Trace inorganics in rural potable water and their correlation to possible sources

Ninety-eight water samples, comprising about 10% of the total sources available to rural homes in Hampton County, South Carolina, were randomly selected and analyzed for inorganic constituents. Chemical contamination is widespread in this area and many people are using substandard quality water.A noticeable number of water samples showed unacceptable levels of arsenic, iron, manganese and mercury. Iron and collodial material were chiefly responsible for turbidity in 19% of the water sources. Acceptable levels of cadmium, chloride, copper, lead, nitrate, phosphate, sodium, total solids and zinc were detected in most of the samples.Statistical analysis indicated that leachings from septic tanks were at least partially responsible for the contamination of shallow water supply sources with nitrate, phosphate, chloride and arsenic. Iron, lead and manganese appear to have come from corrosion of antiquated plumbing in older homes.     

Nitrate and chloride concentrations in the high plains aquifer,Texas

Groundwater nitrate and chloride concentrations were compiled for 122 wells in a rural, three‐county area of northwest Texas. The counties are located on the High Plains aquifer, a major source of groundwater in the region. Cropland/pasture is the predominant land use in the study area. The area also contains numerous cattle feedlots. Fertilizer and manure associated with those land uses are potential sources of ground‐water contamination. Although locally elevated above background levels, none of the chemical concentrations exceeded the primary drinking water standard of 44.27 mg/L for nitrate (10mg/L for NO₃ — N) or secondary standard of 250mg/L for chloride. Rank correlations between nitrate and chloride were statistically significant in two of the three counties, where the solutes may have originated from a common surface source. Denitrification and scant precipitation recharge may account for an absence of nitrate levels above the drinking water standard.     

Modellansätze zur langfristigen Entwicklung der Grundwasserqualität im Bourtanger Moor (Emsland)

Agricultural activities and atmospheric acid deposition are responsible for a significant decline of shallow groundwater quality in the Bourtanger Moor area near the German city Haren (Ems). The main indicators of acidification are low soil and groundwater pH and elevated aluminium concentrations. Agricultural nutrient concentrations, e. g. for potassium and nitrate commonly exceed drinking water limits. Polluted water has partially reached deeper layers where drinking water wells are screened. Contaminant spreading is retarded due to geochemical interactions with reactive aquifer material. Cation exchange and autotrophic denitrification are the main processes. Mass balance calculations, colums experiments and hydrogeochemical modelling show that the vertical propagation velocities of the contaminants are in the range of several centimetres per year.     

Effects of chloride,sulfate and natural organic matter (NOM) on the accumulation and release of trace-level inorganic contaminants from corroding iron

This study examined effects of varying levels of anions (chloride and sulfate) and natural organic matter (NOM) on iron release from and accumulation of inorganic contaminants in corrosion scales formed on iron coupons exposed to drinking water. Changes of concentrations of sulfate and chloride were observed to affect iron release and, in lesser extent, the retention of representative inorganic contaminants (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium, lead and uranium); but, effects of NOM were more pronounced. DOC concentration of 1 mg/L caused iron release to increase, with average soluble and total iron concentrations being four and two times, respectively, higher than those in the absence of NOM. In the presence of NOM, the retention of inorganic contaminants by corrosion scales was reduced. This was especially prominent for lead, vanadium, chromium and copper whose retention by the scales decreased from >80% in the absence of NOM to <30% in its presence. Some of the contaminants, notably copper, chromium, zinc and nickel retained on the surface of iron coupons in the presence of DOC largely retained their mobility and were released readily when ambient water chemistry changed. Vanadium, arsenic, cadmium, lead and uranium retained by the scales were largely unsusceptible to changes of NOM and chloride levels. Modeling indicated that the observed effects were associated with the formation of metal–NOM complexes and effects of NOM on the sorption of the inorganic contaminants on solid phases that are typical for iron corrosion in drinking water.     

Arsenic,Nitrate, Chloride And Bromide Contamination In The Gulf Coast Aquifer,South-Central Texas,USA

Arsenic, nitrate, chloride, and bromide concentrations in the Gulf Coast Aquifer of south-central Texas, USA, were compiled, mapped, and evaluated in the context of local land use and geology. Agriculture and oil production are predominant land uses and potential sources of groundwater contamination in the study area. Data were compiled from 69 wells with a median depth of 160.5 v m. Eight observations surpassed the 44.3 v mg/L standard for nitrate (10 v mg/L NO 3 -N), and 24 observations exceeded the 10 v µg/L standard for arsenic. There was a statistically significant, inverse correlation between nitrate and well depth, and a direct correlation between nitrate and arsenic. Arsenic concentrations were significantly higher in a uranium-bearing sand formation compared to other formations in the study area. Chloride concentrations were also high relative to the (secondary) drinking water standard (250 v mg/L), with a median of 342 v mg/L and maximum of 6840 v mg/L. Most chloride/bromide ratios were near 300, but there were four significantly lower values, consistent with oilfield brine or evaporite dissolution. Results of this study suggest that (1) geology exerts a major control on arsenic concentrations in groundwater, (2) agricultural activity contributes substantially to nitrate and chloride and, to a lesser extent, arsenic concentrations in groundwater, and (3) oilfield brine has locally impacted groundwater in the study area.     

Impact of geochemical stressors on shallow groundwater quality

Groundwater monitoring wells (about 70 wells) were extensively installed in 28 sites surrounding Lake Texoma, located on the border of Oklahoma and Texas, to assess the impact of geochemical stressors to shallow groundwater quality. The monitoring wells were classified into three groups (residential area, agricultural area, and oil field area) depending on their land uses. During a 2-year period from 1999 to 2001 the monitoring wells were sampled every 3 months on a seasonal basis. Water quality assay consisted of 25 parameters including field parameters, nutrients, major ions, and trace elements. Occurrence and level of inorganics in groundwater samples were related to the land use and temporal change. Groundwater of the agricultural area showed lower levels of ferrous iron and nitrate than the residential area. The summer season data revealed more distinct differences in inorganic profiles of the two land use groundwater samples. There is a possible trend that nitrate concentrations in groundwater increased as the proportions of cultivated area increased. Water-soluble ferrous iron occurred primarily in water samples with a low dissolved oxygen concentration and/or a negative redox potential. The presence of brine waste in shallow groundwater was detected by chloride and conductivity in oil field area. Dissolved trace metals and volatile organic carbons were not in a form of concentration to be stressors. This study showed that the quality of shallow ground water could be related to regional geochemical stressors surrounding the lake.     

Identifikation und Regionalisierung von Nitratabbauprozessen in einem Grundwasserleiter – Möglichkeiten und Nutzen für die Wassergewinnung

Denitrification with pyrite or organic carbon compounds in aquifers can lead to the release of ferrous iron, sulfate and bicarbonate into the groundwater. For the water catchment, Ortheide (Emsdetten, Germany), nitrate reduction with pyrite also causes an increased well clogging with iron hydroxides in some of the wells. With the help of hydrogeochemical modelling (PhreeqC), the main processes in the aquifer of the catchment area were identified and quantified. The presence or absence of pyrite in the aquifer sediments was determined based on groundwater compositions. This allowed the regionalization of autolithotrophic denitrification in the aquifer and the distinction of so called “origin zones” of nitrate, ferrous iron and bicarbonate. Based on these zones, the comparative sensitivity of agricultural areas towards nitrate concentrations in the raw water and the clogging tendency of the wells could be estimated.     

Groundwater quality impacts from the land application of treated municipal wastewater in a large karstic spring basin: Chemical and microbiological indicators

Geochemical and microbiological techniques were used to assess water-quality impacts from the land application of treated municipal wastewater in the karstic Wakulla Springs basin in northern Florida. Nitrate-N concentrations have increased from about 0.2 to as high as 1.1 mg/L (milligrams per liter) during the past 30 years in Wakulla Springs, a regional discharge point for groundwater (mean flow about 11.3 m³/s) from the Upper Floridan aquifer (UFA). A major source of nitrate to the UFA is the approximately 64 million L/d (liters per day) of treated municipal wastewater applied at a 774 ha (hectare) sprayfield farming operation. About 260 chemical and microbiological indicators were analyzed in water samples from the sprayfield effluent reservoir, wells upgradient from the sprayfield, and from 21 downgradient wells and springs to assess the movement of contaminants into the UFA. Concentrations of nitrate-N, boron, chloride, were elevated in water samples from the sprayfield effluent reservoir and in monitoring wells at the sprayfield boundary. Mixing of sprayfield effluent water was indicated by a systematic decrease in concentrations of these constituents with distance downgradient from the sprayfield, with about a 10-fold dilution at Wakulla Springs, about 15 km (kilometers) downgradient from the sprayfield. Groundwater with elevated chloride and boron concentrations in wells downgradient from the sprayfield and in Wakulla Springs had similar nitrate isotopic signatures, whereas the nitrate isotopic composition of water from other sites was consistent with inorganic fertilizers or denitrification. The sprayfield operation was highly effective in removing most studied organic wastewater and pharmaceutical compounds and microbial indicators. Carbamazepine (an anti-convulsant drug) was the only pharmaceutical compound detected in groundwater from two sprayfield monitoring wells (1-2 ppt). One other detection of carbamazepine was found in a distant well water sample where enteroviruses also were detected, indicating a likely influence from a nearby septic tank.     

Nitrate contamination in private wells in rural Alabama, United States

Nitrate-N (NO(3)(-)-N) concentrations in random water samples from rural residential wells in Alabama, USA, were analyzed over an 8-year period from 1992 to 1999. Data collected included land use, well depth, septic tank use and distance from the well and also livestock and cropping activities around wells. Of 1021 available data sets, 36% of samples showed nitrate-N concentration of higher than 1.0 mg/l, indicating the possible influence of anthropogenic activities. About 1.7% of samples had a nitrate-N concentration of higher than 10 mg/l. Results indicate nitrate contamination in groundwater was relatively low and stable in Alabama. Logistic regression analysis indicated that well depth, pH, and cropping activity were factors of statistical significance in influencing nitrate-N concentration in these wells. Factors such as septic tank use and livestock activities did not show a close link to nitrate-N concentration in wells tested.     

Einfluss von Methaneinträgen auf die Hydrochemie des Münsterländer Kiessandzuges

The Münsterländer Kiessandzug, a Quaternary trench structure, forms an important groundwater reservoir and is of great importance for the regional drinking water supply in north-west Germany (“Münsterland”). Since 2004, the Ruhr-University Bochum has been investigating the Aldruper Mark, evaluating the quantitative and qualitative potential for drinking water abstraction in the area. Due to intensive agricultural utilisation, a high nitrate influx into groundwater is expected. Therefore, this study was focused on contamination of groundwater with nitrate as well as on the nitrate degradation capacity of the sediments. However, present analyses show low nitrate concentrations and a reductive groundwater environment. To find the causes of these reducing conditions, it is necessary to examine the geological and hydrochemical situation with respect to the environment and the substratum of the investigated area: the MünsterländerCretaceous basin is underlain by Carboniferous sand- and mudstones which are degasing methane to some extent. This methane was detected in deep observation wells in the second aquifer of the Münsterländer Kiessandzug. In its central area, low concentrations of nitrate as well as low sulphate concentrations and positive δ³⁴S_sulfate-isotope data indicate active sulphate reduction is occurring in the groundwater. Furthermore, a corresponding sulphide content was found in these Quaternary soils (“secondary pyrite”). An input of methane in the aquifer is discussed as a possible reason for sulphate reduction in the deep aquifer.     

Groundwater contamination from well points -- an experience from the Norwegian groundwater monitoring network

Until 2005 the observation wells of the Norwegian Groundwater Monitoring Network in Quaternary aquifers were equipped with metal well points with brass lining. A laboratory leaching test using a new well point demonstrated that the well point material (galvanized iron pipe), the brass lining and the solder used to fix the lining could cause substantial contamination of the collected well water with a long list of chemical elements (Sn, Zn, Pb, Sb, Cd, Fe, Cu, Mn and Al), depending on well capacity, contact time water/well point and pH. Because groundwater chemistry is receiving increased attention in groundwater monitoring all wells were equipped with high density polyethylene (HDPE) points during the years 2004-2005. The HDPE points did not return any values above detection in a similar leaching test, with some minor values of Zn being the only exception.     

Microbiological quality of water from hand-dug wells used for domestic purposes in urban communities in Kumasi,Ghana

Assessment was done on the microbiological quality of water in hand-dug wells in urban communities in Kumasi, Ghana. A total of 256 water samples were taken from eight wells and examined for faecal coliforms, enterococci and helminths. High contamination levels were recorded in the wells, more so in the wet season, with faecal coliforms levels between 6.44 and 10.19 log units and faecal enterococci between 4.23 and 4.85 CFU per 100 ml. Influence on protection and lining of wells on water quality was not pronounced but mechanization reduced contamination significantly by about 3 log units. This study shows a stronger influence of poor sanitation and improper placement of wells on water quality compared to improvements made from lining and protection of wells. In the race to increase access to drinking water in poor urban settlements, quality of groundwater could be a major barrier, if provision of drinking water is not matched with improvements in sanitation and urban planning.     

Hydrogeologie des Kabul-Beckens (Afghanistan), Teil II: Beschaffenheit des Grundwassers

Shallow groundwater is the main source for drinking water in Kabul. It comes from a multitude of shallow handpumped wells spread over the whole city area. The groundwater is characterised by slightly oxic redox conditions. Interactions with aquifer carbonates lead to high degrees of hardness and near-neutral pH. The mostly negative water budget of the Kabul basin results in strong evaporation which leads to an increase in salt content and some undesirable constituents, including borate. Several years of drought have aggravated this problem. The shallow groundwater in the city has received tremendous amounts of pollutants due to a lack of proper waste and wastewater disposal. Common indicators are elevated concentrations of nutrients such as nitrate and faecal bacteria. The high infant mortality can at least partially be attributed to insufficient water hygiene. Acid generated during the mineralization of the waste water is hidden due to the strong pH buffering capacity. Redox and pH conditions preclude significant mobilisation of trace metals and metalloids.     

Characterization of elemental and structural composition of corrosion scales and deposits formed in drinking water distribution systems

Corrosion scales and deposits formed within drinking water distribution systems (DWDSs) have the potential to retain inorganic contaminants. The objective of this study was to characterize the elemental and structural composition of extracted pipe solids and hydraulically-mobile deposits originating from representative DWDSs. Goethite (α-FeOOH), magnetite (Fe₃O₄) and siderite (FeCO₃) were the primary crystalline phases identified in most of the selected samples. Among the major constituent elements of the deposits, iron was most prevalent followed, in the order of decreasing prevalence, by sulfur, organic carbon, calcium, inorganic carbon, phosphorus, manganese, magnesium, aluminum and zinc. The cumulative occurrence profiles of iron, sulfur, calcium and phosphorus for pipe specimens and flushed solids were similar. Comparison of relative occurrences of these elements indicates that hydraulic disturbances may have relatively less impact on the release of manganese, aluminum and zinc, but more impact on the release of organic carbon, inorganic carbon, and magnesium.     

Microbial contamination of two urban sandstone aquifers in the UK

Development of urban groundwater has historically been constrained by concerns about its quality. Rising urban water tables and overabstraction from rural aquifers in the UK have led to a renewed interest in urban groundwater, particularly the possibility of finding water of acceptable quality at depth. This study assessed the microbial quality of groundwater collected from depth-specific intervals over a 15-month period within the Permo-Triassic Sherwood Sandstone aquifers underlying the cities of Nottingham and Birmingham. Sewage-derived bacteria (thermotolerant coliforms, faecal streptococci and sulphite-reducing clostridia) and viruses (enteroviruses, Norwalk-like viruses, coliphage) were regularly detected to depths of 60 m in the unconfined sandstone and to a depth of 91 m in the confined sandstone. Microbial concentrations varied temporally and spatially but increased frequency of contamination with depth coincided with geological heterogeneities such as fissures and mudstone bands. Significantly, detection of Norwalk-like viruses and Coxsackievirus B4 in groundwater corresponded with seasonal variations in virus discharge to the sewer system. The observation of low levels of sewage-derived microbial contaminants at depth in the Triassic Sandstone aquifer is explained by the movement of infinitesimal proportions of bulk (macroscopic) groundwater flow along preferential pathways (e.g., fissures, bedding planes). The existence of very high microbial populations at source (raw sewage) and their extremely low detection limits at the receptor (multilevel piezometer) enable these statistically extreme (microscopic) flows to be traced. Rapid penetration of microbial contaminants into sandstone aquifers, not previously reported, highlights the vulnerability of sandstone aquifers to microbial contamination.     

Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities

The status of nitrate (NO(3)(-)), nitrite (NO(2)(-)) and ammonium (NH(4)(+)) contamination in the water systems, and the mechanisms controlling their sources, pathways, and distributions were investigated for the Southeast Asian cities of Metro Manila, Bangkok, and Jakarta. GIS-based monitoring and dual isotope approach (nitrate delta(15)N and delta(18)O) suggested that human waste via severe sewer leakage was the major source of nutrient contaminants in Metro Manila and Jakarta urban areas. Furthermore, the characteristics of the nutrient contamination differed depending on the agricultural land use pattern in the suburban areas: high nitrate contamination was observed in Jakarta (dry fields), and relatively lower nutrients consisting mainly of ammonium were detected in Bangkok (paddy fields). The exponential increase in NO(3)(-)-delta(15)N along with the NO(3)(-) reduction and clear delta(18)O/delta(15)N slopes of NO(3)(-) ( approximately 0.5) indicated the occurrence of denitrification. An anoxic subsurface system associated with the natural geological setting (e.g., the old tidal plain at Bangkok) and artificial pavement coverage served to buffer NO(3)(-) contamination via active denitrification and reduced nitrification. Our results showed that NO(3)(-) and NH(4)(+) contamination of the aquifers in Metro Manila, Bangkok, and Jakarta was not excessive, suggesting low risk of drinking groundwater to human health, at present. However, the increased nitrogen load and increased per capita gross domestic product (GDP) in these developing cities may increase this contamination in the very near future. Continuous monitoring and management of the groundwater system is needed to minimize groundwater pollution in these areas, and this information should be shared among adjacent countries with similar geographic and cultural settings.     

The Impact of Plastic Materials on Iron Levels in Village Groundwater Supplied in Malawi

I ron is not normally considered to be a constituent of health significance, and recommended limits for iron in drinking water supplies are based on aesthetic considerations. Experience in Malawi has demonstrated that, even when present in only trace amounts, iron can influence the consumer's acceptance of an improved borehole supply. The effect of the use of plastic construction materials on the iron content of village groundwater supplies was investigated using a statistical approach. The majority of groundwater points using only plastic materials was found to supply water containing less than the WHO guideline value of 0.3 mg/l iron. In contrast, the use of ferrous-materials increased the iron content of the water to unacceptable levels, sometimes causing the consumers to reject the borehole as a source of drinking water.
Bacteriological data show that the quality of the alternative, traditional supply is far inferior to the new improved supply. An otherwise perfectly safe supply may therefore be abandoned as a direct result of contamination introduced by 'down the hole' components. This frustrates efforts to improve the well-being of rural communities, and is a waste of precious development resources.     

生物除铁除锰在地下水处理厂的应用

黑龙江省兰西镇地下水处理厂采用生物除铁除锰技术取得了满意的铁、锰去除效果。尽管原水含铁量为10～14mg/L、含锰量为0．65～1．1mg/L，出厂水水质仍然优于国家饮用水标准，总铁＜0．05～0．1mg/L，总锰＜0．05mg/L，彻底解决了兰西镇居民的生产和生活用水问题。     

Long-term monitoring of arsenic and selenium species in contaminated groundwaters by HPLC and HG-AAS

The long-term concentration and distribution of species of arsenic and selenium in contaminated groundwaters from Kelheim was monitored. Most of the groundwater wells contained elevated concentrations of iron, manganese and sulfur. Arsenic (III), arsenic (V), selenium (IV) and selenium (VI) were separated using high performance liquid chromatography (HPLC) based on phosphate buffers and collected in fractions. Due to the complex matrix, the fractions were analyzed element-specifically by hydride-generating atomic absorption spectrometry (HG-AAS). The combination of HPLC and HG-AAS was selected due to the authors' intention of developing an easy-to-handle, but nonetheless reliable, method suitable for the long-term monitoring of species distribution in an almost routine way, and taking account of the threshold values of 10 microg/l for each element, indicated by German drinking water regulations. To enhance the reliability of the method, analytical quality control experiments were carried out. When applied to groundwater wells from Kelheim (Germany) they revealed that arsenic (V) and selenium (VI) were the dominating species. The presence of arsenic (III) and selenium (IV) was assumed to be supported by organic matter.     

A potential approach for monitoring drinking water quality from groundwater systems using organic matter fluorescence as an early warning for contamination events

The fluorescence characteristics of natural organic matter in a groundwater based drinking water supply plant were studied with the aim of applying it as a technique to identify contamination of the water supply. Excitation-emission matrices were measured and modeled using parallel factor analysis (PARAFAC) and used to identify which wavelengths provide the optimal signal for monitoring contamination events. The fluorescence was characterized by four components: three humic-like and one amino acid-like. The results revealed that the relative amounts of two of the humic-like components were very stable within the supply plant and distribution net and changed in a predictable fashion depending on which wells were supplying the water. A third humic-like component and an amino acid-like component did not differ between wells. Laboratory contamination experiments with wastewater revealed that combined they could be used as an indicator of microbial contamination. Their fluorescence spectra did not overlap with the other components and therefore the raw broadband fluorescence at the wavelengths specific to their fluorescence could be used to detect contamination. Contamination could be detected at levels equivalent to the addition of 60 μg C/L in drinking water with a TOC concentration of 3.3 mg C/L. The results of this study suggest that these types of drinking water systems, which are vulnerable to microbial contamination due to the lack of disinfectant treatment, can be easily monitored using online organic matter fluorescence as an early warning system to prompt further intensive sampling and appropriate corrective measures.