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Diverting, Remixing of Excess Wastewater Allowed Under Certain Conditions, EPA Says
Sewage treatment plants would be able to route excess wastewater around part of their treatment system during wet weather and remix it with treated wastewater if certain conditions are met according to a draft guidance announced by the Environmental Protection Agency Nov. 2.
Referred to as "blending," the practice, which has been used by sewage
treatment plants since the 1970s, is designed to prevent the biological
treatment system from being inundated during wet weather when wastewater flows
often exceed the facilities' storage capacity. The Clean Water Act requires all
discharges to meet secondary or biological treatment standards, which address
biochemical oxygen demand compounds.
EPA officials said that in practice, the resulting flows--in which discharges
that have been treated are blended with wastewater that has been routed around
the biological system--still meet secondary standards and National Pollutant
Discharge Elimination System permit limits. The blended discharges get
disinfected, usually through chlorination, before being discharged.
Environmental groups and some in the agency's Office of Enforcement and
Compliance Assurance said blending may violate the Clean Water Act's prohibition
on bypasses. Essentially, the bypass regulations (40 CFR 122.41(m)) prohibit
allowing wastewater treatment plants to bypass any aspect of the treatment
process except in extreme circumstances, such as to prevent a loss of life or if
no feasible alternative was available.
James Hanlon, director of the EPA Office of Wastewater, told BNA the draft
policy, which was not yet available, lays out six conditions under which
blending would be allowed and not considered an illegal bypass.
The treatment plant, he said, would have to:
meet all the conditions of the NPDES permit, including secondary treatment
standards and any other requirements imposed by the permitting authority;
lay out in its permit application the treatment scheme that will be used to
manage these flows, including design capacity and application of generally
accepted practices;
ensure that flows routed around the biological treatment process be provided
with primary treatment, which essentially involves solids removal;
operate the facility in accordance to the plan laid out in the permit
application;
continue to appropriately operate and maintain the collection system; and
increase monitoring and data collection during blending events to assess the
impacts on the receiving waters.
The conditions in the Nov. 2 draft are nearly identical to provisions in the
December 2001 draft guidance that was circulated widely, he said (4 DEN AA-1,
E-1; 1/7/02). The one exception is that the agency added the monitoring
requirements to the current draft.
Hanlon said the draft guidance also recommends that if the POTW discharges to
sensitive waters or areas near beaches or other recreational places, the
permitting authority may consider additional limits regarding how and when
blending would be authorized in the permit.
The agency is seeking comment on whether the blending guidance should have a
"reopener clause" in which a permit may be reopened during its five-year
duration if monitoring data reveal a problem caused by the blending that needs
to be addressed, Hanlon said.
Environmental groups oppose the blending concept on two counts. They have argued
that blending does not address the critical problem of pathogens and that it
violates the bypass provisions of the Clean Water Act.
The Natural Resources Defense Council said in a Nov. 2 statement that the
secondary treatment process is a critical stage during which most of the
pathogenic organisms and other pollutants are removed from wastewater. This is
accomplished through biological treatment that uses microbial digestion to
render pathogens and other pollutants harmless.
"Neither solids removal nor disinfection effectively removes viruses or
parasites, such as cryptospiridium and giardia, and it has limited effectiveness
in removing bacteria," NRDC said.
The Association of Metropolitan Sewerage Agencies, which represents large
publicly owned treatment works, has been urging EPA to issue the guidance in
order to establish a consistent national policy on the practice that has been
employed for decades. While it may be true that blending mean increased pathogen
loadings during wet weather, the alternative would be even worse--a complete
washout of the biological system that would mean no secondary treatment at all
until the facility could be brought on line again, an AMSA official told BNA.
"POTWs are not designed to treat every single ounce of water on the planet," the
official said. The only way to avoid blending in many cases would be to build
extra storage capacity that would be able to hold the extra flows until they
could be routed through the biological system, an option that would be
prohibitively expensive, AMSA has said.
Municipalities have been pushing EPA to issue guidance because they said the
some of the agency's regional offices have barred the use of blending when they
issued permits to several POTWs. In July 2002, three municipal groups sued the
agency alleging that the agency's Region III office in Philadelphia, Region IV
office in Atlanta, and Region VI office in Dallas specifically ban blending and
that the prohibition is an uneven application of a policy that is not supported
by the agency's Clean Water Act bypass regulation (Pennsylvania Municipal
Authorities Ass'n v. Whitman, D.D.C., 1:02-01361, 7/8/02; 138 DEN A-8, 7/18/02).
Comments will be accepted on the draft guidance until Jan. 9, 2004.
The draft blending guidance and instructions for submitting comments will soon
be available at http://www.epa.gov/npdes/blendingon the World Wide Web.