(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.
020-11 Wyo. Code R. § 11-21