【作者】 张艳丽；

【导师】 吴晓芙； 胡曰利；

【作者基本信息】 中南林业科技大学 ， 环境科学， 2007， 硕士

【摘要】 水资源的日益短缺和水环境的污染制约了人类社会和经济的可持续性发展。特别是随着工业化进程的加快,大量的含重金属废水被直接排入江河湖泊造成水体重金属含量急剧升高,导致我国各大水系受到不同程度的重金属污染,其中Zn、Pb、Cd、Cu、Cr等元素污染严重。水体重金属污染不仅加剧了可用水资源的短缺,而且直接影响到饮水安全、粮食生产和农作物安全,最终危害人类健康。因此探寻多元化的治理重金属废水方法成为世界各国治理环境的一个重要方向。人工湿地技术是20世纪70年代发展起来的一种废水处理新技术,由于其具有投资少、能耗低、效果好、运行管理简单且处理彻底、不产生二次污染等优点成为国内外污水处理技术中的研究热点。近年来的一些研究表明人工湿地独特而复杂的净化机理能够在含重金属工业废水的处理中发挥重要作用。有效降低废水中的重金属离子浓度是治理重金属废水的关键,其中基质吸附和植物吸收作用对重金属离子的去除是最主要的途径之一,因此基质和植物的选择及其吸附/吸收行为的研究在应用人工湿地治理重金属废水上具有重大意义。重金属废水可能影响普通湿地植物的正常生长,进而降低整个系统去除重金属的能力。同时,“超富集”植物又因为种类有限,专一性和生物量小等特点难以引入湿地进行重金属废水的治理。因此,为人工湿地处理重金属废水的应用探索新途径,这对人工湿地处理重金属废水技术的推广和应用具有重要意义。针对这些问题,本研究选用高吸附容量的蛭石作为基质,在潜流湿地单元建立离子吸附缓冲体系来调节系统污染离子的水平,经调节后的离子再经过植物的吸收,通过基质吸附和植物吸收建立可达标排放的可持续平衡系统。研究结果表明：1.天然蛭石具有储量丰富、价格低廉、吸附容量大、对环境无毒无害且容易再生等优点,采用蛭石作为吸附介质应用于人工湿地重金属废水处理当中,不仅具有较好的去除锌、镉效果,同时还具有高效低廉的特点。2.动态吸附、温度影响、pH值影响的试验结果表明：蛭石对锌、镉离子具有较快的吸附能力,建议人工湿地潜流单元(缓冲系统)的最佳吸附时间为60 min；蛭石处理含锌、镉废水的适宜温度条件是15-45℃,适宜pH值是3.5～7。3.校园废水中锌、镉离子浓度分别6.20 mg/L和0.8 mg/L,计算得出蛭石基质对锌的设计负荷率是30 mg/kg(蛭石)；对镉的设计负荷率是11 mg/kg(蛭石)。4.供试的四种水生植物对锌、镉离子具有不同的耐受能力,对锌的耐受浓度上限分别是水葫芦10 mg/L,蕹菜5 mg/L,水花生5 mg/L,荇菜1 mg/L。对镉的耐受浓度上限分别是水葫芦2 mg/L,蕹菜1 mg/L,水花生和荇菜均为0.5 mg/L。5.水葫芦和蕹菜对锌、镉具有较强的耐受能力和富集能力,通过植物对锌、镉去除率影响的实验结果计算得出,水葫芦和蕹菜去除废水中锌、镉离子并使之达标排放的锌、镉的浓度范围(最大限度)分别是：1.84-10mg/L(Zn),0.32-2mg/L(Cd); 1.8-5mg/L(Zn),0.29-1mg/L(Cd)。6.通过培养箱试验,设定水葫芦和蕹菜的收获时间长度设计参数T=15～20天。进一步确定水葫芦去除锌、镉废水的最佳浓度分别是1.84～4.00 mg/L和0.320.50 mg/L；确定蕹菜去除锌、镉废水的最佳浓度范围是1.80～4.0 mg/L和0.290.50 mg/L。7.通过计算得出水葫芦的水力负荷设计参数：对镉0.05g/kg(植物).m3(污水).d,对锌0.44g/kg(植物).m3(污水).d；蕹菜的水力负荷设计参数：对镉0.16g/kg(植物).m3(污水).d,对锌1.30g/kg(植物).m3(污水).d。8.根据上述的试验结果进行分析计算,最终确定蛭石吸附和植物吸收平衡模型的工程参数：蛭石单元的水力停留时间HRT=2.1h；表面水力负荷=11.9 m3/m2.d；容积水力负荷=7.94 m3/m3.d；表面镉离子负荷=9.52 g/m2.d；表面锌离子负荷=73.78g/m2.d；镉容积离子负荷=6.35g/m3.d；锌容积离子负荷=49.21g/m3.d。表流单元的水力停留时间HRT=12h；表面水力负荷=3.97 m3/m2.d；容积水力负荷=1.98 m3/m3.d；表面镉离子负荷=1.59g/m2.d；表面锌离子负荷=4.17g/m2.d；镉容积离子负荷=0.79g/m3.d；锌容积离子负荷=2.08g/m3.d。更多还原

【Abstract】 The renewable development of human world and economy was restricted increasingly due to shortage of the water resources and pollution of the water environment. In particular, along with the accelarated industrialization course, a mass of heavy metal containing waste waters was discharged into rivers and lakes, resulting in sever pollutions of heavy metals, in particular Zn、Pb、Cd、Cu and Cr, in water ecosystems. Not only the shortage of useable water resource was directly affected by heavy metal pollution, but also the security of drinking water, food and crop production, and the health of human being were endangered. Thus, an important orientation of manage environment is looking for a multiprocessing with waste water containing heavy metal.Constructed wetland, a new wastewater treatment technology, was developed in 1970s. On account of the merit of low investment, low energy consumtion, relatively high treatment efficiency, and easy operation and management, it has become a hotspot in the research field of sewage treatment. Recently, some studies indicated that the special and complex mechanism of constructed wetlands can play an important role in dispose of industry wastewater containing heavy metals. Effectively depression of the heavy metals in wastewater is the key to heavy metal sewage disposals. Physichemical adsorption and bio-absorption are uppermost approaches to wipe off the heavy metal hydronium. Thus, choose of proper adsorbents used as wetland fillers and determination of their adsorption characteristics, as well as selection of adequate plant species and study of their absorption natures are important topics for removale of heavy metals from wastewater using constructed wetland techniques. Heavy metal ions can affect the growth of plants in wetland and depress the treatment capacity of the whole system. On the other hand, there are limitations for introduction of "high-accumulative" plant species into constructed wetlands targeted at specific metal element. There are few sources of such plants available for selection and furthermore they are usually adopted to specific environmental conditions with low growth rates, It is therefore of significance to find altanative solutions with purpose to increase the treatment capacity and sustainability of constructed wetland system for disposal of heavy metal containing wastewaters.Aiming at these issues, we established an ion adsorption buffering system with vermiculite as adsorbent to accommodate the plant absorption system in constructed wetlands. Based on the established treatment systems experiments were carried out to investigate the essential factors that determine the treatment efficiency. The results obtained from the study indicated:1) Accounted for by its abundance in natural resource,, low price, high adsorption capability and re-generable nature, vermiculite can be used as wetland fillers for removal of heavy metals from wastewaters.2) The adsorption capacity of vermiculite samples was determined as X for zinc and Y for cadmium. The optimal adsorption time in terms of cost-efficiency was found to be 60 min within the proper temperature range 15～45℃and pH range 3.5-7.3) For the campus sewage containing 6.20 mg/L of Zn2+ and 0.8 mg/L of Cd2+,the designed load rate of vermiculite is 30 mg/kg for zinc and 11 mg/kg for cadmium.4) The four selected hydrophyte plants had different endurance to zine and cadminm concentration levels. The highest endurable concentration of zine was found to be 10 mg/L for Eichhornia crassipes,5 mg/L for Ipomoea aquatica Forsskal and Alternanthera philoxeroides, and 1 mg/L for Nymphoides peltatum. In comparison, The highest endurable concentration of cadmium was found to be 2 mg/L for Eichhornia crassipes,1 mg/L for Ipomoea aquatica Forsskal and 0.5 mg/L for Alternanthera philoxeroides and Nymphoides peltatum.5) Eichhornia crassipes and Ipomoea aquatica Forsskal had the stronger endurance capability and enrichment capability. The maxmum concentration in the enfluent for respective metal species that the selected plant species can not only stand for but also be able to fulfill the GB discharge standars was 1.84-10 mg/L(Zn) and 0.32～2mg/L(Cd) for Eichhornia crassipes;1.8～5mg/L(Zn) and 0.29～1 mg/L (Cd) for Ipomoea aquatica Forsskal. 6) Based on tank culture tests the designed parameter of harvest time for Eichhornia crassipes and Ipomoea aquatica Forsskal is 15-20 days. The proper range of zinc and cadmum concentration for Eichhornia crassipes is, respectively,1.84～4.00 mg/L and 0.32-0.50 mg/L, and that for Ipomoea aquatica Forsskal is 1.84～4.00 mg/L and 0.32～0.50 mg/L.7) The designed parameter for water load for Eichhornia crassipes is 0.05 g/kg.m3.d for Cd and 0.05g/kg.m3.d for Zn, and that for Ipomoea aquatica Forsskal is 0.16 g/kg.m3.d and 1.30 g/kg.m3.d for the respective metal species.8) Based on the tested results, the engineering parameters for the established vermiculite adsorption and plant absorption equilibrium model are:Vermiculite adsorption unit:HRT=2.1 h, exterior waterpower charge= 11.9 m3/m2.d, cubage waterpower charge=7.94 m3/m3.d, exterior charge of cadmium= 9.52 g/m2.d, exterior charge of zine= 73.78 g/m2.d, cubage charge of cadmium=6.35 g/m3.d, cubage charge of zine=49.21 g/m3.d.Plant absorption unit:HRT=12 h, surface hydraulic load=3.97 m3/m2.d, volume hydraulic load=1.98 m3/m3.d, surface cadmium load=1.59 g/m2.d, surface zinc load= 4.17 g/m2.d, volume cadmium load=0.79 g/m3.d, volume zinc load=2.08 g/m3.d.更多还原