R309-520-10. Chlorine Dioxide

  Public water systems must take into consideration that chlorine dioxide and its byproducts may have similar effects as chloramines on sensitive populations. Chlorine dioxide should not be intentionally used as a secondary disinfectant. The water system must monitor the chlorine dioxide residuals and byproducts in the distribution system. If the chlorine dioxide residual in the distribution system may affect sensitive populations, the public water system shall notify the public of the change. Sensitive populations include hospital and kidney dialysis patients. Sensitive industries include fisheries.

  (1) Pre-design Proposal.

  Proposals for the use of chlorine dioxide shall be discussed with the Division prior to the preparation of final plans and specifications. A water system must submit a detailed written proposal to the Director for review, including:

  (a) The make, model, and specifications for proposed chlorine dioxide generator

  (b) References of other U.S. potable water installations of the proposed unit

  (c) Information on the operational and maintenance training program

  (d) The expected total applied dosage of chlorine dioxide and other disinfectants as well as the points of application for all disinfectants and the type and amount of residuals and by-products expected in the distribution system

  (2) Chlorine dioxide generators

  (a) Chlorine dioxide generation should be designed to be efficient compared to industry standard, and production of excess chlorine shall be minimized.

  (b) The generator shall not produce a solution with chlorine dioxide concentration more than 6,000 mg/L to minimize the explosion hazard.

  (c) The design shall include capability to measure concentrations of chlorine dioxide, chlorite, chlorate, and free chlorine of the solution leaving the generator.

  (d) The chlorine dioxide generator shall be equipped with a chlorine dioxide analyzer to measure the strength of the solution leaving the generator.

  (e) Generators which use solid chlorite will not be allowed.

  (3) Chlorine Dioxide Feed and Storage System

  (a) Chlorine Dioxide Feed system.

  (i) Use fiberglass reinforced vinyl ester plastic (FRP) or high density linear polyethylene (HDLPE) tanks with no insulation.

  (ii) If centrifugal pumps are used, provide Teflon packing material. Pump motors must be totally enclosed, fan-cooled, equipped with permanently sealed bearings, and equipped with double mechanical seals or other means to prevent leakage.

  (iii) Provide chlorinated PVC, vinyl ester or Teflon piping material. Do not use carbon steel or stainless steel piping systems.

  (iv) Provide glass view ports for the reactor if it is not made of transparent material.

  (v) Provide flow monitoring on all chemical feed lines, dilution water lines, and chlorine dioxide solution lines.

  (vi) Provide a means to verify calibrated feed flow to each application feed point.

  (vii) Control air contact with chlorine dioxide solution to limit potential for explosive concentrations building up within the feed facility.

  (viii) All chlorite solutions shall have concentrations less than 30%. Higher strength solutions are susceptible to crystallization and stratification.

  (b) Chlorine Dioxide Storage and Operating Area. The following requirements apply to the chlorite storage and chlorine dioxide day tank area.

  (i) The chlorine dioxide facility shall be physically located in a separate room from other water treatment plant operating areas.

  (ii) The chlorine dioxide area shall have a ventilation system separate from other operating areas.

  (iii) Provision shall be made to ventilate the chlorine dioxide facility area and maintain the ambient air chlorine dioxide concentrations below the Permissible Exposure Limit (PEL).

  (A) The ventilating fan(s) take suction near the floor, as far as practical from the door and air inlet, with the point of discharge so located as not to contaminate air inlets of any rooms or structures.

  (B) Air inlets are provided near the ceiling.

  (C) Air inlets and outlets shall be louvered.

  (D) Separate switches for the fans are outside and near the entrance of the facility.

  (iv) The area housing chlorine dioxide facility shall be constructed of non-combustible materials such as concrete.

  (v) There shall be an ambient air chlorine dioxide sensor in the vicinity of the chlorine dioxide operating area. The ambient air chlorine dioxide readouts and alarm or warning light shall be audible and visible in the operating area and on the outside of the door to the operating area. The design shall include distinguishing audible alarms that are triggered by the ambient air chlorine dioxide sensor readings.

  (vi) There shall be observation windows through which the operating area can be observed from outside the room to ensure operator safety.

  (vii) Manual switches to the light in the operating area shall be located outside the door to the room.

  (viii) There shall be an emergency shower and eyewash outside and close to the door to the operating area.

  (ix) An emergency shutoff control to shut flows to the generator shall be located outside the operating area.

  (x) The design shall minimize the possibility of chlorite leaks.

  (xi) The chlorite tank and chlorine dioxide solution tank shall be vented to the outdoors away from any operating areas.

  (xii) Gaseous chlorine feed to the chlorine dioxide generator shall enter the chlorine dioxide facility area through lines which can only feed to vacuum.

  (xiii) The floor of the chlorine dioxide facility area shall slope to a sump.

  (xiv) There shall not be any open drains in the chlorine dioxide operating area.

  (xv) Provide secondary containments with sumps for chlorine dioxide storage, and chlorine dioxide solutions which can hold the entire volume of these vessels. This containment shall prevent these solutions from entering the rest of the operating area.

  (xvi) Provide wash-down water within the operating area.

  (xvii) The operating area shall be designed to avoid direct exposure to sunlight, UV light, or excessive heat.

  (4) Other Design Criteria.

  (a) Provide secondary containment, a sump, wash-down water, and a shower and eyewash at the bulk delivery transfer point.

  (b) Finished water shall be used for chlorine dioxide generation.

  (c) The finished water line to the chlorine dioxide generator shall be protected with a high hazard assembly.

  (d) Provide a water supply near the storage and handling area for cleanup.

  (e) The parts of the chlorine dioxide system in contact with the strong oxidizing or acid solutions shall be of inert material.

  (f) The design shall provide the capability to shut off the chlorine dioxide operation remotely, i.e., from a location that is outside of the chlorine dioxide operating area.

  (5) Operation and Maintenance.

  (a) Do not store or handle combustible or reactive materials, such as acids, reduced metals, or organic material, in the chlorine dioxide operating area.

  (b) Store chemicals in clean, closed, non-translucent containers.

  (c) Personal protective equipment and first aid kits shall be stored at a nearby location that is outside the chlorine dioxide facility area.

  (d) The temperature of the chlorine dioxide operating area shall be maintained between 60 and 100 degrees F.

  (e) After delivery allow chlorite solutions to equalize with the ambient temperature of the operating area to avoid stratification.

  (f) The Operating and Maintenance manual shall include operator safety and emergency response procedures. Personnel shall have ongoing training for operator safety and emergency response procedures.

  (g) All wastes should be disposed of in accordance to any existing solid and hazardous waste regulations.

  (h) The operating area should be inspected daily for chlorite spills and solid chlorite buildup. The daily inspections shall be logged.

  (i) Chlorite leaks and solid chlorite buildup should be cleaned up and disposed of immediately.

  (j) Solid chlorite should be washed down before removal.

  (k) The ventilation system in the chlorine dioxide facility area shall be operated to maintain the ambient air chlorine dioxide concentrations below the Permissible Exposure Limit (PEL).

  (l) Audible alarms shall be programmed to alert water treatment plant personnel when the ambient air chlorine dioxide sensor in the vicinity of the chlorine dioxide operating area detects the chlorine dioxide concentration above the Permissible Exposure Limit (PEL) and the Short Term Exposure Limit (STEL).