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.     

人工湿地工程实例简介

湿地对人类的重要性正逐渐深入人心.从1971年2月2日,18个国家在伊朗拉姆萨尔缔结<关于特别是作为水禽栖息地的国际重要湿地公约>(简称<湿地公约>)以来,到1992年我国正式加入湿地公约,现在已有135个成员国.在<湿地公约>的推动下,一些国家已从调查、保护现有湿地、恢复原有湿地的同时,向建设人工湿地、扩大湿地面积和功能方面发展,其来势凶猛.不论在保护湿地、恢复湿地,还是建设人工湿地活动中,水利工作者都有着义不容辞的责任,也给水利事业造福人类开辟了新天地.     

潜流人工湿地去污机理及影响因子研究进展

在总结潜流人工湿地相关试验研究和工程实践经验的基础上,从湿地植物、基质填料、微生物、溶解氧、水力学条件以及温度等影响因子出发,综合概述了潜流人工湿地对氮磷、有机和悬浮污染物等的去除机理,总结并探讨了影响因子的去污原理和效应,同时提出了需要进一步研究和探讨的问题,为潜流人工湿地系统的设计、运行以及最大化的处理污水提供了参考依据。     

地下水人工回灌和停采对地面沉降控制的影响分析

地面沉降是全世界主要的工程地质灾害之一,而地下水超采是造成地面沉降的主要原因之一。为研究地下水人工回灌和停采对北京平原地面沉降的影响,采用三维地下水模型和情景设计法,设计3个情景(保持现状、人工回灌和地下水停采)对北京平原区域及沉降中心的沉降速率进行模拟。结果表明:保持现状、人工回灌和地下水停采等情景下北京平原在2015、2020和2030年的区域地面沉降分别为24 mm/a左右、12. 7～23. 2 mm/a及12. 4～23. 7mm/a,沉降中心地面沉降分别为39. 30～158. 62 mm/a、21. 09～165. 83 mm/a及16. 5～162. 95 mm/a;人工回灌和地下水停采对研究区地下水水位和含水层储存量的恢复以及地面沉降的控制有显著的促进作用,但地下水停采的效果要优于人工回灌的效果;只有综合考虑社会经济发展和地面沉降控制,才能既控制地面沉降的恶化,又保证北京平原社会的可持续发展。     

辽阳首山地下水人工回灌可行性研究

辽阳首山地区由于地下水长时期的过量开采,地下水位大幅下降,形成了地下水漏斗区,产生了一系列生态环境问题。通过对该地区地下水开发利用现状和供需矛盾分析,研究了实施地下水人工回灌的必要性和可行性;在对水文地质条件、回灌水源条件、水质等进行分析后,认为在首山地区实施地下水人工回灌是可行的,并提出了几点建议。     

地下水含盐量对人工冻结效果影响分析

目前对于人工冻结法的研究主要集中在地下水渗流对冻结效果的影响,未考虑地下水含盐量的影响,对地下水含盐量对冻结效果的影响机制认识不深入。含盐量将会影响地下水的热力学性质,在近海地层和海底进行临时地层冻结加固时,高含盐量地下水将会影响地层冻结效果。基于热流耦合模型,采用COMSOL多场耦合分析软件对双管冻结条件下高含盐量地下水冻结机理展开研究,重点分析冻结温度场、冻结交圈、冻结管间距对冻结效果的影响。研究表明:当地下水含盐量高于4%时,下游的冻结范围受地下水含盐量增加的影响较大。随着地下水含盐量的增加,冻结前期用时较长,积极冻结阶段用时逐渐缩短;当冻结壁完全交圈并冻结完全时,冻结壁中心位置处温度随地下水含盐量的提高而有所升高;冻结管间距的增加将会放大地下水含盐量对冻结的影响。     

Removal efficiency of subsurface vertical flow constructed wetlands for different organic loads.

Using subsurface vertical flow constructed wetlands (SSVFCWs) with intermittent loading it is possible to fulfil the stringent Austrian effluent standards regarding nitrification. For small plants (less than 500 persons) standards for ammonia nitrogen concentration have to be met at water temperatures higher than 12 degrees C, effluent concentrations and treatment efficiencies for organic matter have to be met the whole year around. According to the Austrian design standards the required surface area for SSVFCWs treating wastewater was 5 m2 per person. Within the first part of an Austrian research project the goal was to optimise, i.e. minimise the surface area requirement of vertical flow beds. Therefore, three SSVFCWs with a surface area of 20 m2 each have been operated in parallel. The organic loads applied were 20, 27 and 40 g COD/m2/d, which corresponds to a specific surface area requirement of 4, 3 and 2 m2 per PE, respectively. The paper compares the effluent concentrations and elimination efficiencies of the three parallel operated beds. It could be shown that a specific area demand of 4 m2 per person is suitable to be included in the revision of the Austrian design standard. Additionally it could be shown that during the warmer seasons (May-October) when the temperature of the effluent is higher than 12 degrees C the specific surface area might be further reduced; even 2 m2 per person has been proven to be adequate.     

胶州市前韩水源地地下水回灌修复水质探讨

前韩水源地是胶州市城市供水的重要水源地之一,占城区供水量的1/3。近几年,随着胶州市蔬菜大量种植,使用农药、化肥等越来越多,含氮化肥在水的作用下渗到含水层中,长期积累,致使该水源地地下水质受到不同程度的污染。为了尽快修复水质,通过分析原因,选择使用地表水入渗和井内灌注补给法相结合的方法,提出了利用充足的地表水,逐步改善该水源地水质的方案。     

鸟粪石法去除废水中氨氮的影响因素及应用

以鸟粪石沉淀的形式去除废水中的氨氮,操作简便,反应速度快,是一种较有效的方法。介绍了鸟粪石晶体的性质、反应机理,总结了鸟粪石法反应的主要影响因素及应用,对存在问题进行了分析,并在此基础上对该方法的未来趋势进行了展望。     

安阳市区实施地下水人工回灌的可行性分析

对安阳市区水资源的供需现状和发展趋势进行分析,提出实施地下水人工回灌的必要性和可行性;在对地质构造、水文地质条件、水源条件、工程效益等进行分析后,认为在安阳市区实施地下水人工回灌是可行的,并提出了4条合理化建议。     

人工湿地结合生物生态净化基工艺在人工湖处理中的应用

广东东莞某小区的人工湖中使用人工湿地结合生物生态净化基工艺,对人工湖微污染的修复及控制进行研究。结果表明,人工湿地结合生物生态净化基工艺应用于景观水微污染控制是有效的,CODCr、NH3-N、叶绿素a去除率分别达到75%、85%、90%以上。该工艺具有效果稳定、操作方便、成本低、无二次污染等优点。     

辽阳首山地区地下水人工回灌的可行性研究

辽阳首山地区由于地下水长时期的过量开采,地下水位大幅下降,形成了地下水漏斗区,产生了一系列生态环境问题。通过对该地区地下水开发利用现状和供需矛盾分析,研究了实施地下水人工回灌的必要性和可行性;在对水文地质条件、回灌水源条件、水质等进行分析后,认为在首山地区实施地下水人工回灌是可行的,并从水环境角度提出了3点建议。     

基于人工甜味剂时序特征的白洋淀对地下水补给量研究

研究白洋淀对区域地下水的补给量,对雄安新区生态水城的建设具有重要意义.目前对湖水与地下水补给量的计算,主要基于同位素测试以及水位和水温长序列监测等方法,具有较高的计算成本和局限性.以人工甜味剂为示踪剂,在查明安赛蜜、三氯蔗糖、糖精、甜蜜素4种典型人工甜味剂在白洋淀和浅层地下水空间分布的基础上,通过构建白洋淀的金龙淀内安...     

Removal of organic impurities in waste glycerol from biodiesel production process through the acidification and coagulation processes

Treatment of waste glycerol, a by-product of the biodiesel production process, can reduce water pollution and bring significant economic benefits for biodiesel facilities. In the present study, hydrochloric acid (HCl) was used as acidification to convert soaps into salts and free fatty acids which were recovered after treatment. The pH value, dosages of polyaluminum chloride (PACl) and dosage of polyacrylamide (PAM) were considered to be the factors that can influence coagulation efficiency. The pH value of waste glycerol was adjusted to a pH range of 3-9. The PACl and PAM added were in the range of 1-6 g/L and 0.005-0.07 g/L. The results showed best coagulation efficiency occurs at pH 4 when dosage of PACl and PAM were 2 and 0.01 g/L. The removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD(5)), total suspended solids (TSS) and soaps were 80, 68, 97 and 100%, respectively. The compositions of organic matters in the treated waste glycerol were glycerol (288 g/L), methanol (3.8 g/L), and other impurities (0.3 g/L).     

Development and use of a wetlands information system for assessing wetland functions

A wetlands information management system was developed to assess various wetland functions and values in two townships in Michigan, USA. The goals of the study were to determine the effectiveness of a wetland‐assessment method integrated with a geographical information system (GIS) to assess appropriate environmental criteria, potential effects of wetland size and type on function, and to develop a user–friendly interface that local officials might use in decision‐making related to wetland preservation and land‐use planning. In order to assess seven wetland functions and two values, quantitative measures were incorporated using GIS techniques to derive some of the needed information from existing spatial databases. However, on‐site investigation was required for all assessments. Of 65 wetlands evaluated through the system, no significant difference (P > 0.05) was found between wetland size and its ability to perform a given function. No single wetland type (e.g. forested, shrub/scrub, emergent, open water) had a higher probability of performing all wetland functions or values significantly more than another type. However, the combined application of on‐site evaluation and GIS technology might offer a more efficient method to assess wetland functions and values, with the latter providing an educational tool for local wetland planning and management.     

走集约化农业之路有效利用地下水资源

1 概况镇赉西部地区有10个乡镇,其中有两个乡同内蒙古科右前旗和扎鲁特旗接壤。镇赉西部远离江河,年降水量396mm。年蒸发量1220mm,农田以沙岗地和盐碱地为主,占总耕地面积的76％。农民种地全靠降雨和提取地下水。每年有66～68d刮6级以上大风、年年干旱,特别是春天,降水量极少,种地完全靠井水。在当地有春雨贵如油之说,农民惜水如命,生怕浪费一滴水。     

永济市实施城区地下水限量开采的实践

山西省永济市城区地下水严重超采,出现地质漏斗现象.从20世纪80年代后期开始,永济市采取新工艺、新措施,限量开采地下水,对其调控管理进行试验研究,兴建从黄河滩傍河取水工程,使市区地下水逐步得到回升,有效抑制了降落漏斗现象.     

雷州半岛地表水与地下水联合利用浅析

分析了雷州半岛的水资源情况及其存在的工程性缺水严重,地下水超采导致的地面沉降、海水入侵,等水资源供需矛盾日益突出的问题。论述了地表水--地下水联合利用的必要性,探讨了雷州半岛地表水、地下水资源联合利用的潜力及措施。     

Removal of cyanobacterial metabolites through wastewater treatment plant filters

Wastewaters have the potential to proliferate excessive numbers of cyanobacteria due to high nutrient levels. This could translate to the production of metabolites, such as the saxitoxins, geosmin and 2-methylisoborneol (MIB), which can impair the quality of wastewater destined for re-use. Biological sand filtration was assessed for its ability to remove these metabolites from a wastewater. Results indicated that the sand filter was incapable of effectively removing the saxitoxins and in some instances, the effluent of the sand filter displayed greater toxicity than the influent. Conversely, the sand filter was able to effectively remove geosmin and MIB, with removal attributed to biodegradation. Granular activated carbon was employed as an alternative filter medium to remove the saxitoxins. Results showed similar removals to previous drinking water studies, where efficient removals were initially observed, followed by a decrease in the removal; a consequence of the presence of competing organics which reduced adsorption of the saxitoxins.     

天水市城区地下水资源可持续利用对策探讨

<正>一、城区地下水资源概况甘肃省天水市城区河谷地下水主要为第四系松散岩类孔隙水。渭河河谷含水层厚度较大,为13.40～35.17m,藉河河谷含水层厚度较小,仅为2.0～23.65m。总的趋势是自西向东逐渐增