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Oklahoma Administrative Code (Last Updated: March 11, 2021) |
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TITLE 252. Department of Environmental Quality |
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Chapter 656. Water Pollution Control Facility Construction Standards |
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Subchapter 21. Disinfection Standards |
SECTION 252:656-21-2. Chlorine disinfection systems
Latest version.
- (a) Equipment capacity. The following requirements are for the chlorination of non-industrial wastewater. The equipment shall be capable of supplying the following dosage as applicable:(1) Trickling filter plant effluent - 10 mg/l;(2) Activated sludge plant effluent - 8 mg/l;(3) Tertiary filtration effluent - 6 mg/l;(4) Nitrified effluent - 6 mg/l; and(5) Category 2 water reuse chlorination systems - 12 mg/l or a dose sufficient to achieve high level disinfection for water reuse requirements.(b) Chlorine mixing.(1) Mixing. The disinfectant shall be mixed as rapidly as possible to ensure complete mixing.(2) Contact period. Provide the following contact periods:(A) For OPDES permit compliance or Categories 3 and 4 water reuse chlorination systems, provide a minimum contact period of 15 minutes at peak hourly wastewater flow or maximum pumping rate after mixing.(B) For Category 2 water reuse chlorination systems, alone or in combination with UV, provide sufficient free chlorine residual concentration at the end of the contact tank and modal contact time sized using the anticipated design flow after mixing at a design temperature of 5 °C (41 °F) and a pH of 8.0 to meet the micro-organism log removal requirements in 252:656-27-3(a)(6).(3) Contact tank. Construct chlorine contact tanks to minimize short-circuiting. "Over-and-under" or "end-around" baffling shall be provided to reduce short-circuiting. Design the tanks for easy maintenance and cleaning without reducing the effectiveness of disinfection. Provide duplicate tanks, mechanical scrapers or portable deck-level vacuum cleaning equipment. Provide skimming devices on all contact tanks, and provide for draining the tanks.(c) Gas chlorine equipment rooms.(1) Separation. If the building that houses the gas chlorine equipment is used for other purposes, a gas-tight room shall be provided to separate the gas chlorination equipment and chlorine cylinders from other parts of the building. Do not connect floor drains from the chlorine room to floor drains from other rooms. Doors to this room shall open only to the outside of the building, with panic hardware, at ground level and allow easy access to all equipment. For one-ton chlorine cylinders, separate the storage area from the feed area. Locate chlorination equipment as close to the application point as is reasonably possible. Certify the installation will meet OSHA standards, and that the doors and emergency equipment are compatible with chlorine.(2) Inspection window. Install a shatter resistant, clear glass, gas-tight window in an exterior door or interior wall of the chlorinator room so the units can be viewed without entering the room.(3) Heating. Heat disinfection equipment rooms to maintain at least 60 °F. Protect the gas chlorine cylinders from excess heat, and maintain the cylinders at essentially room temperature.(4) Ventilation. Provide mechanical ventilation capable of one air change per minute for chlorine. The entrance to the room exhaust duct shall be near the floor. The point of discharge shall not contaminate inhabited areas or the air inlet to any buildings. Locate fresh air inlets to provide cross ventilation with air and at a temperature that will not adversely affect the chlorination equipment. Discharge the chlorinator vent hose above-grade to the outside atmosphere.(5) Electrical controls. Locate fan and light switches outside the room near the entrance. A labeled signal light indicating fan operation shall be provided at each entrance when the fan can be controlled from more than one point.(d) Water supply. Provide an ample supply of water to operate the chlorinator and protect it according to 252:656-9-2(b). Back up any booster pumps according to the power requirements of 252:656-9-2(a).(e) Scales. Provide corrosion-resistant scales to weigh chlorine gas cylinders. Provide at least a platform scale. Provide a recording device for the weight of the chlorine gas cylinders for installation where one-ton cylinders or larger are used.(f) Containers. One-ton containers or larger are required if more than 150 pounds of chlorine per day is needed. Limit the withdrawal rate to 40 pounds per day per cylinder for cylinders up to 150 pounds, and to 400 pounds per day for one-ton cylinders.(g) Handling equipment. For cylinders up to 150 pounds, provide securing restraints and a hand-truck designed for the cylinders. For one-ton cylinders, provide:(1) a hoist with 4,000-pound capacity;(2) a cylinder lifting bar;(3) a monorail or hoist with sufficient lifting height to pass one cylinder over another; and(4) a cylinder trunnion(s) to allow exchanging the cylinders for proper connection.(h) Manifolds. Gaseous chlorine cylinders may be connected to a manifold, only when all cylinders are maintained at the same temperature or the system is designed for gas transfer from a warm container to a cooler one. Do not connect liquid chlorine cylinders to a manifold.(i) Leak detection and controls. Provide an emergency response plan for chlorine leaks. Provide a bottle of 56% ammonium hydroxide solution for detecting chlorine leaks. Where one-ton containers are used, provide a leak repair kit approved by the Chlorine Institute, include caustic soda solution reaction tanks to absorb leaks. Provide automatic gas detection and related alarm equipment. Air Pollution Control regulations may also require air scrubbing equipment.(j) Evaporators. Demonstrate the required volume of chlorine can be supplied.(k) Respiratory protection. Where chlorine gas is handled, provide respiratory air-pac protection equipment that meets the National Institute for Occupational Safety and Health (NIOSH) standards. Store the equipment and operating instructions at a convenient location outside the room where chlorine is used or stored. The units shall use compressed air, with at least a 30-minute capacity, and be compatible with units used by the local fire department. In the emergency response plan, describe how to maintain the equipment.(l) Sodium hypochlorite. Follow equipment standards in OAC 252:626-11-4(g).(1) On-site Generation of Sodium Hypochlorite:(A) Contact Time. On-site generation is limited by the upper concentration of the chlorine solution produced. Design should account for concentration limit where contact time is required. Contact time is determined from free chlorine concentration only.(B) Ventilation. A by-product of on-site generation is the formation of hydrogen gas. Design shall meet the following:(i) Ventilation shall be designed to take suction from as near the ceiling as practical.(ii) Ventilation piping shall slope towards an outlet and in a manner that does not trap hydrogen gas.(iii) Provide hydrogen gas sensing equipment capable of interlocking with sodium hypochlorite generation equipment.(iv) System shall have automatic turn off of the equipment in the event that one-half (½) the lower explosive limit (LEL) is reached.(v) Separate gas sensing equipment shall interlock with the ventilation equipment.System shall automatically turn on in the event that one-fourth (¼) the LEL for hydrogen is reached.(vi) Provide at least one hydrogen sensor for any space that hydrogen gas is likely to accumulate.(vii) Piping penetrating the roof must have a "T" or an "L" shape and a 24 mesh corrosion resistant screen.(C) Pretreatment. To avoid fouling of the electrolytic cell, a water softener or other pretreatment method is required to prevent scaling during the process.(D) Brine Solution. The salt used for the brine shall be high grade (99% pure) and shall be certified for use by the NSF for electrochlorination (NSF Standard 60). Provide the capability for diluting 12.5% bulk sodium hypochlorite to create less than one percent (1%) solution.(E) Storage. Design shall meet the following:(i) All chemical handling and storage shall be in accordance with OAC 252:626-11(ii) Provide at least two (2) tanks with thirty (30) hours storage capacity at average daily for usage solution.(iii) Protect concrete from corrosion.(iv) Tanks shall be located in a structure to prevent freezing of all system components.(v) Tanks shall be clear or provide a sight glass to determine brine level.(F) Waste Disposal. Design shall be in accordance with OAC 252:626-13 to ensure proper disposal of the waste stream.(G) Warranty. Provide a two (2) year warranty and maintenance on all equipment.(H) Redundancy. Provide multiple units to meet maximum daily demand with the largest unit out of service.(m) Dechlorination. When dechlorination is required by DEQ, the discharges shall have less than 0.1 mg/l total residual chlorine.(1) Equipment. Do not chlorinate and dechlorinate with the same units. Handle aqueous solutions of sulphite or bisulfite with positive displacement pumps. Sulfur dioxide (SO2) feed equipment shall account for the property of the gas to easily liquefy. With one-ton containers, take special precautions to prevent chemicals from liquefying. Provide multiple units to meet the operating requirements between the minimum and maximum wastewater flow rates and to avoid depleting dissolved oxygen in receiving waters.(2) Mixing. Mechanical mixers are required unless the design will provide hydraulic turbulence to assure thorough and complete mixing.(3) Sulfonator water supply. Provide an ample supply of water to operate the sulfonator, and protect it according to 252:656-9-2(b). Back up booster pumps according to the power requirements of 252:656-9-2(a).(4) Housing. Storage and feed equipment for SO2 shall be in a separate room from chlorine gas storage and feed equipment. The same storage requirements apply to SO2 as for chlorine gas in (c) of this Section. Mixing, storage, and feed equipment areas shall be designed to contain spillage or leakage or to route it to an appropriate containment unit.(5) Respiratory protection. Same as for chlorine gas in (k) of this Section.