回流立式组合人工湿地对农村混合废水中重金属的净化效果

针对农村分散式混合废水中的重金属难以集中处理的问题,提出一种占地面积小、操作灵活、维护简单的新型回流立式组合人工湿地工艺,研究其对重金属混合废水的处理效果以及进水水质与运行条件对重金属去除的影响。结果显示,回流立式组合人工湿地在运行时间为6 h,回流周期T=30 min的条件下对CODCr、TN、TP和TSS的平均去除率分别为82.83%、27.67%、64.64%和92.58%,对As、Cd、Pb、Cu和Zn的平均去除率分别为50.01%、62.43%、91.02%、63.37%和51.92%;其去除负荷高达92.4、12.1、160.9、1 214.9、1 989.0 mg·m-2·d-1,约为其他研究平均值的4～27倍。进水pH和CODCr的波动以及回流周期的变化对重金属去除无显著影响(P0.05);将运行时间由6 h延长至24 h时,重金属的去除效率有明显的提高(Zn除外)。回流立式组合人工湿地对重金属的去除快速高效、去除负荷高,在农村分散式含重金属混合废水处理方面具有较好的利用前景。

Application of a recycled standing combined constructed wetland system for the treatment of heavy metals from mixed wastewater in a rural area

With the aim to solve problems caused by disordered drainage of heavy metals from mixed wastewater and the difficulty of centralized treatment in rural areas, a new type of recycled standing combined constructed wetland system (RSCCWS) with the advantages of a small footprint, simple operation, and easy maintenance was used in this study to treat heavy metals wastewater. The objectives of this research were to study the treatment of a RSCCWS for mixed wastewater containing heavy metals and general water pollutants and the effect of different operating conditions on the RSCCWS performance. The results showed that average removal efficiencies of COD_Cr, TN, TP, and TSS were 82.83%, 27.67%, 64.64%, and 92.58%, respectively, under the operation conditions of a 6-hour run time and 30-minute circulation time. Simultaneously, the average removal efficiencies of As, Cd, Pb, Cu, and Zn were 50.01%, 62.43%, 91.02%, 63.37%, and 51.92%, respectively. Moreover, the removal loads of heavy metals were up to 2.4, 12.1, 160.9, 1 214.9, and 1 989.0 mg·m^-2·d^-1, respectively, which were 4 to 27 times greater compared with those of other research. The changes in pH, COD_Cr, and circulation time had no significant effect on the removal efficiency of heavy metals (P>0.05). When the run time was extended to 24 hours, increased removal rates of four kinds of heavy metals, except Zn, were observed compared with those of the 6-hour run time. With the advantages of high and quick removal of heavy metals, the RSCCWS has great potential in treating heavy metals from mixed wastewater in rural areas.