Section 58.01.08.531 - DESIGN STANDARDS FOR CHEMICAL APPLICATION01.General Equipment Design. General equipment design must be such that:a. Feeders will be able to supply, at all times, the necessary amounts of chemicals at an accurate rate, throughout the range of feed.b. Chemical-contact materials and surfaces are resistant to the aggressiveness of the chemical solution.c. Corrosive chemicals are introduced in such a manner as to minimize potential for corrosion.d. Chemicals that are incompatible are not stored or handled together. At facilities where more than one (1) chemical is stored or handled, tanks and pipelines must be clearly labeled to identify the chemical they contain.e. All chemicals are conducted from the feeder to the point of application in separate conduits.f. Chemical feeders are as near as practical to the feed point.g. Chemical feeders and pumps must operate at no lower than twenty percent (20%) of the feed range unless two fully independent adjustment mechanisms such as pump pulse rate and stroke length are fitted, then the pump must operate at no lower than ten percent (10%) of the rated maximum.h. Spare parts must be on hand for parts of feeders that are subject to frequent wear and damage.i. Redundant chemical feeders with automatic switchover must be provided when necessary to ensure adequate treatment. If the water treatment system includes at least two (2) process trains of equipment so that the plant design capacity can be maintained with any component out of service, redundant chemical feeders are not required on each process train.02.Facility Design.a. Where chemical feed is necessary for the protection of the supply, such as disinfection, coagulation or other essential processes, a minimum of two feeders must be provided and a separate feeder will be used for each chemical applied.b. Chemical application control systems must meet the following requirements: i. Feeders may be manually or automatically controlled, with automatic controls being designed so as to allow override by manual controls.ii. Chemical feeders will be energized by a flow sensing device so that injection of the chemicals will not continue when the flow of water stops.iii. Automatic proportioning chemical feeders are required where the rate of flow is not reasonably constant.iv. A means to measure water flow must be provided in order to determine chemical feed rates.v. Provisions will be made for measuring the quantities of chemicals used.vi. Weighing scales will be provided for weighing cylinders at all plants utilizing chlorine gas, fluoride solution feed.vii. Weighing scales must be capable of providing reasonable precision in relation to average daily dose.viii. Where conditions warrant, for example with rapidly fluctuating intake turbidity, coagulant and coagulant aid addition may be made according to turbidity, streaming current or other sensed parameter.c. Dry chemical feeders will measure chemicals volumetrically or gravimetrically, provide adequate solution water and agitation of the chemical in the solution pot, and completely enclose chemicals to prevent emission of dust to the operating room.d. Positive displacement type solution feed pumps must be capable of operating at the required maximum head conditions found at the point of injection.e. Liquid chemical feeders must be such that chemical solutions cannot be siphoned or overfed into the water supply, by assuring discharge at a point of positive pressure, or providing vacuum relief, or providing a suitable air gap, or providing other suitable means or combinations as necessary.f. Cross connection control must be provided to assure that the following requirements are satisfied. i. The service water lines discharging to solution tanks must be properly protected from backflow.ii. No direct connection exists between any sewer and a drain or overflow from the feeder, solution chamber or tank by providing that all drains terminate at least six (6) inches or two pipe diameters, whichever is greater, above the overflow rim of a receiving sump, conduit or waste receptacle.g. Chemical feed equipment must be readily accessible for servicing, repair, and observation of operation.h. In-plant water supply for chemical mixing must be:i. Ample in quantity and adequate in pressure.ii. Provided with means for measurement when preparing specific solution concentrations by dilution.iii. Properly treated for hardness, when necessary.iv. Properly protected against backflow.v. Obtained from a location sufficiently downstream of any chemical feed point to assure adequate mixing.i. Chemical storage facilities must satisfy the following requirements:i. Storage tanks and pipelines for liquid chemicals must be specified for use with individual chemicals and not used for different chemicals. Off-loading areas must be clearly labeled to prevent accidental cross-contamination.ii. Chemicals will be stored in covered or unopened shipping containers, unless the chemical is transferred into an approved storage unit.j. Bulk liquid storage tanks must comply with the following requirements: i. A means which is consistent with the nature of the chemical stored will be provided in a liquid storage tank to maintain a uniform strength of solution. Continuous agitation will be provided to maintain slurries in suspension.ii. Means will be provided to measure the liquid level in the tank.iii. Bulk liquid storage tanks will be kept covered. Bulk liquid storage tanks with access openings will have such openings curbed and fitted with overhanging covers.iv. Subsurface locations for bulk liquid storage tanks will be free from sources of possible contamination, and assure positive drainage for groundwaters, accumulated water, chemical spills and overflows.v. Bulk liquid storage tanks will be vented, but may not vent through vents common with other chemicals or day tanks. Acid storage tanks must be vented to the outside atmosphere, but not through vents in common with other chemicals or day tanks.vi. Each bulk liquid storage tank will be provided with a valved drain, protected against backflow and cross-connections.vii. Bulk liquid storage tanks will have an overflow, when provided, that is turned downward with the end screened with a twenty-four (24) mesh or similar non-corrodible screen, have a free fall discharge, and be located where noticeable.viii. Where chemical feed is necessary for the protection of the supply, a means to assure continuity of chemical supply while servicing a bulk liquid storage tank will be provided.ix. Bulk liquid storage tanks will be provided with secondary containment so that chemicals from equipment failure, spillage, or accidental drainage will not enter the water in conduits, treatment, or storage basins. A common receiving basin may be provided for each group of compatible chemicals. The bulk liquid storage tank basin or the common receiving basin will provide a secondary containment volume sufficient to hold one hundred ten percent (110%) of the volume of the largest storage tank. Piping will be designed to minimize or contain chemical spills in the event of pipe ruptures.k. Day tanks will be provided where bulk storage of liquid chemical is provided. However, upon approval by the Department, chemicals may be fed directly from shipping containers no larger than fifty-five (55) gallons. For the purposes of Section 531, day tanks are defined as liquid chemical tanks holding no more than a thirty (30) hour chemical supply.i. Day tanks are subject to the requirements in Subsections 531.02.j.i. through 531.02j.vii. except shipping containers do not require overflow pipe and drains.ii. Where feasible, secondary containment will be provided so that chemicals from equipment failure, spillage, or accidental drainage of day tanks will be fully contained. A common receiving basin may be provided for each group of compatible chemicals. The common receiving basin will provide a secondary containment volume sufficient to hold the volume of the largest storage tank. If secondary containment is not feasible, day tanks will be located and protective curbings provided so that chemicals from equipment failure, spillage, or accidental drainage of day tanks will not enter the water in conduits, treatment, or storage basins. Secondary containment is not required for a day tank if an Idaho licensed professional engineer demonstrates to the Department that the chemical concentration and volume, if spilled, will not be a safety hazard to employees, will not be hazardous to the public health, and will not harm the environment.iii. Day tanks and the tank refilling line entry points will be clearly labeled with the name of the chemical contained.iv. Filling of day tanks may not be automated unless otherwise approved by the Department.l. Provisions must be made for measuring quantities of chemicals used to prepare feed solutions.m. Vents from feeders, storage facilities and equipment exhaust must discharge to the outside atmosphere above grade and remote from air intakes.03.Chemicals. Chemical shipping containers must be fully labeled to include chemical name, purity and concentration, supplier name and address, and evidence of ANSI/NSF certification where applicable.04.Safety Requirements for Chemical Facilities. a. The following requirements apply to chlorine gas feed and storage rooms:i. Each storage room will be enclosed and separated from other operating areas. They will be constructed in such a manner that all openings between the chlorine room and the remainder of the plant are sealed, and provided with doors equipped with panic hardware, assuring ready means of exit and opening outward only to the building exterior.ii. Each room will be provided with a shatter resistant inspection window installed in an interior wall.iii. Each room will have a ventilating fan with a capacity which provides one (1) complete air change per minute when the room is occupied. Where this is not appropriate due to the size of the room, a lesser rate may be allowed by the Department on a site specific basis.iv. The ventilating fan will take suction near the floor as far as practical from the door and air inlet, with the point of discharge located as far away as possible from doors, air inlets to any rooms or structures, or occupied areas. Air inlets will be through louvers near the ceiling.v. Louvers for chlorine room air intake and exhaust will facilitate airtight closure.vi. Separate switches for the fan and lights will be located outside of the chlorine room and at the inspection window. Outside switches will be protected from vandalism. A signal light indicating fan operation will be provided at each entrance when the fan can be controlled from more than one (1) point.vii. Vents from feeders and storage will discharge to the outside atmosphere, above grade.viii. Where provided, floor drains will discharge to the outside of the building and will not be connected to any internal drainage systems or external drainage systems unless the external drainage systems drain to an approved discharge point.ix. Chlorinator rooms will be heated to sixty degrees Fahrenheit (60°F) and be protected from excessive heat. Cylinders and gas lines will be protected from temperatures above that of the feed equipment.x. Pressurized chlorine feed lines may not carry chlorine gas beyond the chlorinator room.xi. Critical isolation valves will be conspicuously marked and access kept unobstructed.xii. All chlorine rooms, buildings, and areas will be posted with a prominent danger sign warning of the presence of chlorine.xiii. Full and empty cylinders of chlorine gas will be isolated from operating areas and stored in definitely assigned places away from elevators, stairs, or gangways. They will be restrained in position to prevent being knocked over or damaged by passing or falling objects. In addition, they will be stored in rooms separate from ammonia storage, out of direct sunlight, and at least twenty (20) feet from highly combustible materials. Cylinders may not be kept in unventilated enclosures such as lockers and cupboards.b. Where acids and caustics are used, they must be kept in closed corrosion-resistant shipping containers or storage units. Acids and caustics may not be handled in open vessels, but will be pumped in undiluted form from original containers through suitable hose to the point of treatment or to a covered day tank.c. Proposals for the storage and use of sodium chlorite must be approved by the Department prior to the preparation of final plans and specifications. Provisions must be made for proper storage and handling of sodium chlorite to eliminate any danger of fire or explosion associated with its oxidizing nature.i. Chlorite (sodium chlorite) will be stored by itself in a separate room. It must be stored away from organic materials. The storage structure will be constructed of noncombustible materials. If the storage structure must be located in an area where a fire may occur, water must be available to keep the sodium chlorite area cool enough to prevent heat-induced explosive decomposition of the chlorite.ii. Care will be taken to prevent spillage. An emergency plan of operation will be available for the clean up of any spillage. Storage drums will be thoroughly flushed prior to recycling or disposal.d. Where ammonium hydroxide is used, an exhaust fan must be installed to withdraw air from high points in the room and makeup air must be allowed to enter at a low point. The feed pump, regulators, and lines must be fitted with pressure relief vents discharging outside the building away from any air intake and with water purge lines leading back to the headspace of the bulk storage tank.e. Where anhydrous ammonia is used, the storage and feed systems (including heaters where required) must be enclosed and separated from other work areas and constructed of corrosion resistant materials.i. Pressurized ammonia feed lines will be restricted to the ammonia room.ii. An emergency air exhaust system, as described in Subsection 531.04.a., but with an elevated intake, must be provided in the ammonia storage room.iii. Leak detection systems must be fitted in all areas through which ammonia is piped.iv. Special vacuum breaker/regulator provisions must be made to avoid potentially violent results of backflow of water into cylinders or storage tanks.v. Consideration must be given to the provision of an emergency gas scrubber capable of absorbing the entire contents of the largest ammonia storage unit whenever there is a risk to the public as a result of potential ammonia leaks.05.Operator Safety. The Idaho General Safety and Health Standards, referenced in Subsection 002.02, may be used as guidance in designing facilities to ensure the safety of operators. Facilities must meet applicable regulations from the Occupational Health and Safety Administration.06.Design Requirements for Specific Applications. In addition to Subsection 531.01 through 531.03, the following design requirements apply for the specific applications within Subsection 531.06 of this rule. a. Positive displacement feeders will be provided for sodium chlorite used for chlorine dioxide generation. Tubing for conveying sodium chlorite or chlorine dioxide solutions must be Type 1 PVC, polyethylene or materials recommended by the manufacturer. Chemical feeders may be installed in chlorine rooms if sufficient space is provided. Otherwise, facilities meeting the requirements of chlorine rooms will be provided. Feed lines will be installed in a manner to prevent formation of gas pockets and will terminate at a point of positive pressure. Check valves will be provided to prevent the backflow of chlorine into the sodium chlorite line.b. Hypochlorite facilities must meet the following requirements:i. Hypochlorite will be stored in the original shipping containers or in hypochlorite compatible containers. Storage containers or tanks will be sited out of the sunlight in a cool and ventilated area.ii. Stored hypochlorite will be pumped undiluted to the point of addition. Where dilution is unavoidable, deionized or softened water will be used unless otherwise approved by the Department.iii. Storage areas, tanks, and pipe work will be designed to avoid the possibility of uncontrolled discharges and a sufficient amount of appropriately selected spill absorbent will be stored on-site.iv. Hypochlorite feeders will be positive displacement pumps with compatible materials for wetted surfaces.v. To avoid air locking in smaller installations, small diameter suction lines will be used with foot valves and degassing pump heads. In larger installations flooded suction will be used with pipe work arranged to ease escape of gas bubbles. Calibration tubes or mass flow monitors which allow for direct physical checking of actual feed rates will be fitted.vi. Injectors will be made removable for regular cleaning where hard water is to be treated.c. When ammonium sulfate is used, the tank and dosing equipment contact surfaces must be made of corrosion resistant non-metallic materials. Provision will be made for removal of the agitator after dissolving the solid. The tank will be fitted with a lid and vented outdoors. Injection of the solution will take place in the center of treated water flow at a location where there is high velocity movement.d. When aqua ammonia (ammonium hydroxide) is used, the feed pumps and storage will be enclosed and separated from other operating areas. The aqua ammonia room will be equipped as required for chlorinator rooms with the following changes: i. A corrosion resistant, closed, unpressurized tank will be used for bulk storage, vented through an inert liquid trap to a high point outside and an incompatible connector, or lockout provisions will be made to prevent accidental addition of other chemicals to the storage tank.ii. The storage tank will be designed to avoid conditions where temperature increases cause the ammonia vapor pressure over the aqua ammonia to exceed atmospheric pressure. This capability can be provided by cooling/refrigeration or diluting or mixing the contents with water without opening the system.iii. The aqua ammonia will be conveyed direct from storage to the treated water stream injector without the use of a carrier water stream unless the carrier stream is softened.iv. The point of delivery to the main water stream will be placed in a region of turbulent water flow.v. Provisions will be made for easy access for removal of calcium scale deposits from the injector.Idaho Admin. Code r. 58.01.08.531