Research Of Haasformation And Its Precursors In Municipal Sewage Treatment Process

With the social and economic development, the issue of water resources hasbecome a pressing issue in the world, which is also a significant source andenvironmental problem for our country. The development and utilization of reclaimedwater is one of the most effective ways to ease the water shortage in cities. In order toensure the security of recycled water, disinfection has become an essential link in therenewable water treatment process. Reseachers have found a wide variety ofdisinfection by-products, of which the highest content is THMs. HAAs is second, butthe dangers far greater than THMs. Therefore, this study is mainly based on HAAs andits precursors as the research object, using three-dimensional fluorescencespectroscopy and resin separation analytical techniques, analysis HAAs and itsprecursor, to explore disinfection byproducts’ and its precursors’ migration andtransformation. Separation of acidic organic matter further explore its precursor andformation of disinfection by-products, thus complete the sewage disinfection anddisinfection byproducts precursors theory, to improve the sewage treatment process,provided the control disinfection byproducts theoretical basis.Studies have shown that:1. In the sewage treatment process, the removal efficiency for DOC, UV254is verysignificant, especially after biotechnology-based secondary treatment. HAAFP did notdecrease, While the Value of HAAFP, SUVA increased significantly after secondarytreatment, that means high aromaticity and unsaturation dissolved organic matter(DOM) are important precursors of HAAs in sewage.2. HAAs, including dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), bromine acid (BCAA), a bromoacetic acid (MBAA) and dibromoacetic acid (DBAA),can be detected in influent. DCAA and TCAA accounting for over90%of HAAs, andthey all slight decreased after the secondary processes. Disinfectant added leads theHAAs increased in tertiary treatment, but DCAA,TCAA did not exceed our drinkingwater health standards (GB5749-2006) about DCAA and TCAA the maximum limitsspecified value (less than50ug/L and100ug/L respectively).3. Within a certain range (24h), chloroacetic acid generation and disinfection timewas positively correlated. With the consumption of organic matter and chlorine, thereaction gradually levels off. The amount of chloroacetic acid generated rapidly withthe increasing of chlorine dosage. When the chlorine dosage overdose, trichloroaceticacid generates more rapidly than dichloroacetic acid.4. Compared to the raw water, the low removal rate of acidic organic matter madeHOA and HIA based in secondary effluent,especially the high aromaticity organicmatter. In secondary effluent, SUVA value of HOA and HIA rising leads to theincreasing of HAAFP, accounted for75.3%of the the raw water HAAFP. It indicatesthat the newly generated organic matter containing aromatic rings and unsaturateddouble bond, which is the precursors for HAAFP, is mostly acidic organic matter.5. Using three-dimensional fluorescence spectroscopy technical analysis DOM insewage water, secondary effluent and tertiary effluent. The results show that theremoval efficiency of F1, F2, F3, F4is very significant after secondary biologicaltreatment (Orbal oxidation ditch), while a lot of F5, F6generate. For THAAFPsignificantly increasing in secondary effluent, F5, F6are important precursors ofHAAs.