Influence of groundwater composition on subsurface iron and arsenic removal

Subsurface arsenic and iron removal (SAR/SIR) is a novel technology to remove arsenic, iron and other groundwater components by using the subsoil. This research project investigated the influence of the groundwater composition on subsurface treatment. In anoxic sand column experiments, with synthetic groundwater and virgin sand, it was found that several dissolved substances in groundwater compete for adsorption sites with arsenic and iron. The presence of 0.01 mmol L(-1) phosphate, 0.2 mmol L(-1) silicate, and 1 mmol L(-1) nitrate greatly reduced the efficiency of SAR, illustrating the vulnerability of this technology in diverse geochemical settings. SIR was not as sensitive to other inorganic groundwater compounds, though iron retardation was limited by 1.2 mmol L(-1) calcium and 0.06 mmol L(-1) manganese.     

Removal of arsenic from groundwater by arsenite-oxidizing bacteria

The presence of arsenic in groundwater has been of great public concern because of its high toxicity. For purification of arsenic-contaminated groundwater, bacterial oxidation of arsenite, As(III), with a chemical adsorption process was examined in this study. After As(III) oxidation to arsenate, As(V), arsenic is easily removable from contaminated groundwater because As(V) is more adsorptive to absorbents than As(III). By acclimation to As(III) of high concentrations, a mixed culture of heterotrophic bacteria with high As(III)-oxidizing activity was obtained from a soil sample that was free from contamination. With initial concentration up to 1,500 mg l(-1) As(III), the mixed culture showed high As(III)-oxidizing activity at pH values of 7-10 and at temperatures of 25-35 degrees C. The mixed culture contained several genera of heterotrophic As(III)-oxidizing and arsenic-tolerant bacteria: Haemophilus, Micrococcus, and Bacillus. Activated alumina was added to the basal salt medium containing 75 mg l(-1) As(III) before and after bacterial oxidation. Arsenic removal by activated alumina was greatly enhanced by bacterial oxidation of As(III) to As(V). The isotherms of As(III) and As(V) onto activated alumina verified that bacterial As(III) oxidation is a helpful pretreatment process for the conventional adsorption process for arsenic removal.     

地下水硝酸盐污染原位微生物修复技术研究进展

对于地下水中硝酸盐污染,原位微生物修复技术是一种有发展潜力、效率高且投资少的环境修复技术。但是这种技术也受一些因素的限制。对渗透反应墙技术进行了回顾,讨论了该技术中的有机碳源、电子供体和反硝化细菌的固定等问题,用实例说明应用该技术时需要注意的问题和监测参数,对注射井技术修复地下水硝酸盐污染进行了简单讨论。最后指出,应用微生物法修复地下水硝酸盐污染时要注意细菌污染和修复过程中含水层的渗透性降低或堵塞问题,应加强对治理大面积地下水硝酸盐污染在经济和技术上的可行性论证和研究。     

强化混凝-电气浮工艺除藻试验研究

采用强化混凝—电气浮联合工艺对三种主要水华藻类(铜绿微囊藻、水华鱼腥藻和水华束丝藻)进行处理,考查其工艺的可行性,并通过正交试验分析得出了最优反应条件。选取了pH、混凝剂投加量、电流密度、混凝时间四个主要因素,设计了对三种水华藻类的强化混凝—电气浮工艺的正交试验方案。在试验因素范围内,对铜绿微囊藻、水华鱼腥藻和水华束丝藻的最大去除率分别达到93.33%、96.3%和66.67%;混凝条件是藻类处理的关键条件;pH为首要影响因素。     

微污染水源水预氧化除藻试验研究

以微污染水库水为原水 ,采用臭氧、过氧化氢、高锰酸钾、紫外线及其不同组合作为预氧化剂 ,进行了预氧化除藻的中试研究。试验结果表明 ,预氧化能够明显提高水中藻类的去除率 ,这些预氧化方法都可达到 90 %以上的除藻率。其中以紫外线对藻类的去除率最高 ,可达 97.8% ,但紫外线在生产上的应用受到限制 ;而单独使用臭氧时除藻效果相对较差。实际应用中预氧化除藻可采用臭氧 过氧化氢联合方案 ,或者在接触氧化时间允许情况下选用高锰酸钾方案     

聚合铝盐混凝剂混凝除藻机理与强化除藻措施

针对微污染水处理中藻细胞的去除,研究聚合氯化铝形态分布对混凝除藻效率的影响。结果表明,混凝剂水解产物中,中等聚合物含量影响混凝过程中藻细胞去除率。中等聚合物含量越大,藻细胞去除率越高;在一定条件下,藻细胞去除率与中等聚合物含量线性相关,混凝出水中残铝含量与单体和低聚物含量线性相关。对聚合氯化铝,中等聚合物含量与碱化度线性相关。适量加聚磷酸根、硅酸根可以提高混凝除藻效率,并能显著降低混凝出水中残铝含量,所阐述的混凝除藻机理可以较好地解释实验现象。     

沸石去除地下水源水中氨氮的试验研究

地下水源水中氨氮的去除有其特殊性,研究利用沸石直接过滤氨氮超标地下水,并对沸石去除氨氮的机理进行了探讨。试验结果表明,滤速和进水氨氮浓度对沸石柱运行效果有很大影响,沸石对低浓度氨氮具有良好的去除作用。在滤速为6m/h,进水氨氮浓度分别为0.8mg/L和1.42mg/L时,以《城市供水水质标准》(CJ/T 206—2005)规定的0.5mg/L为出水水质标准,沸石柱可以分别运行65h和18h。沸石柱对氨氮的去除是吸附和离子交换共同作用的结果。     

除藻技术的现状分析及瞻望

随着对水体中藻类性质的研究,各种除藻方法逐步被提出并得以运用.对目前常用的除藻方法做了概况介绍,认为除藻应以生物方法为主,在水源上加强除藻措施,形成生态的除藻系统,同时促进水处理系统的综合发展.     

Arsenic removal from groundwater by a newly developed adsorbent.

A novel adsorbent, which had been developed for phosphate adsorption, was adopted for arsenic removal from groundwater. Adsorption isotherm, pH dependence of the isotherm and adsorption rate were studied by batch method. Furthermore, by using a granular adsorbent of 1.8 mm diameter which is commercially available, lab-scale experiments of continuous adsorption treatment of actual groundwater containing arsenic at 50 mg m(-3) were conducted to examine the performance of the adsorbent. A large amount of arsenic, i.e., 10 g As kg(-1), was adsorbed at pH 7.0 and 10 mg As m(-3) in equilibrium concentration. It was only a 5% higher amount compared to conventional activated alumina. However, twice the bed volume, i.e., total volume of effluent divided by empty column volume, was achieved till breakthrough by using this novel adsorbent. This may be because the pH decrease, which enlarges apparent adsorption capacity of the adsorbent, is caused by a self-pH decrease function of the adsorbent. The self-pH decrease function must be delivered by dissociation of Al (III) aquoion. The proton release was clearly observed in batch experiments.     

地下水有机污染的生物修复技术及应用

分析了生物修复技术的优势及影响地下水生物修复的因素,其中主要包括碳源和能源、微生物的种类、生物降解的电子受体、营养物质及环境因素等。结合实例说明了天然生物修复作用的存在性及重要性,指出强化生物修复技术中的就地生物修复耗时少,所需费用较低,但对于难降解的有机污染物及渗透性较差的含水层实施有困难,而异地生物修复更强调人为控制和创造更加优化的降解环境。最后,就我国与国外先进技术水平的差距进行了分析,认为我国虽然在生物修复技术应用工程实践方面有许多空白,但已具备大力发展的基础。     

吸附法去除饮用水中砷的研究进展

介绍砷的分布以及饮用水中砷超标的危害,综述当前国内外用不同吸附方法去除饮用水中砷的研究进展,分析其吸附性能和特点。结果表明,在归纳的6种吸附除砷方法中,复合材料与改性材料除砷效率高,处理费用低,目前最具有市场应用前景;活性材料的吸附效果受pH值控制;含铁矿物材料在除砷过程中易导致二次污染;纳米材料除砷效率最高,应是今后的主要发展方向。     

Use of low-cost materials in the removal of arsenic from aqueous solution

The arsenic-removing capacity of some low-cost materials was tested by passing aqueous arsenic solutions (16 and 57 ppb) of pH 7 through materials packed in plastic buckets. It was found that the initial concentration of arsenic solutions and their retention time in adsorbents greatly affected the removal of arsenic from the aqueous solution. Maximum arsenic removal was observed when the packed materials were exposed to 16 ppb of arsenic solution. With 57 ppb of arsenic solution, arsenic removal was reduced on that of 16 ppb; however, the reduced arsenic concentration was close to the recommendations of the World Health Organization drinking water quality guidelines.     

Heavy metals removal from contaminated sewage sludge by naturally fermented raw liquid from pineapple wastes.

The large amount of unutilised pineapple wastes produced every year in tropical countries, particularly in Thailand, adds to the existing environmental pollution problems of the country. This study investigated the utilisation of pineapple wastes to treat another form of waste (sludge) from wastewater treatment facilities in Thailand. Laboratory scale studies were carried out to determine the potential of using naturally fermented raw liquid from pineapple wastes as a source of citric acid in the extraction of Cr, Cu, Pb, Ni and Zn from anaerobically digested sewage sludge. Results of the leaching study revealed its effectiveness in extracting Zn (at 92%) at pH 3.67 and a short leaching time of only 2 h, and Ni at almost 60% removal at the same leaching time. Chromium removal was also high at almost 75% at a longer leaching time of 11 days. Variation in metal removal efficiencies may also be attributed to the forms of metals in sludge, with metals predominantly in the exchangeable and oxidisable phases showing ease of leachability (such as Zn). Compared to citric acid, at pH approaching 4.0, naturally fermented raw liquid seemed to be more effective in the removal of Zn and Cu at the same leaching time of 2 h, and Cr at a longer leaching time of 11 days. The pineapple pulp, which is a by-product of the process, can still be used as animal feed because of its high protein content.     

傍河污染地下水立体循环修复数值模拟

为了解决傍河地下水污染问题,在通州某水系新建傍河污染地下水立体循环修复示范工程。利用GMS软件中的Modflow模块和RT3D模块建立地下水流-溶质运移耦合模型,预测不同工况下地下水水质修复效果。模拟显示:在开挖河道不减渗立体循环水量10 000m3/d的工况下,10年后其沿岸地下水氨氮质量浓度由Ⅴ类降到Ⅲ类,局部为Ⅱ类;在减渗条件下,自然入渗量仅为2 000m3/d,无法形成地下水立体循环,10年后其沿岸地下水氨氮质量浓度为Ⅳ类,局部仍为Ⅴ类。因此,开挖河道河床不采用黏土减渗,傍河污染地下水抽出-自然入渗可形成立体循环,水质修复效果显著。     

地下水砷污染防治试验研究

针对我国地下水砷污染及饮用水质健康风险问题,以地下水中砷这种特征污染物的净化及安全供水为研究目标,为了寻求治理地下水砷污染途径,提出了石英砂原位改性除砷的方法。采用化学沉淀法制备改性石英砂,在室内开展镀铁条件试验研究,确定注入试剂种类、注入方式、持续时间及强度等重要参数。进而,对改性石英砂进行了表面特征分析并开展了静态吸附试验和动态除砷试验。研究成果旨在为我国地下水污染控制和饮用水安全供给工程提供相关的技术支撑。     

富营养湖泊的藻类现存量控制和供水处理的藻类去除

我国城镇供水正面临湖泊(水库)富营养化的严峻挑战.评述了高藻类现存量干扰水处理过程导致的供水问题,以及高藻类生物量控制对策和供水处理除藻工艺的国内外发展现状.就国内外现有藻类生物量控制对策和供水处理除藻工艺提出若干结论,并对我国今后在该领域的进一步研究提出建议.     

地下水脆弱性评价方法的探讨及实例

本文对当前地下水脆弱性评价的方法进行了评述。指出了目前应用最为广泛的DRASTIC法的局限之处,在充分考察中国平原盆地水文地质条件的前提下,提出了基于层次分析的DRUA评价方法。该方法是选取影响地下水脆弱性的地下水埋深等4个评价参数作为评价因子,应用层次分析法确定各因子的权重,结合GIS空间分析功能对地下水本质脆弱性进行评价。     

改进的逼近理想解在地下水资源承载力评价中的应用

应用多目标决策的逼近理想解技术(TOPSIS),建立了地下水资源承载力评价的模型。并采用正交投影法对方法进行改进。为客观反映评价指标的重要性,根据粗糙集理论,从属性的差异度出发,确定评价指标的权重,并与专家的主观权重相结合,生成TOPSIS法评价指标的权重;通过计算地下水资源承载力分级标准和待评价方案贴近各自理想方案的贴近度,确定待评价方案的承载能力。实例计算表明,本文得到的评价结果与实际情况基本吻合。     

改性凹凸棒土/纳米铁复合材料去除地下水NO_3~--N的研究

采用液相还原法制备改性凹凸棒土/纳米铁复合材料(简称复合材料),考察了该复合材料的稳定性及其作用下"三氮"(NO_3~--N、NH_4~+-N、NO_2~--N)的变化情况,阐明了地下水环境因素(DO、温度、光照)对复合材料去除NO_3~--N的影响。模拟地下水环境时,3种材料去除NO_3~--N的反应活性顺序为:复合材料纳米铁改性凹凸棒土,且复合材料作用下NH_4~+-N的转化率低,几乎无NO_2~--N生成。DO、温度对复合材料去除地下水NO_3~--N的影响较大;而光照和黑暗环境下,地下水中NO_3~--N的去除率及NH_4~+-N、NO_2~--N的生成量均无明显差异。研究成果旨在为NO_3~--N污染地下水工程修复提供理论依据和技术支撑。     

Biodegradation of chlorobenzene in a constructed wetland treating contaminated groundwater.

Monochlorobenzene (MCB) is an important groundwater contaminant world-wide. In this study, a horizontal subsurface flow constructed wetland with an integrated water compartment was fed with MCB contaminated groundwater originating from the local aquifer. Analysis of spatial concentration dynamics of MCB and oxygen was combined with isotope composition analysis of MCB for assessing in situ biodegradation. Removal of MCB was most effective in the upper layer of the soil filter, reaching up to 77.1%. Trace oxygen concentrations below 0.16 mg L(-1) were observed throughout the wetland transect, suggesting a considerable limitation of aerobic microbial MCB degradation. Enrichment of 13C in the residual MCB fraction at increasing distance from the inflow point indicated microbial MCB degradation in the wetland. The observed isotope shift was higher than expected for aerobic MCB degradation and thus pointed out a significant contribution of an anaerobic degradation pathway to the overall biodegradation.