Results and discussion3.1 Effect of CW on the removal of HMs from YRU waterA summary of the concentrations of the main contaminations in the samples The YR and CW water are shown in Table 1. The concentration of HM in the CW system water was much lower than that of the YR throughout the experimental period. The average removal rates (RR) in CW were 86.2%, 61.7%, 82.9% and 76.7% for Cd, Cu, Pb and Zn, respectively (this is i.e. in the order Cd>Pb>Zn>Cu). , showing that CW effectively removed HMs from YR water. Importantly, the concentrations of all studied HMs were reduced by CW below the permissible limits set in the Tier III guidelines of China Surface Water Environmental Quality Standard (GB 3838- 2002). Our results agree with previously published results [19], confirming that CWs are effective in removing HMs from contaminated wastewater and that RRs are different for different metals. Furthermore, it appears from the current results that the efficiency of wastewater removal on HMs would be different due to the state of water pollution in the year as well as the growth cycle of cattails. That is, during stages III to V, the removal efficiency was relatively lower than that of stages I to II, this was attributed to the relatively slow growth of cattails which in turn , would produce less biomass. This has been confirmed by previous studies (Rousseaua et al. 2008; Si et al. 2011). Concentrations of Cd, Cu, Pb, and Zn in YR and CW wetland substrate samples are shown in Table 2. HM concentrations were significantly higher in YR sludge samples than in CW substrate samples, except Pb, and furthermore, no significant variation in water concentration YR......middle of paper......etlands coupled with micro-electric field for treatment wastewater contaminating heavy metals. Ecological engineering. 37(12), 2061-2065, 2011.32. Szyczewski, P., Siepak, J., Niedzielski, P., Sobczynski, T. Heavy metal research in Poland. Pol. Haras J. Approx. 18(5), 755-768, 2009.33. Wang, Y., Chen, P., Cui, R., Si, W., Zhang, Y., Ji, W. Concentrations of heavy metals in water, sediment and tissues of two fish species (Triplohysa pappenheimi, Gobio hwanghensis) from the Lanzhou section of the Yellow River, China. Evaluation Environ Monit. 165(1-4), 97-102, 2010.34. Zhang, T., Xu, D., He, F., Zhang, Y., Wu, Z. Application of artificial wetlands for water pollution control in China between 1990 and 2010. Ecological engineering. 47(0), 189-197, 2012.35. Zhao, AF Preliminary studies on the embryonic development of the toad (Bufo raddei). Chinese Journal of Zoology, 26, 11-16, 1991.