极浅型潜流人工湿地改良风沙土时水力负荷的优化

发布时间：2018-09-08 15:30

【摘要】：对极浅型潜流人工湿地在同步处理城市污水和改良风沙土的关键运行参数即湿地水力负荷进行了研究,同时探讨了湿地填料风沙土中营养物质的富集特性。试验系统位于西安市某污水处理厂内,极浅型潜流人工湿地填料床深0.1 m,种植植物分别为高羊茅、黑麦草、狗牙根、芦苇和香蒲;对照组分别为1组填料床深0.1 m,填料同为风沙土、无栽培植物的慢速渗滤土地处理系统和2组填料床深0.6m湿地。0.6 m湿地的种植植物为狗牙根、高羊茅、黑麦草混种和芦苇、香蒲混种。试验系统进水为污水厂初沉池出水。主要研究内容包括:(1)极浅型潜流湿地夏季和冬季水力负荷的优化;(2)各湿地长期运行出水水质和风沙土中有机质、全氮和全磷的变化特征;(3)系统碳、氮和磷的迁移转化规律。主要得出以下结论:(1)夏季,极浅型潜流湿地正常运行、不出现局部漫流现象的最优水力负荷的上限为15 mm/d,其能维持正常运行水位的下限为7.5 mm/d。冬季,可满足湿地出水达标排放的上限为7.5 mm/d(其中COD和TN达到一级B、TP达到二级排放标准)。(2)0.1 m各湿地出水COD、TN和TP浓度均极显著低于原水(P=0.0000.01),其平均去除率分别在74.39%、68.60%和64.78%之上;0.1 m土地处理系统出水水质差,在运行2个月后即出现堵塞现象,需定期进行人工疏通;0.6 m湿地在运行8个月后出现堵塞,导致湿地运行方式由潜流转变为表面流。(3)各湿地风沙土中有机质、全氮和全磷含量与原土相比有极显著性差异(P=0.0000.01),表明各湿地有机质、全氮和全磷均有显著性增长,说明湿地可快速富集营养物质,有利于风沙土的快速改良。(4)0.1 m各湿地对COD、TN和TP处理效果好,长期运行稳定,且对风沙土中营养物质的富集速率较高,能够同步实现风沙土快速改良和污水净化的效果。(5)以黑麦草、高羊茅作为湿地栽培作物,具有较强的适应性,冬季仍能表现出旺盛的生长能力,且能够在风沙土表面形成一层致密的根系网,利于风沙土的固定,因此,可作为风沙土改良的优选植物。(6)通过对极浅型潜流湿地系统碳、氮和磷的物料平衡分析可知:微生物的降解作用是湿地除碳的主要途径。微生物的硝化和反硝化作用是湿地脱氮的最主要途径,其次是填料的富集作用,植物吸收作用只占2.05%~11.35%。填料富集作用是人工湿地系统除磷的主要途径,此外,植物吸收以及微生物同化作用也可去除少量的磷。
[Abstract]:The key operating parameters of the extremely shallow subsurface flow constructed wetland in simultaneous treatment of municipal sewage and improved wind-sand soil, I. e., the hydraulic load of the wetland, were studied. The enrichment characteristics of nutrients in the wind-sand soil filled with the wetland were also discussed. The test system is located in a sewage treatment plant in Xi'an. The filling bed depth of very shallow subsurface flow constructed wetland is 0.1 m. The planting plants are tall fescue, ryegrass, dogtooth, Reed and cattail respectively. In the control group, the filling bed depth was 0.1 m, the filling was wind sand soil, the slow infiltration land treatment system without cultivated plants, and the planting plants of the 0.6 m wetland with 0.6 m bed depth in the two groups were dogtooth, tall fescue, ryegrass mixed species and Reed. A mixture of cattails. The influent of the test system is the effluent of the primary settling tank of the wastewater treatment plant. The main research contents are as follows: (1) optimization of hydraulic load in summer and winter of extremely shallow subsurface flow wetland; (2) variation characteristics of effluent water quality and organic matter, total nitrogen and total phosphorus in aeolian sandy soil in long-term operation of each wetland; (3) migration and transformation of carbon, nitrogen and phosphorus in the system. The main conclusions are as follows: (1) in summer, the upper limit of optimal hydraulic load of extremely shallow subsurface flow wetland is 15 mm/d, and the lower limit of maintaining normal operating water level is 7.5 mm/d.. Winter, The upper limit to meet the discharge standard of wetland effluent was 7.5 mm/d (where COD and TN reached the second class). (2 discharge standard). The effluent COD,TN and TP concentrations of each wetland were significantly lower than that of raw water (P0. 0000. 01), and the average removal rates were above 74.39% and 64.78%, respectively. The effluent quality of 0.1 m land treatment system is poor. After 2 months of operation, the phenomenon of blockage occurs, and it is necessary to conduct manual dredging of 0.6 m wetland regularly after 8 months of operation, which results in the change of wetland operation mode from subsurface flow to surface flow. (3) Organic matter in the sandy soil of each wetland is changed from subsurface flow to surface flow. The contents of total nitrogen and total phosphorus were significantly different from those of the original soil (P0. 0000.01), which indicated that the organic matter, total nitrogen and total phosphorus of the wetland increased significantly, indicating that the wetland could rapidly enrich nutrients. It is beneficial to the rapid improvement of wind-sand soil. (4) 0.1 m wetland has good effect on COD,TN and TP treatment, stable operation for a long time, and high enrichment rate of nutrients in wind-sand soil. The effects of rapid improvement of wind-sand soil and purification of sewage can be achieved simultaneously. (5) using ryegrass and tall fescue as cultivation crops in wetland has strong adaptability, and still shows strong growth ability in winter. And it can form a dense root net on the surface of wind-sand soil, which is beneficial to the fixation of wind-sand soil. Therefore, it can be used as an excellent plant for improving wind-sand soil. (6) the carbon of extremely shallow subsurface flow wetland system, The material balance analysis of nitrogen and phosphorus shows that the degradation of microorganisms is the main way to remove carbon from wetland. Nitrification and denitrification of microorganisms were the main way of denitrification in wetland, followed by enrichment of fillers, and plant absorption accounted for only 2.05% 11.35%. The enrichment of fillers is the main way to remove phosphorus in constructed wetland system. In addition, plant absorption and microbial assimilation can also remove a small amount of phosphorus.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S156

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