人工湿地处理农业径流的研究进展

人工湿地（CW）是独特的土壤-植物-微生物-动物系统。按水流方式分为表面流湿地（FWS）和潜流湿地（SFW）。FWS投资低，但占地大，低温地区冬季运行需要独特的考虑。SFW的保温保水效果好，卫生条件较好，但投资高，易堵塞。SFW分为水平潜流湿地（HF）和垂直潜流湿地（VF）。HF床供氧较差，适于去除SS和BOD，但NH3-N的去除较差。VF床供氧好，占地小，适于硝化和去除BOD，但对SS的去除不如HF床，而且构建费高，易堵塞。FWS按系统中的主体植物的不同分为大型自由漂浮植物湿地、大型沉水植物湿地和大型挺水植物湿地。农业径流（AR）由农田排水、灌溉余水、村落污水、畜禽养殖污水和部分雨水径流组成。其污水源具有面广、量大、分散、间歇的峰值和高无机沉淀物负荷的特点。中国大多数农村经济基础薄弱，管理水平不高。农村中的低洼地、低产田和公共用地均可作为生态环境保护用地。农村的污水收集系统欠完善。传统污水处理技术处理AR时难度大、维护管理复杂、投资和运行费高。而CW的耐冲击负荷能力强、投资低、运行费低、维护管理简便，但占地较大。因此CW适合于有地可用的农村的AR的处理。小结了1982年起CW技术在AR处理中的研究和应用。已有研究结合AR的水质、水量规律及农村的特点，进行了CW的设计与工艺改进。对氮、磷、有机物、农药和杀虫剂等污染物的去除效果有较多的研究。关于CW的运行、维护和管理的研究有沉积物积累、水量平衡、去除效果的衡量、植物收割和费用分析。CW的运行效果的衡量应当基于进出水负荷量而非基于进出水浓度。总之CW在AR污染控制中具有良好的应用前景。CW经合理设计和管理后有望实现“零费用运行”或者“盈利性运行”。

Research progress of constructed wetland treating agricultural runoff

Constructed wetland (CW) is unique soil-plant-microbe-system, CW can be divided into free surface CW (FWS) and subsurface flow CW (SFW) according to various water flow direction. FWS has low investment but large land consumption, and need unique consideration in winter for its operation. SFW have better temperature and water maintain capability, better sanitary condition, but high investment and high risk of clogging. SFW is divided into horizontal SF (HF) and vertical SF (VF). HF bed has weak oxygen supply, is suitable for SS and BOD removal, but not for ammonia removal. VF bed has sound oxygen supply, is suitable for nitrification and BOD removal, but not for SS. VF has high construction fee and is easy for clogging. FWS is divided into floating helophyte CW, submerged helophyte CW and emerged helophyte CW. Agricultural runoff (AR) has relative sophisticated composition, which mainly including agricultural discharge, irrigation residual water, village wastewater, poultry and animal wastewater and some rain-water runoff. Source of AR own characteristics of widespread distribution, large quantity, dispersion, intermittent peak value and high inorganic deposition load. Lots of rural in China have weak economic foundation and low management level. Some lands in the rural, including low land, low-producing farmland and public land, can be utilized for eco-environmental protection. Wastewater collection systems are under-perfect. Traditional wastewater treatment technology for AR treatment will have large difficulty for water collection. It also needs sophisticated maintenance and management, high investment and high running cost. CW has strong impact load resistant capability, low investment and running cost, easy maintenance and management, but has high land use requirement. Thus CW is suitable for wastewater treatment in rural with land available. Study and application of CW technology for AR treatment since 1982 were summarized in this paper. Some design and technology modification have been made based on combined water quality, water quantity regularity and characteristics of rural. Effects of nitrogen, phosphorus, carbon, insecticide and pesticide removal by CW were made by many researchers. Operation, maintenance and management of CW were focused on the accumulation of sediment, water budget, judge of removal efficiency, plant harvesting and cost analysis. The weigh of performance of CW, should be based on the inflow and outflow contaminants load but not on the inflow and outflow contaminants concentration. CW has sound application foreground for control of AR. CW Appropriately designed and managed can realize the non-cost performance or revenue-producing performance.