020-11 Wyo. Code R. §§ 11-21 - Disinfection
(a)
Chlorination/dechlorination.
(i) Chlorination.
The disinfection capacity shall be sized to provide the coliform concentrations
required by the discharge permit. Feeders shall be sized to provide the minimum
dosage at the minimum flow rate and to the maximum dosage at the maximum flow
rate.
(ii) Dechlorination.
Dechlorination feeders shall be sized for the final effluent dechlorination
dosage required by the discharge permit requirements.
(iii) Chlorination.
(A) Number of units. Feeders shall be able to
supply, at all times, the necessary amounts of chemical at an accurate rate
(±3%) throughout the range of feed. The number of units shall provide
capacity for effluent disinfection with the largest unit out of service and a
separate feeder or feeders for ancillary uses, such as prechlorination or
intermediate process control chlorination. The number of feeders shall be
selected to permit feeding chemicals over the range of required dosage while
only varying a single feeder over a 10:1 range.
(B) Chemical storage. Chlorine shall be
stored in a heated, ventilated space. Space shall provide at least thirty (30)
days of chemical supply, convenient and efficient handling, and dry conditions.
Cylinders or other containers of chlorine gas should be isolated from operating
areas and restrained in position to prevent upset.
(C) Piping. Piping systems carrying gaseous
or liquid chlorine shall be schedule 80 black steel pipe with forged steel
fittings. Bushings shall not be used. Vacuum piping for gaseous chlorine may be
polyethylene tubing.
Gas piping between the chlorine pressure reducing valve of the chlorinator and the ejector shall be PVC or polyethylene. Piping for aqueous solutions of chlorine beyond the ejector shall be PVC, fiberglass, or steel pipe lined with PVC or saran.
(D) Maximum withdrawal. The maximum
withdrawal rate of gaseous chlorine shall be limited to 40 lbs/day (18.1
kg/day) for 100 or 150 lb (45.4 or 68.0 kg) cylinders and 400 lbs/day (181
kg/day) for 2,000 lb (907 kg) cylinders, unless chlorine evaporators are
used.
(iv)
Dechlorination.
(A) Number of units.
Dechlorination equipment shall be provided to permit feeding the design dosage
with the largest unit out of service. Feeders shall be sized for a 10:1 feed
range.
(B) Chemical storage.
Chemical storage shall be in a heated, ventilated room, separate from chlorine
cylinder storage. Provisions for heating the storage area or the S0 cylinders
shall be provided. Where used, bin storage shall be provided with desiccated
vents.
(C) Piping. Piping for
liquid or gaseous S0 shall be schedule 80 black steel pipe with forged steel
fittings. Bushings shall not be used. Piping for aqueous solutions of
dechlorination chemicals shall be PVC, fiber glass, or steel pipe lined with
PVC or saran. All valves for liquid and gaseous sulfur dioxide shall be as
approved by the Chlorine Institute. Valves for aqueous solution of
dechlorination chemicals shall be PVC or saran lined.
(D) Maximum withdrawal.
(I) The maximum withdrawal rate for sulfur
dioxide from 2,000 lb (907 kg) cylinders shall be 200 lb (90.7 kg) per day,
unless sulfur dioxide evaporators are used.
(v) Makeup water. Water used for dissolving
dry chemicals, diluting liquid chemicals or operating chlorine or S0 injectors
shall be chlorinated and strained for filtered (65 mesh) final effluent or
potable water. Where potable water is used, backflow prevention shall be
achieved by (a) a six (6) inch (15.2 cm) air gap between the potable water
supply pipe and the maximum water level of a receiving tank; or (b) an approved
reduced-pressure-zone backflow preventer.
(vi) Mixing requirements. The feed point for
chlorination or dechlorination chemical shall be at a location of high
turbulence. At points of critical flow, specially designed static tube mixers
or artificial mixing are required.
(vii) Contact basins.
(A) Detention time. The chlorine contact
period shall provide a minimum of fifteen (15) minutes contact time at the peak
hour design flow. The contact period shall be from the point of chemical
injection into the flow to the outfall point or dechlorination feed
point.
(B) Baffling. Baffling of
the chlorine contact basin shall provide a length-to-width ratio of 5:1 or
greater.
(viii)
Controls. The minimum control for chlorination-dechlorination facilities shall
include manual variation of feed rate and a portable chlorine residual
monitor.
(b) Ozonation.
(i) Applied dosage rates. Ozonation system
for disinfection shall provide a range of chemical feed as follows:
Secondary effluents | 5-15 mg/L |
Advanced treatment effluents | 5-10 mg/L |
(ii) Piping. Injection equipment and piping
in contact with ozonated air and air water emulsions shall be of stainless
steel, Teflon or other material resistant to ozone. Valves carrying ozonized
air shall be made of metal coated with ozone-resistant materials.
(iii) Mixing requirements. Ozone shall be fed
to a contact tank along the length of the tank. The ozone contact tank shall be
at least fifteen (15) feet (4.6 m) deep and provided with vertical serpentine
baffles. Fine bubble diffusers shall be used in areas where the flow is
downward.
(iv) Detention time. The
minimum contact time for ozone is 15 minutes at peak hourly flow. Ozone contact
basins shall be covered and provided with means to collect and destroy
unreacted ozone. The contact basin shall be designed to facilitate maintenance
and cleaning without reducing the effectiveness of the ozonation
process.
(c) Housing.
(i) Access. Where housing is specially
designed for equipment, structures, rooms and areas containing chemical feed
equipment used in disinfection, convenient access should be provided. Access to
chemical feed rooms shall only be from the outside. Doors shall be provided
with panic hardware, and open from the inside to the outside.
(ii) Heating and ventilation. Chemical feed
rooms and chemical storage rooms shall be heated and ventilated. Ventilation
shall exhaust continuously from near the floor to an outside area that will not
contaminate an air inlet to any building. The exhaust shall be screened and
turned downward. Continuous ventilation shall provide a complete air change six
times per hour. Emergency exhaust ventilation shall provide a complete room air
change thirty (30) times per hour. The control for the emergency ventilation
fan shall be on the outside of the room.
(iii) Visual inspection. A clear glass,
gas-tight window shall be installed in an exterior door or interior wall of the
disinfection chemical feed room.
(iv) Isolation. Chemical feed and storage
rooms shall be gas-tight. Ventilation, plumbing and access shall be separated
from other building parts. When ton cylinders are used for chlorine or sulfur
dioxide storage, storage and feed rooms will be separate. Where powdered or
granular chemicals are used, they will be stored in separate rooms from the
feed room. Switches for fans and lights shall be outside the room at the
entrance. Vents from feeders and storage shall discharge to the outside
atmosphere above grade. Pipes and feed lines through interior walls shall be
gas-tight.
(d) Safety.
(i) Leak detectors. A bottle of ammonium
hydroxide shall be available for chlorine leak detection. For plants that store
1,000 lbs (454 kg) or more of chlorine, continuously monitoring leak detectors
shall be provided that sound an alarm in the event of an escape of
gas.
(ii) Repair kits. Repair kits
approved by the Chlorine Institute shall be provided for plants using ton
containers or tank cars.
(iii)
Personnel equipment. Protective clothing, rubber gloves, and U.S. Bureau of
Mines approved industrial canister gas masks shall be provided for each
operator who will handle or prepare chemical solutions/mixtures. A respiratory
protection program shall be available for all employees.
(iv) Emergency breathing apparatus.
Industrial size canister gas masks of the type designed for chlorine gas and
approved by U.S. Bureau of Mines shall be available at all installations where
chlorine gas is handled. Pressure-demand, self- contained breathing apparatus
shall be provided for repairing leaks to chlorine systems. A respiratory
protection program shall be available for all employees.
(v) Instruction manuals. Instruction manuals
for all elements of the disinfectant storage, preparation and application
system shall be provided. These instruction manuals shall describe each
component of the system, and provide a complete discussion of the operation and
maintenance requirements.
Notes
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