Pre-ozone prior to microfiltration membranes was operated at the pilot scale to evaluate the benefits ofenhanced organic carbon removal and advanced oxidation of Tuolumne River water in California. The pilotstudy was conducted to support the design and construction of a new treatment plant for the TurlockIrrigation District, an irrigation and power company in California. It was anticipated that pre-ozone inconjunction with alum would increase iron, manganese, color, turbidity, and organic carbon removal andimprove membrane performance compared to coagulant addition alone. As a result of improved organiccarbon removal, it was anticipated that a decrease in disinfection by-product (DBP) formation would beobserved. Results from the pilot evaluation, however, showed that although iron, manganese, and turbiditylevels were significantly decreased through membrane filtration, the reduction was consistent with andwithout pre-ozone. Increased reduction in the UV254 and total organic carbon (TOC) concentrations wasobserved in conjunction with a decrease in the total trihalomethane (THM) and haloacetic acid (HAA)formation for pre-ozone and alum addition compared to membrane treatment alone or with post-ozonetreatment. Oxidation with ozone resulted in a reduction in organic carbon, a DBP precursor, and thechlorine dose necessary to provide adequate disinfection residual. Combined, these two factors reduced thetotal THM and HAA formed during 7-day simulated distribution system (SDS) evaluations. Impact of preozoneon membrane system performance was membrane system dependent. Pretreatment with pre-ozoneand alum combined and alum only were found to enhance membrane performance by significantly decreasingthe rate of membrane fouling for one system, to increase the fouling rate for another membrane system, andto result in similar fouling for the third system as observed without chemical addition. Issues with solidscarryover due to poor sludge drainage was likely the cause of some of the membrane fouling for one of themembrane systems. However, one membrane system did not appear to be impacted by the solids carryoverand continued to show improved membrane performance during this period. Based on these piloting results,the recommended treatment train for the new water treatment plant for Turlock Irrigation District includespre-ozone, alum coagulation, flocculation, plate settlers, microfiltration membranes, and post-chlorination.
展开▼
