Current through Register Vol. 46, No. 12, March 20, 2024
These systems consist of filtration equipment which use
activated carbon to remove organic chemicals from individual water supplies. They
also may be used to improve the aestetic quality of drinking water. These systems
are normally installed between the water source and the first point of use in the
water distribution system.
(a) When an
activated carbon filter unit is installed to treat an individual water supply
containing organic chemicals, it must meet all of the following conditions:
(1) The units are installed in-line and serve
the whole household. Faucet or undersink units shall not be used for the removal
of organic chemicals.
(2) The
treatment unit must be capable of processing water at a flow rate of at least
five gallons per minute (gpm). Flow rates may be reduced if additional
pressurized storage is provided after the treatment unit to insure the system
will provide at least five gpm of treated water to the household continuously for
a minimum of 20 minutes.
(3) The
maximum application rate shall be 10 gpm per square foot of activated carbon
surface area. Flow rates shall be controlled by a flow limiting device.
(4) The minimum empty bed contact time shall be
three minutes. This should be accomplished with at least two filter units of
equal size placed in series.
(5) Only
virgin carbon shall be used. The cylinder should be recharged at a point outside
the residence and the spent activated carbon properly disposed of by the
vendor.
(6) Disinfection must be
provided after the activated carbon unit. The preferred method of disenfection is
an ultraviolet unit with a minimum rating of five gpm. The unit shall have a
fail-safe device that detects the intensity of the ultraviolet light and
automatically shuts down the system when the intensity decreases to below the
minimum effective level specified for the unit. A manual or automatic wipe must
be provided. An alternate method of disinfection would be sodium hypochlorite. If
sodium hypochlorite is used, contact time adequate to eliminate, pathological
organisms must be provided after the point of injection and prior to consumption.
The local health unit having jurisdiction may allow the use of activated carbon
units without disinfection upon the adoption of a formal procedure for the
approval of treatment systems installations, and notification to homeowners of
the need for disinfection.
(7)
Treatment units capable of backwashing shall only use treated water for that
purpose. Backwashing should be at a minimum flow rate of 10 gpm for at least two
minutes. The backwashing must be accomplished in a manner that does not create a
cross-connection. The wastewater shall not be discharged to the ground surface
but may be discharged to a septic system.
(8) All components of treatment units must
safely withstand the highest water pressure in the system.
(9) The following must be provided:
(i) A flow meter to record total
flow.
(ii) Sampling taps for raw,
partially treated and treated water.
(iii) adequate valving to isolate the various
components, and for backwashing of filters.
(iv) Only nontoxic materials and
coatings.
(v) Ease of access to all
components.
(vi) Prefiltration where
appropriate to remove turbidity and bacteria.
(vii) Pressure gauges before and after the
activated carbon unit.
(b) Other than whole-house units. Because
organic chemicals can be inhaled and absorbed through the skin during baths and
showers, the following types of point-of-use activated carbon units are not
suitable for use where the water contains organics:
(1) Pour-through units - a stand-alone device,
not attached to the water supply system, and normally manually
operated.
(2) Faucet-mount units - a
unit mounted directly at the outlet of an individual tap or faucet.
(3) In-line, one-tap units - a unit mounted in
a supply line that serves only one tap or faucet.
(4) Line-bypass units - an in-line unit that
serves a separate tap or faucet intended for drinking water use only.