AWWA ACE92162

As a result of the current and anticipated disinfection byproduct (DBP) regulations, there has been an increasing interest in employing pressure driven membrane processes for DBP precursor removal. Although previous work has primarily focused on groundwaters, greater emphasis is now being placed on using membrane technology for surface waters. Consequently, studies were undertaken to evaluate the use of low pressure membrane filtration for removal of DBP precursors from three untreated surface water supplies. Pilot studies were conducted on two waters in northern California and one in Ottawa, Canada. One ultrafiltration (UF) membrane with a molecular weight cutoff (MWCO) of 100,000 daltons and four nanofiltration (NF) membranes with MWCOs ranging from 200 to 800 daltons were evaluated. Results indicated that UF was ineffective for removal of substantial concentrations of precursor materials from any of the surface waters. When little or no bromide was detected in the permeate, hollow fiber NF membranes with MWCOs ranging from 400 to 800 daltons effectively controlled DBP formation. The primary advantage of this membrane configuration was that little pretreatment was required for operation of the membrane modules. In the waters containing bromide, a shift to the brominated DBPs was observed after chlorination of membrane-filtered water. For the two low pressure hollow fiber NF membranes (400 to 800 MWCO), higher bromoform concentrations were observed after chlorination of the permeate as compared to the raw water. Use of a lower MWCO spiral wound NF membrane (200 to 300 daltons) was necessary to control the formation of brominated THMs. However, it was necessary to pretreat the surface waters before employing these membranes.