New York Codes, Rules and Regulations › Title 10 - DEPARTMENT OF HEALTH › Chapter - APPENDICES › Appendix 4-A

Current through Register Vol. 46, No. 28, July 10, 2024
(
cf. Part 4
)
Interpretation of Legionella Culture Results from Cooling
				Towers
Legionella Test Results in
							 CFU/mL1
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 disinfection2 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
							 disinfection2 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. 2 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 decontamination3 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 disinfection2 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.2 Re-test and repeat
							 attempts at control strategy until < 20 CFU/mL attained. * If any retest is
>
1000 CFU/mL: * carry out system
							 decontamination4
1 Colony forming units per
				milliliter.
2 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.
3 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.
4 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.
Stabilized halogen products should not be used for online
				  decontamination or system decontamination as defined in this Appendix per
				  footnotes 3 and 4.