EPA POSITION ON WATER ENVIRONMENT FEDERATION RESEARCH ON
VIABLE, BUT NON-CULTURABLE BACTERIA STUDY
EPA has known about this phenomenon since the 1980s. EPA has several pathogen experts including M.C. Meckes and
James Smith. If we are to believe the It would appear PR surrounding this study, no one at EPA or WEF/WERF has
every read any of the 400 + papers published on the subject - including those related to sludge. EPA continues to have
a complete disregard for public health as well as individuals exposed to this deadly mixture they playfully call biosolids.
This study as well as the 400 + papers on viable, but non-culturable bacteria and the ten year PR program to discredit
victims, indicate this is a confirmed case of agroterrorism against the American people.
EPA Position
EPA will continue to evaluate this phenomenon in partnership with WERF through additional WERF-sponsored research
projects and other research efforts. The results of these efforts should help develop a better understanding of this
phenomenon. WERF is also proposing to expand the scope of this ongoing work and better explain the phenomenon.
When warranted by adequate data, EPA may provide updated technical guidance or propose appropriate amendments
to Part 503 requirements relative to pathogen reduction technologies and pathogen bacteria or pathogen indicator
monitoring techniques. The Agency continues to believe that the pathogen requirements and operational standards of
Subpart D of the 40 CFR Part 503 regulations are protective of public health.
Fact Sheet: A WERF Study Finds Fecal Coliforms Appear to Reactivate
In Centrifuge Dewatered Solids at Four of Seven Facilities Tested
http://www.wef.org/NR/rdonlyres/996A7216-71E5-41FE-B652-84E2F6C5577A/0/EPAStatement_ReactivFecalColi.pdf
Background
The Water Environment Research Foundation (WERF) recently published a report titled Examination of Reactivation
and Regrowth of Fecal Coliforms in Centrifuge Dewatered, Anaerobically Digested Sludges. WERF-sponsored
researchers sampled seven full-scale publicly owned treatment facilities several times to determine if bacterial indicator
organisms (e.g., fecal coliforms and E. coli) could become reactivated or if regrowth occurs after anaerobic digestion
and high-solids centrifugation. Wastewater treatment facilities often use dewatering processes after anaerobic digestion
to reduce the water content of sewage sludge thereby significantly reducing the volume and associated handling and
transport costs. A high-solids centrifuge is a high-speed process that uses the force from rapid rotation of a cylindrical
bowl to separate water from the wastewater solids.
Results from the WERF Study
Four out of seven facilities processing sewage sludge via anaerobic digesters and high-solids centrifuge dewatering
demonstrated higher levels of fecal coliforms after dewatering than before. The other three facilities did not show an
increase. Researchers theorize that some bacteria populations may enter a viable but non culturable (VBNC) state after
prolonged stress experienced during anaerobic digestion and are not accurately measured by standard culturing
methods. The high shear during high-solids centrifuge dewatering may release compounds that stimulate reactivation.
Other possibilities include a change in environmental conditions or removal of bacterial growth inhibitors. The study did
not identify all the conditions that caused dewatered biosolids from some plants to have reactivation while others did not.
Study Implications
The WERF study raises the possibility that in some site-specific situations reactivation following anaerobic digestion and
centrifugation may be occurring. However, neither WERF nor EPA can assess how widespread this occurrence is
because of the small sample size.
The information from this study may be useful for utilities that use anaerobic digestion in combination with high-solids
centrifuge dewatering. The results can help utilities to determine whether similar increases in measured fecal coliform
concentrations are observed following high-solids centrifuge dewatering at their facilities. Utilities can then determine if
process design, operational modifications, or additional treatment, such as low dose lime addition to the sewage sludge
cake, is needed to further reduce pathogen indicators.
Next Steps
These are important areas of research and warrant further study. A follow-up study by WERF is looking at both how the
treatment processes and bacteria test methods could be contributing to an increase in the measured level of fecal
coliforms following high-solids centrifuge dewatering. EPA will continue to evaluate this phenomenon in partnership with
WERF through additional WERF-sponsored research projects and other research efforts. The results of these efforts
should help develop a better understanding of this phenomenon. WERF is also proposing to expand the scope of this
ongoing work and better explain the phenomenon.
When warranted by adequate data, EPA may provide updated technical guidance or propose appropriate amendments
to Part 503 requirements relative to pathogen reduction technologies and pathogen bacteria or pathogen indicator
monitoring techniques. The Agency continues to believe that the pathogen requirements and operational standards of
Subpart D of the 40 CFR Part 503 regulations are protective of public health.
Further Information
To obtain more information please contact Rick Stevens at 202-566-1135 or [email protected]
In Centrifuge Dewatered Solids at Four of Seven Facilities Tested
http://www.wef.org/NR/rdonlyres/996A7216-71E5-41FE-B652-84E2F6C5577A/0/EPAStatement_ReactivFecalColi.pdf
Background
The Water Environment Research Foundation (WERF) recently published a report titled Examination of Reactivation
and Regrowth of Fecal Coliforms in Centrifuge Dewatered, Anaerobically Digested Sludges. WERF-sponsored
researchers sampled seven full-scale publicly owned treatment facilities several times to determine if bacterial indicator
organisms (e.g., fecal coliforms and E. coli) could become reactivated or if regrowth occurs after anaerobic digestion
and high-solids centrifugation. Wastewater treatment facilities often use dewatering processes after anaerobic digestion
to reduce the water content of sewage sludge thereby significantly reducing the volume and associated handling and
transport costs. A high-solids centrifuge is a high-speed process that uses the force from rapid rotation of a cylindrical
bowl to separate water from the wastewater solids.
Results from the WERF Study
Four out of seven facilities processing sewage sludge via anaerobic digesters and high-solids centrifuge dewatering
demonstrated higher levels of fecal coliforms after dewatering than before. The other three facilities did not show an
increase. Researchers theorize that some bacteria populations may enter a viable but non culturable (VBNC) state after
prolonged stress experienced during anaerobic digestion and are not accurately measured by standard culturing
methods. The high shear during high-solids centrifuge dewatering may release compounds that stimulate reactivation.
Other possibilities include a change in environmental conditions or removal of bacterial growth inhibitors. The study did
not identify all the conditions that caused dewatered biosolids from some plants to have reactivation while others did not.
Study Implications
The WERF study raises the possibility that in some site-specific situations reactivation following anaerobic digestion and
centrifugation may be occurring. However, neither WERF nor EPA can assess how widespread this occurrence is
because of the small sample size.
The information from this study may be useful for utilities that use anaerobic digestion in combination with high-solids
centrifuge dewatering. The results can help utilities to determine whether similar increases in measured fecal coliform
concentrations are observed following high-solids centrifuge dewatering at their facilities. Utilities can then determine if
process design, operational modifications, or additional treatment, such as low dose lime addition to the sewage sludge
cake, is needed to further reduce pathogen indicators.
Next Steps
These are important areas of research and warrant further study. A follow-up study by WERF is looking at both how the
treatment processes and bacteria test methods could be contributing to an increase in the measured level of fecal
coliforms following high-solids centrifuge dewatering. EPA will continue to evaluate this phenomenon in partnership with
WERF through additional WERF-sponsored research projects and other research efforts. The results of these efforts
should help develop a better understanding of this phenomenon. WERF is also proposing to expand the scope of this
ongoing work and better explain the phenomenon.
When warranted by adequate data, EPA may provide updated technical guidance or propose appropriate amendments
to Part 503 requirements relative to pathogen reduction technologies and pathogen bacteria or pathogen indicator
monitoring techniques. The Agency continues to believe that the pathogen requirements and operational standards of
Subpart D of the 40 CFR Part 503 regulations are protective of public health.
Further Information
To obtain more information please contact Rick Stevens at 202-566-1135 or [email protected]