Issues in Potable Reuse The Viability of Augmenting Drinking Water Supplies with Reclaimed Water (1998) / Chapter Skim
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6 Reliability and Quality Assurance Issues for Reuse Systems
6 Reliability and Quality Assurance Issues for Reuse Systems
Pages 208-240
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From page 209... ...
Thus, watershed protection programs, engineered water treatment processes such as disinfection and filtration, and maintenance of the water distribution infrastructure are all considered barriers to certain types of contamination (even though some of these might cause certain aspects of water quality to deteriorate)
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From page 210... ...
. In places where reclaimed water is used to augment natural supplies or where source water cannot be protected from upstream discharges of water with impaired quality, the importance of the barriers at the water treatment plant or wastewater reclamation plant is correspondingly increased.
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From page 211... ...
but the train that includes the membrane process provides considerably greater protection against pathogens C and D USE OF ENVIRONMENTAL BUFFERS IN REUSE SYSTEMS By definition, indirect potable reuse projects include an "environmental buffer," that is, a natural water body that physically separates the product water from the wastewater reclamation plant and the intake to the drinking water treatment plant.
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From page 214... ...
The differences between surface water and ground water storage as environmental buffers are profound, both in terms of processes that may reduce the levels of contaminants of concern and in terms of the degree to which the environmental buffer can be influenced by short circuiting. The potential for short-circuiting of flows introduced into a surface water body deserves special attention.
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From page 215... ...
is often a sound one for indirect potable reuse projects. One of the principal reasons for this is the fact that treated wastewater is usually as warm or warmer than the epilimnion for most of the year.
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From page 216... ...
216 ~_ Kllometers 0 5 10 15 20 25 o 5 10 E 15 20 (~) o Kllometers 0 5 10 15 20 25 ~ go.
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From page 217... ...
The literature also suggests that the removal of some particularly volatile synthetic organic contaminants can be expected during storage in a large surface water body, but the committee is unaware of data demonstrating removal of disinfection by-product precursors or other organic components of health concern. In summary, present evidence suggests that some contaminant removal does occur during storage in or passage through environmental buffers for soil-aquifer treatment systems and in aquifer and surface water systems where residence times are long and short-circuiting is avoided.
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From page 218... ...
These storage times seem appropriate for allowing the development and execution of alternative actions if needed. Loss of Identity of the Water of Wastewater Origin "Loss of identity," meaning mixing of the reclaimed water with water in a natural system, is certainly an important element in the conceptual view of water reuse by both public health authorities and the average citizen.
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From page 219... ...
CONSEQUENCE-FREQUENCY ASSESSMENT A water reclamation plant is an engineered system. Environmental engineering texts have stated that "every water treatment facility must be so designed that, when properly operated, it can produce continuously the design rate of flow and meet the established water quality standards" (Tames M
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From page 220... ...
Conceptually, the reliability of the overall treatment train can be approximated using event chain analysis, which has been formulated as a systematic technique for some other types of engineered systems (Kumamoto and Henley, 1996~. The application of event chain analysis to a portion of a hypothetical reclamation facility is indicated in Figure 63, following Keeney et al.
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From page 221... ...
221 ~4 ~ ~ fi ~ o be au p ~ ~ au ~ X~ 5- ~ ~ o , au vat ~ au o ¢ 5- · ad ~ ~ o ~ ~ o U)
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From page 222... ...
The use of sentinel parameters, combined with a sufficiently large environmental buffer or alternatives for diversion, might permit rapid operational adjustments to prevent microbial or other contaminant exposure of the population. The application of sentinel parameter monitoring to water reclamation facilities is analogous to the application of HACCP (hazard analysis and critical control points)
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From page 223... ...
Monitoring and Response To ensure safety, every treatment facility should have in place rigorous monitoring and control systems to detect and correct lapses in performance. Monitoring The role of monitoring in a water reclamation plant, as in any water treatment plant, is to verify that the routine operational characteristics are in fact achieving the intended objectives.
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From page 224... ...
Another example might be an ad hoc program to characterize the components of the organic carbon that still persist in the advanced wastewater treatment (AWT) product water.
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From page 225... ...
The nature of any public health response will depend on the duration and magnitude of process excursions and the delay time provided by the environmental buffer and by finished water storage. The existence of finished water storage (including perhaps storage of injected product water into an aquifer prior to use)
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From page 227... ...
While concern about chemical risk from reclaimed water remains, the potential for risk management is greater today than in 1982. The largely uncharacterized organic matter in natural water, in conventionally treated wastewater, and in reclaimed water consists of large organic macromolecules usually identifiable in only the broadest way (e.g., by functional groups, molecular weight, aromacity, or acid/base solubility)
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From page 228... ...
The additional barriers in indirect potable reuse, such as dilution, soil-aquifer treatment, and long retention times in surface reservoirs and/or ground water aquifers, will contribute to the overall reduction of organic carbon of wastewater origin to the water supply. As TOC of wastewater origin diminishes, so do the health concerns associated with it.
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From page 229... ...
Adequate disease surveillance requires continuing scrutiny of all aspects of occurrence and spread of a disease that are pertinent to effective control. The most comprehensive and internationally accepted definition of public health surveillance is that found in the American Public Health Association report entitled Control of Communicable Diseases Manual (Benenson, 1995~.
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From page 230... ...
In most waterborne diseases, there is normally a low level of sporadic cases in the population, known as "endemic" illness. As the number of exposed individuals increases, the number of recognized cases will rise.
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From page 231... ...
· testing hypotheses; · evaluating control and prevention measures; · monitoring changes in infectious agents; · detecting changes in health practice; and · planning. Surveillance may be used to identify and track waterborne health hazards even when the water reclamation facility is operating in accordance with applicable regulations and within generally accepted standards.
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From page 232... ...
. provides the ultimate feedback on the efficacy of the standard industry safety plans." Public Health Surveillance and Water Reclamation Recent developments in the application of public surveillance to drinking water uses in general are also relevant to reclaimed water projects.
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From page 233... ...
The approach of the New York advisory panel on waterborne disease assessment was similar to that of the CDC workshop, and its conclusions are likewise relevant to the issue of augmenting potable water supplies with reclaimed water. The panel made five major recommendations: 1.
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From page 234... ...
No state used computerized illness data from health maintenance organizations or the Indian Health Service as a waterborne disease surveillance tool. With fewer than half of the state/territorial epidemiology programs having a designated coordinator for waterborne disease outbreaks and with few of these coordinators having training or experience in drinking water treatment or maintaining contact with the state water treatment specialists, the timeliness of initiation and the effectiveness of outbreak investigations may be compromised.
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From page 235... ...
The ultimate purpose of surveillance systems is to prevent or control the occurrence of adverse health events associated with the ingestion of drinking water sources augmented with reclaimed water. Therefore, any such surveillance system must be jointly planned and operated not only by those who collect the data, but by those who would use these data in conjunction with other monitoring processes to ensure the quality of the water delivered to the consumer.
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From page 236... ...
Where reclaimed water is used to augment natural supplies or where source water cannot be protected from upstream discharges of water with impaired quality, the importance of the barriers at the water treatment plant or wastewater reclamation plant is correspondingly increased. · Because the performance of wastewater treatment processes may vary considerably from time to time, such systems should employ
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From page 237... ...
· Utilities using surface waters or aquifers as environmental buffers should take care to prevent "short-circuiting," by which influent treated wastewater either fails to mix with the ambient water fully or moves through the system to the drinking water intake faster than expected. In addition, the buffer's expected retention time should be long enough to give the buffer time to provide additional contaminant removal.
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From page 238... ...
Further, appropriate interested consumer groups should be involved and informed as to the public health surveillance plan and its purpose. · Operators of water reclamation facilities should receive adequate training that should include the principles of operation of advanced treatment processes, a knowledge of pathogenic organisms, and the relative effectiveness of the various treatment processes in reducing pathogen concentrations.
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From page 239... ...
1994. Report of New York City's Panel on Waterborne Disease Assessment.
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