| China is facing severe water environmental pollution and water resources shortage. Drinking water resources often suffer various emergent pollutions, which threaten the safety of drinking water. When phosphorus concentration exceeds 0.1 mg/L in drinking water source, it will pollute the waterworks inflow, reduce the water quality, and affect the stability of the water supply and water quality. For waterworks emergent phosphorus pollution caused by non-point source pollution, conventional technology is difficult to guarantee the phosphorus removal effect and the emergency mechanism start slowly. It is important to study the control technology of emergent water pollution for the drinking water security.Iron-carbon method has been proposed to treat emergent phosphorus pollution in waterworks inflow in this paper. The phosphorus removal was investigated by static test and dynamic test. The kinetic was calculated based on the dynamic equations, and the mechanism of phosphorus removal was discussed based on oxidation reduction potential, and iron concentration, which provide theoretical and technical basis to establish process of treating inflow phosphorus pollutions for water supply factory. The results are as follows:(1)The best reaction conditions were obtained by changing the iron carbon mass ratio, iron carbon dosage, rotating speed and reaction time to study the effect of phosphorus removal. The optimum condition was obtained by using the iron carbon dosage of 15.00 g/L, iron carbon mass ratio of 3/2, rotate speed of 120 r/min, and reaction time 60 min to treat flow of phosphorus concentration 1.0 mg/L, which resulted in significant efficiency (97%).(2) An L9(34) orthogonal test was carried out based on the single-factor experiment. The orthogonal test results showed that in the experimental study of iron-carbon method treatment of phosphorus pollution in waterworks inflow. The order of each important factor affecting the phosphorus removal effect are:iron carbon dosage, rotate speed, reaction time and iron carbon mass ratio.(3) Electrochemical mechanism experiments were carried out to investigate the iron ions concentration influence for phosphorus removal effect. The results showed that the max total iron ions concentration was 3.86 mg/L, which increased by 16% compared to single scrap iron method. There is a closely relation between oxidation reduction potential (ORP) and iron ions concentration. The more concentration of Fe2+ was, the lower ORP. The iron carbon method remove phosphorus is not simple addition of iron scrap effect and activated carbon function. The more iron ions concentration, the better total phosphorus removal effect. The iron ion concentration of iron carbon method is high, which can significantly improve the phosphorus removal rate.(4) Dynamics analysis shows that, the removal of phosphorus can be well fitted by zero-order kinetics (R"= 0.93115).(5) According to the above experimental results, continuity test was further conducted. The iron carbon mass ratio is 3:2 of reaction column filled with 350 g iron carbon dosage. The water flow rate is 330 mL/h and phosphorus concentration is 1.0 mg/L. The results indicated that the rest of total phosphorus concentration is less than 0.02 mg/L before operating 25 days which removal rate as high as 98% above. After 55 days the total phosphorus concentration and the iron ions concentration of effluence are less than 0.1 mg/L and 0.3 mg/L, respectively. The effluence reach the standard Ⅱ water quality of 《Environmental quality standard for surface water》 (GB 3838-2002).The effective operating time is at least 55 days.Iron-carbon method can be used as emergency process for tap water plant influent pretreatment to prevent high total phosphorus concentration effect of water stability. Moreover iron-carbon method has the advantages of low cost, simple operation, fast start-up and no secondary pollution. |
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