Effects of pre-ozonation of high humic content waters on direct filtrationin a pilot plant

Direct filtration and the effects of pre-ozonation on direct filtration per formance were evaluated and compared with conventional water treatment perf ormance in a pilot plant study. performance measures including coagulant de mand, turbidity, colour, total organic carbon, head loss development, filte r run time, back wash water consumption, filtration solids volume and iron and manganese were examined for a water source with low turbidity and high organic matter content. The optimal coagulant dosage established for in-lin e direct filtration was much lower than that required for conventional trea tment of the same raw water. Direct filtration preceded by ozonation achiev ed similar, or substantially higher, turbidity removal efficiencies with a significantly lower alum coagulant dosage. Pre-ozonation was effective in l owering turbidity, colour, head loss development and iron and manganese lev els but was not significant in removing TOC. Pre-ozonation increased filler run time by about 7% when compared with the case of no ozonation treatment . The back wash consumption was 5% of total water produced and solids volum e produced by coagulation and direct filtration alone was 8% of the back wa sh water used. There were no significant differences for the latter two par ameters by pre-ozonation treatment.