Treatment Of The Water From Reservoirs Of Yellow River Using The Combination Processes Of Coagulation And Adsorption

Recently the Yellow River is seriously polluted. In order to remove the natural organic matter (NOM) especially the DBPs precursors and ensure the safety of drinking water, PFC and PAC were applied to treat the reservoir of the Yellow River in this study. The floc property and the DBPs potential production were investigated. Powder activated carbon and modified wheat straw were used coupled with coagulation. The performance and disinfection effect of the combination treatment were discussed. The main conclusions are as follows:(1) NOM and turbidity removal were increased with the increasing dosage of coagulants in treating the reservoir of the Yellow River. But the turbidity removal was decreased at the high dosage of PAC. NOM removal was favored at pH 6, while the alkaline solution was favored for turbidity removal. Electric neutralization played an important role in the PAC coagulation process. Both adsorption bridging and electric neutralization performed when PFC was used.(2) Flocs gave much lower growth rate and the peak flocs did not appear within the coagulation time at the low dosage of coagulants (3 mg/L for PFC,1 mg/L for PAC). At high dosage of coagulants, flocs formed quickly during the coagulation process and the PAC-flocs were much smaller. The pH had a greater influence on the PAC-flocs than on the PFC-flocs.(3) At the low dosage of PFC (3 mg/L), the strength and regrowth factors were larger while the strength factor at the high dosage of PAC (3 mg/L) was larger. In the coagulation process, the flocs were better able to resistant the increasing shear as the pH increased, but the reformation capability was decreased.(4) The flocs formed by PFC were more compact than the flocs formed by PAC. The fractal dimension of the flocs was decreased at higher dosages of PFC. The floes formed by PAC were loosely compacted at the low and high dosage. As the pH increased, the flocs were more compact.(5) The increasing PFC dosage resulted in more residual free chlorine, less chlorine demand and less DBPs production. The coagulated effluent at a PAC dosage of 12mg/L would possibly produce minimal amount of DBPs due to the minimal reducing organic compounds present in the water. The results were in accordance with the DOC outcome.(6) The combination treatment of coagulation and adsorption can enhance the NOM removal and the removal efficiency was increased by the dosage of coagulant and adsorbent. But adding adsorbents can improve floc settlement performance. There were more free chlorine remained in the combination treatment. Furthermore adsorption first was favored to maintain persistent disinfection effect.