Pilot Study On Ozonation Process Optimization For By-products Control In Drinking Water Treatment

As a kind of advanced treatment of drinking water, O3-GAC process has beenmore and more widely used in our Country. But ozonation of drinking watercontaining bromide may lead to the formation of bromate and the increase of AOCcontent, the removal effect of nitrobenzene and petroleum remains to be verified. Bytaking the raw water in Shenzhen area as the research object, the best way ofpre-oxidation and the main ozone dosage were obtained by the optimization ofO3-GAC process. The optimized process can reduced the concentration ofby-products while removing pollutants effectly, and ensure the safety of effluent.Firstly, the pre-oxidation way of conventional water treatment process wasstudied in detail. The results showed that pre-oxidation significantly improved thewater treatment effect of conventional process, and the removal rate of TOC, UV²⁵⁴,petroleum and nitrobenzene was increased27%,47%,22%and59%, respectively.Compared with water treatment effect and by-products control effect of potassiumpermanganate pre-oxidation and pre-ozonation, the results showed that petroleumhas a better removal effect by potassium permanganate per-oxidation, and nobromate in effluent, the formation amount of AOC was lower than pre-ozonation.The removal capacity of nitrobenzene was powerful by pre-ozonation. TOC, UV²⁵⁴,turbidity have a better removal effect.Secondly, we made an optimization study on the main ozone dosing quantity ofadvanced treatment. The rusults showed that each pollutant has a good removaleffect when the ozone concentration was1.5mg/L. In the ozone concentration, thebromate of effluent could reach the standard, and AOC could drop to a lower level,the effluent belonged to bio-stability. The removal effect of pollutants changed verylittle when the concentration of ozone was increased, the bromate content exceedingstandard in effluent.Finally, the optimized condition of different water quality was proposed by thecomprehensive analysis of pre-oxidation way and the main ozone dosing quantity,and verifying its effect. The results showed that the turbidity of optimized processeffluent was stabilized under0.1NTU. The removal rate of UV²⁵⁴, TOC andpetroleum was improved1%⁶%,5%²9%and20%separately, the bromate andAOC of effluent could reach the standard. Through a month continuous running, theremoval rate of UV²⁵⁴, TOC and petroleum were91%,59%,95%and100%separately, the standard-reaching rate of effluent was high, and the process hadlower cost. Therefore, the optimized condition （0.5mg/L potassium permanganatepre-oxidation, main ozone concentration1.5mg/L） was feasible in Shenzhen District.