Regulation Method For Ozone Process To Remove Refractory Organic Pollutants

It becomes a hot topic that to remove refractory micro-pollutants in drinkingwater. Ozonation is widely used for the treatment of drinking water for degradationof organic compands. But in the practical application of the ozone process, there’sno basis for evaluation of refractory organics removal effect and regulation of ozonedosage. The purpose of this paper is to study a methematic model of therepresentative organic nitrobenzene ozonation base on Instantaneous Ozone Demand（IOD）, ozone exposure （CT） which are used to characterize the two phase ofozonation respectively and regulation methods of ozonation process base on thismodel.A tube reactor （TR） for ozonation was designed to measure the dissolved ozoneconcentration from the starting2.2s after ozone addition. By using this reactor weobtained variation law of the IOD and CT: the ozone dosage, pH, DOC, alkalinityare positively correlated with the IOD; in addition to ozone dosage, the CT isnegative related with the other three factors.Due to ozonation process is divided into two stages, the integral nitrobenzeneremoval rate of ozonation process was equal to the sum of the removal rate in twophases, η=η₁^°+η₂=η₁+η₁+η₂. η₁^°（η₁^°=a₁×IOD+b₁） and η₂（η₂=a₂×CT+b₂） are theremoval rates in the first and second phase, respectively, while△η₁represents thevariation caused by changes of water quality.The model for the nitrobenzeneoxidation by ozone in the testing water quality is shown as follows:η=η₁+η₂=40.43×IOD+△η₁+12.4×CT+8.2. The similar model for other water quality can be obtainedas the same method adopted in this paper.Based the ozone oxidation nitrobenzene model, three methods to improve theperformance of nitrobenzene ozonation been obtained: increasing ozone dosage,reducing DOC or alkalinity in raw water.Based on the conclusion that reduce DOCconcentration can raise nitrobenzene removal rate in ozone process, we try to usetwo pretreatment methods-potassium permanganate oxidation and enhancedcoagulation to improve oxidation rate of nitrobenzene. Although potassiumpermanganate oxidation cannot change the raw water DOC but can remove part ofUV₂₅₄,nitrobenzene removal rate was improved. KMnO₄dosage of1.0mg/L,nitrobenzene removal rate was as three times as that of no pretreatment ozoneprocess. But unfortunately bromate generation amount also increases45%.