La. Admin. Code tit. 51 § XII-179

Current through Register Vol. 50, No. 11, November 20, 2024

Section XII-179 - Disinfection

A. Disinfection may be accomplished with gas and liquid chlorine, calcium or sodium hypochlorites, chlorine dioxide, chloramines, ozone, or ultraviolet light. Other disinfecting agents will be considered, providing reliable application equipment is available and testing procedures for a residual are recognized in "Standard Methods for the Examination of Water and Wastewater,". Disinfection is required for all water systems in accordance with §355 and §357 of this Part, other than those public water systems holding valid disinfection variance in accordance with §361 of this Part.

B. Chlorination. Design criteria for chlorination shall be as follows.

1. Chlorination Equipment Type. Solution-feed gas chlorinators or hypochlorite feeders of the positive displacement type shall be provided. (see §201-209 "Chemical Application" of this Part).

2. Capacity. The chlorinator capacity shall be sufficient to comply with minimum chlorine residuals required in §355 and §357 of this Part. The equipment shall be of such design that it will operate accurately over the desired feeding range.

3. Standby Equipment. Standby equipment shall be available to replace/repair a critical unit unless an alternative is approved by the state health officer. Spare parts shall be readily available to replace parts subject to wear and breakage. If there is a large difference in feed rates between routine and emergency dosages, a gas metering tube should be provided for each dose range to ensure accurate control of the chlorine feed.

4. Automatic Switch-Over. Automatic switch-over of chlorine cylinders shall be provided to assure continuous disinfection.

5. Eductor. Each eductor shall be selected for the point of application with particular attention given to the quantity of chlorine to be added, the maximum injector water flow, the total discharge back pressure, the injector operating pressure, and the size of the chlorine solution line. Gauges for measuring water pressure and vacuum at the inlet and outlet of each eductor should be provided.

6. Injector/Diffuser. The chlorine solution injector/diffuser shall be compatible with the point of application to provide a rapid and thorough mix with all the water being treated.

C. Criteria for Contact Time and Point of Application

1. Due consideration shall be given to the contact time of the disinfectant in water with relation to pH, ammonia, taste-producing substances, temperature, bacterial quality, disinfection byproduct formation potential and other applicable factors. The disinfectant should be applied at a point which will provide adequate contact time (CT). All basins used for disinfection shall be designed to minimize short circuiting.

2. For treating surface waters and groundwaters under the direct influence of surface water, the system shall be designed to meet the CT standards set in Chapter 11 of this Part.

D. Residual Chlorine. Systems shall be designed to meet the minimum disinfectant residual per §355 and §357 of this Part.

E. Testing Equipment. Testing equipment used for compliance monitoring shall comply with approved analytical methods set forth in this Part.

F. Chlorinator Piping. Design criteria for chlorinator pipping shall be as follows.

1. Cross-Connection Protection. The chlorinator water supply piping shall be designed to prevent contamination of the treated water supply in accordance with the backflow prevention requirements set forth in §344 of this Part.

2. Pipe Material. The pipes carrying elemental liquid or dry gaseous chlorine under pressure shall be Schedule 80 seamless steel tubing or other materials recommended by the Chlorine Institute. PVC is not acceptable upstream of the vacuum regulator. Vacuum piping for gaseous chlorine shall be polyethylene tubing or Schedule 80 PVC pipe. Rubber, Schedule 80 PVC, or polyethylene shall be used for chlorine solution piping and fittings.

G. Chloramination. Chloramination is an application of ammonia and chlorine at a proper mass ratio of chlorine to ammonia to produce a combined chlorine residual predominantly in form of monochloramine. Proper chlorine to ammonia ratio shall be maintained to prevent the formation of dichloramine and trichloramine which create taste and odor in drinking water.

1. Type. The chlorine system shall comply with the applicable requirements of §179.B Ammonia systems shall supply either anhydrous ammonia, ammonium sulfate or aqua ammonia in compliance with the requirements of §§201-209 "Chemical Application" of this Part.

2. Capacity. The ammonia supply system shall have sufficient capacity to comply with minimum disinfectant residuals required in §355 and §357 of this Part. The equipment shall be of such design that it will operate accurately over the desired feeding range.

3. Standby Equipment. Standby equipment shall be available to replace/repair a critical unit. Spare parts shall be made available to replace parts subject to wear and breakage.

4. Injector/Diffuser. The ammonia injector/diffuser shall be compatible with the point of application to provide a rapid and thorough mix with all the water being treated. If injectors are used, provisions for scale formation shall be considered.

a. Ammonia solution shall be fed through injectors/diffusers made of appropriate material installed per manufacturers recommendations for even distribution of the solution. Materials containing copper shall not be used in contact with the ammonia.

5. Cross-Connection Protection. The aqua ammonia water supply piping shall be designed to prevent contamination of the treated water supply in accordance with the backflow prevention requirements set forth in §346 of this Part.

6. Pipe Material. The pipes carrying anhydrous ammonia shall be black iron or stainless steel. Aqua (Aqueous) ammonia or ammonium sulfate piping shall be stainless steel, polyethylene tubing or schedule 80 PVC. Stainless steel, rubber, polyethylene tubing or PVC shall be used for aqueous ammonia solution piping and fittings.

H. Ozone

1. Design considerations include the following.

a. Ozonation systems are generally used for the purpose of disinfection, oxidation and microflocculation.

b. Bench scale studies shall be conducted to determine minimum and maximum ozone dosages for disinfection "CT" compliance and oxidation reactions. More involved pilot studies shall be conducted when necessary to document benefits and DBP precursor removal effectiveness. Consideration shall be given to multiple points of ozone addition. Pilot studies shall be conducted for all surface waters. Particularly sensitive measurements include gas flow rate, water flow rate, and ozone concentration.

c. Following the use of ozone, the application of a disinfectant which maintains a measurable residual will be required in order to ensure bacteriologically safe water is carried throughout the distribution system.

d. Furthermore, because of the more sophisticated nature of the ozone process a higher degree of operator maintenance skills and training is required. The ability to obtain qualified operators must be evaluated in selection of the treatment process. The necessary operator training shall be provided prior to plant startup. An operation and maintenance manual shall be provided and maintained onsite while the ozone unit is in operation.

2. Feed Gas Preparation. General design criteria for feed gas preparation shall be as follows.

a. Feed gas can be air, oxygen enriched air, or high purity oxygen. Sources of high purity oxygen include purchased liquid oxygen; on site generation using cryogenic air separation; or temperature, pressure or vacuum swing (adsorptive separation) technology. For high purity oxygen-feed systems, dryers typically are not required.

i. Air handling equipment on conventional low pressure air feed systems shall consist of an air compressor, water/air separator, refrigerant dryer, heat reactivated desiccant dryer, and particulate filters. Some "package" ozonation systems for small plants may work effectively operating at high pressure without the refrigerant dryer and with a "heat-less" desiccant dryer. The maximum dew point of -76°F (-60°C) will not be exceeded at any time.

b. Air compression. Design criteria for air compression shall be as follows.

i. Air compressors shall be of the liquid-ring or rotary lobe, oil-less, positive displacement type for smaller systems or dry rotary screw compressors for larger systems.

ii. The air compressors shall have the capacity to simultaneously provide for maximum ozone demand, provide the air flow required for purging the desiccant dryers (where required) and allow for standby capacity.

iii. Air feed for the compressor shall be drawn from a point protected from rain, condensation, mist, fog and contaminated air sources to minimize moisture and hydrocarbon content of the air supply.

iv. A compressed air after-cooler and/or entrainment separator with automatic drain shall be provided prior to the dryers to reduce the water vapor.

v. A back-up air compressor must be provided so that ozone generation is not interrupted in the event of a break-down.

c. Air drying. Design criteria for air drying shall be as follows.

i. Dry, dust-free and oil-free feed gas must be provided to the ozone generator. Dry gas is essential to prevent formation of nitric acid, to increase the efficiency of ozone generation and to prevent damage to the generator dielectrics. Sufficient drying to a maximum dew point of -76°F (-60°C) shall be provided at the end of the drying cycle.

ii. Drying for high pressure systems may be accomplished using heatless desiccant dryers only. For low pressure systems, a refrigeration air dryer in series with heat-reactivated desiccant dryers shall be used.

iii. A refrigeration dryer capable of reducing inlet air temperature to 40°F (4°C) shall be provided for low pressure air preparation systems.

iv. For heat-reactivated desiccant dryers, the unit shall contain two desiccant filled towers complete with pressure relief valves, two four-way valves and a heater. External type dryers shall have a cooler unit and blowers. The size of the unit shall be such that the specified dew point will be achieved during a minimum adsorption cycle time of 16 hours while operating at the maximum expected moisture loading conditions.

v. Multiple air dryers shall be provided so that the ozone generation is not interrupted in the event of dryer breakdown.

vi. Each dryer shall be capable of venting "dry" gas to the atmosphere, prior to the ozone generator, to allow start-up when other dryers are "on-line".

d. Air filters. Design criteria for air filters shall be as follows.

i. Air filters shall be provided on the suction side of the air compressors, between the air compressors and the dryers and between the dryers and the ozone generators.

ii. The filter before the desiccant dryers shall be of the coalescing type and be capable of removing aerosol and particulates larger than 0.3 microns in diameter. The filter after the desiccant dryer shall be of the particulate type and be capable of removing all particulates greater than 0.1 microns in diameter, or smaller if specified by the generator manufacturer.

e. Preparation piping. Piping in the air preparation system can be common grade steel, seamless copper, stainless steel or galvanized steel. The piping must be designed to withstand the maximum pressures in the air preparation system.

3. Ozone Generator. Design criteria for ozone generators shall be as follows.

a. Capacity. Design criteria for ozone generator capacity shall be as follows.

i. The production rating of the ozone generators shall be stated in pounds per day and kWhr per pound at a maximum cooling water temperature and maximum ozone concentration.

ii. The design shall ensure that the minimum concentration of ozone in the generator exit gas will not be less than 1 percent (by weight).

iii. Generators shall be sized to have sufficient reserve capacity so that the system does not operate at peak capacity for extended periods of time.

iv. The production rate of ozone generators will decrease as the temperature of the coolant increases. If there is to be a variation in the supply temperature of the coolant throughout the year, then applicable data shall be used to determine production changes due to the temperature change of the supplied coolant. The design shall ensure that the generators can produce the required ozone at maximum coolant temperature.

v. Appropriate ozone generator backup equipment must be provided.

b. Electrical. The generators can be low, medium or high frequency type. Specifications shall require that the transformers, electronic circuitry and other electrical hardware be proven, high quality components designed for ozone service.

c. Cooling. Adequate cooling shall be provided. The cooling water must be properly treated to minimize corrosion, scaling and microbiological fouling of the water side of the tubes. Where cooling water is treated, cross connection control shall be provided to prevent contamination of the potable water supply in accordance with the backflow prevention requirements in §344 of this Part.

d. Materials. The ozone generator shell and tubes shall be constructed of Type 316L stainless steel.

4. Ozone Contactors. The selection or design of the contactor and method of ozone application depends on the purpose for which the ozone is being used.

a. Bubble Diffusers. Design criteria for bubble diffusers shall be as follows.

i. Where disinfection is the primary application a minimum of two contact chambers each equipped with baffles to prevent short circuiting and induce counter current flow shall be provided. Ozone shall be applied using porous-tube or dome diffusers.

ii. The minimum contact time shall be 10 minutes. A shorter contact time may be approved by state health officer.

iii. The contactor must be kept under negative pressure and sufficient ozone monitors shall be provided to protect worker safety. The secondary enclosure for the ozone contactor shall be open to the atmosphere.

iv. Large contact vessels made of reinforced concrete shall comply with ACI 350. All reinforcement bars shall be covered with a minimum of 2.0 inches of concrete. Smaller contact vessels can be made of stainless steel, fiberglass or other material which will be stable in the presence of residual ozone and ozone in the gas phase above the water level.

v. Where necessary a system shall be provided between the contactor and the off-gas destruct unit to remove froth from the air and return the other to the contactor or other location acceptable to the state health officer. If foaming is expected to be excessive, then a potable water spray system shall be placed in the contactor head space.

vi. All openings into the contactor for pipe connections, hatchways, etc. shall be properly sealed using welds or ozone resistant gaskets such as Teflon or Hypalon.

vii. Multiple sampling ports shall be provided to enable sampling of each compartment's effluent water and to confirm "CT" calculations.

viii. A pressure/vacuum relief valve shall be provided in the contactor and piped to a location where there will be no damage to the destruction unit.

ix. The diffusion system shall work on a countercurrent basis such that the ozone is fed at the bottom of the vessel and water is fed at the top of the vessel.

x. The depth of water in bubble diffuser contactors shall be a minimum of 18 feet. The contactor should also have a minimum of 3 feet of freeboard to allow for foaming.

xi. All contactors shall have provisions for cleaning, maintenance and drainage of the contactor. Each contactor compartment shall also be equipped with an access hatchway.

xii. Aeration diffusers shall be fully serviceable by either cleaning or replacement.

b. Other Contactors. Other contactors, such as the venturi or aspirating turbine mixer contactor, may be approved by the state health officer provided adequate ozone transfer is achieved and the required contact times and residuals can be met and verified.

5. Ozone Destruction Unit. Design criteria for ozone destruction unit shall be as follows.

a. A system for treating the final off-gas from each contactor shall be provided in order to meet safety and air quality standards. Acceptable systems include thermal destruction and thermal/catalytic destruction units.

b. The maximum allowable ozone concentration in the discharge is 0.1 ppm (by volume).

c. At least two units shall be provided which are each capable of handling the entire gas flow.

d. Exhaust blowers shall be provided in order to draw off-gas from the contactor into the destruct unit.

e. Catalysts shall be protected from froth, moisture and other impurities which may harm the catalyst.

f. The catalyst and heating elements shall be located where they can easily be reached for maintenance.

6. Piping Materials. Only low carbon 304L and 316L stainless steels shall be used for ozone service.

7. Joints and Connections. Design criteria for ozone joints and connections shall be as follows.

a. Connections on piping used for ozone service are to be welded where possible.

b. Connections with meters, valves or other equipment are to be made with flanged joints with ozone resistant gaskets, such as Teflon of Hypalon.

c. A positive closing plug or butterfly valve plus a leak-proof check valve shall be provided in the piping between the generator and the contactor to prevent moisture reaching the generator.

8. Instrumentation. Design criteria for ozone instrumentation shall be as follows.

a. Pressure gauges shall be provided at the discharge from the air compressor, at the inlet to the refrigeration dryers, at the inlet and outlet of the desiccant dryers, at the inlet to the ozone generators and contactors and at the inlet to the ozone destruction unit.

b. Electric power meters shall be provided for measuring the electric power supplied to the ozone generators. Each generator shall have a trip which shuts down the generator when the wattage exceeds a certain preset level.

c. Dew point monitors shall be provided for measuring the moisture of the feed gas from the desiccant dryers. Because it is critical to maintain the specified dew point, it is recommended that continuous recording charts be used for dew point monitoring which will allow for proper adjustment of the dryer cycle. Where there is potential for moisture entering the ozone generator from downstream of the unit or where moisture accumulation can occur in the generator during shutdown, post-generator dew point monitors shall be used.

d. Air flow meters shall be provided for measuring air flow from the desiccant dryers to each of other ozone generators, air flow to each contactor and purge air flow to the desiccant dryers.

e. Temperature gauges shall be provided for the inlet and outlet of the ozone cooling water and the inlet and outlet of the ozone generator feed gas, and, if necessary, for the inlet and outlet of the ozone power supply cooling water.

f. Water flow meters shall be installed to monitor the flow of cooling water to the ozone generators and, if necessary, to the ozone power supply.

g. Ozone monitors shall be installed to measure zone concentration in both the feed-gas and off-gas from the contactor and in the off-gas from the destruct unit. For disinfection systems, monitors shall also be provided for monitoring ozone residuals in the water. The number and location of ozone residual monitors shall be such that the amount of time that the water is in contact with the ozone residual can be determined.

h. A minimum of one ambient ozone monitor shall be installed in the vicinity of the contactor and a minimum of one shall be installed in the vicinity of the generator. Ozone monitors shall also be installed in any areas where ozone gas may accumulate.

9. Alarms. The following alarm/shutdown systems shall be considered at each installation:

a. dew point shutdown/alarm. This system should shut down the generator in the event the system dew point exceeds -76°F (-60°C);

b. ozone generator cooling water flow shutdown/alarm. This system should shut down the generator in the event that cooling water flows decrease to the point that generator damage could occur;

c. ozone power supply cooling water flow shutdown/alarm. This system should shut down the power supply in the event that cooling water flow decreases to the point that damage could occur to the power supply;

d. ozone generator cooling water temperature shutdown/alarm. This system should shutdown the generator if either the inlet or outlet cooling water exceeds a certain preset temperature;

e. ozone power supply cooling water temperature shutdown/alarm. This system should shutdown the power supply if either the inlet or outlet cooling water exceeds a certain preset temperature;

f. ozone generator inlet feed-gas temperature shutdown/alarm. This system should shutdown the generator if the feed-gas temperature is above a preset value;

g. ambient ozone concentration shutdown/alarm. The alarm should sound when the ozone level in the ambient air exceeds 0.1 ppm or a lower value chosen by the water supplier. Ozone generator shutdown should occur when ambient ozone levels exceed 0.3 ppm (or a lower value) in either the vicinity of the ozone generator or the contactor; and

h. ozone destruct temperature alarm. The alarm should sound when temperature exceeds a preset value.

10. Safety. Design criteria for ozone safety shall be as follows.

a. The maximum allowable ozone concentration in the air to which workers may be exposed must not exceed 0.1 ppm (by volume).

b. Emergency exhaust fans shall be provided in the rooms containing the ozone generators to remove ozone gas if leakage occurs.

c. A sign shall be posted indicating "No smoking, oxygen in use" at all entrances to the treatment plant. In addition, no flammable or combustible materials shall be stored within the oxygen generator areas.

I. Chlorine Dioxide. When choosing chlorine dioxide, consideration must be given to formation of the regulated byproducts and chlorite.

1. Chlorine Dioxide Generators. Chlorine dioxide generation equipment shall be factory assembled pre-engineered units with a minimum efficiency of 95 percent. The excess free chlorine shall not exceed five percent of the theoretical stoichiometric concentration required. Generators designed or intended to operate outside of this criteria shall require justification and be considered on a case-by-case basis. Generator yield shall be defined as the ratio of chlorine dioxide generated to the theoretical stoichiometric maximum, as presented in EPAs Alternative Disinfectants and Oxidants Guidance Manual, Section 4.2 2 (EPA 815-R-99-014, April 1999).

a. Generators shall be designed, built and certified in compliance to NSF 61.

b. Bench scale testing shall be conducted to determine chlorine dioxide demand and decay kinetics for the specific water being treated in order to establish the correct design dose for required log inactivation compliance (if required), oxidation reactions, and chlorite generation.

c. An operation and maintenance manual (O&M) shall be provided. The O&M shall cover, at a minimum, operating instructions, identification and location of components, maintenance information and checklists; manufacturers product information (including trouble shooting information, a parts list and parts order form, special tools, spare parts list, etc.) and a chlorine dioxide and chlorite residual monitoring action plan (RMAP). The RMAP shall identify actions to be taken by properly trained certified operators in the event that the chlorine dioxide residual or chlorite level meet or exceed specified maximum levels at specified testing locations (e.g., generator effluent, treatment units, point-of-entry).

d. Certified operators charged with handling and/or conducting chlorine dioxide and chlorite testing shall be properly trained on the production and testing equipment, the generator O&M manual, and the RMAP. Documentation of training shall be signed by the individual having responsible authority over the operators. Training documentation shall be provided to the OPH District Office and maintained on-site for review during sanitary surveys.

2. Feed and storage facilities. When chlorine gas and sodium chlorite are used feed and storage facilities shall comply with §209. A and §209. C of this Part, respectively. Sodium hypochlorite feed and storage facilities shall comply with §209. D of this Part. All chlorine dioxide feed and storage facilities shall comply with §179. 1.5 and §179.1 6 of this Part.

3. Other design requirements shall include the following.

a. The design shall comply with all applicable portions of §179 B, §179 C, and §179. F of this Part.

b. Alarms shall be provided to indicate a lack of chemical (chlorine and sodium chlorite) or motive water flow.

4. Public Notification. Notification of a change in disinfection practices and the schedule for the changes shall be made known to the public; particularly to hospitals, kidney dialysis facilities, and fish breeders, as chlorine dioxide and its byproducts may have similar effects as chloramines.

5. Chlorine Dioxide Feed System. Design criteria for chlorine dioxide feed system shall be as follows.

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

b. 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.

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

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

e. All chlorite solutions shall have concentrations less than 30 percent. Higher strength solutions are susceptible to crystallization and stratification.

6. Chlorine Dioxide Storage Requirements. Design criteria for chlorine dioxide storage shall be as follows.

a. Chlorine dioxide storage and operating area shall conform to the following.

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

v. Manual switches to the light in the operating area shall be located outside the door to the room.

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

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

viii. There shall not be any open drains in the chlorine dioxide operating area.

J. Ultraviolet Light. Any Ultraviolet unit installed for treatment of cryptosporidium is required to meet the requirements of the USEPAs 2006 Ultraviolet Disinfection Guidance Manual.

K. Other disinfecting agents. Use of disinfecting agents other than those listed shall be approved by the state health officer prior to preparation of final plans and specifications.

La. Admin. Code tit. 51, § XII-179

Promulgated by the Department of Health, Office of Public Health, LR 44318 (2/1/2018), effective 8/1/2018.

AUTHORITY NOTE: Promulgated in accordance with the provisions of R.S. 40:4.A.(8), 40:4.13.D.(1)(2) and 40:5.A.(2)(3)(5)(6)(7)(17).