二级生物措施削减面源污染负荷的初步试验

2012年6-11月在武汉市江夏区梁子湖周边小流域的面源污染汇流区建设二级人工湿地生物净化系统,开展面源污水净化试验。试验区总面积4 657 m2,其中一级人工湿地面积2 844 m2、二级人工湿地面积1 813 m2。6-7月为试验区试运行时期,试验区未栽种水生植物和放养水生动物;8-11月为试验区运行时期,其中8-9月为水生植物净化期,10-11月为水生植物+水生动物净化期。8月初,一级人工湿地栽种鸢尾(Iris tectorum)、香蒲(Typha orientalis Presl)、梭鱼草(Pontederia cordata)和再力花(Thalia dealbata),二级人工湿地栽种美人蕉(Canna indica L)、香蒲、鸢尾和睡莲(Nymphaea alba);9月底在二级人工湿地中投放三角帆蚌(Hyriopsis cumingii)1 747个、1.4个/m3,放养鲢(Hypophthalmichthy smolitrix)280尾、鳙(Hypophthalmichthys nobilis)80尾,规格80~120 g/尾,密度28.3 g/m3。结果表明,试验区对面源污水中总氮、总磷和叶绿素的去除效果较好。试验区对总氮、总磷、氨氮、叶绿素、高锰酸盐指数的去除率,8-9月分别为24.9%、42.6%、20.0%、21.4%和8.2%,10-11月分别为33.0%、45.2%、17.9%、34.3%和11.6%。

Assessment of a Two-stage Constructed Wetland for Removal of Non-point Source Pollutants

Constructed wetlands are widely used for removing and mitigating non-point source pollution in aquatic systems. The plants in a constructed wetland play the primary role in water purification. Research has shown that the purification capacity of constructed wetlands cannot be increased much by manipulation of plant species due to limits on the rate of nutrient uptake and primary production. However, research has also shown that adding aquatic animals to the wetland can enhance water purification and increase water clarity. In this study, we assessed the effectiveness of a two-stage constructed wetland for removal of non-point source pollutants. The study was carried out in Wuhan from June to November of 2012 on a constructed wetland receiving 120-900m3/d of runoff water from Liangzi Lake. The study area was 4657 m2, with a 2844 m2 first-stage wetland and a 1813 m2 second-stage wetland. In June and July, the wetland had no aquatic plants or animals present. In early August, Iris tectorum, Typha orientalis Presl, Pontederia cordata and Thalia dealbata were planted in the first-stage of the wetland and Canna indica L, Typha orientalis Presl, Iris tectorum and Nymphaea alba were planted in the second-stage of the wetland. During August and September, water was tested while being purified by aquatic plants. At the end of September, three filter feeding animal species were added to the second-stage wetland, one mussel species and two species of carp; Hyriopsis cumingii (number, 1747; density, 1.4ind/m3), 280 Hypophthalmichthy smolitrix and 80 Hypophthalmichthys nobilis (initial weight, 80-120g; density, 28.3g/m3). During October and November, water purification was carried out by both aquatic plants and animals. Physicochemical parameters of the water body in the experimental zone were monitored from June to November 2012. During August and September, the removal rates of TN, TP, NH3-N, Chl-a and CODMn were 24.9%, 42.6%, 20.0%, 21.4% and 8.2%, respectively. During October and November, the removal rates of those parameters were 33.0%, 45.2%, 17.9%, 34.3% and 11.6%. Results indicate that the biological purification system was quite effective at removing TN, TP and Chl-a. Integrated analyses of all indices shows that biological treatment effectively removed non-point source pollutants and that the aquatic animals enhanced water purification in the constructed wetland ecosystem.