Experimental Study On Enhanced Coagulation And Sedimentation Process For Micro-polluted Source Water Treatment

Songhua River is located in the northeast cold area, the water quality has the characteristics of low temperature and turbidity and high concentration of ammonia nitrogen concentration in the winter, and the characteristics of high concentration of organic matter in summer, the conventional coagulation sedimentation process is difficult to ensure the water quality. In order to restart the Songhua River as a drinking water source of Harbin, the subject do the the research on micro-polluted raw water of Songhua River, to carry out the kinetic parameters optimization experiment, mixed coagulant and coagulant aid preferred test, strengthening coagulation sedimentation test process capability studies and enhanced coagulation and sedimentation of organic matter removal efficiency experiment.Through pilot test that coagulation kinetics parameters were optimized as: mixed phase stirring speed of 300 ram / min, mixing time 1.0 min; flocculation is divided into two stages, The first stage stirring speed n1=100 ram / min, the time for first stage is t1=2.0 min; the second stage stirring speed n2 = 40 ram / min, the time t2 = 8 min. The shear strength and energy consumption of the first and second stages are: Fr1=0.06, h1=0.323 J/L, Fr2=0.01, h2=0.08 J/L. Sedimentation experiments, it was found that the single coagulant settling time should be controlled above 25 min, the coagulant and coagulant aid settling time should be controlled above 10 min.coagulant and coagulant aid optimization test to select the best coagulant for the raw water of Songhua River is PAF and to determine the optimal dosage of 100 mg/L, the best coagulant aid is anionic PAM, The best coagulant aid dosage condition is 1.0 mg/L and 2 min after mixed phase. Research of raw water p H value of the coagulation were investigated. The results showed that, PAF and Mopanshan PAC best raw water p H value interval respectively for 4~6.5 and 6.0~7.0.Enhanced coagulation precipitation process performance test research leads to the conclusion that best PAF dosage is 100mg/L, 1.0 mg/LPAM dosed in the shaft of 17# investment sink water turbidity can be controlled below 0.5 NTU; sedimentation water residual aluminum, iron coagulant dosage increased first and decreased then increased with trend, residual aluminum and iron respectively in PAF investment dosage range of 60~100 mg/L, 100~140 mg/L when the sink after water can meet the water quality standard for drinking water requirements, and residual effluent manganese are far less than 0.1 mg/L.Test of impact load test showed that, enhanced coagulation equipment running at 1.2 times the design flow when the effluent turbidity is less than 1.0 NTU; the water quality impact load, respectively at the optimum dosage of raw water turbidity 10~40 NTU, precipitation turbidity can be controlled at below 1.0 NTU, the 40~250 NTU precipitation water turbidity after the turbidity can be controlled under 3.0 NTU; sedimentation tank in the optimization experiments of sedimentation tank should be controlled at 5~11 h mud cycle; strengthening coagulation and coagulation the precipitation process comparison experiment, enhanced coagulation sedimentation process turbidity and particle number is far lower than that of the conventional coagulation sedimentation device, the removal rate of CODMn and ammonia than the conventional process of high 10%~20%, 5%~10%.Experimental study on Enhanced coagulation on removal of organic pollutants in Songhua River showed that precipitation in PAF coagulation, Mopanshan PAC optimal dosage range of coagulation precipitation of water organic pollutants have different removal effect, adding PAF and Mopanshan PAC deposition were 4.0~4.6 mg/L, 4.4~4.9 mg/L and TOC, the removal rate respectively. 30~37%, 23~31% settled TOC; the removal rates were 27~31%, 24%~27% settled AOC, showed enhanced coagulation and sedimentation has certain protective effect on water biological stability; the removal rate of 23%~26%, 26%~31% respectively in the sink after the THMFP, THMFP precipitation after the removal rates were respectively 15%~21%, 20%~26%, coagulation precipitation can effectively reduce the disinfection the by-product of coagulation precipitation; 3D-EEM analysis showed that enhanced coagulation can effectively remove humic substances in water, two kinds of coagulant under the optimal dosage of humus organic matter removal rate were 31.55%, 26.15%.