Wand H, Vacca G, Kuschk P, Krüger M, Kästner M
Saxon Institute of Applied Biotechnology, Permoserstrasse 15, 04318 Leipzig, Germany.
Water Res. 2007 Jan;41(1):159-67. doi: 10.1016/j.watres.2006.08.024. Epub 2006 Nov 7.
In order to diminish hygienic hazards from pathogens, the elimination of pathogenic bacteria in a pre-treatment step is important for the use of domestic wastewater for irrigation purposes. Therefore, we analysed the removal of bacteria in laboratory-scale model sand filters simulating vertical flow systems of constructed wetlands (CW). Sand-filled glass columns were planted with Juncus effusus or Phragmites australis and non-planted columns were used as controls. Processes of bacteria removal such as adsorption, lysis, and the biotic effects caused by plants, protozoa, and Bdellovibrio were studied with E. coli as a model bacterium. E. coli suspensions (10(8) cellsml(-1)) were trickled on the columns by intermittent loading under non-water-saturated operation conditions. In non-planted and sterilized sand columns, an initial removal of cells was observed in the range as expected by the adsorption capacity of the sand columns. After loading of the sand with cells, an increasing reduction of the cell concentrations by 3-4 orders of magnitude in the effluent was registered up to volumetric loads of more than 548mll(-1) day(-1) (230mm day(-1)). In planted columns, no higher levels of removal were observed. Predation by protozoa, which were found in concentrations up to 10(4)ml(-1) in the effluent, is considered to be the main reason for the elimination. However, Bdellovibrio bacteriovorus was also found in plaque-forming units of about 10(4)g(-1) sand, suggesting that this bacteriovorous bacterium plays an additional role in the removal process. In a second series of experiments, domestic wastewater was applied and removal efficiencies up to four orders of magnitude of the cfu's of coliform bacteria, faecal streptococci, and salmonellae were observed. Considering the transpiration of the plants, higher removal efficiencies were found in the planted variants. Protozoa and Bdellovibrio were detected in the domestic wastewater in varying concentrations, suggesting that predation and lysis were the major removal mechanisms.
为了减少病原体带来的卫生危害，在预处理步骤中消除致病细菌对于将生活污水用于灌溉目的而言至关重要。因此，我们在模拟人工湿地（CW）垂直流系统的实验室规模模型砂滤器中分析了细菌的去除情况。装有沙子的玻璃柱种植了灯心草或芦苇，未种植的柱子用作对照。以大肠杆菌作为模型细菌，研究了诸如吸附、裂解以及植物、原生动物和蛭弧菌引起的生物效应等细菌去除过程。在非水饱和运行条件下，通过间歇加载将大肠杆菌悬浮液（10⁸ 个细胞/毫升）滴加到柱子上。在未种植且经过灭菌的砂柱中，观察到细胞的初始去除量在砂柱吸附容量预期的范围内。在用细胞加载砂柱后，在高达548毫升/天（230毫米/天）的体积负荷下，流出物中细胞浓度降低了3 - 4个数量级。在种植的柱子中，未观察到更高水平的去除。在流出物中发现原生动物浓度高达10⁴ 个/毫升，其捕食被认为是去除的主要原因。然而，在约10⁴ 个/克砂的噬菌斑形成单位中也发现了蛭弧菌，这表明这种食细菌细菌在去除过程中起额外作用。在第二系列实验中，应用了生活污水，观察到大肠菌群、粪链球菌和沙门氏菌的菌落形成单位去除效率高达四个数量级。考虑到植物的蒸腾作用，在种植变体中发现了更高的去除效率。在生活污水中检测到不同浓度的原生动物和蛭弧菌，这表明捕食和裂解是主要的去除机制。
