生物塘-人工湿地工艺去除农田灌溉水中镉污染的效果

通过野外大田试验,探讨了生物塘-人工湿地工艺去除农田灌溉水中Cd污染的效果,并进一步分析了水力停留时间对Cd净化效果的影响及净化效果的日变化规律。结果表明:试验区灌溉水中全量Cd平均浓度为13.92 μg/L,是GB 5084—2005《农田灌溉水质标准》中Cd浓度限值的1.39倍,且以溶解态Cd为主,约占77.8%;经生物塘-人工湿地工艺处理后全量Cd平均去除率为42.0%,出水达标天数率为85.2%;组合工艺的Cd去除率随水力停留时间的延长呈先升高后降低趋势,最佳停留时间约为19 h;生物塘和人工湿地的Cd去除率日变化规律均呈早晚低、中午高的单峰曲线,Cd最大去除率出现在13:00左右。

The performance of combined process of biological pond and constructed wetland for cadmium removal from irrigation water

The cadmium removal effect in irrigation water by the combined process of biological pond and constructed wetland was investigated through a field experiment. The influence of hydraulic retention time (HRT) on the cadmium removal effect and the daily variation rules of purification effect were further analyzed. Results show that the average concentration of total cadmium in irrigation water of the experiment area is 13.92 μg/L, which is 1.39 times of the cadmium limit in Standards for Irrigation Water Quality (GB 5084-2005). Most of them are dissolved cadmium, accounting for 77.8%. After the treatment by the combined process, the average removal rate of total cadmium reaches 42.0%, and the effluent in 85.2% of days during experiment can reach the standard. With the extension of the HRT, the cadmium removal rate of the combined process increases at first and then decreases, and the optimal HRT found to be 19 hours. In addition, the daily variation rules of cadmium removal rate by biological pond and constructed wetland both present as a single peak curve which shows lower value in the morning and evening but higher value at noon, and meanwhile the highest efficiency appears at 13:00.