AWWA ACE93125

Biodegradable dissolved organic carbon (BDOC) production is a function of ozone dose and potentially time of pH adjustment. Raw water samples collected from three source waters showed a dissolved organic carbon (DOC) ranging from 3.0-7.1 mg/L for a pH range of 6.8-7.2. Removal of BDOC was optimum at an applied O3/DOC dose of 2:1 and at ambient pH. When pH was artificially adjusted, BDOC removal was greatest when pH was altered prior to ozonation. The described conditions resulted in a BDOC of 0.9-4.2 mg/L (40-50% reduction of DOC), a 90-100% reduction in formaldehyde - the most readily produced aldehyde in the ozonated source water (90-100% reduction total aldehydes), and a 70-80% reduction of trihalomethane formation potential (THMFP). The conservative nature of bromate and dibromoacetic acid (DBAA) through a biotreatment process was confirmed by the use of bromate and DBAA spikes. To supplement our BDOC work, assimilable organic carbon (AOC) levels were measured in parallel experiments. Our observations indicate a positive correlation between BDOC and AOC; both parameters indicate a tendency to plateau at an O3/mg DOC ratio of 2:1. AOC-NOX appeared to mimic BDOC better than AOC-P17. The presence of H2O2 during ozonation did not increase the BDOC or AOC produced. Its presence did indicate differing effects of DBPs, but final biofiltration concentrations were comparable. This research was focused on three points of concern: the reduction of aldehydes, organic acids, HAAFP, CHFP (chloral hydrate), and THMFP; the effect of H2O2 addition prior to ozonation to determine whether OH- radical formation would increase the formation of BDOC within a pH range of 6-9; and the comparison of AOC and BDOC levels.