|
Disinfection workshop summary
Weighing the risks and benefits of wet-weather disinfection
Presented at The Rosamond Gifford Zoo, Syracuse, NY
October 15, 2002
1. County overview
|
|
Wet-weather storage and treatment
|
Mr. Cunningham presented a history of the County's CSO
abatement plan including currently proposed plans and
public concerns with the proposed plans.
of Onondaga, as a result of the creation of the
Syracuse Sewer District, currently assumes all
responsibility with respect to the operation and
maintenance of the Intercepting Sewer System of the
City of Syracuse."
Trunk Sewers and associated CSOs [124] to the County
in 2 actions, one in 1978 and the other 1982 ceding
responsibility to operate and maintain the trunk sewer
system.
1998 the Amended Consent Judgment was executed by the
Federal Court requiring the County to abate CSOs
consistent with the 1972 Clean Water Act/State Laws &
Regulations.
encompasses multiple approaches and technologies for
CSO abatement including: storage/transport, floatables
control, sewer separation, and regional treatment,
disinfection and discharge.
discarded in the development of a 1996 draft Municipal
Compliance Plan (MCP) because those options were too
costly and too disruptive.
regarding the County's CSO abatement proposals, is the
use of chlorine for disinfection of CSO because of the
perceived human safety and ecological impacts.
Mr. Eidt presented the current rational for handling Combined Sewer Overflows and the State's Policy on disinfection.
"fishable/swimmable" provision.
and aquatic health.
supplies or potential for impacts to human health were
present, then disinfection was generally required; if
not then disinfection was not required.
appropriate for the protection of aquatic species when
chlorination is used for disinfection. However, when
dilution in the receiving water is greater than 80:1,
dechlorination may not be required. When dilution is
less than or equal to 30:1, then dechlorination is
required. In the case of Onondaga Lake, dilution
exceeds 80:1, whereas dilution in Onondaga Creek is
less than 30:1.
CSOs is an established and approvable practice for DEC
and USEPA.
Q: What are communities doing regarding disinfection of CSO internationally? Is it true that Europe does not use chlorine for disinfection?
Q: How do you achieve both fishable/swimmable? How do you protect both fish and humans when discharging a chlorinated effluent?
A: The state attempts to balance human health
protection with potential environmental impacts, but
human health protection is the priority. If bathing
beaches, public water supplies or potential for
impacts to human health are present, then disinfection
was generally required. The intent is to introduce
chlorine only where necessary to meet regulatory
requirements.
Clarification: NYSDEC's position on
chlorination-dechlorination is that it is a safe
practice for human contact recreation and sensitive
aquatic organisms.
Q: What are the occupational concerns of chlorine exposure?
A: The chlorine type proposed for use in Onondaga
County is 12-15% liquid sodium hypochlorite. Household
bleach is 6-8% liquid sodium hypochlorite. From an
occupational exposure point of view, liquid sodium
hypochlorite needs to be handled with respect and
workers should be trained in its safe use to minimize
exposure.
Clarification: Chlorine is used for disinfection of
sewage effluent, swimming pools and drinking water,
and as a household bleach. As such, it is in common
use.
Click here for a material safety data sheet (MSDS).
Q: Is the NPDES objective to have zero discharge?
A: The Act does refer to zero discharge.
Clarification: In accordance with the "1977 CWA
Amendments," which replaces language of all previous
Acts, "It is the national goal that the discharge of
pollutants into the navigable waters be eliminated by
1985" (CWA of 1977). The goal is not to eliminate CSO
flow but to eliminate pollutants from the flow. It
would not be possible to eliminate all storm water
flow (95%± of CSO) since runoff discharged to
receiving water is inevitable and desirable (if free
of pollutants). Pollutants are reduced through
treatment and disinfection sufficient to meet State
Water Quality Criteria. Such criteria can be tailored
to the specific water body by the State per the USEPA
Guidance "Coordinating CSO Long-Term Planning With
Water Quality Standards." In the case of the Onondaga
County CSO Control Plan, state water quality criteria
are intended to be met as defined in the ACJ.
For the first time, specific steps to deal with CSOs
were defined by the Clean Water Act Amendment of 1977
(PL95-217). This Amendment required among other things
the development of alternatives for CSO abatement,
which the ACJ process did in fact include. The County
has funded the construction and evaluation of such
alternatives from the 1970s to the present. The
evaluation of alternatives led to the proposed County
Program specifically described in the ACJ.
Q: Does the use of chlorine result in loss of federal funding for neighborhood development?
A: There is no known reason why there should be a loss
of federal dollars since chlorination-dechlorination
was accepted by the state for the ACJ and is
recognized by the USEPA as the best alternative for CSO
at this time.
|
Susan Miller, Project Deputy Director
Onondaga County Dept of Water Environment Protection