Ground Water Recharge Using Waters of Impaired Quality (1994) / Chapter Skim
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4 Public Health Issues
4 Public Health Issues
Pages 132-178
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From page 132... ...
Thus, although indirect potable reuse occurs throughout the nation and world wherever treated wastewater is discharged into a water course or underground and withdrawn downstream or downgradient for potable purposes, such sources are in general less desirable than using a higher quality drinking water source. The central question for artificial recharge then is: Can ground water recharged with source waters of impaired quality satisfy this maxim?
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From page 133... ...
To some extent the assessment of possible health risks can rely on the vast body of knowledge that has been developed for water supplies using conventional source waters, such as ground water from relatively uncontaminated aquifers and surface waters. However, there is a substantial amount of uncertainty even for such waters, principally related to the presence of synthetic organic chemicals, inorganic chemicals disinfection byproducts, and pathogenic organisms.
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From page 134... ...
Such assessments generally contain four steps (NRC, 1983~: hazard identification, dose-response assessment, exposure assessment, and risk characterization. This methodology has been used extensively to characterize the risks associated with environmental and occupational hazards and can be used along with epidemiological information to provide a perspective on the possible risks related to exposures from the use of ground water recharged with waters of impaired quality.
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From page 135... ...
The potential doses to the exposed population are calculated on the basis of known or estimated parameters. For recovered water to be used for potable purposes, the exposure is assumed to be the dose contained in 2 liters (l)
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From page 136... ...
In assessing He potential impacts of long-term human exposure to recharged ground water, the degree to which any recovered water (after treatment) used as a public water supply meets these (enforceable)
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From page 137... ...
The Health Effects Study was conducted at the Whittier Narrows Ground Water Replenishment Project, located in the Montebello Forebay area of Los Angeles County, where disinfected filtered secondary effluent, stormwater runoff, and imported river water have been used for replenishment since 1962. The study was designed to develop a database that would enable health and regulatory authorities to determine whether the use of reclaimed water for ground water replenishment at the project should be maintained or modified.
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From page 138... ...
In addition, based on an evaluation of health and vital statistics data for the period from 1969 to 1980, it was reported that residents of the area that received recovered water experienced no increased rates of infectious diseases, congenital malformations, infant and neonatal mortality, low birth weight, cancer incidence, or death due to heart disease, stroke, stomach cancer, rectal cancer, bladder cancer, colon cancer, or all cancers combined, when compared with residents of two control areas that did not receive recovered water. Concentrated organic residues derived from all replenishment sources and ground waters elicited mutagenic responses in the Ames Salmonella Microsome Mutagen Assey that were related to the presence of a mixture of toxic organic compounds.
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From page 139... ...
Overall, this committee, the National Research Council's Committee on Ground Water Recharge, supports the panel's view that He demographic comparison studies are useful in demonstrating the feasibility of this hypothesis and enabling a rapid assessment of potential threats to public health by using available morbidity, mortality and census information originally collected for other purposes. There is, however, a deficiency because exposure and outcome data describe characteristics of groups, and not individuals.
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From page 140... ...
The concentrations of arsenic and THMs in Miramar water are approximately 2 and 10 percent of the drinking water standards, respectively. The mean cancer risk estimate for Miramar water would be 0.9 in 10,000 when the uncertainty is removed by treating the cancer potency value as a point estimate.
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From page 141... ...
Potable Water Reuse Demonstration Project, Denver, Colorado The Comprehensive Health Effects Testing Program for the Denver Water Department's Potable Water Reuse Demonstration Project was designed to evaluate the relative health effects of two water types: one was highly treated (including lime precipitation, activated carbon filtration, reverse osmosis, and various filtration and disinfection steps) recovered water derived from secondary treated wastewater and the over was Denver's drinking water (Lauer et al., 1990~.
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From page 142... ...
Single-chemical and simple in vitro toxicological evaluations are not likely to be responsive to the question of whether the aggregate organic substances in the recovered water would cause any meaningful risk to populations receiving them. For these reasons, broader evaluation strategies are necessary to estimate health risk.
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From page 143... ...
State-of-~e-art toxicological studies in animals provide the only recognized methods for evaluating risk prior to human exposure. · Chemical analysis and monitoring should be continued on reclaimed wastewater as well as extracted ground water to ensure that concentrations of key identified substances, such as those with drinking water standards, are not exceeded and that any other biologically active chemicals are identified.
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From page 149... ...
149 ~D c ~3 CO _ o ~o (Do G~._ COtC E __ a,0 C ._ O~D (Dac,c _ai ID c _ ,o c W ~,o o, __ C~ _._ ,~ c ._ -.
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From page 150... ...
Therefore, the recharge of ground waters with waters of impaired quality is not likely to present unacceptable risks from these inorganic and organic chemical constituents when the extracted water is used for human consumption. However, at the same time the data indicate that some potential source waters have higher concentrations of chemicals of potential health concern than others.
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From page 151... ...
(0.04) C 0.2 aMa~cimum contaminant levels established by EPA as drinking water standards for chemicals.
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From page 152... ...
D 0.005 Mercury 2-10 2 D 0.0003 Nickel 3-600 100 D 0.02 Zinc 4-350 2,000 (HA) D 0.3 Maximum con~ninant levels established by EPA as drinking water standards for chemicals.
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From page 153... ...
Hazard Identification The microorganisms of concern when using wastewater to artificially recharge ground water can be identified using data available from past waterborne disease outbreaks. Table 4.7 lists the microorganisms that have been identified as causative agents of waterborne disease in the United States from 1971 through 1990.
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From page 154... ...
154 cad cat cat x ._ A: o o ._ o 3 et o C)
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From page 156... ...
Copyright 1991, American Water Works Association. In the 1980s, use of un-disinfected or inadequately disinfected ground water in general was responsible for 44 percent of the waterborne disease outbreaks that occurredin the United States (Craun, 1991~.
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From page 157... ...
There are no methods available for culturing the NorwaLk virus in the laboratory. As methods for the detection of enteric viruses and parasites have improved, the percentage of waterborne disease identified as having a viral or parasitic etiology has increased.
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From page 158... ...
The response used in the dose-response determination depends on the purpose of the risk assessment. For example, in balancing the risks between pathogenic microorganisms and DBPs in water, it might be desirable to use mortality as the end point for both cases.
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From page 159... ...
This phenomenon occurs when an individual who has been infected by consuming water containing pathogenic microorganisms transmits the infection to another individual. Secondary spread can be significant for some enteric microorganisms, as shown in Table 4.8.
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From page 160... ...
Exposure to pathogens may occur by direct ingestion of or contact with the recharge water at the surface if recharge is by infiltration, or it may occur by ingestion of recovered water that has been contaminated by the recharge process. The level of exposure as well as the pathogens of concern depend on the route of exposure.
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From page 161... ...
161 CC I_ Ct Ct ._ e~ V o V Cat U: o x ._ V)
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From page 162... ...
The concentration of microorganisms in the ground water is more difficult to determine because it is dependent on the level of treatment prior to recharge and the removal of the venous microorganisms during infiltration through the soil and aquifer; these removal rates are normally unknown. Risk Characterization Using the data from Table 4.8, and assuming an exposure of 2 liters per day of water containing a known concentration of pathogens, the probability of infection, illness, and death from exposure to a given microorganism can be calculated.
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From page 165... ...
(1992) used the ~ model to calculate the risk associated with exposure to viruses in ground water recharge operations.
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From page 166... ...
An effort to calculate infection risks associated with exposure to recovered water produced by California treatment plants was conducted recently (Tanaka et al., 1993~. In this risk assessment, measured concentrations of enteroviruses in unchlorinated secondary effluent, rather than final effluent (in which viral concentrations are generally below detection limits)
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From page 168... ...
Calculated infection risks for effluent treated beyond unchlorinated secondary ranged from 8 per 100 million to 5.8 per 100 billion. RISKS FROM DISINFECTANTS AND DISINFECTION BY-PRODUCTS VERSUS RISKS FROM PATHOGENS From a public health perspective, a central issue associated with the artificial recharge of ground water is how to balance the risks associated with pathogenic microorganisms against those from disinfection by-products (DBPs)
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From page 169... ...
indicated that the probability of mortality induced by improperly disinfected drinking water would exceed the carcinogenic risks introduced by chlorine by as much as 1,000-fold. If disinfection were removed from a contaminated water system that depends on such disinfection, everyone in We community would contract one or more waterborne diseases during their lifetime.
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From page 170... ...
Environmental Protection Agency, 1973, 1992; Ayers and Westcott, 1985~. In addition, many states have developed comprehensive water reclamation and reuse criteria for nonpotable uses of treated municipal wastewater (State of California, 1978; Florida Depar~nent of Environmental Regulations, 1990; State of Texas, 1990; Pawlowski, 1992; State of Washington, 1993~; hence, state water reuse cntena, which are principally directed at public heals protection from pathogenic microorganisms, often are applicable to extracted ground water containing previously recharged wastewater.
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From page 171... ...
Environmental Protection Agency, 1980~. For intermittent spraying using recovered water, occasional inadvertent contact should pose little microbiological health hazard from inhalation.
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From page 172... ...
Trace elements in treated municipal wastewater normally occur in concentrations of less than a few milligrams per liter, with usual concentrations less than 100 ,ug/1 (Page and Chang, 1985~. Organic constituents may be of concern where recovered water is used for crop irrigation, where the organics may bioaccumulate in the food chain, such as in fish-rearing ponds, or where the water from irrigation or other uses reaches potable supplies, which may result in exposure from direct ingestion or by inhalation or skin contact (Andelman, 1990; WiLkes et al., 1992~.
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From page 173... ...
SUMMARY To evaluate the health implications of the use of reclaimed water for ground water recharge, information including, but not limited to, the following is needed: types and concentrations of chemicals present in the water (source water, recovered water, water at the point of use) ; environmental fate, transport, degradation, transformation, and any effect of treatment or processing of the water on the parent compound and breakdown products; toxicological properties of the chemicals; end use of the water; and characterization of human exposure.
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From page 174... ...
Assessing the risk of an individual from pathogens in recovered water is a difficult and uncertain task. Bacteria and parasites generally are removed to a greater extent than enteric viruses during infiltration through soils; thus viruses are of greater concern when exposure is to the affected ground water.
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From page 175... ...
One limitation is that not all the chemicals identified have drinking water standards for such a comparison. There are other uncertainties, too, in such an evaluation, including We limited chemical and toxicological characterizations of source and recovered waters, and the uncertain environmental fates of the chemicals and microorganisms in the recharge systems, and the limited epidemiological data.
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From page 176... ...
1990. Methods for investigation and prevention of waterborne disease outbreaks.
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From page 177... ...
Comprehensive Health Effects Testing Program for Denver's Potable Water Reuse Demonstration Project.
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From page 178... ...
1993. Analysis of 10 years of virus monitoring data from Los Angeles County treatment plants meeting California Wastewater reclamation criteria.
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