| Generally we take chemical method to treat electroplate wastewater in electroplate plant. Though this developed technology could take fast effects, there are some defects including instability of effluent quality and running costs, so it is necessary to search a new practical method to solve this problem. The study and application of wastewater treatment with constructed wetland started in the end of 1970s, which has many advantages with low capital investment, low energy consumption, low treatment cost, easy maintenance and operation, and high quality effluent. Though it is indicated that constructed wetland is a suitable technology for China, the study application of constructed wetland technology is starting stage. The researches on electroplate wastewater treatment by constructed wetland are seldom.In this paper, we used subsurface flow pilot-scale constructed wetland and combined constructed wetland for advanced treatment of electroplate wastewater after chemical method, and took a series of experiment involving the aspects of removal efficiency and removal way by pilot-scale wetland, effect factors of pilot-scale wetland, removal efficiency in different area of pilot-scale wetland, first-order chemical kinetic model and removal efficiency by combined constructed wetland. The major results were summarized as follows: 1. Removal efficiency and removal way of electroplate wastewater were investigated by subsurface flow pilot-scale wetland. The results showed that the wetland had significant removal efficiency for Cr6+,Zn2+,Mn2+,Cu2+, especially for Cu2+. Compare with removal efficiency three wetlands, plants wetland > non-plants wetland > sterilization wetland. In addition, the high removal efficiency of Cr6+,Zn2+,Mn2+,Cu2+ were all observed in three wetlands. Therefore, we can concluded that the removal of heavy metals resulted from the combined effects of bed medium, plants and metal sedimentation, and bed medium played a most important role.2. Major effect factors of performance were investigated in pilot-scale wetland, which showed that hydraulic load, influent concentration and recirculation affected electroplate wastewater removal. The removal efficiency of Cr6+,Zn2+,Mn(2+,Cu2+ increased first and decreased afterwards with hydraulic load decreased, and the maximum efficiency was in hydraulic load of 0.27 m3/(m2·h). So the optimal hydraulic load in this wetland was 0.27 m3 /(m2·h). The removal efficiency of heavy metals increased when influent concentration was low and decreased with the high influent concentration, but the influence was much smaller, relatively with drastic changes in influent concentration. The experiment also indicated that recirculation was an effective measure to improve the disposal ability of constructed wetland.3. The study was carried out to investigated the disposing rules of Cr6+,Zn2+,Mn2+,Cu2+ in different area of pilot-scale constructed wetland. The results showed the maximum disposing velocity was existed in 35cm distances far away the inflow spot. Then the velocity had a little increased in 55cm distance and gradually kept stable after that. This meant the majority of electroplate wastewater was treated in 35cm-45cm distances far away the inflow spot. The results also indicated the maximum disposing velocity was existed in 30cm depths far away the bottom when wastewater flowed from top to bottom. Besides the removal efficiency in 10cm depths' was greater than 45cm depths'. This meant the majority of electroplate wastewater was treated under 30cm depths far away the bottom.4. The first-order chemical kinetic model of Cr6+,Zn2+,Mn2+,Cu2+was discussed based on the simulation experiment of pilot-scale. The results showed that the first-order chemical kinetic model could be used to simulate the disposing rules in the subsurface flow pilot-scale constructed wetland. The relationship between the concentrations of Cr6+,Zn2+,Mn2+,Cu2+ and time followed the linear equation. The values of relationship equation (R2) were 0.9201, 0.9273, 0.9316 and 0.9495, respectively. Accordingly, the values of disposal velocity equation (K) were 0.0792, 0.0801, 0.0525 and 0.085, respectively.5. A vertical-horizontal subsurface flow combined constructed wetland was used in this investigation for advanced treatment of electroplate wastewater from Qinghu electroplate factory in Jinhua. The results showed this combined constructed wetland had significant removal efficiency. The removal efficiency of Zn2+,Cu2+,Mn2+,Cr6+ were 70%-88%, COD was 60%. Cu2+,Mn2+and COD can meet "Integrated wastewater discharge standard" (GB8978-1996), but Zn2+ and Cr6+ can not. It was also demonstrated an optimal disposal time was existed in this combined constructed wetland. Hydraulic loading had a greater effect on COD than heavy metals. High removal efficiency can be observed for heavy metals even under high hydraulic loading.
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