Experimental Research Of Micro-Polluted Water By Enhanced Coagulation And Filtration

It is essential to remove the trace hazardous organic pollutants and decreasing the disinfection by-products for improving the potable water quality. While water source pollution is tending to become more and more serious, it is unpractical for polluted raw water to be effectively controlled and treated, even to be recovered in a short time under the current situation. As a result, it has become a central selection and an important trend for suiting the situation of our country to enhanc the traditional process of water treatment to adapt to the ceaseless water quality, to show the efficiency of the current technics to the top extent, and to assure the good water quality.Humic acid, which is extensive in normal water body, is the primary component of normal organic, and also is the precursor forming the DBPs, so it is important for its being removed. The experiment showed that, Al₂(SO₄)₃ and FeCl₃ both have favourable coagulation effect for humic acid, but the coagulation efficieny of FeCl₃ was better than that of Al₂(SO₄)₃. The enhanced coagualtion by adding dual PAM could clearly improve the humic acid coagulated effect.Experiment on reservior water coagulation by Al₂(SO₄)₃, FeCl₃ and PAM tested that, it has the low removal rates of COD_mn and UV₂₅₄, among of them, PAM is the worst, Al₂(SO₄)₃ is better than PAM, and FeCl₃ is the best. The compund enhanced coagulation with FeCl₃ + PAM could clearly improve removing the effciency of pollutants, moreover, such factors as coagulant amount, water temperature and pH value all had obvious effect on the treatment efficiency, and the optimal condition was shown as follows: 3.0mg/L FeCl₃+1.0mg/L PAM, water temperature 25～35°C, pH 5.5-7.5. Romval rates of COD_Mn, TOC, UV₂₅₄ and NH₃-N by enhanced coagulation were 77～87ï¼…, 61～74ï¼…, 58～72ï¼…, 53～64% and 35～51%. Then the cooperation coagulation machanism of inorganic and organic coagulats was also pointed out.Normal zeolite is an aliminate-silicate mineral, which has stable framework with rack-shape, a large amount of holes and paths, and large specific aera. Its adsorption for COD_Mn, UV₂₅₄ and NH₃-N is greatly affected by pH, and the optimal pH is 6～7; the adsorption capacity decreases with the increasing of zeolite amount, and rapidly improves as the increasing of influent concentration, while the adsorption capacity is seldom affected when the water temperature is 10～40°C. Roasting could remove moisture and impurity in zeolite holes and paths, and make them unimpeded, and activate the cation on its surface, which increases the zeolite's adsorption capacity greatly. Then dipped in HCl or NaOH or NaCl solution, by which the cations are become the ones suiting for the single demand, that could enhance the zeolite's adsorption capacity further; especially, its adsorption for NH₃-N could be enhanced by one times. It was determined by the experiment comparision that the optimal activation method was being roasted at 700°C for 2.5h and then dipped in 5%NaCl for 3h.The enhanced filtration experiment with activated zeolite tested that the operating filtering velocity was suitable at less than 6m/h, and the designing height of zeolute is appropriate over 80cm. For the used zeolite, its holes and paths accumulate more and more pollutants, its adsorption capacity drops gradually and filtering effect decreases. So it needs regeneration to recover its adsorption efficiency. The experiment addressed that, it had the optimal regeneration effect dipped in NaOH solution for 3h. This is because the alkaline condition is better for transferring adsorpted NH4⁺ into NH₃ and then to be removed, and OH^- could destroy the adsorption balance of certain adsorbed organics and remove them, which generates the better regeneration result.The treatment of Queshan Reservoir water in Jinan by combination technics of enhancing coagulation and activated zeolite filtration tested that the turbidity of raw water was 2.1～3.6, COD_Mn 3.5～5.8mg/L, TOC 2.1～2.9mg/L, UV₂₅₄ 0.058-0.082cm^-1, NH₃-N 0.45～0.61mg/L, and the removal rates of the above indexes were 82～97%, 71～82%, 66～78%, 51～74% and 69～82% seperately, and this offered the referrence for choosing treatment of micro-polluted water source.