| Because special vegetation types and climate condition in northeast of China, humic substances of soil is higher and easily go into the natural water bodies. When such natural water body is used for urban water supply water, it often leads to high color, and it’s difficult for conventional water treatment(coagulation, sedimentation, filtration and disinfection). In this thesis, Harbin Mopanshan Reservoir(a typical high color water-supply reservoir) and water treatment system are chosen as the research object, water treatment process system based on color removal is set up to provide scientific basis for process modification of high color surface water purification.Through test of water quality index from different sampling section during 5 years in Mopanshan Reservoir, the results showed that the main pollutants in Mopanshan Reservoir were represented by natural organic matters such as humic acid and fulvic acid, showing typical seasonal variation, and the average DOC concentration in water was 5~6 mg/L. These natural organic pollutants mainly went into the reservoir through surface runoff, with L river input most. Hydrology and hydraulic characteristics of the reservoir were studied, and it was found that hydraulic retention time was short, with characteristics of stable stratification, but temporary mix could happen in flood season, showing obvious differences between the layers in water quality characteristics. Pollutant balance in reservoirs was accounted, input suspended matters mainly deposited at the mouth of river, which were about 32500 t/a. However, man-made pollution in organic pollutants accounted for only 3.36%, and the left pollutants were NOMs, such as humic acid(ex/em: 330/450 nm) and fulvic acid(ex/em: 260/450 nm).Study on water quality characteristics of Mopanshan Reservoir showed that, the reservoir had four typical water quality period, including the spring flood period and summer stability period, both of witch were greatly influenced by precipitation, winter period, which was a typical pollutants accumulation process, and frozen period, which continuously output the process of water and pollutants The study also found that the correlation relationship between NOM pollutants concentration and color was high, which was the principal causes of color.Nowadays, researches were operated on conventional water purification process of Mopanshan Reservoir for turbidity removal during the last three consecutive years, and the results showed that raw water had typical low turbidity and high color characteristics, which leaded to a large number of aluminum salt coagulants for reducing the water color during the coagulation stage. At the same time, the existing water treatment process only can effectively remove macromolecular humic acid-like matters(>5 k Da), and showed limited removal ability to fulvic acid-like matters(<3 k Da), leading to a higher level of chlorination by-products. Experiments also proved that humic acid had strong ability for color formation, and the remaining NOM pollutantswere mainly fulvic acid. Humic acid contributed the most to HAAs generation, while THMs and HAAs generation potential after fulvic acid chlorination were higher.In order to ensure the safety of water supply, the hydraulic circulated fluidized clarified system was researched and developed to improve the front flocculation. Through the clarification principle, the front-end contact flocculation of hydraulic circulated fluidized clarified system front-end contact had obvious improvement for initial floc size. Deposition ability in the sludge layer for the intercept ability of loose humic acid- aluminum flocs strengthened, effective controlling of the floc breakage, optimization of the front hydraulic gradient, promoted the growth and solid of the flocs and improved of back-end precipitation effect. The results showed that the hydraulic circulated fluidized clarified system could replace the front unit of mechanical mixing flocculation tank, with 20 min of hydraulic retention time, 10% optimum ratio of gas to water, up to about 2 m of the suspended sludge layer. The hydraulic circulated fluidized clarified system could save 40% reagent dosage, and had the obvious control effect on the color, with obviously decrease of natural organic pollutants, leading to improve the system control of disinfection by-products precursor.Through analyzing operating conditions of existed inclined tube sedimentation tank, it was found that the system had high front-end load, high Reynolds number, high water flux, and easily broken floc, leading to larger difference between the front and the end. The problem was more serious when uneven water appeared. In order to solve this problem, it was relied mainly on optimize of the flow field, the inclined tube and inclined plate settling tank were simulated and optimized by Fluent software. It was clear that 37.5% of the water collection weirs should be canceled in the best set in M water plant, high load at the end of the catchment was achieved. Turbidity reduced by 0.55 NTU in Modified Mopanshan plant, chemical reagent dosage was indirectly saved at the same time, Meanwhile, effect of water collection way on sedimentation result of flocs and the effluent quality was great. In order to control floc breakage, a new set of water collection weirs formula was brought out: 1 1 1 0 2L =K L +jL +L(v)Study on the output of pollutants in the water purification process showed that, the sludge produced by high color and low turbidity water was greatly influenced by reagents dosage and color, and the original calculation formula of the sludge quantity was low. So, a new calculation method was put forward:63210)3.053.1)(33.0(-TQSCTODBOAl Cb′++′+-+=出进.Through the research, the water quality changed rule and the pollutants characteristics of the typical, cold, high color and low turbidity water-supply reservoir were clear about. Against the problem of insufficient water purification efficiency, a new water purification technology based on the hydraulic circulated fluidized clarification and Variable level and back-catchment lamellar-type settler was presented for improving water quality of the water plant, reducing the reagent cost and improving the scientific basis. |
PDF Full Text Request