water, the overall DBPFP of the water did not decrease but increased after ozonation. In contrast, adsorption by granular activated carbon could remove the SMP organics from water by more than 60% and reduce the DBPFP by more than 70%. It is apparent that enhanced coagulation and ozonation are not suitable for the removal of SMPs as DBP precursors from polluted water, although enhanced coagulation has been commonly used to reduce the DBP formation caused by natural organic matter. In comparison, activated carbon adsorption is shown as a more effective means to remove the SMP content from water and hence to control the wastewater-derived DBP problem in water supply.

Keywords:

• disinfection by-products (DBPs)
• soluble microbial products (SMPs)
• enhanced coagulation
• ozonation
• activated carbon adsorption

Acknowledgements

This study was supported by grants HKU714811E and HKU714112E from the Research Grants Council (RGC) of the Hong Kong SAR Government and funding for SRT on sustainable water from The University of Hong Kong. The technical assistance of Mr Keith C.H. Wong is highly appreciated.