| (A) Disinfection equipment shall have a capacity at
least 50% greater than the highest expected dosage to be applied at
any time. It shall be capable of satisfactory operation under every
prevailing hydraulic condition.
(B) Automatic proportioning of the disinfectant dosage
to the flow rate of the water being treated shall be provided at plants
where the treatment rate varies automatically and at all plants where
the treatment rate varies more than 50% above or below the average
flow. Manual control shall be permissible only if an operator is always
on hand to make adjustments promptly.
(C) All disinfecting equipment in surface water treatment
plants shall include at least one functional standby unit of each
capacity for ensuring uninterrupted operation. Common standby units
are permissible but, generally, more than one standby unit must be
provided because of the differences in feed rates or the physical
state in which the disinfectants are being fed (solid, liquid, or
gas).
(D) Facilities shall be provided for determining the
amount of disinfectant used daily and the amount of disinfectant remaining
for use.
(E) When used, solutions of calcium hypochlorite shall
be prepared in a separate mixing tank and allowed to settle so that
only a clear supernatant liquid is transferred to the hypochlorinator
container.
(F) Provisions shall be made for both pretreatment
disinfection and post-disinfection in all surface water treatment
plants. Additional application points shall be installed if they are
required to adequately control the quality of the treated water.
(G) The use of disinfectants other than free chlorine
and chloramines will be considered on a case-by-case basis under the
exception guidelines of §290.39(l) of this title. If water containing
chloramines and water containing free chlorine are blended, then a
case-by-case review under §290.39(l) of this title will be required.
(4) Systems that use chlorine gas must ensure that
the risks associated with its use are limited as follows.
(A) When chlorine gas is used, a full-face self-contained
breathing apparatus or supplied air respirator that meets Occupational
Safety and Health Administration (OSHA) standards for construction
and operation, and a small bottle of fresh ammonia solution (or approved
equal) for testing for chlorine leakage shall be readily accessible
outside the chlorinator room and immediately available to the operator
in the event of an emergency.
(B) Housing for gas chlorination equipment and cylinders
of chlorine shall be in separate buildings or separate rooms with
impervious walls or partitions separating all mechanical and electrical
equipment from the chlorine facilities. Housing shall be located above
ground level as a measure of safety. Equipment and cylinders may be
installed on the outside of the buildings when protected from adverse
weather conditions and vandalism.
(C) Adequate ventilation, which includes both high
level and floor level screened vents, shall be provided for all enclosures
in which gas chlorine is being stored or fed. Enclosures containing
more than one operating 150-pound cylinder of chlorine shall also
provide forced air ventilation which includes: screened and louvered
floor level and high level vents; a fan which is located at and draws
air in through the top vent and discharges to the outside atmosphere
through the floor level vent; and a fan switch located outside the
enclosure. Alternately, systems may install negative pressure ventilation
as long as the facilities also have gas containment and treatment
as prescribed by the current International Fire Code (IFC).
(5) Hypochlorination solution containers and pumps
must be housed in a secure enclosure to protect them from adverse
weather conditions and vandalism. The solution container top must
be completely covered to prevent the entrance of dust, insects, and
other contaminants.
(6) Where anhydrous ammonia feed equipment is utilized,
it must be housed in a separate enclosure equipped with both high
and low level ventilation to the outside atmosphere. The enclosure
must be provided with forced air ventilation which includes: screened
and louvered floor level and high level vents; a fan which is located
at and draws air in through the floor vent and discharges through
the top vent; and a fan switch located outside the enclosure. Alternately,
systems may install negative pressure ventilation as long as the facilities
also have gas containment and treatment as prescribed by the current
IFC.
(7) Chloramine disinfection shall be performed in a
manner which assures that the proper chlorine to ammonia (as nitrogen)
ratio is achieved in order to maintain a monochloramine residual and
limit nitrification.
(A) The order of chlorine and ammonia injection must
be accomplished in a manner which allows inactivation of viruses and
oxidation of cyanide.
(i) When chlorine is injected upstream of any other
disinfectant, the ammonia injection point must be downstream of the
chlorine injection point.
(ii) When chlorine and ammonia are added to distribution
water that has a chloramine residual, ammonia should be added first.
(iii) When chlorine and ammonia are added to distribution
water that has a free chlorine residual, chlorine should be added
first.
(B) Mixing shall be provided to disperse chemicals.
(C) Sampling taps must be provided at locations that
allow for chlorine and ammonia to be added to the water to form monochloramine
as the primary chloramine species. These locations must be listed
in the system's monitoring plan as described in §290.121 of this
title (relating to Monitoring Plans). Sample taps must be provided
as follows:
(i) upstream of the chlorine or ammonia chemical injection
point, whichever is furthest upstream;
(ii) between the addition of the chloramine chemicals
at chloramination facilities submitted for plan review after December
31, 2015. For these facilities, an installation without this sample
tap may be approved if an acceptable technical reason is described
in the plan review documents. Technical reasons, such as disinfection
byproduct control, must be supported by bench scale sampling results.
Other technical reasons, such as membrane integrity, must be supported
by documentation; and
(iii) at a point after mixing to be able to measure
fully-formed monochloramine levels.
(D) When using chloramines, the feed and storage must
be designed as described in subsection (f) of this section, regardless
of water source.
(E) When using chloramines, the public water systems
shall provide equipment for making at least the following determinations
for purposes of complying with the requirements in §290.110 of
this title:
(i) free ammonia (as nitrogen);
(ii) monochloramine;
(iii) total chlorine;
(iv) free chlorine; and
(v) nitrite and nitrate (both as nitrogen). The public
water systems must either obtain equipment for measuring nitrite and
nitrate or identify an accredited laboratory that can perform nitrite
and nitrate analysis and can provide results to the public water systems
within 48 hours of sample delivery.
(f) Water treatment plant chemical storage and feed
facilities.
(1) Chemical storage facilities shall be designed to
ensure a reliable supply of chemicals to the feeders, minimize the
possibility and impact of accidental spills, and facilitate good housekeeping.
(A) Bulk storage facilities at the plant shall be adequate
to store at least a 15-day supply of all chemicals needed to comply
with minimum treatment technique and maximum contaminant level (MCL)
requirements. The capacity of these bulk storage facilities shall
be based on the design capacity of the treatment plant. However, the
executive director may require a larger stock of chemicals based on
local resupply ability.
(B) Day tanks shall be provided to minimize the possibility
of severely overfeeding liquid chemicals from bulk storage facilities.
Day tanks will not be required if adequate process control instrumentation
and procedures are employed to prevent chemical overfeed incidents.
(C) Every chemical bulk storage facility and day tank
shall have a label that identifies the facility's or tank's contents
and a device that indicates the amount of chemical remaining in the
facility or tank.
(D) Dry chemicals shall be stored off the floor in
a dry room that is located above ground and protected against flooding
or wetting from floors, walls, and ceilings.
(E) Bulk storage facilities and day tanks must be designed
to minimize the possibility of leaks and spills.
(i) The materials used to construct bulk storage and
day tanks must be compatible with the chemicals being stored and resistant
to corrosion.
(ii) Except as provided in this clause, adequate containment
facilities shall be provided for all liquid chemical storage tanks.
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