Drinking Water Aquifers Research Articles

WATER AND CO SHOULDN'T MIX

THE ENVIRONMENTAL Protection Agency has proposed to broaden the range of geological formations where coal-based electric utilities and companies that generate carbon dioxide may inject the greenhouse gas for sequestration. The Aug. 26 proposal allows CO 2 injection and sequestration at shallower depths that are not necessarily below drinking water aquifers, contrary to what the agency proposed a year ago. Capturing carbon dioxide and sequestering it underground is considered the only way the world can continue to burn coal and avoid the ravages of climate change. Coal supplies half of the electricity in the U.S., but it generates one-third of the 6 billion tons of CO 2 the nation emits annually. However, sequestering CO 2 underground risks damaging drinking water aquifers, and for the past year, EPA has been wrestling with development of regulations that protect groundwater and allow carbon sequestration. Water suppliers tell C&EN they don’t like EPA’s latest plan. They are worried that it won’t protect ...

Macroeconomic and institutional sources of environmental changes–the case of Israel's water sector

The paper examines the macroeconomic and institutional sources of environmental development in Israel's water sector, for example changes in drinking-water quality, sewage treatment and aquifer depletion trends. It is shown that Israel's economic growth process was, by and large, accompanied by environmental improvements in the water sector; but it is the institutional approach which provides a cohesive explanation of how environmental changes took place. Implementing reforms in Israel's water sector without adequately addressing the institutional aspect might thus undermine the success of such plans.

Fluidized bed bioreactor treatment of perchlorate–laden groundwater to potable standards

During the past decade, perchlorate at levels above regulatory standards has become increasingly prevalent in drinking water aquifers. A large pilot‐scale biological fluidized bed reactor (FBR) followed by a surface water treatment plant was tested to demonstrate effective treatment of perchlorate‐laden groundwater to potable water. At perchlorate concentrations up to 1,000 μg/L, nitrate‐nitrogen concentrations of 6.1 mg/L, and flow rates of 95‐189 L/min (25‐50 gpm), the FBR treatment plant was effective in removing perchlorate and producing potable water that met all drinking water regulations before disinfection. The use of on‐line perchlorate and nitrate analyzers allowed for rapid analysis of plant performance and provided continuous electron donor feed control to maintain optimal contaminant treatment rates. Recovery from feed and plant electrical interruptions was rapid in achieving acceptable treatment performance. Study results provided essential design data for a potential full‐scale treatment plant.

Environmental management of the stone cutting industry

Environmental Management of the stone cutting industry in Hebron is required to reduce the industry's adverse impact on the downstream agricultural land and the adverse impact on the drinking water aquifers. This situation requires the implementation of an industrial wastewater management strategic approach and technology, within the available technical and financial resources. Ten pilot projects at different locations were built at Hebron to reduce or eliminate the incompatible discharge of the liquid and solid waste to the environment and improve the stone cutting industry's effluent quality. A review of existing practices and jar test experiments were used to optimize the water recycling and treatment facilities. The factors reviewed included influent pumping rates and cycles, selection of the optimal coagulant type and addition methods, control of the sludge recycling process, control over flow rates, control locations of influent and effluent, and sludge depth. Based on the optimized doses and Turbidity results, it was determined that the use of Fokland polymer with an optimal dose of 1.5 mg/L could achieve the target turbidity levels. The completion of the pilot projects resulted in the elimination of stone cutting waste discharges and an improvement in the recycled effluent quality of 44–99%. This in turn reduced the long term operating costs for each participating firm. A full-scale project that includes all the stone cutting firms in Hebron industrial area is required.

Microbial Characteristics through Drinking Water Aquifer Sand Material

AbstractPublic health concerns about pathogens present in animal manure are emerging constraints to water supplies in many areas of the world. The objective of this study was to examine the microbial community composition in aquifer material impacted by contaminants from different sources. Total microbial community profiles were compared by using eubacterial primers to amplify 16S rRNA genes from total bacterial DNA and RNA. PCR and reverse transcriptase (RT) PCR were used to amplify 16S ribosomal RNA, and the products were subjected to denaturing gradient gel electrophoresis (DGGE). DGGE analysis of RT‐PCR products detected a subset of bands visible in the DNA‐based analysis, indicating that some dominantly detected bacterial populations did not have high levels of metabolic activity. The sequences detected by the RT‐PCR approach were, however, derived from a wide taxonomic range, suggesting that the activity in the aquifer sand material was not determined at broad taxonomic levels but rather was a strain‐ or species‐specific phenomenon. Comparative analysis of DGGE profiles grouped all DNA‐derived aquifer samples together in a cluster. At the end of the experimental period, the aquifer material entered a stable population state, which was characterized by a greater diversity of DNA‐based fingerprints compared to viable bacteria. Our data showed that the active members of the community are a sub‐population of that community that performs certain biological functions during water filtration through aquifer material. Therefore, recharging surface water through aquifer sand material may produce a microbial population quite different from the input source due to the availability of nutrients for bacterial growth.

Small-scale, hydrogen-oxidizing-denitrifying bioreactor for treatment of nitrate-contaminated drinking water

Nitrate removal by hydrogen-coupled denitrification was examined using flow-through, packed-bed bioreactors to develop a small-scale, cost effective system for treating nitrate-contaminated drinking-water supplies. Nitrate removal was accomplished using a Rhodocyclus sp., strain HOD 5, isolated from a sole-source drinking-water aquifer. The autotrophic capacity of the purple non-sulfur photosynthetic bacterium made it particularly adept for this purpose. Initial tests used a commercial bioreactor filled with glass beads and countercurrent, non-sterile flow of an autotrophic, air-saturated, growth medium and hydrogen gas. Complete removal of 2 mM nitrate was achieved for more than 300 days of operation at a 2-h retention time. A low-cost hydrogen generator/bioreactor system was then constructed from readily available materials as a water treatment approach using the Rhodocyclus strain. After initial tests with the growth medium, the constructed system was tested using nitrate-amended drinking water obtained from fractured granite and sandstone aquifers, with moderate and low TDS loads, respectively. Incomplete nitrate removal was evident in both water types, with high-nitrite concentrations in the bioreactor output, due to a pH increase, which inhibited nitrite reduction. This was rectified by including carbon dioxide in the hydrogen stream. Additionally, complete nitrate removal was accomplished with wastewater-impacted surface water, with a concurrent decrease in dissolved organic carbon. The results of this study using three chemically distinct water supplies demonstrate that hydrogen-coupled denitrification can serve as the basis for small-scale remediation and that pilot-scale testing might be the next logical step.

The microbial arsenic cycle in Mono Lake, California

Significant concentrations of dissolved inorganic arsenic can be found in the waters of a number of lakes located in the western USA and in other water bodies around the world. These lakes are often situated in arid, volcanic terrain. The highest concentrations of arsenic occur in hypersaline, closed basin soda lakes and their remnant brines. Although arsenic is a well-known toxicant to eukaryotes and prokaryotes alike, some prokaryotes have evolved biochemical mechanisms to exploit arsenic oxyanions (i.e., arsenate and arsenite); they can use them either as an electron acceptor for anaerobic respiration (arsenate), or as an electron donor (arsenite) to support chemoautotrophic fixation of CO 2 into cell carbon. Unlike in freshwater or marine ecosystems, these processes may assume quantitative significance with respect to the carbon cycle in arsenic-rich soda lakes. For the past several years our research has focused on the occurrence and biogeochemical manifestations of these processes in Mono Lake, a particularly arsenic-rich environment. Herein we review some of our findings concerning the biogeochemical arsenic cycle in this lake, with the hope that it may broaden the understanding of the influence of microorganisms upon the speciation of arsenic in more common, less “extreme” environments, such as drinking water aquifers.

Acetochlor as a soil pollutant

The agricultural use of pesticides leads to diffuse pollution whereby the various contaminants of the soil infiltrate into the groundwater reaching lakes and drinking water aquifers. Due to the extensive application of these chemicals, their leaching presents a high environmental risk. Since the adsorption coefficient (K) characterizes the soil / water partitioning [1] and is also representative for leaching, the first step in understanding of the environmental fate of a pollutant is to study its adsorption properties. Weak binding to the soil constituents (low K) leads to groundwater pollution, while a strong binding (high K) results in surface water pollution through the erosion of the soil. Acetochlor is a widely used herbicide all over the world. Similar to other organic pollutants, the environmental fate of this chemical is strongly related to its adsorption properties. Static adsorption equilibrium measurements were carried out at 25°C on different types of Hungarian soils (chernozem, brown forest and sandy soil) characterized by varying amounts of organic matter and pH values. Acetochlor solutions were prepared in the presence of nitrate and phosphate ions (0.1 mol/L sodium nitrate and 0.1 mol/L phosphate uffer, pH=7) which are constituents of fertilizers occurring in high concentrations in the environment. In order to appreciate their effect, adsorption studies were also performed in pure aqueous medium. The equilibrated liquid was analyzed after centrifugation by two different methods (Total Organic Carbon measurement, High Performance Liquid Chromatography). Isotherms obtained under different conditions, as well as on various soils, exhibit a similar shape, thus indicating a two-step adsorption process. The plots cannot be interpreted according to the classes of isotherms suggested by Giles (H-, L- and C-type, [2]). The adsorption coefficients were estimated from the initial slope of the curves. These values were determined not only by the type of the soil, but also by the composition of the aqueous media. Due to the low value of the adsorption coefficients, the acetochlor is a rather mobile pollutant of the soil posing a potential danger to the aquatic environment. The organic matter adsorption coefficients (Kom) [3] were also calculated and they were approximately identical for soils of high organic matter. For the chernozem and brown forest soils, the values of the K and Kom parameters are increasing in the order from water < phosphate buffer < sodium nitrate. For soils of low organic content, the similarity of the Kom values cannot be expected (due to the hyperbolic nature of the equation) as the data really indicate it for the adsorption behavior of the sandy soil. Here, the organic matter plays a less important role and the adsorption is controlled by the solute / inorganic substance interactions. This conclusion is nicely proved by the adsorption of the acetochlor on quartz resulting thereby in a similar plot being obtained for the soils. According to the hypothesis presented here, the first step of the isotherms is controlled by the solute / surface interactions while the solute / adsorbed solute interactions are operating in the second step of the isotherm. The role of the organic matter in this region of the isotherm is probably negligible. The comparison of the adsorption coefficients leads to the conclusion that the presence of nitrate and phosphate ions enhances the adsorption of acetochlor on the soils containing a high percentage of organic matter. As these ions are present in the environment due to the extensive use of fertilizers, they may increase the acetochlor pollution of water by erosion. This conclusion corroborates those earlier observations that reported frequent acetochlor contamination of the surface waters [4–5]. As the organic matter content of the soils plays an important role in the acetochlor adsorption, humic substances must have a strong influence on the transport of this compound. Experiments to obtain adsorption isotherms of further pesticides and the development of a quantitative model are in progress.

Use of Granular Iron for Remediation of a Drinking Water Aquifer Contaminated with TCE

Use of Granular Iron for Remediation of a Drinking Water Aquifer Contaminated with TCEThe Town of Wellesley Massachusetts obtains more than 50 percent of their drinking water from water-supply wells in the Rosemary Brook basin. An area of this aquifer has been contaminated with a chlorinated solvent groundwater plume, which has been slowly advancing towards the Wellesley water supply wells. In June and July 2001, the Massachusetts Department of Environmental Protection installed a...Author(s)Michael L. DucheneRichard JacobsonSourceProceedings of the Water Environment FederationSubjectSession 32 - Remediation of Soils and Groundwater Symposium: Case Studies of Innovative Remediation TechnologiesDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2002ISSN1938-6478SICI1938-6478(20020101)2002:14L.82;1-DOI10.2175/193864702784248340Volume / Issue2002 / 14Content sourceWEFTECFirst / last page(s)82 - 91Copyright2002Word count252

Chlorinated solvents cometabolism by an enriched nitrifying bacterial consortium

The biodegradability of three of the most frequently halogenated aliphatics (trichloroethene, chloroform and 1.1.1.-trichloroethane) found in drinking water aquifers by a nitrifying enriched mixed biomass was investigated during batch tests. Within this mixed biomass, ammonia oxidisers were the effective degraders. The presence of ammonia stimulated chlorocarbon biodegradation, and the presence of chlorocarbon inhibited ammonia oxidation. This contrasted phenomenon was explained by a balance between electron supply from ammonia necessary to sustain the chlorocarbon oxidation and competitive inhibition for the ammonia monooxygenase active site between both substrates. About 0.03 to 0.2% of the electrons generated by ammonia oxidation were used for chlorocarbon degradation. Trichloroethene and chloroform oxidation induced a biomass inactivation (around 30 to 40 mg of proteins inactivated per μmol of chlorocarbn oxidised). Biomass re-activation due to exergonic ammonia catabolism was estimated to 24±6 mg of proteins reactivated per mmol of ammonia oxidised in both cases. No inactivation of re-activation was observed in the case of 1.1.1-trichloroethane.

Polar and non-polar aromatic micropollutants in water (drinking-water) resources

Aromatic compounds are important contaminants that limit the intended uses of water resources. Both polar and non-polar substances, such as phenols, aromatic sulfonates, lignin-sulfonic acids, humic and fulvic substances (acids) and mono- and poly-aromatic hydrocarbons, their alkyl-substituted derivatives, respectively, are among the potential aromatic micropollutants. During the last 5 - 10 years, an analytical approach has been developed on the basis of total fluorescence measurement of the original water sample and its organic solvent (cyclohexane) extract. It has been demonstrated and verified that polar aromatic compounds fluoresce only in the original water sample, whereas non-polar (hydrophobic) compounds fluoresce in an organic solvent (e.g. cyclohexane) extract. During extraction, polar compounds remain in the water sample. This method has been used in a country-wide survey in drinking water aquifers, as well as in several environmental impact assessment studies, particularly for petroleum-related pollution. It is a very convenient method to determine the naturally occurring humic and fulvic substances in water and has proved to be an appropriate substitute of the infrared spectrophotometric method for oil pollution assessment in the environment, also having the advantage of signalling more harmful, toxic aromatic petroleum hydrocarbons.

Recharge and Retention Time Study of a Partly Karstified Area of Boč (Eastern Slovenia) Using Hydrogen, Oxygen and Carbon Isotope Composition as Natural Tracers

The study is focused on the dolomite-limestone drinking water aquifers in the Boč massif, as well as on the andesite-aquifer containing mineral water in the vicinity of Rogaška Slatina. The catchment area is limited and both drinking and mineral waters are discharged from the same source. The increasing use of deeper aquifers means that natural springs and shallow wells have become sporadic. Consequently new techniques of investigating recharge and aquifer capacity are required which can augment classical hydrogeological methods. Current research into the mineral and drinking water aquifers in the area of Rogaška Slatina is based on measuring the isotopic composition of light elements, (H, C and O) as natural tracers. It can be concluded that all the groundwaters investigated are typically infiltrated meteoric water. The drinking waters are generally young and were infiltrated up to about ten years ago. The isotopic composition of oxygen is similar to recent precipitation (δ18O = -9.3 ± 1‰) and the drinking waters contain tritium. It was found that exploited mineral waters recharged aquifers during colder periods; they are only partly mixed with younger water as can be seen from the isotopic composition of oxygen and corrected 14C dating, which puts the mean ages at between around 100 and 8,000 years. With regard to the “nuclear period” (1960-64) with abnormally high tritium activities of precipitation, all the waters examined can be divided into at least three main infiltration groups depending on their measured tritium content: around 35 years old (> 80 T.U.), older (> 10 T.U.) and younger (10 to 60 T.U.). Detailed dating is possible following the above classification. Isotope exchange between rocks and water is negligible and therefore very deep circulation at the temperature conditions above 80°C does not occur. Dissolved inorganic carbon (DIC) in the drinking waters is the result of equilibrium reactions between carbonates and organically produced CO2 (δ13C = - 14.5 ± ‰), while the high concentrations of DIC (δ13C = + 3 ±‰) and CO2 observed in the mineral waters are generated by low-temperature decarbonatization processes and indicate the deep origin of CO2, from where gas migrates into mineral water aquifers. Correlation analyses between the parameters studied are performed. Useful conclusions concerning water circulation and the capacities of aquifer reservoirs are described which support the future optimal pumping of mineral and drinking water at the limited catchment area of Rogaška Slatina and Boč.

Use of the Gleams Model to Estimate Pesticide Overland and Subsurface Transport in USDA Forest Service Nursery Applications

The USDA Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) model was used to estimate pesticide concentrations entering surface water systems draining USDA Forest Service nurseries and subsequent risks from human oral exposure to the stream water. The GLEAMS model was employed to determine the primary pathways of pesticide loss, pesticide build-up in soil after successive applications, and pesticide concentrations in field runoff, eroded soil, and leachate. Pesticide residues in field runoff and adsorbed to eroded soil, both estimated by GLEAMS, were diluted into runoff volumes from treated and untreated areas to determine pesticide concentrations in the stream systems draining the nurseries. Where appropriate, pesticide residues from leachate were included. Pesticide concentrations in leachate and leachate volumes, both estimated by GLEAMS, and site-specific characteristics were used to make judgements about the susceptibility of drinking water aquifers to contamination by pesticides. The results of the GLEAMS analysis indicated that the pathways for nursery pesticide loss can be determined based on pesticide-specific parameters obtained from the open literature; however, the relative magnitude of the loss through each pathway must be estimated using nursery site-specific parameters.

Techniques for Protecting Groundwater Quality

The ideal goal of complete protection of underground drinking water sources is probably economically and physically infeasible. Relatively few of the nation's drinking water wells have been contaminated, and the most serious instances of contamination can be controlled with proven techniques such as impounding plumes of contamination behind barrier walls or draining and pumping the plume. In the long term, the public should be made aware of the consequences of using certain common household, industrial, and agricultural products that can ultimately seep into drinking water aquifers.

Transport and transportation pathways of hazardous chemicals from solid waste disposal.

To evaluate the impact of hazardous chemicals in solid wastes on man and other organisms, it is necessary to have information about amounts of chemical present, extent of exposure, and chemical toxicity. This paper addresses the question of organism exposure by considering the major physical and biological transport pathways and the physicochemical and biochemical transformations that may occur in sediments, soils, and water. Disposal of solid wastes in both terrestrial and oceanic environments is considered. Atmospheric transport is considered for emissions from incineration of solid wastes and for wind resuspension of particulates from surface waste deposits. Solid wastes deposited in terrestrial environments are subject to leaching by surface and ground waters. Leachates may then be transported to other surface waters and drinking water aquifers through hydrologic transport. Leachates also interact with natural organic matter, clays, and microorganisms in soils and sediments. These interactions may render chemical constituents in leachates more or less mobile, possibly change chemical and physical forms, and alter their biological activity. Oceanic waste disposal practices result in migration through diffusion and ocean currents. Surface area-to-volume ratios play a major role in the initial distributions of chemicals in the aquatic environment. Sediments serve as major sources and sinks of chemical contaminants. Food chain transport in both aquatic and terrestrial environments results in the movement of hazardous chemicals from lower to higher positions in the food web. Bioconcentration is observed in both terrestrial and aquatic food chains with certain elements and synthetic organics. Bioconcentration factors tend to be higher for synthetic organics, and higher in aquatic than in terrestrial systems. Biodilution is not atypical in terrestrial environments. Synergistic and antagonistic actions are common occurrences among chemical contaminants and can be particularly important toxicity considerations in aquatic environments receiving runoff from several terrestrial sources.