Experimental Studies On Enhanced Coagulation Of Tail Water

Test raw water used in the subject was the tailrace of the waster water treatment of a university. By dosing four kinds of coagulants and coagulant aids, such as ferric chloride, aluminum sulfate, ferric chloride polymerization, polymerization aluminum chloride, as well as PAM, zeolite powder, diatomite, activated carbon powder, and three kinds of ammonia nitrogen removal agent "blue water"(No.1),"water detoxification agent"(No.2),"ammonia ion chelating agent"(No.3), and through a variety of different combination process, the enhanced coagulation experiment was done.The concentrations of NH3-N, CODcr, turbidity, TP were65.71mg/L、55.98mg/L、14.95NTU,2.13mg/L in test water. Coagulant comparative test results showed that the optimal dosage of FeCl3, Al2(SO4)3, PFC, PAC were respectively60mg/L,80mg/L,80mg/L.80mg/L. the experimental phenomenon of PAC was the most obvious and the removal effect of PAC was best. In the coagulant aid test of PAM, without changing the dosage of PAC. when the dosage of PAM was1.2mg/L, coagulation effect was remarkable, NH3-N, CODC1turbidity, TP removal rate of coagulation sedimentation effluent were10.7%,72.76%,19.28%,91.69%, and the removal efficiency were increased by6.33%,0.10%,2.41%and34.23%, compared with separately dosing PAC.The concentrations of NH3-N, CODcr, turbidity, TP were78.45mg/L、85.58mg/L3.65NTU、1.21mg/L in test water. The coagulant diatomite test showed that:in the condition of PAC80mg/L and PAM1.2mg/L, the optimal dosage of diatomite was80mg/L, removal rate of NH3-N, CODcr, turbidity, TP was4.63%,25.22%,70.68%,65.87%, respectively. The coagulant zeolite powder test showed that:in the condition of PAC80mg/L, the best dosage of modified zeolite powder was100mg/L, the removal efficiency of NH3-N, CODcr, turbidity, TP in the upper water were10.84%,31.22%,80.88%,47.66%. Therefore, although the zeolite powder was lower than diatomite on the TP removal rate, but the concentration in the effluent had been within the discharge standards range. The zeolite powder was higher than diatomite on the NH3-N removal rate. Considering all the factors,, select modified zeolite powder as a follow-up test chemicals.The combined process tests of zeolite powder and powdered activated carbon showed that:in the PAC dosage amount of80mg/L, the modified zeolite powder dosage of80mg/L, the best dosage of powder activated carbon was30mg/L, the removal rates of NH3-N, CODcr, turbidity, TP were10.9%,30%,82.37%,57.65%, respectively. Therefore,100mg/L modified zeolite powder+30mg/L powdered activated carbon+80mg/L PAC combination process was the optimal process.The further study was done by adding nitrogen removal agent. By adding different ammonia removal agent, the effect of No.1nitrogen removal agent was best under the premise of not changing the posage of PAC, modified zeolite powder and powder activated carbon. In100mg/L zeolite powder and+30mg/L powder activated carbon+80mg/L PAC+NO.1ammonia nitrogen remover combination process, flocculation phenomenon was the most obvious, and the removal effect of ammonia nitrogen was best. The highest removal rate of ammonia nitrogen reached14.19%and the effect was not ideal. Consider the water treatment process and economic issues, nitrogen removal agent was not used in the follow-up process.Therefore, the enhanced coagulation studies was done by using the water of wate treatment station in the University. Modified zeolite powder+powdered activated carbon+PAC combination process was the optimal process for the effluent of the water treatment plant. This process can provide a reference for plant operation in the future.