The Research Of Controlling Disinfection By-products In Municipal Reclaimed Water By Coagulation And Adsorption

The secondary urban sewage treatment plant effluent contain variety of pathogenic microorganisms, trace toxic and hazardous chemical contaminants and plant nutrients,it will produce some harmful disinfection by-products after disinfection treatment, and its presence on the safe use of recycled water certain risks, which restricts the reuse water recycling. Selecting coagulation, adsorption and combination processes to treat the secondary effluent of sewage treatment plant in Jinan. Research the effect of generating THMs by coagulation, adsorption and combination processes. In addition, the secondary effluent of sewage treatment plants was fractionated using ultrafiltration membrane separation technology and resin adsorbents. DOM in water samples and molecular weight distribution and affinity relationships and generate THMs between the amount of disinfection byproducts were analyzed. Molecular weight disinfection byproducts precursors and distribution of hydrophilic and hydrophobic in water samples can help to choose, and to predict the effect of the treatment, so as to evaluate coagulation, adsorption technology to reduce reuse water as wastewater treatment technology applicability of THMs and other disinfection byproducts provide a theoretical basis. The main conclusions in this paper are as follows:(1) FeCl3achieved the highest coagulation removal efficiency.As coagulants and adsorbent dosage increased, the removal efficiency of DOM increased sharply.FeCl3had the highest removal efficiency for UV254and DOC at the dosage of80mg/L and pH value of7.The optimum adsorption conditions for wastewater treatment were determined at PAC dosage of2.0g/L and adsorption equilibrium time of90min. FeCl3-PAC was more effective than PAC-FeCl3for UV254and DOC removal.(2) FeCl3-PAC was more effective than PAC-FeCl3for reducing THMs. FeCl3-PAC and PAC-FeCl3could only remove the DOC efficiently but could not reduce the STHMFP efficiently. It turned out that the reactivity of FeCl3-PAC was the highest.It was found that the THMs concentration do not increase after48h of contacting time during the chlorination. On the premise of guaranteeing the quality of disinfection, controlling disinfection time can effectively reduce the formation of THMs within0.5hours.All kinds of THMs accounted for the proportion of the THMs are roughly the same. They do not change obviously with the change of MW after coagulation compared with raw water.Coagulation processes were more efficiency to remove high MW organics than low MW organics. Adsorption process gave better results for the DOC removal efficiency. FeCl3coagulation treatment of wastewater has better removal effect in the hydrophobic acid, powder activated carbon adsorption has a better removal effect in hydrophilic and hydrophobic organic.(3) DOM of the water sample collected from the secondary effluent of Jinan sewage treatment plant was mainly consisted of high MW(>100KDa). The STHMFP of30KDa-100KDa in municipal secondary effluent was the highest, while the lowest fraction of STHMFP was<1KDa. Hydrophilic and hydrophobic acid material is the main organic matter in jinan secondary sewage treatment plant. In adsorbed effluent, the STHMFP of<10KDa was relatively larger. Coagulation with Ferric chloride can effectively reduce about50%STHMFP production. Activated carbon adsorption could remove large amounts of organic matter, but can greatly increase STHMFP of the low molecular weight organic.(4) HOA and HIS are the main precursor of chlorine disinfection by-products THMs in the secondary effluent of sewage in the process of chlorine disinfection. HON and HOA have stronger THM formation potential than HOB and HIS.Coagulation can reduce hydrotropic substance effectively. Activated carbon adsorption can remove hydrotropic substance and hydrophobic acid effectively. Therefore, coagulation-adsorption combination process can effectively reduce the generation of THMs.