Research progress of constructed wetland treating agricultural runoff
Research progress of constructed wetland treating agricultural runoff
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作者：
Lu Shao
人工湿地（CW）是一种独特的土壤-植物-微生物系统，根据不同的水流方向，人工湿地可分为自由表面湿地（FWS）和地下流湿地（SFW）。 FWS投资低，但用地量大，冬季运行需要特殊考虑。 SFW具有较好的温度和保水能力，卫生条件较好，但投资高，堵塞风险高。 SFW分为水平SF（HF）和垂直SF（VF）。 HF床供氧较弱，适用于去除SS和BOD，但不适用于去除氨。 VF床供氧良好，适用于硝化和BOD去除，但不适用于SS。 VF施工费用高，且容易堵塞。 FWS分为浮游植物CW、沉水植物CW和出水植物CW。农业径流（AR）的成分比较复杂，主要包括农业排放、灌溉残留水、村庄废水、畜禽废水和部分雨水径流。 AR来源具有分布广、数量大、分散、峰值间歇、无机沉降负荷高等特点。我国很多农村经济基础薄弱，管理水平低。农村的一些土地，包括低地、低产田和公共用地，可以用于生态环境保护。废水收集系统不够完善。传统的AR处理废水处理技术，收水难度较大。维护管理复杂，投资大，运行成本高。 CW抗冲击载荷能力强，投资和运行成本低，维护管理方便，但对土地利用要求较高。因此，CW适合在有土地的农村地区进行污水处理。本文对1982年以来CW技术治疗AR的研究和应用进行了总结。结合水质、水量规律和农村特点，进行了一些设计和技术改造。许多研究人员对CW对氮、磷、碳以及杀虫剂和农药的去除效果进行了研究。 CW的运行、维护和管理重点是泥沙积累、水收支、去除效率判断、植物收获和成本分析。 CW性能的权衡，应基于流入和流出污染物负荷，而不是基于流入和流出污染物浓度。 CW在AR控制方面具有良好的应用前景。 CW 适当的设计和管理可以实现非成本绩效或创收绩效。
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.