Biosolids Applied to Land Advancing Standards and Practices (2002) / Chapter Skim
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6 Evaluation of EPA's Approach to Setting Pathogen Standards
6 Evaluation of EPA's Approach to Setting Pathogen Standards
Pages 257-321
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From page 257... ...
. It also reviews approaches for conducting microbial risk assessments and discusses how those approaches might be used to improve EPA's pathogens standards for biosolids.
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From page 258... ...
3. Anaerobic digestion under defined time and temperature conditions.
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From page 259... ...
Nor was the potential transport of pathogens in runoff from the site to neighboring properties considered. In addition, regulations require that public access to the site be restricted for either 30 days or 1 year, depending on the probability of public exposure.
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From page 260... ...
The goal of the treatment processes to achieve Class A biosolids is to reduce pathogen densities to below the following detection limits for these organisms: less than 3 most probable number (MPN) per 4 g of total solids for Salmonella sp.; less than 1 plaque-forming unit (PFU)
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From page 261... ...
. application Class B biosolids may not be applied on home gardens No public access to application sites until at least 1 year after Class B biosolids application No public access to fields until at least 1 year after Class B biosolids applicatton Site restrictions that prevent the harvesting of crops until environmental attenuation has taken place.
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From page 262... ...
, it must produce a pathogen reduction equivalent to that obtained by a good anaerobic digestion. The logic of the definition rests on the observation that agricultural use of anaerobically digested sludge as a fertilizer has been practiced for many years with no evidence that the practice has caused human illness, provided that the digestion is adequate.
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From page 263... ...
Second, as noted by Venosa (1985) , the fundamental basis of biosolids regulations with respect to protection against pathogens rests on the assertion that, historically, agricultural use of anaerobically digested biosolids on herds (with protection from public access)
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From page 264... ...
However, cavitation processes, such as ultrasound or pulse power, have inactivated protozoan oocysts and assisted in enhancing anaerobic digestion processes (Reimers et al. 1985; Arrowood 1995; Patel 1996~.
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From page 265... ...
To yield Class A biosolids, increased temperatures or ammonia are necessary to inactivate highly resistant viruses, protozoan spores, and helminth eggs. Alkaline processes coupled with increased temperature yield a stable Class A product within 3 days.
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1998~. The treatment sequence included anaerobic digestion, dewatering, and long-term lagoon storage.
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From page 267... ...
A selection of these pathogens are discussed below. It must be noted that despite the ability to isolate pathogens from raw sewage sludge and partially and fully treated biosolids, the mere isolation of pathogens does not in and of itself indicate that a risk exists.
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From page 268... ...
268 CD ;= o cn o · _ · _ o I I Ct o Ct so, cn a~ Ct C~ ~n 4 · _ C~ a cn ·~ O O m ~4 z 4 ~n ;= o C~ a; ·~ Ct .
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From page 269... ...
Little is known about the occurrence and environmental fate of these viruses because they cannot be grown in cell culture. Methods using polymerase chain reaction (PCR)
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From page 270... ...
270 Biosolids Applied to Hand. ~dvanci,~g Standards and Practices ·~ 2000)
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It has been reported to grow in cell culture (Wed et al.
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From page 272... ...
1998~. Recently, an outbreak of Pontiac fever was reported among sewage treatment plant workers repairing a decanter for sewage
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From page 273... ...
Legionella has been detected in aerosols at sewage treatment plants (Stamp)
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From page 274... ...
1999~. Helminths EPA considered the human pathogens >4scaris 1~mbricoides, Trich~ris trzchiara, Taenia sagina~a, Taenia holism, Necator Americanizes, and Hymenolepsis nausea in establishing the pathogen standards of the Part 503 rule.
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From page 275... ...
Animal manure would have no or low concentrations of BSE prions except possibly for wastes from slaughterhouses (Ward et al. 1984~; however, the presence of prions in such wastes is uncertain (EPA 2001~.
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From page 276... ...
· Extent of existing data on probability of surviving biosolids treatments. The pathogens that have the greatest probability of surviving biosolids treatment processes are increasingly of concern for land application.
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From page 277... ...
In the Part 503 regulation, fecal coliforms are used as indicator organisms in two ways. First, as an indicator of health hazards, fecal coliform density can be used to classify Class A biosolids.
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From page 278... ...
Yes Low Unknown ozone, tnermophilic alkaline treatment, two-stage anaerobic digestion, composting, anaerobic digestion, and lagoon storage.
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From page 279... ...
Air Land application of biosolids may result in the formation of infectious bioaerosols. Bioaerosols are defined as aerosolized biological particles, ranging in diameter from 0.02 to 100 micrometers (~m)
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From page 280... ...
Although there are reports on pathogen occurrence and survival on agricultural lands and waterways exposed to biosolids, there is surprisingly little information on airborne pathogen occurrence during land application of biosolids. Most aerosol studies have been conducted near water treatment plants, at effluent spray irrigation sites, within waste-handling facilities, and at composting facilities Remake et al.1981; Brenner et al.
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From page 281... ...
Exposed people might develop allergic and toxic reactions to high concentrations of noninfectious microorganisms. The health effects from exposure to such agents have been well documented in sewage treatment plants, animal housing facilities, and biowaste collection sites.
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From page 282... ...
-based methods were used, enteroviruses were detected in soil 3 months after land application (Straub et al.
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From page 283... ...
1983~. Studies on indicator organisms have shown that total and fecal coliforms as well as fecal streptococci can survive for weeks to several months, depending on soil moisture and temperature conditions (Pepper et al.
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From page 284... ...
Transport of indicator organisms from land-applied, anaerobically digested biosolids was evaluated by Pepper et al.
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(1995) reported that flies disseminate helminth eggs from sewage treatment plants.
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From page 286... ...
Land availability and population densityare the most important factors for acceptability of the "experience with biosolids use." In the desert Southwest, agricultural areas are often located far from urban centers, so that there are fewer surrounding residents who may be affected by biosolids applications. In the Northeast, the potential impact of land application is much greater because of the magnitude of land application and the proximity of that land to people.
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From page 287... ...
Thus, the regional differences in land availability for biosolids application relative to the proximity of urban centers mean that "experience with biosolids use" is not uniform nationwide. HOST FACTORS Assessing potential risks from exposure to pathogens is complicated by the need to consider a variety of factors that affect an individual's susceptibility to pathogens.
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From page 288... ...
2001~. These studies have been conducted on biowaste collectors, compost workers, sewage treatment plant workers, and animal house workers, who are constantly exposed to high concentrations of these agents.
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From page 289... ...
However, there are a few studies of exposure and effects observed in workers at wastewater and sewage treatment plants. Although these studies are not substitutes for studies of biosolids exposure, they are useful for identifying potential health concerns and pathogens that might be relevant to biosolids.
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From page 290... ...
1999~; therefore, it is doubtful whether the incorporation and maintenance of antibiotic resistance genes in recipient cells would provide them with any selective advantage. Antibiotics are, however, present in raw sewage sludge and sewage treatment plant effluent.
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From page 291... ...
Drinking Water Historically, the acceptable levels of microorganisms in drinking water, contact recreationalwaters, and shellfish harvestingwaters have been set using indicator organisms, most often either total or fecal coliforms. With the advent of better methods for direct measurement of pathogens in water (Leon" 1983; Ongerth 1989; Gerba and Rose 1990; Gregory 1994; Rose 1990; Rose et al.
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From page 292... ...
Under the Long-Term Enhanced Surface Water Treatment Rule (LT2ESW - ) , surface-water treatment plants will be required to use control strategies based on the concentrations of C~ptospondium oocysts found in their source water.
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293 w o ;e g O O :~ Cal ~ 0 ·00 0~ o 0 o ;~34 = .07 Og sol , o o .
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From page 294... ...
The committee does not recommend that QMRA methods be required by regulation to monitor potential risks at any particular site. Such monitoring should be conducted by using indicator organisms and controlling operational parameters and practices, such as temperature, time, buffer zones, and pH, so that tolerable risk levels are not exceeded.
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From page 295... ...
Currently, there is no standard for assessing occupational exposures from bioaerosols in outdoor environments, such as biosolids-applicatton sites. Although specific microbial pathogens and fecal indicator organisms from biosolids-application sites have been detected using the AGI-30 sampler, there are studies showing that the AGI-30 is relatively inefficient at concentrating bacterial cells from bioaerosols.
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From page 296... ...
have detected Salmonella-specif~c nucleic acids within thermophilic compost piles, suggesting that microbial nucleic acids can be resistant to degradation, even at the raised temperatures found in compost piles. However, the detection of stable nucleic acid sequences does not imply the presence of viable organisms; therefore, molecular analyses, such as gene probe hybridizations and gene amplifications, should be interpreted with caution.
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From page 298... ...
There are many advantages to this method, particularly the prerequisite that the virus grow in cell culture for positive PCR amplification, thus detecting only viable viruses. A comparison of all three virus detection methods (Table 6-9)
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From page 299... ...
2000~. The preservation and pretreatment techniques for protozoan oocysts have not been developed to the level of those for helminth eggs.
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1996) : vital dye staining, animal infectivity, cell culture, or polymerase chain reactions J3-tubulin messenger RNA or RT-PCR)
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1999a, 2000~. Exposures estimated from human infection rates during outbreaks were comparable to the estimated infection rate based on animal dose-response data, thus validating the use of animal data as a quantitative predictor of human response.
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From page 302... ...
Population Level Modeling Two considerations of pathogen risk assessment that have no analog in chemical risk assessment is the need to address the potential for secondary transmission and acquired immunity. Secondary cases of infection may arise by a variety of mechanisms, such as transmission among close family members.
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From page 303... ...
Classification of Class A and Class B biosolids are based largely on fecal coliforms as indicator organisms. Class A biosolids do not have detectable concentrations of pathogens (determined by indicator organisms)
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From page 304... ...
Such indicators and other operationalparameters (e.g., time, temperature, phi, arid chemical dosed may be s~ita61efor assessing day-to-day compliance with the rer~latior's. a As with the chemical standards, EPA based its pathogen standards on selected pathogens and exposure conditions that were expected to be representative and conservative enough to be applicable to all areas of the United States and for all types of land applications.
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From page 305... ...
Microbial risk-assessment methods similar to those used in chemical risk assessments have been developed for pathogens in drinking water and food. These methods are not as well-established as those for chemicals, and there are important differences between the two.
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From page 306... ...
They can also be Ed for sensitivity amasses arid ider~ii~ir~g critical ir~formaiior~ that is reseeded to reduce ~f~certair~y about the risk~from pathogens ire biosolids. To conduct these risk assessments, consideration' mad tee given to assessing risks from all po~er~iial routes of exposure (e.g., bionerosols, gro~ndwalerJ, dose-response relationships, pathogen survival, arid secondary transmission' of disease.
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From page 307... ...
1992. Evaluating the use of Clostridium perfringens spores as indicator of the presence of viable Ascaris eggs in chemically treated municipal sludges.
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From page 308... ...
1999. Fate of Cryptosporidium oocysts, Giardia cysts, and microbial inidicators d~nngwastewater treatment and anaerobic sludge digestion.
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From page 309... ...
1999. Idendfying the sources of biosolids derived pathogen indicator organisms in aerosols by ribosomal DNA fingerprinting.
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From page 310... ...
1997. Thermotolerant clostridia as an airborne pathogen indicator d''nog land application of biosolids.
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From page 311... ...
Pp.380-396 in Drinking Water Microbiology: Progress and Recent Developments, G.A. McFeters, ed.
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From page 312... ...
1999. Pontiac fever at a sewage treatment plant in the food industry.
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From page 313... ...
in the dissemination of helminth eggs from sewage treatment plants. [in Slovak]
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From page 314... ...
1988. Evaluation of Temperature Effects on Inactivation of Ascaris Eggs in Both Aerobic and Anaerobic Digestion Processes.
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From page 315... ...
1985. Inactivation of Ascaris Eggs in Municipal Treatment Processes.
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From page 316... ...
1996. Enhancement of Anaerobic Digestion Processes Using Pulse Power Technology.
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From page 317... ...
1996. Occurrence of airborne bacteria and pathogen indicators duringland application of sewage sludge.
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From page 318... ...
1992. Land application of lime stabilized septage.
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From page 319... ...
2000. Occurrence and seasonal variation of airborne gram negative bacteria in a sewage treatment plant.
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From page 320... ...
1995. Comparison of PCR and cell culture for detection of enteroviruses in sludge-amended field soils and determination of their transport.
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From page 321... ...
2000. A spore counting method and cell culture model for chlorine disinfection studies of Encephalitozoon syn.
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