Using Graywater and Stormwater to Enhance Local Water Supplies An Assessment of Risks, Costs, and Benefits (2016) / Chapter Skim
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5 Characterizing and Mitigating Human Health and Environmental Risks
5 Characterizing and Mitigating Human Health and Environmental Risks
Pages 77-93
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From page 77... ...
When methods that can be used to assess human health risk asthere is little potential for human exposure to the water (such sociated with graywater or stormwater use. The chapter also as subsurface irrigation with graywater)
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From page 78... ...
health effects are long-lasting and typically occur after repeatIn the case of graywater, because it is derived from domes- ed, long-term exposures, most commonly by ingestion of contic wastes, the contaminants of most concern include hu- taminated water. Examples of possible chronic health effects man pathogenic microorganisms and inorganic and organic include various cancers and adverse reproductive outcomes.
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From page 79... ...
Many waterborne disease outbreaks concentrations include whether best management practices have occurred in which indicator bacteria were absent but are followed, such as bypassing laundry water when washing pathogenic microorganisms were present in sufficient numdiapers or other soiled clothing, not disposing of hazardous bers to cause illness (e.g., MacKenzie et al., 1994)
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From page 80... ...
2.5 16 Ingestion on playground by child (frequent hand-to-mouth activity) 4 130 Indirect ingestion of spray from public fountain with spray element 0.1 130 Infrequent ingestion of public fountain water from standing pool 130 4 on hot days Home garden drip or 50 Ingestion of irrigated vegetables and fruit 7 spray irrigation Commercial farm produce drip 140 Ingestion of irrigated vegetables and fruit 10 or spray irrigation Home car wash spray application Ingestion of water and spray 5 24 Commercial car wash spray Ingestion of water and spray by car wash operator 3 250 Toilet Ingestion of aerosol spray 0.01 1100 Washing machine use Ingestion of sprays 0.01 365 Fire fighting Ingestion of water and spray 20 50 NOTE: In a correctly designed subsurface irrigation system (with no surface ponding and no application to food crops)
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From page 81... ...
For example, about the effects on the dose-response relationship of conhuman pathogenic microorganisms have a finite lifetime in taminants when an individual is exposed to more than one the environment. This may range from less than a day to sev- contaminant at a time.
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From page 82... ...
As a point of reference, the "acceptable" dosage may be compared to drinking water maximum contaminant levels (MCLs) , which, for carcinogenic chemicals, are typically set at a level associated with 1 additional cancer death per 100,000 to 1 million persons over the course of a lifetime.
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From page 83... ...
Drinking Water Standard Higha Mediumb Lowc Benzene 0.41 210 550 6,000 Cadmium 18 9,100 25,000 270,000 Helptachlor 0.015 7.5 20 220 Polybrominated biphenyls 0.0022 1.1 3 32 Polychlorinated biphenyls 0.50 250 670 7,300 Trichloroethylene 2.0 1,000 2,700 29,000 Zinc 11 5,500 15,000 160,000 a High exposure includes applications such as commercial farm produce drip or spray irrigation, firefighting, and commercial car washes. b Medium exposure includes public fountains, spray irrigation of playgrounds, home garden spray irrigation, home drip irrigation of fruits and vegetables, and home car washing.
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From page 84... ...
(2010) concluded that most of in three scenarios -- direct contact, spray irrigation of sports the exposure scenarios examined would result in exposure fields, and daily consumption of groundwater recharged that would exceed the acceptable safe dose and that using graywater for spray irrigation or food crop irrigation would 2 The treatment system included settling tanks, activated sludge, a necessitate disinfection to protect against rotavirus.
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From page 85... ...
One report on the concentrations of patho- unclear for conventional drinking water sources, and typigens in untreated graywater was located (see Table 4-2; Birks cal nonpotable graywater exposures under best management and Hills, 2007) , and these data were used to perform ex- practices would be lower.
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From page 86... ...
To achieve the same risk level as is acceptable from drinking water, the concentration of Giardia cysts in the graywater would have to be reduced from 1.5 cysts/liter to 0.46/liter, a reduction of approximately 70 percent. These calculations are meant only to illustrate what risk might be present in one situation and cannot be extrapolated to other environ ments and conditions.
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From page 87... ...
The reduction levels that would be required to meet the tolerable risk level of 10-6 DALYs per person per year were as follows: • For open space irrigation: 1.6 log10 reduction of viruses, 0.6 log10 reduction of protozoa, and 1.2 log10 reduction of bacteria • For nonpotable residential uses (e.g., toilet flushing, laundry) : 2.7 log10 reduction of viruses, 1.8 log10 reduction of protozoa, and 2.3 log10 reduction of bacteria • For drinking water: 5.8 log10 reduction of viruses, 4.8 log10 reduction of protozoa, and 5.3 log10 reduction of bacteria.
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From page 88... ...
(2012) described several cases in is the unplanned recharge of stormwater or graywater into Australia in which cross-connections between potable water an aquifer used for a drinking water supply.
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From page 89... ...
With the growing practice of "enhanced ron) , pathogens, and organic contaminants from cleaning or infiltration" for groundwater replenishment, there is concern personal care products.
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From page 90... ...
Few studies have examined the efficacy of infiltration experience significant contaminant exposures. For stormwapractices for removing pathogenic organisms (Weiss et al., ter capture projects, ecological exposure scenarios may not 2008)
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From page 91... ...
In a study of seven U.S. these studies, animals were known to contribute to indicahouseholds using graywater for irrigation, soil SAR levels tor organisms in both graywater- and potable water-irrigated were elevated in graywater-irrigated soil compared to fresh- areas, and it was not possible to differentiate the contribution water-irrigated soil, and the soil SAR at a site with more than of indicator organisms from graywater from other natural 30 years of graywater irrigation was 2-22 times greater than contributions of indicator organisms.
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From page 92... ...
with minimal human exposures might allow for much higher The risk of groundwater contamination from stormwater reconcentrations of contaminants in graywater or stormwater charge is related to the contaminants present, any pretreatand still result in acceptably low health risks. Risk assess- ment processes installed, the capacity for the subsurface soil ment tools provide a ready means for developing such cri- and engineered media used in the infiltration basin to remove teria for many chemicals and microbes for which drinking them, and the proximity to groundwater used as a drinking water criteria exist.
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From page 93... ...
If not sidering the overall environmental benefits provided by such controlled at the source, then long-term build-up of boron or features, including reduced pollution to other surface waters, salt can pose risk to plant and soil health, depending on soil but the ecological objectives of such projects are often unand climatic conditions. Constructed stormwater ponds and clear, hindering efforts to limit ecological risks through imwetlands typically contain elevated contaminant levels suf- proved management and design.
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