Visesmanee Varangkana, Polprasert Chongrak, Parkpian Preeda
Inter-University Program on Environmental Toxicology, Technology and Management, School of Environmental Resources and Development, Asian Institute of Technology, Klong Luang, Pathumthani, Thailand.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Jun;43(7):765-71. doi: 10.1080/10934520801960078.
This study was conducted to investigate the long-term performance of subsurface-flow constructed wetland (SFCW) units treating a wastewater containing cadmium (Cd). The hydraulic retention time (HRT) was found to have significant effects on the SFCW performance, especially on Cd removal. During the 320 days of Cd feeding, the HRTs of 1, 3, 5 and 8 days resulted in the Cd removal efficiencies of 50, 90, 99 and 99%, respectively. The actual Cd breakthrough times in the SFCW effluent were found to be longer than the theoretical values calculated from the maximum adsorption capacities only, especially at the HRTs longer than 1 day, and were dependent on the operating HRT and Cd loading. Other mechanisms such as filtration, sedimentation and plant uptake were also responsible for Cd removal in the SFCW beds. The extents of Cd plant uptake were 21 and 6% of the Cd inputs for the SFCW units operating at the HRTs of 3 and 1 days, respectively. Based on Cd mass balance and fractionation analysis, the SFCW media were found to be most effective in Cd removal through adsorption of the residual and Fe/Mn oxide bound fractions. The results of this long-term study re-affirmed the necessity to determine actual breakthrough times of Cd or other heavy metals in the SFCW effluent which are dependent on HRT and Cd loading and are usually longer than the theoretical values calculated from the maximum adsorption capacity only.
本研究旨在调查潜流人工湿地（SFCW）单元处理含镉（Cd）废水的长期性能。发现水力停留时间（HRT）对SFCW性能有显著影响，尤其是对Cd的去除。在320天的Cd投加期间，1、3、5和8天的HRT分别导致Cd去除效率为50%、90%、99%和99%。发现SFCW出水的实际Cd穿透时间比仅根据最大吸附容量计算的理论值更长，尤其是在HRT大于1天的情况下，并且取决于运行HRT和Cd负荷。其他机制如过滤、沉淀和植物吸收也对SFCW床中Cd的去除有作用。对于在3天和1天HRT运行的SFCW单元，Cd植物吸收量分别占Cd输入量的21%和6%。基于Cd质量平衡和分级分析，发现SFCW介质通过吸附残留和铁/锰氧化物结合部分对Cd去除最有效。这项长期研究的结果再次证实，有必要确定SFCW出水中Cd或其他重金属的实际穿透时间，这些时间取决于HRT和Cd负荷，并且通常比仅根据最大吸附容量计算的理论值更长。
