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。     

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。     

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。     

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。     

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).     

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.     

大连沿海中小流域地下水人工调控研究

分析大连沿海地区中小流域水资源系统的自然特点、开发利用条件及存在的问题,得出:利用汛期排泄入海的大量地表径流,可缓解大连地区供水矛盾.探讨在沿海独立入海流域实施地下水人工调控的内涵,包括必要性、可行性及技术要点等,结合旅顺区三涧堡地下水库实例进行了论证。     

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.     

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。     

The artificial recharge of groundwater: A solution by successive variations of steady states

The artificial recharge of groundwater aims at the modification of water quality, an increase of groundwater resources, and the optimization of the exploitation and recovery of contaminated aquifers. The purpose of this work is to develop a new mathematical model for the problem of an artificial recharge well, using the method of successive variations of steady states. Applying this method, one arrives at an expression of time as a double integral. This integral contains the time-dependent radius of the recharge boundary and the piezometric head of the well, calculated with the finite-element method. The new model is simple and useful, and can be applied to many practical problems, using the designed dimensionless graphs.Notations A area of the finite element (m²) - c the Euler constant (0.5772156649...) - e index of the finite element - E _i the exponential integral function - F _j nodal values of the functionF - h piezometric head, (m) - h ₀ piezometric head at timet=0 (m) - h _w piezometric head on the well contour (m) - i, j, k nodal indices of the finite element - K hydraulic contactivity (ms^–1) - N _i interpolation function - Q discharge (m³ s^–1) - r cylindrical coordinate (m) - r ₀ the action radius of the well (m) - r _w the radius of the well (m) - S the effective porosity - t the time (s) - T the transmissivity of the aquifer (m²s^–1) - V the stored water volume (m³) - x, y, dummy variables     

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     

Winery wastewater treatment by constructed wetlands and the use of treated wastewater for cash crop production.

A 45 m long, 4 m wide and 1 m deep wetland was constructed at Goudini in 2002 to treat distillery and winery effluent. After the plants were fully established, the wastewater with an average chemical oxygen demand (COD) of 14,000 mg/l was introduced to the wetland system at a rate of 4,050 litres per day. After treatment, wastewater at the outlet had an average COD of 500 mg/l, indicating more than 90% COD removal. After treatment, the wastewater was used to irrigate cash crops as part of poverty alleviation for farm workers. The experiment consisted of four treatment: clean irrigation water with fertilizer applied (B1); clean irrigation water without fertilizer applied (B2); wastewater irrigation with fertilizer applied (B3); and wastewater irrigation without fertilizer applied (B4). These were replicated seven times. Cabbage was cultivated as a cash crop. The results indicated that cabbage could be irrigated with winery wastewater treated by wetlands. The study found that there was significant difference between treatments that were fertilized compared with those that were not fertilized. The results indicated that wastewater irrigation improved the nutritional status of the soil.     

Infiltration of a copper roof runoff through artificial barriers.

On-site infiltration of a copper roof runoff may contribute to deterioration of the ground and ground water. To avoid such a negative effect the performance of two different technical systems, equipped with four different barrier materials, regarding copper elimination was examined in a field study. During the period March 2004 to January 2005, 16 rain events were examined. Copper concentrations between 200 and 11,000 microg/L in the roof runoff during a rain event were observed. The cover material of the roof and the drainage system were responsible for the high concentrations of copper in the roof runoff. It was evident that roof aspects facing towards the wind direction were receiving higher rainfall, thus were establishing higher copper runoff rates. The retention facilities have reached a performance of up to 97% regarding copper elimination.     

人工振动对多孔介质中液体流动的影响

人工振动增产技术是一种新的提高采收率方法。人工振动模拟系统主要由函数/任意波发生器、功率放大器和激振器等组成．该系统与岩心流动实验系统配合．进行了人工振动对多孔介质中单相、两相液体流动的影响，进行了不同振动参数的影响程度研究。研究表明。人工振动可以提高单相液体通过多孔介质的流速，提高幅度与振动参数有关，振动结束后具有一定的滞后效应；人工振动能够提高水驱采收率，并降低含水率，而且人工振动增产效果与振动参数有关，同时介绍了人工振动增产技术的现场应用情况。     

Removal of hexavalent chromium in soil and groundwater by supported nano zero-valent iron on silica fume

Silica fume supported-Fe(0) nanoparticles (SF-Fe(0)) were prepared using commercial silica fume as a support. The feasibility of using this SF-Fe(0) for reductive immobilization of Cr(VI) was investigated through batch tests. Compared with unsupported Fe(0), SF-Fe(0) was significantly more active in Cr(VI) removal especially in 84 wt% silica fume loading. Silica fume had also been found to inhibit the formation of Fe(III)/Cr(III) precipitation on Fe nanoparticles' surface, which was increasing the deactivation resistance of iron. Cr(VI) was removed through physical adsorption of Cr(VI) onto the SF-Fe(0) surface and subsequent reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) could be expressed by pseudo first-order reaction kinetics. The rate constant increased with the increase in iron loading but decreased with the increase in initial Cr(VI) concentration. Furthermore, column tests showed that the SF-Fe(0) could be readily transported in model soil.