Indicators for Waterborne Pathogens (2004) / Chapter Skim
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6 A Phased Approach to Monitoring Microbial Water Quality
6 A Phased Approach to Monitoring Microbial Water Quality
Pages 243-266
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From page 243... ...
Technological advances described in Chapter 5 provide new opportunities for revising these monitoring procedures. Our increased understanding of microbiology at the molecular level allows existing indicators to be measured using faster and cheaper methods.
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From page 244... ...
For example, warning systems for groundwater typically focus on the presence or absence of bacterial indicators of fecal contamination because high-quality groundwater does not normally contain fecal bacteria and is often used without disinfection. In contrast, quantitative tests for indicator bacteria are used in monitoring surface drinking water intakes because these waters often show some evidence of fecal contamination and are usually treated with filtration and disinfection.
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From page 245... ...
is important because managers should not miss potential microbial water quality problems. Method precision and a definitive (quantitative)
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From page 246... ...
Since confirmation studies focus on assessing health risk, the most important indicator biological attributes during this phase are correlation with contamination sources and transport or survival behavior similar to pathogens. Desirable method attributes include quantifiability and effectiveness at measuring viability or infectiousness, while logistical considerations, rapid turnaround, and broad applicability become less important.
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From page 247... ...
The remainder of this chapter describes application of this framework to three typical monitoring situations: marine beaches, surface water sources of drinking water, and groundwater sources of drinking water. The following sections also provide recommendations regarding the most appropriate indicators at present, in the near-term future (including the proposed Ground Water Rule and Interim Enhanced Surface Water Treatment Rule provisions)
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From page 248... ...
When enterococci have been measured concurrently with fecal coliforms, total coliforms, and E coli, enterococci were the sole indicator failing water quality standards at most sites that failed and exceeded standards at the vast majority of sites where standards failures occurred for other indicators (Noble et al., 2003)
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From page 249... ...
Such etiological studies are recommended and will be important in developing the pathogen-health effects relationships that will form the basis for water quality standards. Level B -- Investigations to Confirm Health Risk Confirmation sampling is standard practice in marine beach monitoring.
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From page 250... ...
, and because current techniques are not sensitive enough to generate meaningful data in a screening mode. Pathogen measurements are suitable at the present time for confirmation sampling; however, because the presence of pathogens along with other data on screening indicators (especially the co-occurrence of high concentrations of indicator organisms)
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From page 251... ...
methods are potentially pow erful tools that are increasingly being used to identify sources of fecal contamination in surface waters, but these methods have been subjected to limited comparative testing. The Southern California Coastal Water Research Project recently led an effort (Griffith et al., 2003)
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From page 252... ...
, but this monitoring applies only to treated water. A requirement for monitoring untreated surface drinking water sources for total coliforms or fecal coliforms is included in the Surface Water Treatment Rule (EPA, 1989a)
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From page 253... ...
Different intakes from the same waterbody should be considered different sources because contamination is sometimes very local in nature. Level B -- Investigations to Confirm Health Risk Health risk or Level B assessment for surface drinking water sources has typically taken place via direct pathogen monitoring.
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From page 254... ...
Testing water for other waterborne pathogens is conducted only via special monitoring studies with experimental or non-EPA-approved methods. Such special studies can target a specific pathogen or utilize a representative protozoan, virus group, and/or enteric bacteria for a broader and more complete source water quality assessment.
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From page 255... ...
promote their use in special studies and monitoring efforts in microbial water quality. Level C -- Source Investigations Monitoring for the presence of fecal contamination is no longer seen as sufficient to establish a priority for public health concerns or as an approach for mitigating or establishing best management practices for reduction of a microbial contaminant in surface water sources of drinking water.
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From page 256... ...
Because of its ubiquitous nature as intestinal flora, as discussed in Chapter 4, Escherichia coli is the most commonly used organism in surface water source tracking investigations. For example, if E
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From page 257... ...
Lastly, it must be kept in mind that all detection methods must be developed in tandem with water concentration and sample preparation methods. APPLICATION TO GROUNDWATER SOURCES OF DRINKING WATER When considering the use of indicators and indicator approaches for monitoring the quality of groundwater, important differences between groundwater and surface waters must be understood.
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From page 258... ...
The use of coliphages, or the joint use of coliphages and one of the bacterial indicators, as suggested by the Drinking Water Committee of the EPA's Science Advisory Board1 (EPA, 2000b) , would avoid many of these potential problems.
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From page 259... ...
For example, detection of fecal indicators demonstrates that groundwater is vulnerable to contamination by surface sources of fecal material. This may be sufficient to spur action, such as installation of on-site treatment in the case of a drinking water well.
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From page 260... ...
Further complicating matters is that many of the manifestations of infection are relatively nonspecific, such as gastroenteritis, so it is not possible to differentiate sources based on the prevalence of a particular type of illness in the community. In urban areas, there may be multiple point and nonpoint sources of human waste, including septic systems, leaking sewer lines, sites at which reclaimed sewage effluent is being used for irrigation or artificial groundwater recharge, and surface waters receiving treated sewage effluent.
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From page 261... ...
IMPEDIMENTS AND DRIVERS TO IMPLEMENTATION The principal impediments to the development and implementation of a phased monitoring framework for the selection and use of indicators and indicator approaches are the requirements for technical development, the cost of more sophisticated monitoring, and institutional resistance to change. Investment by the government in research designed to develop and standardize new molecular techniques will be an important contributor to resolving the first two impediments.
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From page 262... ...
. Under any circumstances, time is of the essence in all three levels of microbial water quality monitoring whenever there exists a possibility that the public may be at risk.
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From page 263... ...
· That tool box should include the following: -- the development of new indicators, particularly direct measures of pathogens that will enhance health risk confirmation and source identification; -- the use of coliphages, as suggested by EPA's Science Advisory Board, in conjunction with bacterial indicators as indicators of groundwater vulnerability to fecal contamination; and -- the use of routine microbiological monitoring of surface water sup plies of drinking water before as well as after treatment. · A significant portion of that investment should be directed toward concentration methods because existing technology is inadequate to measure pathogens of concern at low concentrations.
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From page 264... ...
2003. National Primary Drinking Water Regulations: Long Term 2 Enhanced Surface Water Treatment Rule; Proposed Rule.
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From page 265... ...
2003. Comparison of total coliform, fecal coliform, and enterococcus bacterial indicator response for ocean recreational water quality testing.
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