RECLAIMED WATER -- Studies are not complete for pathogens
National Research Council 1998
http://books.nap.edu/openbook.php?record_id=6022&page=74
"Giardia is one of the most frequently identified microbial pathogens, occurring consistently in high
numbers in untreated wastewater, secondary effluent, and secondary effluent receiving sand filtration
and disinfection. However, the health threat it poses is relatively low because the resulting
gastroenteritis is less severe and more amenable to treatment than infections caused by the viruses or
Cryptosporidium."
[ the scientist really should do proper research rather than depending on drug treatment]]
P, 74
Microbial Contaminants in Reuse Systems
Traditionally, bacterial and other indicators have been used to evaluate the effectiveness of water and wastewater
treatment systems in inactivating microorganisms. Except for special studies, relatively little occurrence information is
available for the pathogens that actually pose health risks. Over the past few years, however, renewed attention has
been given the health risks from microbial contamination of drinking water, and nationwide monitoring programs are
being instituted. In the meantime, much of the information available on specific pathogens comes from microbial
monitoring and studies of nonpotable and some potable reuse projects. 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.
P.75
[This is 20 year old data that does take into account how deadly these pathogens have become]
TABLE 3-1 Common Infectious Agents Potentially Present in Untreated Municipal Wastewater
AGENT DISEASE
Protozoa -- current index
Entamoeba histolytica Amebiasis (amebic dysentery)
Giardia lamblia Giardiasis
Balantidium coli Balantidiasis (dysentery)
Cryptosporidium Cryptosporidiosis, diarrhea, fever
Helminths -- current index
Ascaris (roundworm) Ascariasis
Trichuris (whipworm) Trichuriasis
Taenia (tapeworm) Taeniasis
Bacteria -- current index
Shigella (4 spp.) Shigellosis (dysentery)
Salmonella typhi Typhoid fever
Salmonella (1700 serotypes) Salmonellosis
Vibrio cholerae Cholera
Escherichia coli (enteropathogenic) Gastroenteritis
E. coli 0157:H7 (enterohemorrhagic) Bloody diarrhea
Yersinia enterocolitica Yersiniosis
Leptospira (spp.) Leptospirosis
Legionella pneumophila Legionnaire's disease, Pontiac fever
Campylobacter jejuni Gastroenteritis
Viruses -- current index
Enteroviruses (72 types) [?????]
Poliovirus Paralysis, aseptic meningitis
Echovirus Fever, rash, respiratory illness, aseptic meningitus,
gastroenteritis, heart disease
Coxsackie A Herpangina, aseptic meningitus, respiratory illness
Coxsackie B Fever; paralysis; respiratory, heart, and kidney disease
Norwalk Gastroenteritis
Hepatitis A virus Infectious hepatitis
Adenovirus (47 types) Respiratory disease, eye infections
Rotavirus (4 types) Gastroenteritis
Parvovirus (3 types) Gastroenteritis
Reovirus (3 types) Not clearly established
Astrovirus (7 types) Gastroenteritis
Calicivirus (2-3 types) Gastroenteritis
Coronavirus Gastroenteritis
SOURCE: Adapted from Hurst et al., 1989; Sagik et al., 1978
P. 76
Table 3-1 shows the bacteria, viruses, and protozoan parasites potentially present in untreated municipal
wastewater. Wastewater may also contain helminths (intestinal worms), but these waterborne parasites will not be
discussed in this report because conventional wastewater treatment removes helminths and their relatively large ova
and cysts. 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. Microorganisms were first identified as agents of waterborne disease
during the cholera outbreak in England in the 1860s. In the 1920s, typhoid fever was linked to the waterborne
bacterium Salmonella typhi. Giardia, a water-
P. 77
Enteric bacteria are associated with human and animal feces and may be transmitted to humans through fecal-oral
transmission routes. Most illnesses due to enteric bacteria cause acute diarrhea, and certain bacteria tend to
produce particularly severe symptoms. As measured by hospitalization rates during waterborne disease outbreaks
(that is, the percentage of illnesses requiring hospitalization), the most severe cases are due to Shigella (5.4
percent), Salmonella (4.1 percent), and pathogenic Escherichia coli (14 percent) (Gerba et al., 1994). There is now
evidence suggesting that Campylobacter, Shigella, Salmonella, and Yersinia may also be associated with illness that
causes arthritis in about 2.3 percent of cases (Smith et al., 1993).
P. 78
TABLE 3-2 Waterborne Bacterial Agents of Concern
Bacteria
Average Reported Cases in the United States Annual Case-Fatality Rate (%)a Percent Waterborneb
Campylobacter 8,400,000 0.1 15
Pathogenic Escherichia coli 2,000,000 0.2 75
Salmonella nontyphoid 10,000,000 0.1 3
Shigella 666,667 0.2 10
Yersinia 5,025 0.05 35
a The number of deaths per case expressed as a percentage and based on total cases and deaths reported
annually to the CDC.
b Percentage of cases attributed to water contact or water consumption.
SOURCE: Reprinted by permission of Elsevier Science from Bennett et al., 1987. © 1987 by American College of
Preventive Medicine.
P. 79
The enteric protozoan parasites produce cysts or oocysts that aid in their survival in wastewater. Important
pathogenic protozoa include Giardia lamblia, Cryptosporidium parvum, and Entamoeba histolytica. (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). Giardia is recognized as the most common protozoan
infection in the United States and remains a major public health concern (Craun, 1986; Kappus et al., 1992). The
reported incidence of waterborne giardiasis has increased in the United States since 1971 (Craun, 1986). An
average of 60,000 cases are reported annually, and 60 percent are estimated to be waterborne (Bennett et al.,
1987). Because Giardia is endemic in wild and domestic animals, infection can result from water supplies that have
no wastewater contribution. Densities of Giardia cysts in untreated wastewater have been reported as high as 3375
per liter (Sykora et al., 1991).
TABLE 3-3 Illness Rates From Enteric Viruses
Virus Group
Annual Reported Cases in the United Statesa Fatality Rate (%) Morbidity Rate (%)
Enteroviruses 6,000,000 0.001 Not known
Poliovirus 7 0.90 0.1-1
Coxsackievirus A Not known 0.50 50
Coxsackievirus B Not known
P.80
TABLE 3-4 Emerging and Potential Waterborne Enteric Pathogens
Microorganism
Calicivirus
Astrovirus
Enteric adenovirus
Enteric coronavirus
Torovirus
Picornavirus
Pestivirus
Helicobacter pylori
P. 81
Evidence of Waterborne
Transmission
Numerous reports of
waterborne outbreaks
Waterborne outbreaks
have been reported
None, but known to have
fecal-oral transmission
Petric, 1995
None, but epidemiologic
evidence of fecal-oral
transmission
None
None
None
Probable fecal-oral transmission; some epidemiologic studies have implicated type of water supply as an important risk factor
Lab studies demonstrated H. pylori survival for 10 days in freshwater; also evidence of prolonged survival as viable, nonculturable
coccoid bodies. Recent report of PCR method to detect H. pylori in waterc Enroth and Engstrand, 1995, Shahamat et al., 1989,
West et al., 1990
P.. 82
Microorganism Description Clinical Syndrome
Cyclospora cayetanensis Protozoa with oocysts 8-10 µm in diameter Prolonged, self-limited diarrhea with average
duration of 30 days
a SS RNA = single-strand RNA.
b DS DNA = double-strand DNA.
c PCR = polymerase chain reaction.
Giardia has also been detected in treated effluent and is much more resistant to disinfection with chlorine than
bacteria.
Cryptosporidium was first described as a human pathogen in 1976. Cryptosporidiosis causes severe diarrhea; no
pharmaceutical cure exists. Average infection rates in the United States, as measured by oocyst excretion in a
population, have ranged from 0.6 to 20 percent (Fayer and Ungar, 1986). The disease can be particularly hazardous
for people with compromised immune systems (Current and Garcia, 1991). Since 1985, seven reported waterborne
outbreaks of cryptosporidiosis have occurred in the United States (Lisle and Rose, 1995). In 1993, Cryptosporidium
was responsible for the largest waterborne disease outbreak ever recorded in the United States, causing
approximately 400,000 illnesses in Milwaukee, Wisconsin. This outbreak was attributed to contamination of the
surface water supply by either animal or human wastes (MacKenzie et al., 1995). All research to date suggests that
the current standards for water chlorination are inadequate for inactivation of Cryptosporidium oocysts (Korick et al.,
1990; Peeters et al., 1989). 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. Viruses are
the smallest pathogenic agents. Their simple structure of a protein coat surrounding a core of
P.83
Epidemiologic case- control study in Nepal implicated consumption of untreated water as a risk factor; 1990 outbreak
in Chicago associated with rooftop water storage tanks
Methods to detect in water are currently under development
Ortega et al., 1993 Shlim et al., 1991
genetic material (DNA or RNA) allows prolonged survival in the environment. There are more than 120 identified
human enteric viruses. Some of the better described viruses include the enteroviruses (polio-, echo-, and
coxsackieviruses), hepatitis A virus, rotavirus, and Norwalk virus. Most enteric viruses cause gastroenteritis or
respiratory infections, but some may produce a range of diseases in humans, including encephalitis, neonatal
disease, myocarditis, aseptic meningitis, and jaundice (Gerba et al., 1995, 1996; Wagenkneckt et al., 1991; see
Table 3-1). Cases of poliovirus are low in the United States due to almost universal immunization. Table 3-3 shows
the average number of viral illnesses that occur annually in the United States for the different enteric viral groups. No
general estimates exist regarding the percentage of viral illnesses attributable to contaminated water supplies.
Norwalk and Norwalk-like viruses cause most waterborne viral diseases. 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. (1982)
suggested that such viruses may cause 23 percent of all waterborne outbreaks reported as AGI. From 1989 to 1992,
contaminated drinking water was implicated in four outbreaks associated specifically with Norwalk-like viruses and
hepatitis A virus (Herwaldt et al., 1992; Moore et al., 1993). During the same period, 37 waterborne outbreaks of AGI
affected 15,769 people. In 85 percent of the outbreaks, the water quality met national drinking water standards for
coliform bacteria.
P. 84
Emerging and Unknown Waterborne Pathogens
One concern about potable reuse of reclaimed water is the potential health risk from little-known or unknown
pathogens. In more than half of all reported outbreaks of waterborne disease, no etiologic agent was ever
determined. Some outbreaks that were thoroughly investigated suggest the existence of unrecognized pathogens.
For example, "Brainerd diarrhea," first described in an outbreak in Brainerd, Minnesota, in 1983 (Osterholm et al.,
1986), is characterized by chronic diarrhea lasting an average of 12 to 18 months. Similar symptoms were noted in
several subsequent outbreaks in seven other states where the disease etiology was associated with poor-quality or
untreated drinking water (Parsonnet et al., 1989). Intense microbiological analyses failed to identify any etiologic
agent for this syndrome.
"Emerging" infectious diseases have been defined as those whose incidence in humans has increased within the
past two decades or threatens to increase in the near future (Institute of Medicine, 1992). 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. The occurrence and health significance of
many of these agents in finished drinking water are currently unknown.
Table 3-4 summarizes information on a number of recently recognized enteric pathogens known to have waterborne
transmission or to have the potential for waterborne transmission via fecal-contaminated water. The table includes
the sizes of these organisms (when known), since this may be relevant to their removal by specific water and
wastewater treatment processes. (Several emerging enteric waterborne pathogens that are important outside the
United States e.g., hepatitis E virus, group B rotavirus, and Vibrio cholerae O139 are not discussed here because
these infections have not been transmitted within the United States.)
Norwalk virus and related human caliciviruses are considered emerging pathogens because new diagnostic
techniques have recently identified their roles as major waterborne and foodborne pathogens. A number of other
viruses are known or putative enteric pathogens. However, little or no evidence exists regarding waterborne
transmission of these organisms. Methods to detect them in water and wastewater have not been developed, and
little or no information exists about their survival or transmission in water. For instance, astroviruses are recently
recognized
P. 85
enteric pathogens. Initially there were only a few anecdotal reports of transmission by contaminated water in the
literature (Kurtz and Lee, 1987). More recently, large outbreaks and the importance of astroviruses have been
recognized, and evidence for waterborne transmission is mounting (Abad et al., 1997). Enteric adenoviruses
(serotypes 40 and 41, also known as subgenus F) are DNA viruses that are a common cause of pediatric diarrhea.
Although adenoviruses have been recovered from sewage (Foy, 1991), there has been no evidence of drinking
water waterborne transmission, though recreational outbreaks have been reported (Crabtree et al., 1997).
Coronaviruses were first observed in feces of persons with gastroenteritis by electron microscopy in 1975, but since
then they have also been frequently detected in the feces of healthy people; their etiologic role in human diarrhea
remains doubtful. Epidemiologic evidence suggests that fecal-oral transmission and personal hygiene may be key
factors in transmission since several studies have noted that the highest prevalence rates were among populations
with poor personal hygiene (Caul, 1994).
Toroviruses, which are well-established enteric pathogens of cattle and horses, have been found in stool samples
from children and adults with diarrhea (Koopmans et al., 1991, 1993) but have remained unconfirmed as human
pathogens. Similarly, picornavirus and pestivirus have been detected in fecal specimens from adults and children
with diarrhea, but their clinical significance is not known.
The pathogenic bacterium Helicobacter pylori, formerly referred to as Campylobacter pylori, causes indigestion and
abdominal pain, and chronic infection may result in peptic ulcers and gastric cancer. H. pylori infections occur
throughout the world, and the prevalence of infection increases with age. Fecal-oral transmission of H. pylori
infection has been suggested by several studies that implicated crowding, socioeconomic status, and consumption of
raw, sewage-contaminated vegetables as risk factors for infection (Hopkins et al., 1993; Mendall et al., 1992; Mitchell
et al., 1992). Studies in Peru have identified type of water supply (municipal vs. community wells) 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 high income children who drank well
water, with community wells posing a higher risk than treated municipal supplies (Klein et al., 1991). Yet a
seroprevalence survey of 245 healthy children in Arkansas found no relation between H. pylori seropositivity and
type of water supply (municipal or well) (Fiedorek et al., 1991). However, the levels of fecal contamina-
P. 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.
Aeromonads are commonly found in water and soil. Densities in water are related to fecal pollution and temperature,
and aeromonads proliferate in domestic and industrial wastewater (Schubert, 1991). Some evidence suggests that
Aeromonas may produce enterotoxins (Mascher et al., 1988), and several reports have suggested an association
between gastroenteritis and Aeromonas in drinking water (Burke et al., 1984; Schubert, 1991). One study in Iowa
concluded that three strains of Aeromonas were capable of causing diarrhea and that consumption of untreated
water was a risk factor for Aeromonas infection (Moyer, 1987). A study in London found a correlation between
Aeromonas isolates from water and iso-
P.88
lates from fecal specimens (Nazer et al., 1990). However, two other studies reported little similarity between
aeromonads isolated from diarrheal feces and those found in drinking water (Havelaar et al., 1992; Millership et al.,
1988). Concern in the Netherlands about the possible health significance of aeromonads has led to the development
of drinking water guidelines of less than 20 colony forming units (CFU) per 100 ml for drinking water leaving the
treatment plant and less than 200 CFU/100 ml for drinking water in the distribution system (van der Kooij, 1993).
Cooper and Danielson (1996) describe several methods of detecting these organisms in water and wastewater.
P. 91
Secondary treatment, however, is designed to remove soluble and colloidal biodegradable organic matter and
suspended solids. In some cases it also removes nitrogen and phosphorus. Secondary treatment consists of an
aerobic biological process whereby microorganisms oxidize organic matter in the wastewater. The aerobic biological
processes include activated sludge, trickling filters, rotating biological contactors, and stabilization ponds. 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.
Conventional secondary treatment reduces pathogens but does not eliminate them from the effluent, even with
disinfection. A Florida sur-
P. 92
TABLE 3-7 Typical Percentage Removal of Microorganisms by Conventional Treatment Processes
Secondary Treatment
Microorganism Primary Treatment Activated Sludge Trickling Filter
Fecal coliforms <10 0-99 85-99
Salmonella 0-15 70-99 85-99+
Mycobacterium tuberculosis 40-60 5-90 65-99
Shigella 15 80-90 85-99
Entamoeba histolytica 0-50 Limited Limited
Helminth ova 50-98 Limited 60-75
Enteric viruses Limited 75-99 0-85
SOURCE: Reprinted, with permission, from Crook, 1992. © 1992 by
vey of wastewater treatment plants using activated-sludge secondary treatment after disinfection found viruses
averaging 10 to 130 PFU/100 liters in 40 to 100 percent of the samples (Rose and Gerba, 1990). In a similar survey
in California, 67 percent of the samples taken from secondary wastewater treatment facilities following disinfection
contained viruses at levels ranging from 2 to 200 PFU/100 liters (Asano et al., 1992). Other studies of secondary
effluent report similar findings, ranging from 3.5 to 650 PFU/100 liters (Rose et al., 1996, 1997; Yanko, 1993).
However, Irving (1982) reported levels of enteroviruses as high as 715,000 viral PFU/100 liters. Likewise, protozoa
can survive secondary treatment and disinfection. Cryptosporidium oocysts have been reported in secondary
effluent at a level of 140 oocysts/100 liters (Rose et al., 1996), while Giardia cysts were found to range from 440 to
2297 cysts/100 liters (Rose et al., 1996, 1997). Table 3-8 summarizes the reported levels of pathogenic and
indicator microorganisms in secondary effluent. These data suggest that wastewater discharges are contributing
enteric pathogens to ambient waters, many of which may be used downstream for drinking purposes. 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.
P.93
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. Besides bacterial pathogens, viruses were a major concern, and almost all of the
reuse projects and studies undertaken, whether pilot scale or full
P,94
TABLE 3-8 Reported Levels of Pathogenic and Indicator Microorganisms in Secondary Effluent From
Wastewater Treatment Plants
Average Levels Reported (CFU, PFU, or cysts/oocysts per 100 liters)
Reference Clostridium Total Fecal Enterococci Coliphage Enterovirus Cryptosporidium Giardia
coliform coliform oocysts cysts
Occoquan, 4,452 170,000 7,764 2,186 1,821 75.8 Not detected 2,297
Virginia
(Rose et al.
1997)
St. Not tested 1.5 x 106 190,000 Not tested 5 x 105 20 140 440
Petersburg,
Florida (Rose
et al., 1996)
Tampa, Not tested Not tested Not tested Not tested Not tested 3.5 Not tested 5
Florida (a)
(City of
Tampa,
1990)
California Not tested Not tested Not tested Not tested Not tested 650 Not tested Not tested
Yanko 55
1993 (b) 56
a Denitrified secondary effluent.
b Data reported from three reclamation plants.
P. 95
TABLE 3-9 Survival of Enteric Pathogens and Indicator Bacteria in Fresh Waters
[If coliforms die at 10 to 20°C or less, why is the test done at 37°C? What about viable, but nonculturable
pathogens?]
Microorganism Time Reported (days) for 90 Percent Reduction in Viable Concentrations
Coliforms 0.83 to 4.8 days at 10 to 20°C, average 2.5 days
E. coli 3.7 days at 15°C
Salmonella 0.83 to 8.3 days at 10 to 20°C
Yersinia 7 days at 5-8.5°C
Giardia 14 to 143 days at 2 to 5°C , 3.4 to 7.7 days at 12 to 20°C
Enteric viruses 1.7 to 5.8 days at 4 to 30°C
SOURCES: Feachem et al., 1983; Korhonen and Martikainen, 1991; Kutz and Gerba, 1988; McFeters and Terzieva,
1991.
scale, began monitoring for enteric viruses in addition to the routine indicator bacteria.
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. Instead, microbial water quality standards have largely
relied on bacterial indicators or treatment performance. Total coliform is used as a national standard for drinking
water (the standard is less than 1/100 ml), while total or fecal coliforms are used in some states for reclaimed water.
Indicators of treatment performance and water quality have been based on measurements of turbidity and
suspended solids. More recently, enterococci, coliphage (a bacterial virus), and the Clostridium bacterium have been
examined as biological indicators of treatment performance. (Chapter 4 further discusses microbial indicators.)
The increase in identified waterborne giardiasis and cryptosporidiosis outbreaks has made the drinking water
industry more sensitive to protozoan contamination of water supplies. Through the Surface Water Treatment Rule
(U.S. EPA, 1989), EPA developed performance standards for drinking water that require a 99.9 percent reduction of
Giardia cysts and a 99.99 percent reduction of viruses by filtration and/or disinfection. EPA's goal is to achieve an
annual risk no greater than a 1 in 10,000 chance of infection by a waterborne microbe from drinking water (Regli et
al., 1991). While the rule does not specifically address wastewater contamination, it
P. 96
TABLE 3-10 Concentrations of Parasites and Viruses in Disinfected Secondary Effluents Used for Crop Irrigation in
Arizona
Microbial Agent Plant 1 Activated Sludge (aeration, chlorination) Plant 2: Activated Sludge (aeration, denitrification, chlorination)
Giardia cysts/100 liters (positive samples) 66.8 (5/5) 1.57 (2/4)
Cryptosporidium oocysts/100 liters (positive samples) (0/1) No data
Enteroviruses PFU/100 liters (positive samples) 0.125 (3/52) (0/54)
NOTES: Numbers in parentheses are number of positive samples per total samples taken. Treated wastewater is
being used for cotton crop irrigation. The Arizona standard for public access irrigation was less than 2.5 PFU or cysts
per 100 liters.
states that greater reductions may be required if a source water is of poor quality. 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 supplies influenced by upstream wastewater discharges
P. 97
Plant 3: Lagoon (5 days
retention time,
mechanical aeration,
UV light disinfection
18.3 (6/11) 26 (35/38) 43.5 (36/42) (0/7)
11.4 (2/2) 3.4 (16/30) 3.7 (15/34) 1.5 (2/5)
7.75 (11/45) 0.725 (6/16) 0.75 (3/47) No data
SOURCE: C. P. Gerba, personal communication, 1996.
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. Monitoring frequency is established on a case-by-case basis and is determined partly by the flow,
treatment design, and designated reuse application. Frequency ranges from once per month to twice per year. Table
3-10 summarizes the monitoring results for six reclamation facilities that use a variety of secondary treatment options
followed by disinfection with chlorination or ultraviolet light. The effluents were used primarily for irrigating cotton
crops.
Collectively, Giardia was found in 78.5 percent of the effluent samples from all plants at an average concentration of
31.3 cysts/100 liters. Cryptosporidium was found in 59 percent of the samples from all plants at an average
concentration of 5 oocysts/100 liters. Viruses were found in 18 percent of the samples from all plants at an average
concentration of 2.2 most probable number (MPN) PFU per 100 liters. No differences in protozoa levels were readily
detected in the two plants using lagoon effluents.
Table 3-11 illustrates the efficacy of combining sand filtration and
P. 98
TABLE 3-11 Concentrations of Parasites and Viruses in Filtered, Disinfected Secondary Effluents in Arizona
Microbial Agent
Giardia cysts/
100 liters
(positive samples) 11.25 (10/16) 7.4 (4/9) 6.98 (25/50)
Cryptosporidium
oocysts/100 liters
(positive samples) No data 1.88 (1/2) 3.02 (17/50)
Enteroviruses PFU/
100 liters (positive
samples) No data No data 0.15 (2/45)
NOTE: Numbers in parentheses are number of positive samples per total samples taken. Arizona's standard for
public access irrigation was less than 2.5 PFU or cysts per 100 liters.
a Plant 9 operated with secondary treated sewage from Plant 4 in Table 3-10.
SOURCE: C. P. Gerba, personal communication, 1996.
disinfection after secondary treatment. The effluents from these three plants are used to irrigate golf courses.
Giardia was found in 55 percent of all the samples from the three plants at an average concentration of 10 cysts/100
liters. This represents a reduction of 70 percent compared to the nonfiltered effluents in Table 3-10. Cryptosporidium
oocysts were detected in 56.2 percent of all samples at an average concentration of 2.5 oocysts/100 liters,
representing a reduction of 51 percent compared to nonfiltered effluent.
The filter plants varied in design; however, none of the plants used coagulants during the filtration process, which
would have further improved protozoa removal. Viruses were detected in only 4.4 percent of the samples in Plant 9
(the only plant that sampled for viruses) at a level of 0.15 MPN-PFU/100 liters. This represents a reduction of 93.5
percent compared to nonfiltered effluents. Dual-media filtration is particularly effective in removing suspended solids
and turbidity, which enhances the efficacy of chlorination.
P. 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. However, Campylobacter, nontyphoid Salmonella, and
pathogenic Escherichia coli still cause a significant number of illnesses, and new emerging diseases also pose
potentially significant health risks.
Historically, coliforms have served as an effective indicator for many bacterial pathogens of concern. However, most
recognized outbreaks of waterborne disease in the United States are caused by protozoan and
P. 109
viral pathogens in waters that have met current coliform standards. Table 3-17 summarizes how the three main
microorganisms of concern, Giardia, Cryptosporidium, and the enteric viruses, rank with regard to their occurrence in
wastewater, resistance to water treatment, adequacy of monitoring, and severity of health risk. Giardia is one of the
most frequently identified microbial pathogens, occurring consistently in high numbers in untreated wastewater,
secondary effluent, and secondary effluent receiving sand filtration and disinfection. However, the health threat it
poses is relatively low because the resulting gastroenteritis is less severe and more amenable to treatment than
infections caused by the viruses or Cryptosporidium. Cryptosporidium, which may cause severe diarrhea in
immunocompromised individuals, is found in highly variable levels in wastewater. It is highly resistant to disinfection
and difficult to detect in untreated wastewater with current methods. Studies in California show that disinfection
standards using a concentration/contact time approach can reliably reduce enteroviruses in reclaimed waters.
However, monitoring has not been conducted for other viruses of concern, such as adenoviruses, rotaviruses, and
Norwalk and related human caliciviruses.
Wastewater may also contain a number of newly recognized or ''emerging" waterborne enteric pathogens or potential
pathogens. For some of these organisms there is no evidence of waterborne transmission, and their occurrence in
wastewater is suspected but not documented.
Description
Group of ''small round structured viruses" approx.
27-35 nm diameter, SSa RNA. Includes Norwalk
virus, Snow Mountain virus, and Hawaii virus
Small, round structured virus approx. 28-30 nm
diameter, SS RNA, 7 serotypes
Approx. 70-80 nm diameter, DS DNAb virus, mainly
serotypes 40 and 41
Between 100 and 150 nm diameter, enveloped SS
RNA virus; major gastrointestinal pathogens of
animals, putative enteric pathogens for humans
Enveloped. Approx. 100-150 nm diameter, SS RNA
viruses; well-established enteric pathogens for
animals, putative enteric pathogens for humans
Approx. 25-30 nm diameter, double-stranded RNA
viruses
Single-stranded RNA viruses
Typically, curved, gram- negative rods 3 x 0.5µm,
microaerophilic
Reports of Occurrence
Methods to detect in water are currently being
developed
No methods to detect in water
Has been recovered from sewage
No methods to detect in water
No methods to detect in water
No methods to detect in water
No methods to detect in water
Clinical Syndrome
Acute gastroenteritis, major cause of outbreaks of
nonbacterial, acute gastroenteritis
Acute gastroenteritis, mainly in children and the
elderly
Gastroenteritis with duration of 7-14 days;
associated with 5-12% of pediatric diarrhea
Acute gastroenteritis
Acute gastroenteritis
Diarrhea
Pediatric diarrhea
Colonization of stomach causes persistent
low-grade gastric inflammation; chronic
infections may result in peptic ulcers and gastric
cancer
References
Kapikian et al., 1996
Matsui and Greenberg, 1996
Foy, 1991
McIntosh, 1996
Koopmans et al, 1991,1993
Pereira et al., 1988
Yolken et al., 1989
Plant 4: Biotowers
(compressed air,
chlorination)
Plant 5: Activated
Sludge (oxygen,
chlorination)
Plant 6: Lagoon
(mechanical aeration,
chlorination)
Plant 7: Lagoon (aeration,
filtration, chlorination)
Plant 8: Activated Sludge
(aeration, filtration, chlorination)
Plant 9a: Filtration (deep bed dual media
sand and coal pressure filters, chlorination)