H < Sub > 2 < / Sub > O < Sub > 2 < / Sub > / O < Sub > 3 < / Sub > Process Control Bromate Formation And The Study Of Organic Matter Removal

Ozone-Biological Activated Carbon（O₃-BAC） process is by far one of the mostpopular treatment technologies in drinking water. However BrO₃^-, which is classified as2B grade potential carcinogen, can be formed during ozonation process when bromideexists in raw water. Bromate control and NOM removal should be considerd at the sametime，when the ozone-BAC process is applied. In this study, three stages of studies werecarried out:1. Characteristics of bromate formation in synthetic water system wereinvestigated in batch experiments, by which formation mechanisms of bromate wereproposed.2. Based on the result of stage one, O₃/H₂O₂processes was applied forbromate control and NOM removal during ozonation. Meanwhile, the influences of theammonia on the effect of bromate control and NOM removal during the O₃/H₂O₂processes were also discussed.3. Pilot scale experiments of the influences of O₃/H₂O₂process on bromate control and NOM removal were also carried out. The resultsshowed that:During ozonation in synthetic water system （1000μg/L of [Br-] and no organicmatter）, the main pathway to formate bromate are direct and direct-indirect pathways.About95%of bromate was formed via the pathway of ozonation. In deionized water,H₂O₂/O₃process turned out to be very feasible for the bromate control. The bromatecontrol mechanism of H₂O₂/O₃process is the changing of the main bromate formationpathway.In the batch experiments, BrO₃^-formation was inhibited when adding NH₃or H₂O₂during ozonation of Yellow River water （122-130μg/L of [Br-]）. The optimal dosage ofammonia-nitrogen was0.3-0.5mg/L in the O₃/NH₃-N system，whereas，1-1.5is the bestmole ratio of H₂O₂/O₃in the H₂O₂/O₃process. Applying H₂O₂/O₃process only can notfulfilled the standard（10μg/L） at a ozone dose over2mg/L in Yellow River water.Through ammonification the concentration of bromate in effluent can not be controlledbelow the limit of national standard, when the dose ozone is over1.5mg/L. Whenammonia exists in water, the process of H₂O₂/O₃has a strengthen effect on bromatecontrol. The optimal operating conditions are concluded as following: H₂O₂/O₃（M/M）=1-1.5. NOM can be effectively removed by applying Ozone process in Yellow River water. With the increasing of ozone concentration, NOM removal rate increasesgradually. The effect on NOM removal enhanced by adding H₂O₂during ozonation, and1-1.5is the best mole ratio of H₂O₂/O₃in the H₂O₂/O₃process.In pilot scale test, bromate formation amount is8-25μg/L, when the ozone dosageis2-2.5mg/L. The standard can be fulfilled by adding H₂O₂. Compared with the soleozonation process, the H₂O₂/O₃process can enhance the removal effect of turbitidy,CODMnand TOC. The optimal H₂O₂/O₃molar ratio is0.5-1. In order to enhance theeffect of NOM removal and bromate control at the same time, the molar ratio ofH₂O₂/O₃should be controlled about1in the real application of H₂O₂/O₃process.