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Abstract

The presence of disinfection byproducts (DBPs) in drinking water is becoming increasingly important public health concern because of the long-term detrimental effects of these compounds on human health. DBPs have been linked to low birth weight, stillbirths and carcinogenicity and hence there is increased effort to regulate and control their presence in drinking water. In this research, the reduction of DBPs in raw surface water by the removal of their precursors was examined using UV-H202 based advanced oxidation process (AOP) and biological activated carbon (BAC) treatment. The effects of UV photolysis, H2O2 treatment, and UV-H202 oxidation were investigated using a collimated beam UV reactor and bench-scale annular flow through reactor. Downstream BAC treatment was assessed by using the laboratory scale parallel columns, with one column receiving AOP treated water and the other one receiving raw water (as control). UV-H2O2 AOP was effective at removing DBP precursors and reducing DBPs but only at extremely high UV fluences (greater than 1000 mJ.crn⁻²). On the other hand, the combination of UV-H2O2 AOP at moderate UV fluences with downstream BAC was equally (or more) effective at removing DBP precursors and reducing DBPs. AOP pretreatment at 500 mJ.cm⁻² and 20 mg.L⁻¹ H2O2 and BAC with an empty bed contact time (EBCT) of 8 minutes, resulted in reductions of 42, 37, 50, 52 and 59% in THM-FP, DCAA-FP, TCAA-FP, TOC and UV₂₅₄ , respectively, with respect to raw water (no treatment). These reductions were due to the increased biodegradability of the water, which on average increased five fold and the subsequent removal of biodegradable compounds by BAC. UV-H202 AOP combined with a downstream BAC treatment has tremendous potential in water treatment for the reduction of DBPs. This treatment process is feasible because of the moderate levels of UV fluences required to increase the biodegradability of the DBP precursors during the AOP pretreatment and the implementation of an inexpensive BAC step to remove biodegradable compounds.