Electrocoagulation as post-treatment of the effluent from a vertical flow constructed wetland

ABSTRACT Electrocoagulation (EC) was applied as a tertiary treatment for the effluent of a vertical flow constructed wetland (VFCW). The EC system was composed of a cylindrical glass reactor (1 L) and aluminum electrodes connected to a DC power supply. The study was developed in two stages. In the first, the reactor operating conditions were set by a 32 (3×3) two-factor experiment, quantitative × quantitative, analyzing current intensity and time (current × time). Based on the results, the linear regression resulted in the combination of 1.3 A and 18 min, with an electric operation cost of 2.71 $.m−3. Next, the monitoring stage was conducted for four months, applying the EC under the established conditions. The mean removal efficiencies were 99.6% for P-PO43-, 20.6% for N-NO3−, 2.37 log of total coliforms, 2.35 log of Escherichia coli, 84.8% for chemical oxygen demand, 94.9% for turbidity, 95% for apparent color, an increase of 18.9% in pH and of 18.6% in temperature, and a decrease of 15.8% in electrical conductivity. The treatment showed high and homogeneous pollutant removal efficiencies, mainly for P-PO43-, indicating that the EC produces an effluent with lower polluting potential and it is recommended in the tertiary treatment of domestic wastewater.

摘要 本研究采用电凝法（Electrocoagulation, EC）作为垂直流人工湿地（vertical flow constructed wetland, VFCW）出水的深度处理工艺。该电凝系统由容积为1 L的圆柱形玻璃反应器与连接至直流电源的铝电极构成。实验分为两个阶段开展：第一阶段通过3²（3×3）双因素定量实验，考察电流强度、电解时间及其交互作用，以优化反应器运行参数。经线性回归分析得到最优工况为1.3 A与18 min，此时运行电耗为2.71美元·立方米⁻¹。第二阶段为工况验证监测阶段，持续四个月，按照上述优化工况实施电凝处理。结果显示，各污染物的平均去除率分别为：正磷酸盐（P-PO₄³⁻）99.6%、硝酸盐氮（N-NO₃⁻）20.6%、总大肠菌群对数去除率2.37、大肠埃希氏菌对数去除率2.35、化学需氧量84.8%、浊度94.9%、表观色度95%；同时出水pH值提升18.9%、水温升高18.6%，电导率降低15.8%。本工艺对污染物展现出高效且均匀的去除效果，尤其对正磷酸盐的去除效果突出，表明电凝法可产出污染潜能更低的出水，推荐应用于生活污水的三级处理环节。