§ 8-05 Water Treatment.
RCNY § 8-05
Prior to changing an existing chemical treatment system or introducing a new chemical treatment agent, cooling tower design, installation, operation, and maintenance must be evaluated by a qualified person to ensure compatibility between the chemicals and the cooling tower system's materials, and to minimize microbial growth and the release of aerosols. The evaluation must describe the optimum level of chemicals to achieve the desired result in a manner which can be used as a system performance measure. All records required pursuant to this section must be retained and produced in accordance with subdivision (a) of 24 RCNY § 8-07.
(a)Daily automatic treatment while in operation. Water in a cooling tower system must be treated at least once a day when the system is in operation and such treatment must be automated, unless the maintenance program and plan explicitly states how manual or less frequent biocide additions will provide effective control of Legionella growth.
(b)Recirculating system. A cooling tower system must continually recirculate the water when it is in operation. Any period of no circulation lasting three (3) days or more in any part of the cooling tower system requires that applicable risk management procedures described in the maintenance program and plan be carried out and documented to achieve effective biofilm and microorganism control.
(c)Chemicals and biocides. Chemicals and biocides must be used in quantities and combinations sufficient to control the presence of Legionella, minimize biofilms, and prevent scaling and corrosion that may facilitate microbial growth. Only New York State Department of Environmental Conservation approved oxidizing chemicals may be used as the primary biocide control. For systems where oxidizing chemicals cannot be used as the primary biocide to control the presence of Legionella building owners must submit an alternative plan for effective bacteriological control for approval by the Department.
(1)Biocide applications. Any person who performs cleaning and disinfection or applies biocides in a cooling tower system must be a commercial pesticide applicator or a pesticide technician certified in accordance with the requirements of Article 33 of the New York State Environmental Conservation Law and 6 NYCRR Part 325, or a pesticide apprentice under the supervision of a certified applicator.
(2)Registered biocides. Only biocide products registered with the New York State Department of Environmental Conservation may be used to meet the disinfection requirements of this Chapter.
(3)Records. Water treatment records must be kept for all chemicals and biocides added, noting the purpose of their use, the manufacturer's name, the brand name, the safety data sheet, the date and time of each addition, and the amount added each week.
(4)Chemical and biocide additions. Chemicals and biocides must be added in accordance with this section and the procedures described in the maintenance program and plan addressing, as applicable, feeding mechanism, feeding location, frequency, set timer, duration, triggering events, control procedures, and target biocide residuals. Water treatment chemicals and biocides must be used in accordance with the product label and manufacturer's instructions.
(d)Non-chemical water treatment devices restricted. Only biocide products registered with the New York State Department of Environmental Conservation may be used to meet the disinfection requirements of this Chapter. Non-chemical water treatment devices that employ alternative technologies to control biological growth may not be used in lieu of chemical biocide unless approved by the Department. Nonchemical water treatment devices may be installed as part of a cooling tower system as specified in the management program and plan, provided that the required chemical water treatment also being used adequately controls for Legionella.
(e)Fill / makeup water. Fill water for commissioning or startup of a cooling tower system must be obtained from a municipal water supply. For makeup water, owners may use municipal water or water derived from a nonpotable water source. If water from a nonpotable water source is used, the owner must submit an alternative water source plan. This plan is a separate document in addition to the maintenance program and plan required by 24 RCNY § 8-03 and must be approved by the Department. The alternative water source plan must identify each nonpotable water source and include provisions for adequate design of the treatment and control components and on-going evaluation to eliminate any risk to public health.
(f)Water quality monitoring.
(5)Water quality corrective actions. The maintenance program and plan must identify the procedures, responsible parties, required response time(s) and notification protocol for corrective actions and must include, at a minimum, corrective actions that must be implemented according to the result levels in Table 8-1 and Table 8-2. For hyperhalogenating, as indicated in Table 8-1, dose the cooling tower water system with 5 to 10 ppm Free Halogen Residual for at least 1 hour. The hyperhalogenation must be carried out with the appropriate pH level for effective disinfection. The disinfectant and pH level must be documented in the corrective action procedures. Table 8-1. Corrective actions required for Legionella culture results. LevelLegionella Culture ResultProcess Triggered by Legionella Culture Results1 <10 CFU/ml If not detected, maintain water chemistry and biocide levels.If Legionella is detected but <10 CFU/ml, review water treatment program and adjust water chemistry and biocide levels, if needed.2 ≥10 CFU/ml to <100 CFU/mlInitiate disinfection by increasing biocide concentration or using a different biocide within 24 hours; review treatment program; and retest water within 3 - 7 days. Subsequent test results must be interpreted in accordance with this Table until level 1 is reached.3 ≥ 100 CFU/ml to <1,000 CFU/mlInitiate disinfection by increasing biocide concentration or using a different biocide within 24 hours, reviewing treatment program, performing visual inspection to evaluate need to perform cleaning and further disinfection. Retest water within 3 - 7 days. Subsequent test results must be interpreted in accordance with this Table until level 1 is reached.4 ≥ 1,000 CFU/mlInitiate disinfection by increasing biocides within 24 hours. Within 48 hours perform full remediation of the tower by hyperhalogenating, draining, cleaning, and flushing. Review treatment program, retest water within 3 - 7 days. Subsequent test results must be interpreted in accordance with this Table until level 1 is reached. For Legionella results at this level, notify Department within 24 hours of receiving test results. Table 8-2. Corrective actions required for bacteriological indicator results. Level Heterotrophic Plate Count and Dip Slide ResultProcess Triggered by Test Results1 <10,000 CFU/ml Maintain water chemistry and biocide levels.2≥10,000 CFU/mlThe management and maintenance team must initiate monitoring of disinfectant residual three times per day until water treatment achieves target biocide residuals for a minimum of 24 hours. If this is not achieved within three days, collect a Legionella sample and continue to adjust water treatment program.Conduct a quality control review of the water treatment program and make modifications to dosing, chemicals and biocides, bleed off or other process controls to achieve bacteriological control. Retest water for bacteriological indicators 48 hours after achieving target biocide residual. Subsequent test results must be interpreted in accordance with this Table until level 1 is reached. (Added City Record 4/7/2016, eff. 5/7/2016; amended City Record 4/8/2026, eff. 5/8/2026)
