Appendix 4-A., Appendices, TITLE 10. Department of Health, New York Codes Rules Regulations

New York Codes Rules Regulations (Last Updated: March 27,2024)

TITLE 10. Department of Health

Appendices

Appendix 4-A.

(cf. Part 4)

Interpretation of Legionella Culture Results from Cooling Towers

Legionella Test Results in CFU/mL	Response
No detection (<20 CFU/mL)	Maintain treatment program and Legionella monitoring in accordance with the maintenance program and plan.
For levels at ≥20 CFU/mL but <1000 CFU/mL perform the following:	○ Review treatment program. ○ Institute immediate online disinfection to help with control. ○ Retest the water in 3-7 days. • Continue to retest at the same time interval until one sample retest result is < 20 CFU/mL. With receipt of result < 20 CFU/mL, resume routine maintenance program and plan. • If retest is ≥ 20 CFU/mL but < 100 CFU/mL, repeat online disinfection and retest until < 20 CFU/mL attained. • If retest is ≥100 CFU/mL but < 1000 CFU/mL, further investigate the water treatment program and immediately perform online disinfection. Retest and repeat attempts at control strategy until < 20 CFU/mL attained. ○ If retest is ≥ 1000 CFU/mL, undertake control strategy as noted below.
For levels ≥1000 CFU/mL perform the following:	○ Review the treatment program and provide appropriate notifications per section 4-1.6 of this Subpart. ○ Institute immediate online decontamination to help with control. ○ Retest the water in 3-7 days. • Continue to retest at the same time interval until one sample retest result is < 20 CFU/mL. With receipt of result < 20 CFU/mL, resume routine maintenance program and plan. • If any retest is ≥ 20 CFU/mL but < 100 CFU/mL, repeat online disinfection and retest until < 20 CFU/mL attained. • If any retest is ≥ 100 CFU/mL but < 1000 CFU/mL, further investigate the water treatment program and immediately perform online disinfection. Re-test and repeat attempts at control strategy until < 20 CFU/mL attained. • If any retest is ≥ 1000 CFU/mL: • carry out system decontamination

Colony forming units per milliliter.

Online disinfection means – Dose the cooling tower water system with either a different biocide or a similar biocide at an increased concentration than currently used.

Online decontamination means – Dose the recirculation water with a halogen-based compound (chlorine or bromine) equivalent to at least 5 milligrams per liter (mg/L) or parts per million (ppm) free residual halogen for at least one hour.

System decontamination means – Maintain between 5 to 10 mg/L (ppm) free residual halogen for a minimum of one hour; drain and flush with disinfected water; clean wetted surface; refill and dose to 1 – 5 mg/L (ppm) of free residual halogen and circulate for 30 minutes. Refill, re-establish treatment and retest for verification of treatment.

For chlorine treatment the pH range should be 7.0 to 7.6; for bromine treatment the pH range should be 7.0 to 8.7. At higher pH values the treatment times may need to be extended.

NOTE: Stabilized halogen products should not be used for online decontamination or system decontamination as defined in this Appendix per footnotes 3 and 4.