EPA Maximum Contaminant Level Research Articles

Point-of-use chlorine residuals and disinfection byproduct occurrences in rural households served by public water utilities in Appalachian Virginia

ABSTRACT We characterized concentrations of trihalomethanes (THMs), a measure of disinfection byproducts (DBPs), in tap water samples collected from households with utility-supplied water in two rural counties in Appalachian Virginia, and assessed associations with pH, free chlorine, and metal ions which can impact THM formation. Free chlorine concentrations in all samples (n = 27 homes) complied with EPA drinking water guidelines, though 7% (n = 2) of first draw samples and 11% (n = 3) of 5-min flushed-tap water samples exceeded the US Safe Drinking Water Act (SDWA) maximum contaminant level (MCL) for THM (80 ppb). Regression analyses showed that free chlorine and pH were positively associated with the formation of THM levels above SDWA MCLs (OR = 1.04, p = 0.97 and OR = 1.74, p = 0.79, respectively), while temperature was negatively associated (OR = 0.78, p = 0.38). Of the eight utilities serving study households, samples from water served by three different utilities exceeded the EPA MCL for THM. Overall, these findings do not indicate substantial exposures to DBPs for rural households with utility-supplied water in this region of southwest Virginia. However, given the observed variability in THM concentrations between and across utilities, and established adverse health impacts associated with chronic and acute DBP exposure, more research on DBPs in rural Central Appalachia is warranted.

Occurrence and Health Risk Assessment of Phthalates in Municipal Drinking Water Supply of a Central Indian City.

In this study, the occurrence of phthalates in the municipal water supply of Nagpur City, India, was studied for the first time. The study aimed to provide insights into the extent of phthalate contamination and identify potential sources of contamination in thecity's tap water. We analyzed fifteen phthalates and the total concentration (∑15phthalates) ranged from 0.27 to 76.36µgL-1. Prominent phthalates identified were di-n-butyl phthalate (DBP), di-isobutyl phthalate (DIBP), benzyl butyl phthalate (BBP), di (2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), and di-nonyl phthalate (DNP). Out of the fifteen phthalates analyzed, DEHP showed the highest concentration in all the samples with the median concentration of 2.27µgL-1, 1.39µgL-1, 1.83µgL-1, 2.02µgL-1, respectively in Butibori, Gandhibaag, Civil Lines, and Kalmeshwar areas of the city. In 30% of the tap water samples, DEHP was found higher than the EPA maximum contaminant level of 6µgL-1. The average daily intake (ADI) of phthalates via consumption of tap water was higher for adults (median: 0.25µgkg-1day-1) compared to children (median: 0.07µgkg-1day-1). The hazard index (HI) calculated for both adults and children was below the threshold level, indicating no significant health risks from chronic toxic risk. However, the maximum carcinogenic risk (CR) for adults (8.44 × 10-3) and children (7.73 × 10-3) was higher than the threshold level. Knowledge of the sources and distribution of phthalate contamination in municipal drinking water is crucial for effective contamination control and management strategies.

Assessing environmental and radiological impacts and lithological mapping of beryl-bearing rocks in Egypt using high-resolution sentinel-2 remote sensing images

Emerald and other beryls represent a family of the most valuable gemstone around the world and particularly in Egypt. Beryllium (Be) contents in beryl-bearing bedrocks in south Sinai (Wadi Ghazala and Wadi Sedri), and in central and south Eastern Desert of Egypt (Igla area, Zabara-Um Addebaa belt, Homret Akarem, and Homret Mukpid) were investigated in this study. The environmental risk levels of Be, associated major ions, and heavy metals in groundwater nearby to beryl-bearing mineralization were also evaluated. Results showed that Be contents ranged from 1 to 374 ppm in beryl-bearing bedrocks, while in nearby groundwater, Be content has a range of 0.0001–0.00044 mg/L with an average of 0.00032 mg/L, which is within the permissible levels and below (0.004) the U.S. EPA maximum contaminant level (MCL). Most levels of heavy metals (e.g., Be, B, Ni, V, Fe, and Al) in the investigated groundwater of central and south Eastern Desert and south Sinai are within the permissible levels and below their corresponding U.S. EPA MCLs. This study also investigated the radiological risk of natural radionuclides distributed in beryl-bearing bedrocks in the study area using gamma spectrometry; Sodium Iodide [NaI(Tl)] scintillation detector. Among the estimated mean 238U, 232Th, and 226Ra activity concentrations of the studied beryl-bearing rocks, Homret Mukpid (79, 87.15, 60.26 Bq kg−1) and Homret Akarem (111.6, 51.17, 85.1 Bq kg−1) contain the highest values. This may be attributed to their highly fractionated granitic rocks that host uranium and thorium reservoir minerals such as zircon, allanite, and monazite. The estimated data of multi-radiological parameters such as absorbed gamma dose, outdoor and indoor annual effective dose, radium equivalent activity, internal and external indices, index of excess cancer, and effective dose to human organs reflecting no significant impacts from the emitted natural gamma radiation.

Implementing Service-Focused Activities Focused on Water Quality While Teaching a Freshmen Undergraduate Course During the COVID-19 Pandemic

Historically, high levels of self-reported stress, anxiety, and depression are quite common among STEM students. Unfortunately, after multiple semesters of disrupted education due to COVID-19, these mental struggles among students, especially first-year (freshmen) undergraduate engineering students, have only been exacerbated. To mitigate these struggles, active and thoughtful engagement in learning can be implemented. The main goal of this study was to implement an engaging, teamwork building, service-focused Environmental Engineering activity in a freshmen Civil Engineering course (CE 101, Introduction to Civil Engineering) where students performed a water quality monitoring campaign using two commercially available low-cost test strips (2:1 and 5:1) while returning to campus. Additionally, the quality of the results obtained and the students’ reception of this service-focused activity were evaluated. This activity (1) engaged the students, (2) had a positive impact on their environmental engineering knowledge, and (3) generated useful water quality data related to tap water and surficial water in northern Mississippi. Results highlighted the (1) overall good quality of the tap water collected, with the analyzed analytes significantly below the U.S. EPA maximum contaminant levels, (2) ability of low-cost test strips to generate trustworthy data (results obtained by the students were not statistically different, p > 0.05, compared to the quality assurance and quality control samples implemented) that can help local communities in assessing the quality of their water, and (3) ability to perform service-focused activity while teaching STEM courses. Students positively valued this service-focused activity, and they were enthusiastic about further experiencing this approach in other classes.

Nitrate-Stimulated Release of Naturally Occurring Sedimentary Uranium.

Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 μg/L) in many U.S. aquifers, including in areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has been correlated to uranium groundwater concentrations in two major U.S. aquifers. However, to date, direct evidence that nitrate mobilizes naturally occurring U from aquifer sediments has not been presented. Here, we demonstrate that the influx of high-nitrate porewater through High Plains alluvial aquifer silt sediments bearing naturally occurring U(IV) can stimulate a nitrate-reducing microbial community capable of catalyzing the oxidation and mobilization of U into the porewater. Microbial reduction of nitrate yielded nitrite, a reactive intermediate, which was further demonstrated to abiotically mobilize U from the reduced alluvial aquifer sediments. These results indicate that microbial activity, specifically nitrate reduction to nitrite, is one mechanism driving U mobilization from aquifer sediments in addition to previously described bicarbonate-driven desorption from mineral surfaces, such as Fe(III) oxides.

Examining Relationships Between Groundwater Nitrate Concentrations in Drinking Water and Landscape Characteristics to Understand Health Risks.

Nitrate ingested from drinking water has been linked to adverse health outcomes (e.g., cancer, birth defects) at levels as low as ∼2 mg/L NO3‐N, far below the regulatory limits of 10 mg/L. In many areas, groundwater is a common drinking water source and may contain elevated nitrate, but limited data on the patterns and concentrations are available. Using an extensive regulatory data set of over 100,000 nitrate drinking water well samples, we developed new maps of groundwater nitrate concentrations from 76,724 wells in Michigan's Lower Peninsula, USA for the 2006–2015 period. Kriging, a geostatistical method, was used to interpolate concentrations and quantify probability of exceeding relevant thresholds (>0.4 [common detection limit], >2 mg/L NO3‐N). We summarized this probability in small watersheds (∼80 km2) to identify correlated variables using the machine learning method classification and regression trees (CARTs). We found 79% of wells had concentrations below the detection limit in this analysis (<0.4 mg/L NO3‐N). In the shallow aquifer (focus of study), 13% of wells exceeded 2 mg/L NO3‐N and 2% exceeded the EPA maximum contaminant level of 10 mg/L. CART explained 40%–45% of variation in each model and identified three categories of critical correlated variables: source (high agricultural nitrogen inputs), vulnerable soil conditions (low soil organic carbon and high hydraulic conductivity), and transport mechanisms (high aquifer recharge). These findings add to the body of literature seeking to identify communities at risk of elevated nitrate and study associated adverse health outcomes.

Spatial relationship between well water arsenic and uranium in Northern Plains Native lands

BACKGROUND AND AIM: Arsenic and uranium in unregulated private wells affect many rural populations across the US, including American Indian communities. The current EPA maximum contaminant level (MCL) is 10 µg/L for arsenic and 30 µg/L for uranium. Here, we evaluate the association between drinking water arsenic and uranium levels in three tribal regions in North Dakota and South Dakota participating in the Strong Heart Water Study. METHODS: Well water samples were collected in 2014-2020. Metal concentrations from 441 wells were dichotomized by their MCL for a graduated visualization across the regions. Spearman correlations and region-specific semivariograms were computed. Spatial interpolation using inverse distance weighting was conducted by region. RESULTS:Groundwater contamination was extensive; 29% and 7% of wells exceeded maximum contaminant levels for arsenic and uranium respectively. 81% of wells had both arsenic and uranium concentrations at one-tenth of their human-health benchmark (arsenic, 1 μg/L; uranium 3 μg/L). Well arsenic and uranium concentrations were uncorrelated (rs=0.06); however, there appeared to be a spatial correlation of wells co-contaminated by arsenic and uranium associated with flow along a geologic contact. CONCLUSIONS:Elevated arsenic and uranium in drinking water are common across Northern Plains Tribal Lands in the US. More than a third of all wells sampled contained either arsenic or uranium at levels exceeding the MCL, but co-contamination was more common in Region 3. These findings indicate the importance of measuring multiple metals in well water, and to understand underlying hydrogeological conditions. The underlying mechanisms for the prevalence of arsenic and uranium across Northern Plains Tribal Lands in the US, and in particular the occurrence of both elevated arsenic and uranium in drinking water wells in this region, demands further study. KEYWORDS: water quality, multi-pollutant, environmental disparities

Utica Shale Play Oil and Gas Brines: Geochemistry and Factors Influencing Wastewater Management.

The Utica and Marcellus Shale Plays in the Appalachian Basin are the fourth and first largest natural gas producing plays in the United States, respectively. Hydrocarbon production generates large volumes of brine ("produced water") that must be disposed of, treated, or reused. Though Marcellus brines have been studied extensively, there are few studies from the Utica Shale Play. This study presents new brine chemical analyses from 16 Utica Shale Play wells in Ohio and Pennsylvania. Results from Na-Cl-Br systematics and stable and radiogenic isotopes suggest that the Utica Shale Play brines are likely residual pore water concentrated beyond halite saturation during the formation of the Ordovician Beekmantown evaporative sequence. The narrow range of chemistry for the Utica Shale Play produced waters (e.g., total dissolved solids = 214-283 g/L) over both time and space implies a consistent composition for disposal and reuse planning. The amount of salt produced annually from the Utica Shale Play is equivalent to 3.4% of the annual U.S. halite production. Utica Shale Play brines have radium activities 580 times the EPA maximum contaminant level and are supersaturated with respect to barite, indicating the potential for surface and aqueous radium hazards if not properly disposed of.

ASSESSMENT OF RADON CONCENTRATION AND ASSOCIATED HEALTH IMPLICATIONS IN GROUND WATER AND SOIL AROUND RIRUWAI MINE SITE, KANO STATE, NIGERIA AND ITS ENVIRONS

In this study 10 soil and 11 ground water samples were randomly collected, and the 222Rn concentrations were measured using a DURRIDGE RAD7 electronic radon detector. The radon concentration in ground water ranged from 0.53 BqL-1 to 5.13 BqL-1 with a mean value 2.37 BqL-1. The results show that all the groundwater samples collected have 222Rn concentrations below the US EPA Maximum Contaminant Level (MCL) of 11.1 BqL–1 (for states without radon monitoring policy and enhanced indoor air programs). All the ground water samples also have 222Rn concentrations below MCL of 100 BqL–1 recommended by EU. The annual effective dose due to ingestion (Hing) of 222Rn in the groundwater ranged from 0.00386 – 0.03744 mSvyear-1 with a mean value of 0.01706 mSvyear-1. These values are within the ICRP recommended reference level of 1 mSvy–1 for the intake of the radionuclide in water by the general public for a prolonged exposure. The effective radium content, radon mass exhalation rate and alpha index of the soil samples varied from 0.574 – 1.170 Bqkg-1, 0.104 Bqkg-1d-1 – 0,212 Bqkg-1d-1 and 0.00287 – 0.00585 respectively. The alpha index suggests that none of the selected soil samples have a radon mass exhalation that could cause indoor radon concentrations exceeding 200 Bqkg-1. Therefore, it is concluded that the radon concentration in ground water and soil in the study area indicate that the ground water is safe for drinking and it is safe to use the soil as a building material.

Recommended Sampling Intervals for Arsenic inPrivate Wells.

Geogenic arsenic in drinking water is a worldwide problem. For private well owners, testing (e.g., private or government laboratory) is the main method to determine arsenic concentration. However, the temporal variability of arsenic concentrations is not well characterized and it is not clear how often private wells should be tested. To answer this question, three datasets, two new and one publicly available, with temporal arsenic data were utilized: 6370 private wells from New Jersey tested at least twice since 2002, 2174 wells from the USGS NAWQA database, and 391 private wells sampled 14 years apart from Bangladesh. Two arsenic drinking water standards are used for the analysis: 10µg/L, the WHO guideline and EPA standard or maximum contaminant level (MCL) and 5µg/L, the New Jersey MCL. A rate of change was determined for each well and these rates were used to predict the temporal change in arsenic for a range of initial arsenic concentrations below an MCL. For each MCL and initial concentration, the probability of exceeding an MCL over time was predicted. Results show that to limit a person to below a 5% chance of drinking water above an MCL, wells that are ½ an MCL and above should be tested every year and wells below ½ an MCL should be tested every 5 years. These results indicate that one test result below an MCL is inadequate to ensure long-term compliance. Future recommendations should account for temporal variability when creating drinking water standards and guidance for private well owners.

Occurrence and distribution of hexavalent chromium in groundwater from North Carolina, USA

Hexavalent chromium (Cr(VI)) is a groundwater contaminant that is potentially harmful to human health. Understanding the occurrence of Cr(VI) in groundwater resources is critical for evaluating its risks to human health. Here we report a large dataset (n = 1362) of Cr(VI) and total chromium (CrT) concentrations in public, private, and monitoring wells from different aquifers across North Carolina. These water quality data come from new and previous measurements conducted at Duke University, as well as data reported by the U.S. Environmental Protection Agency, the N.C. Department of Environmental Quality, and the U.S. Geological Survey. The data confirm that Cr(VI) is the predominant species of dissolved Cr and that groundwater from aquifers in the Piedmont region contain significantly higher concentrations than groundwater from the coastal plain. Though there is only one exceedance of the U.S. EPA Maximum Contaminant Level (100 µg/L for CrT) in the dataset, over half of all wells measured for Cr(VI) (470 out of 865) in the dataset exceeded the N.C. Health Advisory Level of 0.07 µg/L. Using information from this dataset, we explore three different approaches to predicting Cr(VI) in groundwater: (1) CrT concentrations as a proxy for Cr(VI); (2) Exceedance probabilities of health goals for groundwater from aquifers located in specific geologic areas; and (3) Censored linear regression using commonly measured field parameters (pH, electrical conductivity, dissolved oxygen) with relationships to Cr(VI) as regressors. Combining these approaches, we have identified several areas in the Piedmont region where Cr(VI) in drinking water wells is expected to be higher than the advisory level, which coincide with large population groundwater reliant populations. While this study focuses on N.C., the wide-spread occurrence of Cr(VI) in groundwater at concentrations above health guidelines in aquifers of the Piedmont region could pose high human health risks to large populations in the eastern U.S.

In situ bioremediation of 1,2-dibromoethane (EDB) in groundwater to part-per-trillion concentrations using cometabolism

1,2-Dibromoethane (ethylene dibromide; EDB) is a probable human carcinogen that was historically added to leaded gasoline as a scavenger to prevent the build-up of lead oxide deposits in engines. Studies indicate that EDB is present at thousands of past fuel spill sites above its stringent EPA Maximum Contaminant Level (MCL) of 0.05 μg/L. There are currently no proven in situ options to enhance EDB degradation in groundwater to meet this requirement. Based on successful laboratory studies showing that ethane can be used as a primary substrate to stimulate the aerobic, cometabolic biodegradation of EDB to <0.015 μg/L (Hatzinger et al., 2015), a groundwater recirculation system was installed at the FS-12 EDB plume on Joint Base Cape Cod (JBCC), MA to facilitate in situ treatment. Groundwater was taken from an existing extraction well, amended with ethane, oxygen, and inorganic nutrients and then recharged into the aquifer upgradient of the extraction well creating an in situ reactive zone. The concentrations of EDB, ethane, oxygen, and anions in groundwater were measured with time in a series of nested monitoring wells installed between the extraction and injection well. EDB concentrations in the six monitoring wells that were hydraulically well-connected to the pumping system declined from ~ 0.3 μg/L (the average concentration in the recirculation cell after 3 months of operation without amendment addition) to <0.02 μg/L during the 4-month amendment period, meeting both the federal MCL and the more stringent Massachusetts MCL (0.02 μg/L). The data indicate that cometabolic treatment is a promising in situ technology for EDB, and that low regulatory levels can be achieved with this biological approach.

Spatial and temporal variations in the geochemistry of shallow groundwater contaminated with nitrate at a residential site.

The concentrations of nitrate (NO3-), major ions, and dissolved inorganic carbon (DIC) and the stable carbon isotopes of DIC (δ13CDIC) in shallow groundwater below a 45 × 60m residential property was investigated over a period of 38months. Our aim was to identify the processes which control the spatial and temporal distribution of NO3- in the shallow groundwater and assess water-rock interactions linked to denitrification. Groundwater sampled quarterly from eight locations showed an average NO3- concentration of 36.8mg/L and a range between 0.1 and 214.9mg/L compared to the US EPA maximum contaminant level of 10mg/L. Heterogeneity in nitrate distribution was from residential application of N-based fertilizers offsite and from onsite application on flower beds and for lawn care. The temporal behavior of nitrate at all eight groundwater locations was markedly different and independent of seasonal hydrologic variations. Nitrate attenuation was spatially controlled by heterogeneous denitrification and rain dilution near roof drains. Groundwater locations with active denitrification were characterized by higher DIC concentrations and lower δ13CDIC from organic carbon mineralization and by higher ionic concentrations from weathering of aquifer minerals. The variation in the relative standard deviations (RSD) of the measured parameters over space (RSD-s) and time (RSD-t) was highest for NO3- associated with variable spatiotemporal input and lowest for pH, pCO2, and δ13CDIC indirectly controlled by denitrification. Denitrification induced mineral weathering products such as DIC, Ca2+, Mg2+, and HCO3- showed medium to high RSD-s and RSD-t. The RSD-s and RSD-t were positively correlated (R2 = 0.85) with the RSD-s showing approximately twofold higher magnitude than RSD-t due to greater variability between monitoring wells locations than variability at each groundwater location over time. Nitrate contamination and denitrification represent important long-term driver of aquifer weathering and changes in groundwater geochemistry below residential communities.

Removal of heavy metals by conventional water treatment plants using poly aluminum chloride

In this study, trace heavy metals, such as aluminum (Al), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mn), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), and zinc (Zn) were investigated in the water of the Karun River that enters the water treatment plants (WTP1 and WTP2) in Ahvaz City, Iran. Removal efficiency of these heavy metals was assessed in various units of WTP1 and WTP2, as well. For this purpose, water samples were collected from four different points of the WTP1 and WTP2, namely, the influent (raw water, RW), the effluent of the clarifier (clarifier effluent, CE), and the effluent of the filter (filter effluent, FE). A total of 72 water samples were collected and analyzed for heavy metals using ICP-OES apparatus. The results indicated that all RW samples contain Ba, Cd, Co, Cr, Cu, Ni, Pb, V, and Zn within the US EPA maximum contaminant levels (MCLs), except Al, Fe, Mn, and Sb that crossed the MCLs. High levels of Al (649.9 (±171.6) µg/L, 806.4 (±135.1) µg/L), Fe (484.95 (±127.05) µg/L, and 529.7 (±119.6) µg/L) were found in finished water of WTP1 and WTP2, respectively. Experimental results showed that level of all studied heavy metals except Al reduced in WTP1 and WTP2 effluent. From the observed data, it is found that effluent Al concentration was over influent Al concentration in both WTP1 and WTP2. It is concluded that using PACl as coagulant in WTP1 and WTP2 can increase concentration of aluminum.

Adsorption of 1,2,3-Trichloropropane (TCP) to meet a MCL of 5ppt.

1,2,3-Trichloropropane (TCP) is a groundwater contaminant in the drinking water aquifers in Hawaii and some other states. Granular activated carbon (GAC) has been used for 30 years to treat approximately 60 million gallons per day of TCP-contaminated groundwater in Hawaii. The State of Hawaii's current maximum contaminant level (MCL) for TCP is 600ng/L (ppt), and consideration is being given to lower the MCL to 5ppt. There is no EPA MCL for TCP. A study was conducted to determine if any GAC could meet a 5ppt MCL for TCP, and if so, how many bedvolumes (BVs) could be treated prior to breakthrough. Constant Diffusivity-Rapid Small-Scale Column Tests (CD-RSSCTs) were performed to evaluate GAC adsorption of TCP. Three different groundwaters and six different GACs were utilized. The RSSCTs with the currently-utilized GAC were predictive of the performance of the GAC contactors (50,000 BVs to breakthrough). Any of the six GACs could meet a MCL of 5ppt and some could do so for 150,000 or more BVs. No single GAC was optimal for all three well sites, indicating effects of subtle undefined differences in the water matrix and/or GAC physiochemical properties. The coal-based direct-activated carbon currently being used is the least optimal for all three well sites with respect to meeting a potential new TCP MCL of 5ppt. The most effective GACs for Kunia were the Calgon coal-based GAC and the Siemens enhanced coconut shell GAC, while the most effective for Waipahu were the Siemens regular and enhanced coconut shell GACs, and the most effective for Mililani was the Calgon coal-based GAC. Choosing just one GAC for use at all three well sites (rather than the optimal for each site) would result in a reduction of treatment run time of 1yearat one well site (63% reduction).

A comparison of arsenic exposure in young children and home water arsenic in two rural West Texas communities

BackgroundIn a previously conducted Health Impact Assessment of a well-water dependent southwest community, arsenic (As) levels greater than the EPA Maximum Contaminant Level (10 μg/L) were identified in home water samples. The goals of this study were to test whether children from the previously studied well-water dependent community (Community 1) had higher blood As levels than children from a demographically similar and geographically nearby community dependent on a municipal water supply (Community 2); to test whether home water As levels predicted child As blood levels; and to examine how child As blood levels changed over time.MethodsThis was an observational study of 252 children aged 4 to 12 years from two communities. Children were recruited through elementary schools and tested during the school day; 204 children participated in follow-up testing. Home water samples were collected according to U.S. Environmental Protection agency recommended procedures. Child heavy metal blood levels and home water sample heavy metal levels were analyzed using inductively coupled plasma mass spectrometry. General linear regression analysis was used to test the influence of community on child As levels, and to examine the contribution of home water As levels to child blood As levels.ResultsArsenic was detectable in all children tested. Blood levels ranged from 0.09–2.61 μg/dL; approximately 31% of children tested at Time I (79/252) had blood As values above the current acceptable limit (1.2 μg/dL). Approximately 8% of household water samples (6/76) had As levels higher than 10 μg/L. Community did not predict child blood As levels; seasonal effects differed by Community. At Time II, child blood As levels were higher in Community 2 than in Community 1.ConclusionA large proportion of children in the communities tested had As exposure. Home water As levels did not predict child blood As levels. Fluctuating child blood As levels by season and over time suggested the contribution of multiple factors and the need for further studies.

The application of illite supported nanoscale zero valent iron for the treatment of uranium contaminated groundwater

In this study, nanoscale zero valent iron I-NZVI was investigated as a remediation strategy for uranium contaminated groundwater from the former Cimarron Fuel Fabrication Site in Oklahoma, USA. The 1 L batch-treatment system was applied in the study. The result shows that 99.9% of uranium in groundwater was removed by I-NZVI within 2 h. Uranium concentration in the groundwater stayed around 27 μg/L, and there was no sign of uranium release into groundwater after seven days of reaction time. Meanwhile the release of iron was significantly decreased compared to NZVI which can reduce the treatment impact on the water environment. To study the influence of background pH of the treatment system on removal efficiency of uranium, the groundwater was adjusted from pH 2–10 before the addition of I-NZVI. The pH of the groundwater was from 2.1 to 10.7 after treatment. The removal efficiency of uranium achieved a maximum in neutral pH of groundwater. The desorption of uranium on the residual solid phase after treatment was investigated in order to discuss the stability of uranium on residual solids. After 2 h of leaching, 0.07% of the total uranium on residual solid phase was leached out in a HNO3 leaching solution with a pH of 4.03. The concentration of uranium in the acid leachate was under 3.2 μg/L which is below the EPA's maximum contaminant level of 30 μg/L. Otherwise, the concentration of uranium was negligible in distilled water leaching solution (pH = 6.44) and NaOH leaching solution (pH = 8.52). A desorption study shows that an acceptable amount of uranium on the residuals can be released into water system under strong acid conditions in short terms. For long term disposal management of the residual solids, the leachate needs to be monitored and treated before discharge into a hazardous landfill or the water system. For the first time, I-NZVI was applied for the treatment of uranium contaminated groundwater. These results provide proof that I-NZVI has improved performance compared to NZVI and is a promising technology for the restoration of complex uranium contaminated water resources.

Private well groundwater quality in West Virginia, USA–2010

The Centers for Disease Control and Prevention (CDC), in collaboration with the West Virginia Bureau of Public Health (BPH), initiated an investigation to characterize private well water quality in West Virginia. The objective was to better characterize private well water across various aquifer geologies by testing household drinking water samples and comparing them to EPA's National Primary Drinking Water Standards. The BPH selected ten counties representing three regions to capture geologically diverse areas that represent varying aquifer geology. We collected well-water samples from participating households and analyzed all water samples for 20 constituents currently monitored in public drinking-water systems. We calculated geometric means for each constituent and compared metal concentrations to EPA maximum and secondary contaminant levels by the geologic age of the rock surrounding the aquifer where the sample was obtained. All participating households (n=139) provided a water sample. We detected arsenic at levels higher than the EPA maximum contaminant level in 10 (7.2%) samples. We detected elevated radon-222 in 48 (34.5%) samples. Geologic age of the region was indicative of whether arsenic and radon-222 were present at levels that exceeded current EPA drinking water standards. We found arsenic and radon concentrations were higher in Permian aquifers compared to those of other geologic ages. Homeowners with private wells in areas with Permian aged aquifers could benefit from targeted public health messaging about potentially harmful constituent concentrations in the well water. This may help ensure proper testing and maintenance of private wells and reduce exposure to these constituents.

Concentrations of select dissolved trace elements and anthropogenic organic compounds in the Mississippi River and major tributaries during the summer of 2012 and 2013

The Mississippi River drainage basin includes the Illinois, Missouri, Ohio, Tennessee, and Arkansas rivers. These rivers drain areas with different physiography, population centers, and land use, with each contributing a different suites of metals and wastewater contaminants that can affect water quality. In July 2012, we determined 18 elements (Be, Rb, Sr, Cd, Cs, Ba, Tl, Pb, Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) and chlorophyll-a (Chl-a) in the five major tributaries and in the Upper Mississippi River. The following summer, we determined both trace elements and 25 trace organic compounds at 10 sites in a longitudinal study of the main stem of the Mississippi River from Grafton, Illinois to Natchez, Mississippi. We detected wastewater contaminants, including pharmaceuticals and endocrine disrupting compounds, throughout the river system, with the highest concentrations occurring near urban centers (St. Louis and Memphis). Concentrations were highest for atrazine (673ngL-1), DEET (540ngL-1), TCPP (231ngL-1), and caffeine (202ngL-1). The Illinois, Missouri, and Yazoo rivers, which drain areas with intense agriculture, had relatively high concentrations of Chl-a and atrazine. However, the Ohio River delivered higher loads of contaminants to the Mississippi River, including an estimated 177kgday-1 of atrazine, due to higher flow volumes. Concentrations of heavy metals (Ni, V, Co, Cu, Cd, and Zn) were relatively high in the Illinois River and low in the Ohio River, although dissolved metal concentrations were below US EPA maximum contaminant levels for surface water. Multivariate analysis demonstrated that the rivers can be distinguished based on elemental and contaminant profiles.

Enhanced disinfection of Escherichia coli and bacteriophage MS2 in water using a copper and silver loaded titanium dioxide nanowire membrane

Titanium dioxide (TiO2) is a widely used photocatalyst that has been demonstrated for microorganism disinfection in drinking water. In this study, a new material with a novel structure, silver and copper loaded TiO2 nanowire membrane (Cu-Ag-TiO2) was prepared and evaluated for its efficiency to inactivate E. coli and bacteriophage MS2. Enhanced photo-activated bactericidal and virucidal activities were obtained by the Cu-Ag-TiO2 membrane than by the TiO2, Ag-TiO2 and Cu-TiO2 membranes under both dark and UV light illumination. The better performance was attributed to the synergies of enhanced membrane photoactivity by loading silver and copper on the membrane and the synergistic effect between the free silver and copper ions in water. At the end of a 30 min test of deadend filtration under 254 nm UV irradiation, the Cu-Ag-TiO2 membrane was able to obtain an E. coli removal of 7.68 log and bacteriophage MS2 removal of 4.02 log, which have met the US EPA standard. The free metal ions coming off the membrane have concentrations of less than 10 ppb in the water effluent, far below the US EPA maximum contaminant level for silver and copper ions in drinking water. Therefore, the photo-activated disinfection by the Cu-Ag-TiO2 membrane is a viable technique for meeting drinking water treatment standards of microbiological water purifiers.