Issues in Potable Reuse The Viability of Augmenting Drinking Water Supplies with Reclaimed Water (1998) / Chapter Skim
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3 Microbial Contaminants in Reuse Systems
3 Microbial Contaminants in Reuse Systems
Pages 74-117
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From page 74... ...
Knowing the occurrence and concentration of specific pathogens in reclaimed water is critical to determining exposure and thus assessing the potential health risks of potable water reuse. WATERBORNE DISEASES Microorganisms associated with waterborne disease are primarily enteric pathogens, which have a fecal-oral route of infection (either human-to-human or animal-to-human)
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From page 75... ...
MICROBIAL CONTAMINANTS IN REUSE SYSTEMS TABLE 3-1 Common Infectious Agents Potentially Present in Untreated Municipal Wastewater 75 Agent Disease Protozoa Entamoeba histolytica Giardia lamblia Balantidium cold Cryptosporidium Helminths Ascaris (roundworm) Trichuris (whipworm)
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From page 76... ...
Other microorganisms, such as Legionella, are sometimes classified as waterborne disease agents but will not be addressed because their airborne routes of transmission are distinctly different from the transmission routes of enteric microbial agents. Concerns over particular waterborne microorganisms have changed over the years due to improved sanitary conditions, the use of preventive medicine, and improved microbiological and epidemiological methods for identifying the microorganisms responsible for outbreaks.
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From page 77... ...
Poor collection of clinical and/or water samples and limitations of diagnostic techniques for many enteric pathogens can prevent accurate determination of the pathogen. Clinical symptoms suggest that many of the AGI outbreaks may be due to viral agents, such as Norwalk virus and related human caliciviruses.
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From page 78... ...
However, Campylobacter, nontyphoid Salmonella, and pathogenic Escherichia cold have been estimated to cause 3 million illnesses per year in the United States (Bennett et al., 1987~. Hence, enteric bacterial pathogens remain an important cause of waterborne disease in the United States.
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From page 79... ...
(Helminth ova are present in untreated wastewater; however, they are relatively large and tend to drop out of effluent after primary and secondary treatment.) Waterborne outbreaks of amebic dysentery, caused by Entamoeba, have not been reported in the United States in over 15 years (Bennett et al., 1987~.
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From page 80... ...
100-150 Acute gastroenteritis nm diameter, SS RNA viruses; well-established enteric pathogens for animals, putative enteric pathogens for humans Picornavirus Pestivirus Approx. 25-30 nm diameter, Diarrhea double-stranded RNA viruses Single-stranded RNA viruses Pediatric diarrhea Helicobacter pylori Typically, curved, gram- Colonization of stomach negative rods 3 x 0.5 ,um, causes persistent low-grade microaerophilic gastric inflammation; chronic infections may result in peptic ulcers and gastric cancer
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From page 81... ...
Recent report of PCR method to detect H pylori in waters Table continues on next page
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From page 82... ...
Cryptosporidium oocysts have been detected in municipal wastewater, but their concentrations and removal by wastewater treatment processes have not been fully evaluated (Madore et al., 1987; Rose et al., 1996; Villacorta-Martinez et al., 1992~. Diseases From Enteric Viruses The enteric viruses are obligate human pathogens, which means they replicate only in the human host.
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From page 83... ...
Norwalk virus usually causes mild diarrhea that lasts on average for two days. A significant portion of the waterborne outbreaks reported as AGI are probably caused by Norwalk-like viruses that are not identified because of diagnostic limitations; Kaplan et al.
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From page 84... ...
Some infectious agents, such as Cryptosporidium, were first described in the past 10 to 20 years but have more recently emerged as major causes of waterborne disease. Drinking water from potable reuse systems may pose a risk of exposure to emerging enteric pathogens because raw wastewater contains many enteric pathogens, the removal of which by treatment processes can only be inferred by other measures of microbial quality.
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From page 85... ...
as a risk factor for infection with H pylori and found that water source appeared to be a more important risk factor than socioeconomic status; children from high-income families who received their water from the Lima municipal water supply, which comes from a surface water source, were 12 times more likely to become ill than highincome children who drank well water, with community wells posing a higher risk than treated municipal supplies (Klein et al., 1991~.
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From page 86... ...
Outbreaks and case reports of Cyclospora diarrhea have been associated with exposure to fecal-contaminated water and fruit that may have been irrigated with fecal-contaminated water (Hale et al., 1994; Shlim et al., 1991~. Cyclospora has also been implicated in waterborne transmission, but not as often as Cryptosporidium and Giardia.
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From page 87... ...
Aquatic Bacterial Pathogens of Possible Concern for Potable Reuse Systems Two types of aquatic microorganisms, aeromonads and cyanobacteria, may be of concern for potable reuse systems because their densities in water and/or their production of toxins could be influenced by wastewater nutrients. Indirect reuse systems that contain sufficient nutrients could create blooms of these organisms that may penetrate the treatment barriers and/or proliferate in the distribution system.
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From page 88... ...
However, further research is needed on the acute and chronic toxicity of cyanobacterial toxins, and suitable methods need to be developed for monitoring the types and concentrations of cyanobacterial toxins in natural and treated water supplies (Elder et al., 1993~. OCCURRENCE OF MICROBIAL CONTAMINANTS IN MUNICIPAL WASTEWATER AND AMBIENT WATER Disease epidemics or outbreaks are dramatic events, and our capability to identify the causes of such outbreaks is improving (described in Chapter 4~.
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From page 89... ...
Fecal coliforms Fecal streptococci Shigella Salmonella Pseudomonas aeruginosa Clostridium perfringens Helminth ova Giardia lamblia cysts Cryptosporidium oocysts Entamoeba histolytica cysts Enteric viruses 105-107 1o4_lo6 1-103 1o2 lo4 03-104 03-105 -103 0-104 o2 lo5 o2 lo5 103-104 SOURCE: Adapted from National Research Council, 1996.
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From page 90... ...
The more recent studies also monitored alternative microbiological indicator species coliphage and Clostridium. The use of these indicators for evaluating potable reuse systems is reviewed in Chapter 4.
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From page 91... ...
Generally, primary treatment precedes these biological processes; however, some secondary processes, such as stabilization ponds and aerated lagoons, are designed to operate without sedimentation. Table 3-7 lists typical microorganism removal efficiencies for activated sludge and trickling-filter secondary treatment processes.
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From page 92... ...
All planned potable reuse projects and demonstration studies in the United States have used treatment in addition to secondary treatment, and such additional treatment is essential for protecting against risks of microbiological contamination. Ambient Waters In indirect reuse (either planned or unplanned)
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From page 93... ...
One can estimate a -0.01 to 0.05 logy per day inactivation rate at low temperatures from their data. MICROBIAL DATA FROM WATER REUSE APPLICATIONS The public health hazards posed by microbial pathogens have been recognized since the practice of water reclamation and reuse began.
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From page 95... ...
Aside from water reuse projects, relatively few data exist regarding the levels of specific pathogenic microorganisms in wastewater or drinking water treatment processes, because monitoring is not routine or required in the United States. Neither federal nor state water quality standards specify concentrations of viruses or protozoa in drinking water, ambient waters, wastewaters, or reclaimed waters.
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From page 96... ...
Due to the lack of monitoring information, EPA has recently promulgated the Information Collection Rule, or ICR, to develop an occurrence database for Cryptosporidium, Giardia, and viruses in source waters, in some treated waters, and in various treatment processes. In light of a national move toward watershed-based requirements, the ICR will likely influence future microbial standards and monitoring requirements pertaining to both planned potable reuse projects and potable water sunplies influenced by upstream wastewater discharges.
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From page 97... ...
Microbial Monitoring in Arizona Data on concentrations of Giardia, Cryptosporidium, and enteroviruses are available from wastewater and reclamation facilities in Arizona where the effluent is used for irrigation. Arizona currently has no requirements for monitoring of Cryptosporidium in reclaimed waters; however, this protozoan was included in most monitoring programs.
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From page 98... ...
disinfection after secondary treatment. The effluents from these three plants are used to irrigate golf courses.
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From page 99... ...
99 5o 59 5 cry m 5E~ o o 5E~ V)
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From page 100... ...
Performance criteria specify secondary treatment plus sand filtration to meet a suspended solids standard and a minimum chlorination level of 1 mg/liter
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From page 101... ...
No studies have examined the inactivation of protozoan cysts and oocysts in wastewater or reclaimed water, leaving the mechanisms for inactivation and the efficacy of chlorine disinfection against Giardia cysts or Cryptosporidium oocysts poorly understood. Advanced Treatment for Potable Reuse Table 3-14 summarizes microbial monitoring data available from seven potable reuse facilities using advanced treatment.
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From page 102... ...
Prechlorination Concentration 0.2/100 liters Positive samples 1/19 Percent reduction 99.4% Potomac study (lime, Concentration <1/1700 liters intermediate chlorination, Positive samples 0/56 dual-media filtration, Percent reduction >87% carbon, chlorination or ozonation) Tampa (lime; sand filtration; After Lime RO, UF, or carbon; Concentration 0.06/100 liters ozonation Positive samples 4/25 or chlorination)
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From page 103... ...
MICROBIAL CONTAMINANTS IN REUSE SYSTEMS 103 Other Microbial Cryptosporidium Giardia Pathogens Examined <1/100 liters <1/100 liters Shigella, Salmonella, 0/4 0/15 Campylobacter, Entamoeba >97.5% >99.4% tested, none detected Not tested Not tested Not tested Not tested Not reported Helminths: none found 0/20 0% A+; after chlorination and RO <0.05/100 liters >86.9% removals Not tested 0.13 /100 liters 1/16 99.6% <1/200 litersb 0/6 >99.8% None detected using Not tested light microscopy <1/200 liters in final effluent >99.97% Table continues on next page
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From page 104... ...
, no samples were positive for viruses in the final effluent, an improvement due to improved disinfection and the reduction of influent virus levels by upgrading the secondary treatment from a trickling filter effluent to an activated sludge system. This study also demonstrated that reverse osmosis was not a good substitute for disinfection.
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From page 105... ...
At two reclamation facilities in San Diego and Denver, seeding studies were conducted in which viruses were artificially inoculated in the secondary influent feedwater to advanced wastewater treatment. The results suggest that as much as a 10 logy reduction of viruses can be achieved by multiple barriers within a reclamation facility (Lauer et al., 1991; Western Consortium for Public Health, 1992~.
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From page 106... ...
. Therefore the removal mechanism for protozoa after chemical lime treatment appears to be physical removal of the oocysts.
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From page 107... ...
Chemical treatment was the next most effective and sand filtration the least. No studies to date have examined the disinfection of cysts and oocysts or the optimization of sand filtration in wastewater or reclaimed water.
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From page 108... ...
CONCLUSIONS Microbial contaminants in reclaimed water include the enteric bacteria, enteric viruses, and enteric protozoan parasites. Classic waterborne bacterial diseases, such as dysentery, typhoid, and cholera, while still important worldwide, have dramatically decreased in the United States.
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From page 109... ...
RECOMMENDATIONS To ensure the safety of drinking water produced from reclaimed water, planners, regulators, and operators of potable reuse systems must account for the various existing and potential health risks posed by microbial contaminants. · Potable reuse systems should continue to employ a combination of advanced physical treatment processes and strong chemical disinfectants as the principal line of defense against most microbial contaminants.
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From page 110... ...
· To provide protection against emerging pathogens, the EPA should support research to develop methods for detecting emerging pathogens in environmental samples. Research is also needed on the effectiveness of various water or wastewater treatment processes and disinfectants in removing or inactivating these pathogens.
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From page 111... ...
Giardia more Enteroviruses by Enteroviruses Cryptosporidium resistant to disinfection directly; diarrhea; 1.0% disinfection than coliphage is hospitalization; bacteria or viruses a possible 50% mortality surrogate in immuno compromized population Enteroviruses more resistant than bacteria Cryptosporid ium by filtration Cryptosporid ium oocysts directly; Clostridium is a possible surrogate Giardia causes diarrhea, sometimes chronic; 0.45% hospitalization; 0.0001% mortality isms within treatment trains and to develop performance goals appropriate to planned potable reuse. Most present regulations and guidelines for microbial water quality and treatment performance are based on nonpotable reuse studies focusing on incidental or recreational contact with reclaimed water.
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From page 112... ...
1996. A microbiological comparison of a drinking water supply and reclaimed wastewater for direct potable reuse.
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From page 113... ...
Pp. 1303-1320 in Proceedings of the American Water Works Association's Water Quality Technology Conference, San Francisco, Calif., November 6-10.
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From page 114... ...
1992. Outbreaks of waterborne disease in the United States: 1989-90.
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From page 115... ...
1991. Water quality for potable reuse.
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From page 116... ...
1990. Assessing potential health risks from viruses and parasites in reclaimed water in Arizona and Florida.
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From page 117... ...
1993. Analysis of 10 years of virus monitoring data from Los Angeles County treatment plants meeting California wastewater reclamation criteria.
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