Stein Otto R, Borden-Stewart Deborah J, Hook Paul B, Jones Warren L
Department of Civil Engineering and Center for Biofilm Engineering, Montana State University Bozeman, MT 59717-3900, USA.
Water Res. 2007 Aug;41(15):3440-8. doi: 10.1016/j.watres.2007.04.023. Epub 2007 May 1.
To characterize the effects of season, temperature, plant species, and chemical oxygen demand (COD) loading on sulfate reduction and metals removal in treatment wetlands we measured pore water redox potentials and concentrations of sulfate, sulfide, zinc and COD in subsurface wetland microcosms. Two batch incubations of 20 day duration were conducted in each of four seasons defined by temperature and daylight duration. Four treatments were compared: unplanted controls, Typha latifolia (broadleaf cattail), and Schoenoplectus acutus (hardstem bulrush), all at low COD loading (267 mg/L), plus bulrush at high COD loading (534 mg/L). Initial SO4-S and zinc concentrations were 67 and 24 mg/L, respectively. For all treatments, sulfate removal was least in winter (4 degrees C, plant dormancy) greatest in summer (24 degrees C, active plant growth) and intermediate in spring and fall (14 degrees C), but seasonal variation was greater in cattail, and especially, bulrush treatments. Redox measurements indicated that, in winter, plant-mediated oxygen transfer inhibited activity of sulfate reducing bacteria, exacerbating the reduction in sulfate removal due to temperature. Doubling the COD load in bulrush treatments increased sulfate removal by only 20-30% when averaged over all seasons and did not alter the basic pattern of seasonal variation, despite tempering the wintertime increase in redox potential. Seasonal and treatment effects on zinc removal were broadly consistent with sulfate removal and presumably reflected zinc-sulfide precipitation. Results strongly suggest that interactive effects of COD loading rate, temperature, season, and plant species control not only sulfate reduction and zinc sequestration, but also the balance of competition between various microbial consortia responsible for water treatment in constructed wetlands.
为了描述季节、温度、植物种类和化学需氧量（COD）负荷对处理湿地中硫酸盐还原和金属去除的影响，我们测量了地下湿地微观世界中的孔隙水氧化还原电位以及硫酸盐、硫化物、锌和COD的浓度。在由温度和日照时长定义的四个季节中，每个季节都进行了为期20天的两批培养。比较了四种处理方式：未种植植物的对照、宽叶香蒲（Typha latifolia）和硬茎芦苇（Schoenoplectus acutus），所有处理的COD负荷均较低（267毫克/升），外加高COD负荷（534毫克/升）的芦苇处理。初始SO4-S和锌浓度分别为67毫克/升和24毫克/升。对于所有处理方式，硫酸盐去除率在冬季（4摄氏度，植物休眠）最低，在夏季（24摄氏度，植物生长活跃）最高，在春季和秋季（14摄氏度）居中，但香蒲处理尤其是芦苇处理的季节变化更大。氧化还原测量表明，在冬季，植物介导的氧气转移抑制了硫酸盐还原菌的活性，加剧了因温度导致的硫酸盐去除率降低。芦苇处理中COD负荷加倍时，平均在所有季节中硫酸盐去除率仅增加了20%-30%，并且尽管缓和了冬季氧化还原电位的升高，但并未改变季节变化的基本模式。季节和处理方式对锌去除的影响与硫酸盐去除大致一致，可能反映了硫化锌沉淀。结果强烈表明，COD负荷率、温度、季节和植物种类的交互作用不仅控制着硫酸盐还原和锌螯合，还控制着人工湿地中负责水处理的各种微生物群落之间的竞争平衡。
