Section 217.280 - Design of Sodium Hypochlorite Disinfection and Sodium Bisulfite Dechlorination Systems(a) Redundancy. Sodium hypochlorite and sodium bisulfite systems must include at least two chemical solution pumps and must ensure that the capacity requirements in subsection (b) of this section are met with the largest pump out of service.(b) Capacity and Sizing. The size of a chemical liquid solution pump and pipe system must be determined as follows: (1) Sodium Hypochlorite. (A) Pounds Per Day of Chlorine Required. Figure: 30 TAC § 217.272(b), Table K.1. and Figure: 30 TAC § 217.272(a), Equation K.1. must be used to determine the pounds per day of chlorine required.(B) Chlorine Determination. The pounds of available chlorine per gallon of sodium hypochlorite solution must be determined using values and appropriate references supplied by the chemical manufacturer.(C) Gallons per Hour Determination. In order to size the chemical metering equipment, the gallons per hour must be calculated using Equation K.4. in Figure: 30 TAC §217.280(b)(1)(C). Attached Graphic
(2) Sodium Bisulfite. (A) Equation K.4. in Figure: 30 TAC §217.280(b)(1)(C) must be used to determine the pounds per day of sodium bisulfite required.(B) The minimum amount of sodium bisulfite needed to dechlorinate one pound of chlorine is 1.465 pounds. The pounds per day of chlorine that must be dechlorinated, as determined in subparagraph (A) of this paragraph, multiplied by 1.465 pounds of sodium bisulfite per pound of chlorine, determines the pounds of sodium bisulfite needed.(C) The gallons per hour of sodium bisulfite solution needed from the chemical metering equipment must be calculated using Equation K.5. in Figure: 30 TAC §217.280(b)(2)(C). Attached Graphic
(c) Dosage Control. A dosage control system may be positive pressure or vacuum and must automatically adjust the sodium hypochlorite or sodium bisulfite feed rate to correspond to the flow of the effluent stream.(d) Chemical Handling. (1) Storage Tank Sizing. (A) A storage facility for sodium hypochlorite with a solution strength greater than or equal to 10% must not be sized to store more than a 15-day supply, based on the design average daily consumption, unless a residual analyzer or oxidation-reduction potential (ORP) monitor provides automatic feed control to compensate for solution degradation. Where a residual analyzer or ORP monitor is included in the design, a storage facility must not be sized to store more than a 30-day supply, based on the daily average consumption.(B) A storage facility for sodium hypochlorite with a solution strength less than 10% must not be sized to store more than a 30-day supply, based on the daily average consumption.(C) A wastewater treatment facility with a design flow greater than or equal to 1.0 million gallons per day must have at least two chemical storage tanks for each chemical.(2) Temperature considerations. (A) A sodium hypochlorite tank that is stored outdoors must be opaque or otherwise block sunlight from penetrating the tank.(B) An outdoor sodium bisulfite storage facility and associated pipes must be insulated and heat traced if located in an area where the ambient temperatures fall below 40 degrees Fahrenheit, based on the lowest 7-day average of the average daily local temperatures over the last 10-years, as measured at the nearest National Oceanic and Atmospheric Administration's National Weather Service weather station with at least ten years of data.(e) Equipment and Materials. (1) Equipment and materials used for storage, pumping, and transport of sodium hypochlorite must be used according to the manufacturer's recommendations and designed for use in a corrosive chemical environment.(2) Equipment and materials used for storage, pumping, and transport of sodium bisulfite must be used according to the manufacturer's recommendations and designed for use in an acidic chemical environment.(f) Safety. (1) Ventilation. A chemical storage area must be ventilated to exhaust fumes.(2) Liquid-depth indicators. A chemical storage tank must have an external liquid-depth indicator.(3) Spill Containment. (A) A chemical storage area for sodium hypochlorite and sodium bisulfite must have secondary containment equal to 125% of the volume of the largest storage tank.(B) Manifolded tanks must have secondary containment equal to 125% of the cumulative manifolded tank volume. If the pipe system is designed to prevent a combined release, then the secondary containment must equal 125% of the largest tank volume.(C) A tank must either: (i) be placed on an equipment pad that is elevated above the secondary containment maximum liquid level; or(ii) be placed in a secondary containment structure that is able to be drained to prevent the tank from floating.(D) A containment structure for sodium hypochlorite must be separate from a containment structure for sodium bisulfite.(4) Emergency and Protective Equipment. A chemical storage area must have at least one emergency eyewash station and personal protective equipment for all wastewater treatment facility staff working in the area.30 Tex. Admin. Code § 217.280
The provisions of this §217.280 adopted to be effective August 28, 2008, 33 TexReg 6843; Amended by Texas Register, Volume 40, Number 47, November 20, 2015, TexReg 8339, eff. 12/4/2015