UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WSG47A
Date Signed: October 1989
Honorable Victor Fazio
House of Representatives
Washington, D.C. 20515
Dear Mr. Fazio:
Thank you for your letter of September 28, 1989, to Mr. Michael B. Cook, Director of the
Office of Drinking Water, regarding the use of point-of-entry (POE) devices to comply with the
Total Coliform Rule and Surface Water Treatment Rule (SWTR).
The Total Coliform Rule and SWTR only apply to public water systems; i.e., systems
serving at least 15 service connections or 25 people per day. Individual households may use POE
devices at their own discretion and have no requirements to meet the Safe Drinking Water Act.
Though generally not recommended, POE devices may in some circumstances be used in lieu of
centralized treatment to comply with the Total Coliform Rule or SWTR, or as a condition for
obtaining an exemption. Exemptions are time delays for meeting the criteria of a National Primary
Drinking Water Regulation (NPDWR). Exemptions may be granted by the State depending upon
the circumstances of a system. Exemptions for systems with 500 or fewer service connections can
be renewed indefinitely if applicable criteria are met.
Section 141.100, Subpart J of the NPDWR (enclosed) specifies conditions which must be
met for POE devices to be used to comply with a Maximum Contaminant Level (MCL) such as
the Total Coliform Rule. Though not stated in Section 141.100, these conditions are also
appropriate for determining if POE devices may be used for complying with a treatment technique
requirement such as the SWTR. In addition, the SWTR requires that alternative filtration
technologies such as POE devices must be demonstrated to the satisfaction of the State that, with
disinfection, they are capable of achieving at least 99.9 and 99.99 percent removal and/or
inactivation of Giardia cysts and viruses, respectively. The characteristics of the POE device and
the maintenance program will determine the amount of monitoring which is appropriate to ensure
that adequate treatment is being provided on an ongoing basis.
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WSG47A
Regarding turbidity monitoring, the SWTR allows for continuous turbidity monitoring with
periodic validation in lieu of grab sample monitoring. If continuous monitoring is used,
measurements are to be read from a recorder at four-hour intervals to determine compliance. For
alternative filtration technologies (which would include POE devices), the SWTR allows the State
to reduce turbidity monitoring to one representative sample of the filtered water per day, depending
upon the characteristics of the technology. If the performance of one POE device cannot be relied
on to reflect the performance of the other POE devices, at least one sample per day from each
device should be required. In some cases it may be possible, depending upon the design of the
POE device and the maintenance program in place, that representative monitoring can be achieved
with one sample from a different POE device each day.
Regarding disinfection with ultraviolet light, the SWTR does not allow for this technology
to be used by itself for providing disinfection. Ultraviolet light is not effective for inactivating
Giardia cysts and it does not provide a disinfectant residual. However, ultraviolet light is effective
for inactivating viruses in non-turbid waters. We did not contemplate the situation which you
describe in your letter. It appears that a POE device which removes at least 99.9 percent of
Giardia cysts followed by disinfection with ultraviolet light, which achieves with filtration at least
99.99 percent removal and inactivation of viruses, could be an effective means of providing
adequate treatment for individual households. We will consider use of ultraviolet light in the
forthcoming disinfection requirements for ground water systems, which we intend to propose by
the end of 1991. At that time, possible adjustments to the SWTR will also be considered. The
effective date for filtered systems to comply with the SWTR is June 29, 1993. In the meantime,
communities intending to use POE devices should work closely with the State of California to
determine whether adequate treatment is being provided.
I hope this letter addresses your concerns. Please contact me if you have further questions
or have your staff contact Stig Regli at (202) 382-7379.
Sincerely,
LaJuana S. Wilcher
Assistant Administrator for Water
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