Effect Of Removing Organic Matter From Raw Water To Control The Chlorine Disinfection By-products By Miex(?) Resin

Chlorination is an important conventional means of ensuring the microbic safety of drinking water,but the chlorine could react with organic matter of raw water to form various disinfention by-products?DBPs?and disrupt the chemical safety of drinking water.Therefore,it is necessary to take measures to control the generation of DBPs.This paper started from enhancing the removal of disinfection by-products precursors and mainly studied on the effect of removing organic matter from the raw water of A water plant in the north of China to control the trihalomethanes?THMs?,trichloroacetaldehyde?CH?and adsorbable organic halogen?AOX?by the magnetic ion exchange resin?MIEX???resin?process and its combined process with coagulation.In addition,the influence of raw water quality and reaction conditions on the control efficiency and the regeneration process of MIEX???resin were investigated as well.The reaction conditions and characteristics of removal of organic matter from raw water by MIEX???resin process were investigated firstly.It was found that the removal effect of organic matter reached a satisfactory level when the resin dosage was lamL/L,the reaction time was 30min and the bed volume?BV:treated water volume/resin dose?was 1000.The M1EXA resin preferentially removed organic matter components with molecular weight in the range of 1-3 KDa and 5-10 KDa,and followed by<lKDa and>10KDa.On the other hand,the organic matter components containing rich carboxyl groups,amino groups,phenolic hydroxyl groups and aromatic carbon,such as humic acid and fulvic acid,were removed better relatively.And then,the effects of separate M1EXA resin process,separate coagulation process and MIEX???resin combined coagulation process on removal of organic matter from raw water were compared and analyzed.The results showed that the dissolved organic carbon?DOC?removal rate was improved by 18.33%and 32.60%respectively by MIEX???resin combined coagulation process compared with separate MIEX?resin process and separate coagulation process,while the dosage of poly aluminum chloride?PAC1?slumped by 95%and the dosage of chlorine was reduced by 14.10%.This was mainly due to the fact that MIEX???resin combined coagulation process could remove organic matter over a wider range of molecular weight and significantly improve the effect of removal of organic matter components with UV-Vis absorption and fluorescence properties.The raw water and its separate MIEX???resin process treatment water,separate coagulation process treatment water and MIEX???resin combined coagulation process treatment water were collected and analyzed for trihalomethanes formation potential?THMs FP?,trichloroacetaldehyde formation potential?CH FP?and adsorbable organic halogen formation potential?AOX FP?.It was found that the organic matter components with molecular weight<1KDa and>5KDa constituted the major component of THMs,CH and AOX precursors,and the effect of removal of the precursors with molecular weight>5KDa was the best under both separate MIEX???resin process and separate coagulation process.The separate MIEX???resin process and its combined process with coagulation could improve the removal rate of THMs FP,CH FP and AOX FP by 10?20%,thus to effectively reduce the risk of excessive exposure.Five influencing factors on the effect of removal of organic matter from raw water were analyzed.The results showed that almost the best removal effect of organic matter was achieved when the pH of raw water was 6?8 and the stirring intensity?G?was more than 71s-1,and temperature had almost no influence on the effect of removal of organic matter in the range of 5?35?.Furthermore,high turbidity?>50NTU?would slightly reduce the removal effect,the competition order for five kinds of inorganic anions to DOC-was SO₄^2->I^->Br^-? NO₃^->F-and high alkalinity and SO42-concentration would markedly reduce the removal effect.Moreover,the influence of Br-and NH3-N content of raw water on the effect of removal of organic matter were also investigated.And it came to a conclusion that the increase of Br-content significantly improved AOX FP,THMs FP and bromine substitution factor?BSF?and distinctly decreased CH FP,while the increase of NH3-N content sharply reduced THMs FP,CH FP and AOX FP.On the other side,the pretreatment of MIEX???resin process could obviously reduce the impact of Br-on the formation of THMs,CH and AOX but didn't work on NH3-N.Finally,the regeneration conditions and effect of MIEX???resin were analyzed.It was found that the optimum regeneration effect of MIEX???resin was achieved when the concentration of regeneration solution?NaCl aqueous solution?was 1.5mol/L,regeneration bed volum?regeneration BV:regeneration solution volume/regenerated resin dose?was 100 and regeneration time was 5min.As a support,the strong base anion exchange capacity of fresh,used and regenerated MIEX?resin were tested and the results were 0.54mmol/L,0.25mmol/L and 0.52mmol/L respectively.Additionally,the DOC removal rate was reduced to below 40%and some fresh MIEX???resin was required to maintain a good treatment effect after the MIEX???resin being regenerated and reused 12 times.