European E. Coli Outbreak and the Implications for Biosolids Recycling
In June, 2011, an outbreak of illnesses that began in Northern Germanywas caused by a new strain of Shiga toxin-producing E. coli, dubbed “E. coli 0104.” As of this writing, it has made over 4000 people sick and claimed 48 lives (per CNN.com 7-6-11) throughoutEurope. The New York Times stated that “the outbreak has been particularly harmful to victims because it has led to a potentially lethal complication, known as hemolytic uremic syndrome, or H.U.S., which causes kidney failure and neurological damage.”
The Times also reported that, by using an epidemiological study of the pattern of infection, German authorities have concluded that contaminated sprouts from an organic farm were the most likely cause. Further investigation by the European Food Safety Authority (EFSA) resulted in a report issued on 7-5-11 concluding that one lot of fenugreek seeds imported fromEgypt, and used to grow the sprouts, is the most likely common link. The EFSA report goes on to say that the contamination by fecal matter of the fenugreek seeds “probably occurred before the seeds left the importer,” possibly when and where they were harvested. It was not due to any biosolids being land applied during subsequent cultivation of the sprouts.
It is possible that the public may now become suspicious that biosolids contain harmful E. coli. However, testing for fecal coliform has shown that, through proper treatment, pathogenic bacteria in biosolids are reduced to safe levels. Research described in the Journal of Applied Microbiology found that “The results provide assurance that residual numbers of pathogens applied to soil in treated biosolids decay to background values well within cropping and harvesting restrictions imposed when sewage sludge is spread on farmland.”
It should also be remembered that there are many types of E. coli, most of which are harmless. Since a small number do come under scrutiny as dangerous pathogens, biosolids are rigorously monitored for indicator organisms, such as fecal coliform, as a means of determining the potential presence or absence of these disease-causing organisms. The term fecal coliform represents a large group of bacteria, most of which are strains of E. coli. Disinfection studies with chlorine shows that one strain of E. coli is no harder to kill than any other strain. There is no difference in how the various strains of bacteria respond. Although E. coli 0104 is a new variant on a strain, having acquired Shiga genes possibly through horizontal gene transfer or plasmid uptake, it is basically a part of the existing enteroaggregative E. coli strain and therefore able to be killed with Class A and Class B pathogen reduction methods.
Biosolids processing methods in the U.S.are rigorously controlled and there is very little chance that pathogenic bacteria would survive in Class A biosolids that are produced for land application or as fertilizer. By USEPA standards, Class B biosolids could be used on soils growing fenugreek however, there would be a waiting period of 30 days before harvesting. It is not known, what types of processing were used in Egyptor whether this contamination was caused by direct application of untreated fecal matter for use as a fertilizer. Proper processing and land application practices to reduce pathogenic bacteria would not only have prevented such a contamination in the first place, but would also destroy any E. coli 0104 present in infected waste that is being treated.
Related Ongoing Research
Patrick Gurian, principal investigator in an ongoing study sponsored by the Water Environment Research Foundation (WERF) entitled “Applying Advances in Pathogen Risk Assessment to Land Application of Biosolids and Communicating the Results,” noted that “the incidence of bacterial and viral pathogens in Class B mesophilic, anaerobically digested biosolids samples,” collected between 2005 and 2008, “were generally low…”, often meeting Class A requirements. The study also stated that “the percent reduction of both indicators and pathogens during anaerobic mesophilic digestion was between 94 and 99% for all organisms, illustrating that such treatment is effective in reducing pathogen loads.” [“Emerging pathogens such as Campylobacter and E. coli 0757:H7 were never detected.”]
A WERF project, undertaken by BucknellUniversityregarding regrowth, odors and sudden increases (ROSI) in indicator organisms in biosolids, is working to quantify fecal coliform and E. coli levels in biosolids. Various test methods are being trialed, including E. coli test methods, to determine which method results in the most accurate numbers of organisms counted. Testing biosolids directly for pathogens, whether before or after treatment, is not feasible because the pathogens are present in such low numbers that it is impossible to measure them. The indicator organisms that are measured are very robust, much more so than the actual disease-causing organisms. This finding strengthens the EPA’s belief that, if we can destroy fecal coliform, we are certainly destroying other pathogens of concern.
Waiting Periods after Biosolids is Land Applied
For a quick refresher on waiting periods when Class B biosolids is land applied to various crops we referred to: “Technical Support Document for Land Application of Sewage Sludge. PB93-110591; Vol. 1, Section 2.1 Agricultural Land.”
Re: land application - “As the sewage sludge dries, exposure to sun and air helps further degrade any organics, partially volatilize other organics, and reduce pathogens.” Other research has shown that bacteria in biosolids are further reduced by predatory bacteria already in the soil.”
Standards for the Use or Disposal of Sewage Sludge. EPA Part 503 Regulations published 2/19/1993; Section 503.32(b)(5) Site Restrictions.
“(i) Food crops with harvested parts that touch the sewage sludge/soil mixture and are totally above the land surface shall not be harvested for 14 months after application of sewage sludge.
(ii) Food crops with harvested parts below the surface of the land shall not be harvested for 20 months after application of sewage sludge when the sewage sludge remains on the land surface for four months or longer prior to incorporation into the soil.
(iii) Food crops with harvested parts below the surface of the land shall not be harvested for 38 months after applications of sewage sludge when the sewage sludge remains on the land surface for less than four months prior to incorporation into the soil.
(iv) Food crops, feed crops, and fiber crops shall not be harvested for 30 days after application of sewage sludge.”
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