Direct Influence Of Surface Water Research Articles

Proposed Drinking Water Standards for PFAS

Proposed Drinking Water Standards for PFAS

Hydrologic interpretation of seasonally dynamic ambient temperature profiles in sealed bedrock boreholes

This study evaluates the utility of ambient temperature profiles collected in sealed bedrock boreholes to assess variability in groundwater flow in discretely fractured shallow bedrock environments. A conceptual model for groundwater flow and groundwater-surface water temperature conditions and their interaction in a temperate climate is developed through a statistical interpretation of time-lapse thermal deviation logs. Temperature profiles were collected in three angled and three vertical boreholes drilled to 24–32 mbgs (meters below ground surface) and temporarily sealed with an impermeable fabric liner in a fractured dolostone bedrock aquifer adjacent to and extending beneath a bedrock river to monitor seasonal hydrodynamics. Ambient borehole temperature profiles collected every 1–8 weeks over a 12 month period identified zones of hydraulic activity during periods of intra-seasonal stability without the interference of open borehole cross-connection. Signal cross-correlation and Fourier spectra analysis of thermal deviation logs provided a novel way to observe the shallow bedrock flow system’s temperature evolution due to advection along discrete fractures in response to seasonal transience, and to identify and isolate noise caused by free-convection cells within the sealed borehole. This approach represents a diagnostic tool that improves confidence in identifying depth discrete, hydraulically active fracture zones from thermal deviation data sets in a shallow, fractured sedimentary bedrock environment. Variably scaled free-convection cells were observed within the borehole water columns during the colder winter periods. Although these periods were accompanied by higher signal noise near the river/atmospheric interface, these cells led to a temporary thermal disequilibrium between the borehole water column and formation water deeper in the bedrock. These conditions increased the maximum depth of thermal detections associated with discrete groundwater flow features from 14 mbgs in the summer to 26 mbgs in the winter, thereby enhancing the understanding of shallow groundwater flow systems under the direct influence of surface water.

Potential use of low-cost data loggers for groundwater temperature in a regulatory program for public water supply: impact of measurement frequency at a karst spring

A simple low-cost procedure for data collection and evaluation was developed to investigate the utility of continuous data loggers and the impact of measurement frequency on a water-quality monitoring method for use in a regulatory program for public water supply and groundwater under the direct influence of surface water (GWUDI). Data loggers were utilized to continuously measure groundwater temperature, descriptive statistics and the coefficient of variation to demonstrate rapid and significant variations. Temperature data were collected from a karst spring located in the Great Valley section of Pennsylvania and reported on daily and 15-min measurement frequencies. In response to five summer rain events, thermographs constructed with the 15-min measurements indicated rapid large-magnitude temperature variations. The average magnitude of change across the five events was 5.3 °C, but the shifts operated on quick timescales; thus, variations were not captured when data were reported on the daily frequency. This resulted in a distorted evaluation on how significant the groundwater temperature variations were, because results were dependent on measurement frequency. The average coefficient of variation percentage for the 15-min datasets was 12%, compared to 3% for the dataset of daily measurements. These findings could have important implications to a public water-supply regulatory program, because the regulatory definition for GWUDI includes those groundwater sources that display rapid and significant variations in water quality. Without high-frequency measurements, one alarming result could be that GWUDI sources, particularly those located in fast-acting hydrogeologic settings, are misevaluated when maximum or minimum water-quality variations are not included in the evaluation. Advancement in science and technology has resulted in data loggers for groundwater temperature that are economical, robust, and easy to install. Thus, their application in regulatory programs should no longer be underutilized, especially in karst spring settings where source construction deficiencies and focused recharge features can result in rain-induced rapid infiltration and water-quality variations on the minute-to-hour timescale.

The precarious freshwater resources of Sable Island, Nova Scotia, Canada: Occurrence and management considerations

This paper presents an overview of the hydrogeology and the freshwater resources of Sable Island, Nova Scotia. The role of the sand deposits, morphology and dynamics of the dune structures and systems, precipitation, and tidal influences are discussed. The distribution, quality, and importance of both surface water and groundwater resources of the island are also presented. Fresh groundwater on the Island occurs in an unconfined sand lens aquifer. Studies to date on the hydrogeology of the island have shown highly variable rates of precipitation, both seasonally and annually, which in combination with the influence of shifting dune structures contribute to a dynamic freshwater /saltwater balance. Infiltration rates into the permeable aquifer system are greater than precipitation rates, precluding surface water flow.The chemical quality of water in the freshwater lens aquifer is generally good and meets the Guidelines for Canadian Drinking Water Quality. The aquifer is vulnerable to surface contamination, however, due to its shallow, unconfined nature, and any water supply wells are highly likely to be classified as being ‘under the direct influence of surface water’ (GUDI). Under these conditions a multi-barrier source water protection plan is considered essential for managing future public drinking water supplies on the Island. Recommendations for future studies, including long-term monitoring of water level trends, are provided to support the sustainable use of groundwater on the Sable Island.

Assessing protozoan risks for surface drinking water supplies in Nova Scotia, Canada.

Protozoa, such as Cryptosporidium parvum and Giardia lamblia, pose a human health risk when present in drinking water. To minimize health risks, the Nova Scotia Treatment Standards for surface water and groundwater under the direct influence of surface water require a 3-log reduction for Giardia cysts and Cryptosporidium oocysts. This study determined the protozoan risk of municipal surface source waters in Nova Scotia, through the use of a pre-screening risk analysis of water supplies, followed by subsequent water quality analysis of the seven highest risk supplies. The water supplies were monitored monthly for 1 year to obtain baseline data that could be used for a quantitative microbial risk assessment (QMRA). The QMRA model outcomes were compared to the Health Canada health target of 10(-6) disability-adjusted life years/person/year. QMRA modeling shows that the treatment facilities meet the required log reductions and disability-adjusted life year target standards under current conditions. Furthermore, based on the results of this work, Nova Scotia should maintain the current 3-log reduction standard for Giardia cysts and Cryptosporidium oocysts. The results of this study show that a pre-screening step can help to inform water sources that are particularly vulnerable to protozoan contamination, which can lead to more focused, cost-effective sampling, and monitoring programs.

Round 1 LT2ESWTR Cryptosporidium Monitoring Results

Cryptosporidium data from the first round of source water monitoring under the Long Term 2 Enhanced Surface Water Treatment Rule were analyzed and evaluated. This rule, promulgated in 2006, requires public water systems treating surface water or groundwater under the direct influence of surface water (GWUDI) to conduct two rounds of source water monitoring and on the basis of the results to implement treatment addressing public health risk from Cryptosporidium. This article summarizes data‐cleaning efforts, sampling and analytical results, binning outcomes, oocyst recovery, and relationships between Cryptosporidium and Escherichia coli measurements. The data indicate that 7% of large systems must implement additional treatment. Small system estimates are unreliable because the data represent only 3% of applicable systems. In aggregate, Cryptosporidium occurrence was higher in flowing stream–type surface water sources compared with reservoir/lake‐type surface water sources or GWUDI supplies.

Groundwater Under the Influence: What to Do When Process Changes Cause Turbidity Problems

Sioux City, Iowa, obtains a large percentage of its drinking water supply from a horizontal collector well and 12 vertical wells adjacent to the Missouri River. Because the water supply is classified as groundwater under the direct influence of surface water, the city was required in the late 1990s to expand its treatment process to deal with potential surface water contaminants. After constructing a chlorine contact chamber to improve the disinfection contact time and replacing filter media to lower iron and manganese levels, the city's treatment plant experienced elevated, fluctuating turbidity levels and manganese oxidation after filtration. The treatment problems led to treatment technique violations, and the city had to conduct an extensive investigation into what caused the problems. After many parameters were investigated, the elevated turbidity levels were attributed to manganese oxidation after filtration, new filter media, and increased contact time. This article discusses the investigation, causes, and the operational changes implemented to control manganese oxidation and turbidity levels.

Zapping Bacteria to Elude the Boiling Point

This article discusses a project where the village of Manteno, Illinois, initiated a boil‐water order when a routine distribution system sample indicated total and fecal coliform bacteria. It was determined that Manteno's aquifer was under the direct influence of surface water and not in compliance with the applicable regulations. As a result, Manteno agreed to either add filtration to its water treatment process or obtain an alternate water supply. The article lists several drawbacks that required a different interim water treatment plan to address these difficulties. It was determined that the most effective method would be the addition of ultraviolet (UV) disinfection ahead of the chlorination process at each wellhouse. Pilot testing plans and results are discussed, along with design and construction, and the good working relationship among Manteno, the consultants, and the Illinois Environmental Protection Agency (IEPA).

Capacity Doubled in Same Footprint

This article discusses an effort by the city of Kennewick, Washington, to increase capacity due to population growth and to operate year‐round to decrease dependence on the collector wells, which had been classified as goundwater under direct influence of surface water. The decision was made to install submerged membranes in lieu of the existing granular media filtration process, thus initiating two other changes: elimination of the ozone contact basin, with a switch to powdered activated carbon and sodium permanganate for taste and odor control; and, a change from chlorine gas to bulk sodium hypochlorite for disinfection. Membrane testing and selection are discussed, along with several incidents of troubleshooting and staying on track to finish the project on schedule. The article finishes with a comparison of granular media versus submerged membranes.

Riverbank Filtration for IESWTR Compliance

The Central Wyoming Regional Water System operates 29 groundwater collection devices in an alluvial aquifer adjacent to the North Platte River. These collection devices were previously designated “groundwater under the direct influence of surface water.” In lieu of constructing a conventional surface water treatment plant, the utility opted to perform a two‐year study to demonstrate that riverbank filtration (i.e., natural filtration) provided the 2.0‐log reduction of Cryptosporidium required under the Interim Enhanced Surface Water Treatment Rule (e.g., riverbank filtration is the primary filtration process). Using multiple surrogates of various sizes encompassing those of Giardia and Cryptosporidium, the utility demonstrated 2.0‐log reductions in more than 90% of matched data pairs. No Giardia cysts or Cryptosporidium oocysts were found in any of the 170 groundwater samples. This level of removal was achieved during the summer months when infiltration rates are high because of increased river stage and well‐field production.

A direct immunoassay for detecting diatoms in groundwater as an indicator of the direct influence of surface water

Groundwater under the direct influence of surface water (GWUDISW) is of concern in communities where growing public demand on groundwater resources has resulted in increased withdrawals and hydraulic stress near surface water bodies. Under these conditions, contaminants such as methyl-tert butyl ether (MTBE) and biological materials have been detected in domestic wells. Other contaminants and pathogens associated with surface water are not routinely tested for in groundwater-supplied systems. To address the need for methods to easily identify potentially vulnerable supplies, a direct immunoassay for the quantitative detection of diatoms in raw water samples was developed as a measure of surface water influence on groundwater. Cell wall preparations from Nitzschia palea Kutzing, a freshwater diatom found throughout North America, were used to produce a polyclonal antibody that was applied in a direct enzyme-linked immunosorbent assay (ELISA) developed to detect the presence of N. palea cell wall components. The direct immunoassay allows detection at 500 cells L−1, a level similar to diatom concentrations observed in samples of groundwater collected near the test site. This investigation was the first attempt to utilize an ELISA as an indicator of surface water influence on groundwater. Further research is needed to develop more specific diatom-based monoclonal antibodies, determine cross-reactivity, and optimize sample processing and ELISA procedures for development of a standardized method.

DETECTION AND IDENTIFICATION OF Legionella SPECIES FROM GROUNDWATERS

Legionellae are opportunistic bacterial pathogens causing Legionnaires’ disease and Pontiac fever and are ubiquitous in surface waters and in infrastructure to contain or distribute water, including pipes, cooling towers, and whirlpool spas. Infection in community-acquired and nosocomial outbreaks is by exposure to contaminated aerosols. Little is known about the presence of legionellae in groundwater. This study used samples from various locations in the United States and Canada to determine if legionellae could be isolated from water and biofilms derived from groundwaters not known to be under the direct influence of surface water. Of the 114 total samples of water and biofilm tested, 29.1% and 28.2% were positive for Legionella by cultivation and polymerase chain reaction (PCR), respectively. Legionellae were found in both warm and colder groundwaters, with more isolates from samples incubated at 30°C than the 35°C conventional temperature for Legionella isolation. The concentration of Legionella found in the water samples ranged from 102 to 105 CFU/L and up to 1.2 × 102 CFU/cm2 in the biofilm. The species of Legionella identified included both known pathogenic species and species that have not yet been identified as human pathogens. Millions of people in Canada, and around the world, rely on groundwater as their source for drinking. This study shows that legionellae are widespread in groundwater and have the potential to seed derived water supplies and biofilms in public distribution systems. This further widens the known sphere of Legionella colonization and the implications of its presence for public health.

Here Is the ‘411’ on Monitoring IFE

This is the fifth and final article on the key components of the Long Term 1 Enhanced Surface Water Treatment Rule (LT1). It discusses the requirement that certain public water systems that serve fewer than 10,000 people using surface water or groundwater under the direct influence of surface water, also referred to as subpart H systems, conduct continuous individual filter effluent (IFE) turbidity monitoring. Previous articles in the series addressed initial steps to comply with the LT1 (August 2002), disinfection profiling (October 2002), benchmarking (March 2003), and combined filter effluent requirements and alternative filtration (July 2003).

Time to Profile and Set the Benchmark

This is the third article in a series on the key components of the Long Term 1 Enhanced Surface Water Treatment Rule (LT1). The first article (August 2002) addressed key provisions of the rule. The second article (October 2002), discussed the necessary components of a disinfection profile. This article discusses developing the profile, plotting the disinfection profile, and identifying the disinfection benchmarks as they apply to public water systems that use surface water or groundwater under the direct influence of surface water and serve fewer than 10,000 people.

Spatial and temporal variation of drinking water quality in ten small Quebec utilities

A comparative study relating to distributed water quality was undertaken in 10 small municipal drinking water utilities in Quebec. All of these utilities apply direct chlorination to surface water or groundwater under the direct influence of surface water without any previous treatment. These utilities were divided into two groups: four utilities that had never or rarely served water violating the provincial drinking water microbiological standards (relating to fecal and (or) total coliform bacteria) and six utilities that very often infringed upon said standards. The objective of this study was to identify key parameters responsible for the differences between the two groups of utilities, to explore the capacity of studied utilities to simultaneously and effectively handle the acute disease risk associated with microorganisms and the chronic health hazard linked to chlorination by-products and to identify the parameters upon which it may be possible to act to achieve better water quality in each of the two utility groups. The study includes comparisons of characteristics of water quality at the source, chlorination conditions in the plant, and water quality from the entrance to the extremity of the distribution system. Results show that the differences between the two groups of utilities are associated essentially with maintained chlorine residuals and heterotrophic plate count bacteria populations in corresponding distribution systems and, to a lesser extent, to the applied chlorine doses. Subsequent multivariate analyses allowed identification of variables (i.e., factors) upon which utility managers may act to improve the quality of distributed water in each group of utilities. For the group of utilities that had very little or no violation, these factors are related to disinfection levels, whereas for the group that often violated quality standards, raw water natural organic matter content reduction through source water protection and raised chlorine doses and residuals appear to be the factors that may lead to better microbiological quality of distributed water. Key words: drinking water, water quality, distribution systems, small utilities, Quebec.

Ground Water under Direct Influence of Surface Water

The Surface Water Treatment Rule and the Interim Enhanced Surface Water Treatment Rule classify some ground-water sources as “ground water under the direct influence of surface water” (GWUDI), and ground waters classified as GWUDI must follow the same treatment guidelines as surface-water sources. The microscopic particulate analysis (MPA) method is the most widely used method to identify GWUDI; however, this method has several deficiencies. An improved protocol for classifying ground-water sources as GWUDI is presented in this paper. The procedure consists of calculating the absolute risk of illness from waterborne Giardia and Cryptosporidium in the pumped water, accounting for the uncertainty in the surface-water concentrations, hydrogeology, straining characteristics, pathogen viability in ground water, and observations of Giardia and Cryptosporidium in samples of the pumped water. In cases where the risk of illness exceeds the acceptable risk, the ground water should be classified as GWUDI. Two examples are presented to illustrate the application of the proposed method.

New Reg Tightens Small System Requirements

This article discusses the three purposes of the proposed Long Term 1 Enhanced Surface Water Treatment and Filter Backwash Rule (LT1FBR), which applies to public water systems using surface water or groundwater under the direct influence of surface water. Other topics of the rule discussed in this article include turbidity, benchmarking, and recycling provisions. The AWWA Filter Backwash Recycle Statement is included.

Introducing the New Federal Regulations for Disinfectants, DBPs, and Microbials

This article discusses two rules published by the US Environmental Protection Agency intended to protect customers against harmful levels of disinfectants (D), disinfection byproducts (DBP), and microbial contaminants. Three major components of the Stage 1 D/DBP Rule are discussed: maximum residual disinfectant level goals and maximum residual disinfectant levels for chlorine, chloramines, and chlorine dioxide; maximum contaminant levels for total trihalomethanes at 0.080 mg/L and the sum of 5 haloacetic acids at 0.060 mg/L; and, precursor removal requirements for surface water systems using conventional treatment. Several major components of the Interim Enhanced Surface Water Treatment Rule (IESWTR) are also discussed: a maximum contaminant level goal of zero for Cryptosporidium; increased turbidity performance standards for filtration; individual filter performance requirements; disinfection profiling and benchmarking requirements; prohibition on construction of new uncovered finished water reservoirs; and, requirements that the state conduct sanitary surveys for all systems using surface water or groundwater under direct influence of surface water. Compliance dates for both the Stage 1 D/DBP Rule and the IESWTR are listed.

Complying with the SWTR: Ohio's experience

Rather than conducting tracer studies, most plant operators elected to use a conservative estimate of effective contact time generated by the state.The Surface Water Treatment Rule (SWTR) stipulates filtration and disinfection requirements for public water systems using surface water or groundwater under the direct influence of surface water. In Ohio, 169 treatment plants serving 5,000,000 people are affected by the SWTR. The authors surveyed these plants to determine how the SWTR's C X T requirements have affected system operation. Existing plants use a wide variety of clearwell configurations. Although tracer studies provide the most reliable estimates of clearwell contact time, few of these systems actually ran tracer tests; instead most accepted a conservative estimate of effective contact time developed by the Ohio Environmental Protection Agency to roughly estimate effective contact time. Determining contact times in the absence of a tracer study presents a unique challenge to enforcement agencies because of the variety of chlorine contact chambers encountered in practice. Under a conservative worst‐case operating scenario, more than half of Ohio's SWTR treatment plants were judged unable to comply with C X T requirements.

Information Collection Rule Delayed

The first rule to be proposed and promulgated as a result of the regulatory negotiation (reg neg) for the Disinfectants‐Disinfection By‐products (D‐DBP) Rule is the Information Collection Rule (ICR). The ICR is designed to fill gaps in the data so that a better scientific basis can be provided for future rules. The reg‐neg advisory committee agreed that the ICR should be proposed December 1993 and promulgated June 1994 so that monitoring could begin October 1994. The proposed rule was published February 10, 1994, in the Federal Register. The rule applies to systems that serve more than 10,000 people and that use surface water or groundwater under direct influence of surface water and the groundwater systems that serve more than 50,000 people. An overview of the July 2, 1993, draft ICR was presented in this column in the October 1993 issue. The proposed ICR is consistent with the requirements summarized in this earlier article, but several important changes have been made. The author lists these changes in the current article.