人工湿地系统水质净化技术的工艺设计刘全中 提要 利用植物根系和微生物的作用并经多层过滤,使水质得到净化,可有效地提高水资源的利用率。
着重介绍了人工湿地系统水质净化技术的工艺原理、流程、特点及设计要点。
关键词 人工湿地 生态工程 工艺原理 设计要点0 前言通常的污水处理方法技术要求高,管理复杂,运行费用、能耗高。
而人工湿地系统具有建造成本较低,运行、管理费用低,能耗低,操作简单等优点。
人工湿地系统可以处理被污染的地表水或市政污水,经过处理后出水水质可以达到地面水水质标准,可应用于饮用水源或景观用水的湖泊、水库或河流中。
因此特别适合处理饮用水源或景观用水区附近的污水,或者为这些水体提供清洁的水量补充。
1 工艺原理图1 人工湿地系统工艺原理示意人工湿地系统是一种生态系统,系统建有一系列水平高差由高到低的植物池,池内填有特殊的填料,在填料上种植特定的湿地植物,当污水在重力作用下依次通过阶梯式植物池,污染物质和营养被植物系统吸收或分解,使水质得到净化(见图1)。
特殊填料是由两部分组成。
网状隔膜下是用不同级配的砾石滤料,网状隔膜上部是特殊土壤,是采用一定材料配比制成的生物载体,既适宜湿地植物的生长,又有一定的孔隙。
污水中的有机物在特殊土壤中被吸附、凝集并在土壤中微生物的作用下得到降解;同时污水中的氮、磷、钾等作为植物生长所需的营养物质被湿地植物根系吸收利用。
经过土壤和土壤中的微生物的吸附降解作用,以及填料的渗滤作用和植物的吸收作用,最终使进入湿地系统的污水得到有效净化。
2 工艺流程及工艺特点211 工艺流程人工湿地系统主要由三部分组成:(1)收集和预处理系统。
由污水集水管网、污水集水池、格栅和沉淀池等组成。
如果取水于被污染的河流,可取消污水集水管网和污水集水池。
(2)配水和集水系统。
由配水井、配水槽、配水管网、布水管、集水管和集水池组成。
(3)植物池。
根据出水水质要求,可设计一级或多级植物池,污水经过滤池多次正向逆向反复过滤。
植物池内可种植美人焦、水葱、芦竹、千屈菜等。
人工湿地系统工艺流程见图2。
图2 人工湿地系统工艺流程示意212 工艺特点人工湿地技术与传统污水处理工艺相比,具有以下显著特点:(1)处理规模根据需要可大可小,污水水源可就地收集,就地处理和就地利用。
(2)取材方便,便于施工,处理构筑物、处理设备少。
给水排水 V ol 127 N o 18 200135 (3)由于植物池内种植的是湿地植物,如果选择合适的植物品种可以美化环境,改善地面景观。
(4)运行管理方便,只需要工人进行简单的操作和维护管理,与相同规模的传统工艺比,人员可减少80%以上。
(5)由于人工湿地工艺无需曝气、投加药剂和回流污泥,也没有剩余污泥产生,因而可大大节省运行费用,通常只消耗少量电能,用于提高进水水位(如果水位无需提升则无此项费用),处理费用一般不会超过0105元/m3。
(6)处理效果好,出水水质可以因植物池内填料的不同达到《地面水环境质量标准》(G B3838-88)Ⅱ类至Ⅴ类标准,处理后的水可用作饮用水水源和景观用水的湖泊、水库或河流中,亦可用作冲厕、洗车、灌溉、绿化及工业回用等。
3 工艺设计与实际应用311 一般原则(1)根据进水水源的污染程度和固体悬浮物的含量来确定污水在沉淀池的停留时间,预处理设施主要包括:污水集水池、提升设备、格栅和沉淀池。
(2)植物池内特殊土壤渗流系数应满足k>1×10-7m/s。
(3)植物池底部和四周宜采用隔水材料制成的不透水层,以便于净化后的水回收利用。
(4)为保证每支配水支管进水流量的均匀性,宜在植物池前设置一级或二级配水槽,再通过配水管网到达布水管,布水管间距不超过2m,每支布水管长不超过6m。
(5)为保证系统的运行稳定性,防止堵塞,调节配水量,每支配水管前装设阀门,集水管上装设反冲洗装置,进行气洗或气水反冲洗。
(6)配水槽上设置溢流管和排空管,以便水位过高时有组织地回流到集水池中。
312 设计要点31211 预处理系统若污水中污染物和固体悬浮物含量高时需设置格栅和沉淀池。
格栅间隙d=20mm,沉淀池表面负荷q=115～310m3/(m2・h),停留时间t=115～210h。
31212 沉淀系统(1)污水经配水槽流进配水管,再经布水管上的布水孔流经植物池,流经湿地的水量同布水管数量以及布水孔的间隙和大小有关,一般流出布水孔的水流流速为012m/s≤v≤016m/s,流速过低会导致污染物沉淀以及管孔堵塞。
(2)湿地系统的主要设计参数。
设计进水水质: BOD≤200mg/L,SS≤120mg/L;BOD表面负荷: N a≤10g/(m2・d),水力负荷:N w≤70L/(m3・d)。
(3)湿地系统的主要构筑物。
配水池及植物池采用钢筋混凝土;配水管、布水管、集水管一般采用PVC-U管;滤料采用一定配比的砂、砾石;特殊土壤选用一定材料,经一定配比制成的微生物载体;湿地植物选用适合当地生长又具有一定景观效果的水生植物。
313 实际应用效果深圳市环境科学研究所于1999年设计并建成的“洪湖人工湿地系统水质净化工程”,经实际运行效果很好(见表1)。
表1 洪湖人工湿地系统水质净化效果项目DO/mg/LCOD Mn/mg/LBOD/mg/LTP/mg/LNH3-N/mg/L 原水014738147381653108201172系统出水6182617151470136101030去除率/%8216851886128216 注:采样时间为1999年11月30日。
4 结语(1)人工湿地系统水质净化技术是一种生态工程方法,该技术简便易行,工艺先进,运行可靠,操作简单,运行管理费用低廉,并不产生剩余污泥。
(2)因植物生长的环境温度不宜低于5℃,因而该技术适合于热带和亚热带区域的水质净化。
(3)该处理系统的缺点是占地面积较大,易滋生蚊蝇。
⊙作者通讯处:518018深圳市城市绿化管理处 电话:(0755)3211719 收稿日期:20002122536 给水排水 V ol127 N o18 2001WATER&WASTEWATER ENGINEERING Vol127No18August2001ABSTRACTS…………………………………………On Advanced T reatment of High Q u ality Drinking W ater Chen Xiangming et al(1) Abstract:Nanofiltration has been adopted to treat slightly organics polluted water in a city water distribution net2 work.By this way the hazard substances are removed and the favorable elements reserved.The out p ut water is good enough to meet the requirement of high quality drinking water.………………………………………On the E levated R oad R ain w ater Drainage F acility in Shanghai W ang Ronghe et al(5) Abstract:Under the research and investigation on the inner ring elevated road of Shanghai,this paper begins with the infections of the road slop to the storm catchment’s distance.It presents the relationship of catchment’s distance, time and rainstorm intension.It also presents the relationship of road slop,rainfall and rainwater de pth of the road and the relationship of gully,rainfall and the gully overflow.This paper presents an idea that we should se parate the drainage system into4parts to compute.It concludes that the type and size of gully,short drainpipe and suspended drainpipe are the main infectors for the storm drainage system of the elevated road.…………………On Purif ication of Slightly Polluted R a w W ater by Coagulant and microf iltration Process Mo L i et al(12) Abstract:By an improved jar test the suitable dosage of coagulant PAC for a combination process of coagulation and microfiltration(MF)was determined as2～3mg/L.Under this dosage condition,a laboratory test of coagulation2MF process was continuously conducted to treat slightly polluted raw water.It was found that the removal ratios were85%～95%,37%～52%and58%～81%for turbidity,OC and UV254respectively.These were24%and26%higher for OC and UV254respectively than those of the direct membrane filtration process without coagulation.In the continuous operation,the characteristics of MF fell down fast at beginning and then decreased slowly and went stable.At the stable period,MF characteristics of the coagulation2MF process were found to be lower than that of the membrane filtration without coagulation.The mechanism needs to be studied further.……………………………………Sludge Dew atering Operation in U rb an W astew ater T reatment Plant Zhao Fuxin et al(16) Abstract:The operating and management of sludge dewatering facility serving for A2/O process in the urban WTP in Baoding City are presented.Factors,which influence the sludge dewatering,are discussed and an optimized manipu2 lation for this unit operation has been obtained.By this way the sludge is dewatered duly and the water content of the sludge cake is in the range of75%to80%.The ex pense for chemical dosage decreases because the consum ption of cation coagulant polyacrylamide(PAM)is reduced.The management of sludge dewatering operation is also reviewed in this paper.Study on Computational Method for On2Line N od al Demand Forecasting in Microcosmic Model of W ater Supply N etw ork ………………………………………………………………………………………………………………Tao Jianke et al(25) Abstract:In this article collating hour system water demand data,forecasting hour system demand and making patterns of water consumption and calculating nodal water demand forecasting value researched area are elaborated.On this basis a microcosmic mathematical model of water su pply network had been established for on2line computing of nodal water demand.This method has been verified in practice.…………………………………………Process Design of Artif icial Wetland S ystem W ater Purif ication L iu Quanz hong(35) Abstract:The utilization of nature water resource will be im proved because the water could be purified through the biological function of microbes living around the root system of plants and the multi2layer filtration of soil in the wetland circumstance.In this paper the mechanism,process and feature of wetland purification are presented emphatically.The design of artificial wetland system is also described with a practical wastewater treatment project with capacity of1000 m3per day.……………………………………………………………W ater Dechlorination by K DF55Filtration Zhang S houkai et al(37) Abstract:The residual chlorine in water could be changed into Cl anion by electro2chemical reaction(oxidation reduction)on K DF55filtration medium,which is made of high pure Cu/Zn alloy.The mechanism and experiment are introduced and the chlorine removal com parison test by K DF55and granulated activated carbon is listed with two practi2 cal examples.T reatment of Ash2W ashing W astew ater by a High2E ff iciency Solid/Liquid Separator Using Fluidized Pellet B ed T echnique ………………………………………………………………………………………………………W ang Xiaochang et al(39) Abstract:A high2efficiency solid/liquid separator was developed using fluidized pellet bed technique and used for the。