NSF P453-2017 Cooling Tower Water Systems - Treatment Operation and Maintenance to Prevent Legionellosis.pdf

1、 NSF International Protocol NSF P453 - 2017 Cooling Tower Water Systems - Treatment, Operation, and Maintenance to Prevent Legionellosis The Public Health and Safety Company.TM NSF International, an independent, not-for-profit, non-governmental organization, is dedicated to being the leading global

2、provider of public health and safety-based risk management solutions while serving the interests of all stakeholders. This Protocol is subject to revision. Contact NSF to confirm this revision is current. Users of this Protocol may request clarifications and interpretations, or propose revisions by

3、contacting: Standards Department NSF International 789 North Dixboro Road, P. O. Box 130140 Ann Arbor, MI 48113-0140, USA Phone: (734) 769-8010 Telex: 753215 NSF INTL FAX: (734) 769-0109 E-mail: infonsf.org Web: http:/www.nsf.org i NSF International Protocol 453 Cooling Tower Water Systems Treatment

4、 Operation, and Maintenance to Prevent Legionellosis Standard Developer NSF International ii Published by NSF International P.O. Box 130140, Ann Arbor, Michigan 48113-0140, USA For ordering copies or for making inquiries with regard to this Protocol, please reference the designation “NSF P453 2017.

5、 Copyright 2017 NSF International Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from NSF International. Printed in the United States of

6、America. iii Disclaimers NSF, in performing its functions in accordance with its objectives, does not assume or undertake to discharge any responsibility of the building owner or any other party. The opinions and findings of NSF represent its professional judgment. NSF shall not be responsible to an

7、yone for the use of or reliance upon this Protocol by anyone. NSF shall not incur any obligation or liability for damages, including consequential damages, arising out of or in connection with the use, interpretation of, or reliance upon this Protocol. NSF Standards and Protocols provide basic crite

8、ria to promote sanitation and protection of the public health. Provisions for mechanical and electrical safety have not been included in this Protocol because governmental agencies or other national Standards-setting organizations provide safety requirements. This page is intentionally left blank.v

9、Contents 1 Purpose 1 2 Scope 1 3 Definitions . 1 4 General requirements . 5 4.1 The program plan (Plan) 6 4.2 Cooling tower program team (Team) . 6 4.3 System description . 6 4.4 Analysis of the cooling tower system . 7 4.5 Control measures . 8 4.6 Monitoring 8 4.7 Corrective action 9 4.8 Informatio

10、n about the cooling tower . 9 4.9 Verification and validation10 5 Treatment chemicals 10 5.1 Biocides 11 5.2 Other treatment chemicals . 12 6 Equipment . 12 6.1 Chemical feed equipment 12 6.2 Monitoring equipment . 13 6.3 Personal protective equipment 14 7 Start-up procedures 14 7.1 Initial / season

11、al start-up 14 7.2 Re-start after short-term shutdown (idle period) 15 8 Routine inspection, maintenance and service 16 8.1 Weekly inspection and evaluation 16 8.2 Quarterly inspection and evaluation . 16 8.3 Inspection and evaluation prior to start-up or re-start 16 8.4 Cleaning, preventive mainten

12、ance and service . 18 9 Routine operation . 19 9.1 Cycles of concentration 19 10 Routine treatment . 20 10.1 Microbial control treatment 20 10.2 Corrosion control treatment . 22 10.3 pH control treatment 22 10.4 Scale and deposits control treatment 22 10.5 Foam control treatment . 23 11 Monitoring .

13、 23 11.1 Monitoring of oxidizing biocides. 23 11.2 Monitoring of non-oxidizing biocides . 24 11.3 Monitoring of pH 25 11.4 Monitoring of conductivity 25 11.5 Monitoring of flow 25 11.6 Monitoring of temperature . 25 11.7 Monitoring of other control measures 25 12 Validation 25 12.1 Total aerobic bac

14、teria 26 12.2 Legionella 26 12.3 Sampling supplies . 27 12.4 Sample handling 27 12.5 Interpretation and use of validation results 27 vi 13 Remedial treatment 29 13.1 On-line remedial treatment 29 13.2 Off-line remedial treatment 30 14 Siting . 31 15 Shut down procedures 31 15.1 Short-term shut down

15、wet lay up) 31 15.2 Long term/seasonal shut down (dry lay up) 32 15.3 Discontinued use . 32 16 Contingency response plan 32 17 Audit requirements 33 17.1 On-site audits. 33 17.2 Desk audits 33 17.3 Audit reports and required action resolution 33 vii Foreword Legionella bacteria occur naturally in r

16、ivers, lakes, and streams, and can enter buildings through a number of ways. In the case of cooling tower water systems, these sources include the makeup from the municipal water supply and from scrubbing dirt and debris from the air. In the absence of control, Legionella can amplify in building wat

17、er systems and then be released into the air in Legionella-contaminated aerosols. Based on data from the Centers for Disease Control and Prevention (CDC), the greatest number of outbreaks of Legionnaires disease investigated between 2000 and 2014 were associated with premise plumbing (56%), followed

18、 by cooling tower water systems (22%)11. Because relatively more cases were associated with cooling tower outbreaks, the total number of outbreak cases from premise plumbing and cooling towers were roughly equivalent. Each building water system is important and should be addressed by comprehensive w

19、ater management programs. This Protocol specifically addresses the treatment, operation, and maintenance of cooling tower water systems to prevent Legionellosis from these systems. Cooling towers remove heat from recirculating water used in water-cooled chillers, heat pumps, air compressors, and oth

20、er equipment. Heat is rejected from recirculating water in the cooling tower primarily through evaporation. Under certain conditions, the water-associated piping, heat exchangers and other component surfaces, and the bulk water in cooling towers can become contaminated with microbes, including patho

21、genic bacteria such as Legionella. Appropriate treatment, operation, and maintenance practices can control microbial contamination, amplification, and transmission, and help prevent waterborne disease, such as Legionnaires disease, associated with cooling tower water systems. The technology of evapo

22、rative cooling water systems has advanced steadily since its origin over 100 years ago. Drift has been reduced, fan efficiency has improved, and fill effectiveness has increased. Cooling towers are now lighter and more corrosion resistant than ever before. Cooling towers offer significant environmen

23、tal benefits over alternative heat rejection systems, such as air-cooled systems, in terms of total system energy savings, carbon footprint, space, and capital cost. These benefits are enhanced by appropriate treatment, maintenance, and operation consistent with the provisions of this NSF Protocol.

24、This NSF Protocol provides auditable requirements including means, methods, and frequencies for treating cooling towers using readily available chemicals that are identified by their generic names. It provides simple, easy-to-implement procedures as a minimum benchmark. Alternative practices are all

25、owed by this Protocol so long as there is independent, documentary evidence demonstrating that such alternatives can achieve at-least-equivalent efficacy to the benchmark performance of the processes and procedures set forth here. In some jurisdictions, there are rules, regulations, and codes that c

26、over owners and operators of buildings that are equipped with cooling tower water systems. Where there are differences between the requirements of this Protocol and such rules, regulations, and codes, the more stringent or specific shall apply. Throughout the development process of NSF P453 Cooling

27、Tower Water Systems - Treatment, Operation, and Maintenance to Prevent Legionellosis, NSF International has worked closely with experts from a number of organizations, including government agencies, academic institutions, and the private sector; however, the viewpoints expressed in the document do n

28、ot necessarily represent the official position of the organization, agency, or institution. This Protocol has benefitted from the public comment process. All comments were carefully considered, and many adjustments were made accordingly. 1 Garrison LE, Kunz, JM, Cooley LA, et al. Vital Signs: Defici

29、encies in Environmental Control Identified in Outbreaks of Legionnaires Disease North America, 200-2014. MMWR Morb Mortal Wkly Rep 2016; 65: 576 584 viii NSF International recognizes and is grateful for the efforts of the Protocol review committee below in the development of NSF P453 Cooling Tower W

30、ater Systems - Treatment, Operation, and Maintenance to Prevent Legionellosis: Cesar Cordero Office of Ground Water and Drinking Water US EPA Washington, DC Justin DeWitt, PE Division of Environmental Health Illinois Department of Public Health Chicago, IL David Dziewulski, PhD Center for Environmen

31、tal Health New York State Department of Health Albany, NY Aaron Rosenblatt Gordon the heat is then rejected from the heated water by means of evaporation from the cooling tower. The cooled water, plus make-up water added to replace the water lost to evaporation (and to other, non-evaporative losses)

32、 is returned to the chiller and the process is repeated. 3.9 combined halogen residual: The halogen species in the water bound to nitrogen-containing molecules, such as amines. The halogen in covalent bonds with nitrogen comprise the “combined halogen residual.” 3.10 conductivity: Conductivity is a

33、 measure of the capacity of ions in water to carry electric current. Results of conductivity measurements are expressed as microsiemens/cm (S/cm) or mmho/cm. Both measurements are temperature dependent. Conductivity measurement is used to estimate the amount of total dissolved solids (TDS) in the re

34、circulating cooling water. Conductivity is used to initiate blowdown, thereby managing TDS levels and determining cycles of concentration. Proper control of blowdown based on measurement of conductivity is essential to effective control of the cooling water system. 3.11 control limits: A maximum val

35、ue, minimum value, or a range of values to which a chemical or physical parameter associated with a control measure must be maintained in order to reduce the occurrence of a hazardous condition to an acceptable level. 3.12 control location: A point where a physical, mechanical, operational, or chemi

36、cal control measure is applied in order to reduce the occurrence of a hazardous condition to an acceptable level. 3.13 control measure: A practice or procedure used to maintain the physical or chemical conditions of water in a cooling tower or associated components to within parameters that reduce t

37、he occurrence of a hazardous condition to an acceptable level. 3.14 cooling capacity: The amount of cooling a cooling tower can provide and is rated in tonnage. A ton is a unit of power used to describe the heat extraction capability of a chiller. A ton refers to the approximate amount of cooling po

38、wer a ton of ice would provide if it melted over a 24-hour period. A refrigeration ton is equal to 12,000 BTU/hr. A refrigeration ton is the heat rejected by the associated chiller while 15,000 BTU/hr is the heat rejected by the cooling tower when producing cooling. 3.15 cooling tower: Open cooling

39、tower, closed-loop cooling tower, evaporative condenser, or fluid cooler that is part of a recirculated water system incorporated into a buildings cooling, industrial process, refrigeration, or energy production system. A cooling tower may be comprised of individual cells. Multi-cell crossflow or co

40、unterflow towers can run on variable speeds, utilizing multiple piping and cell configurations. 3.16 cooling tower water system: One or more cooling towers and all associated equipment, such as chillers, condensers, and piping with shared water where shared water is defined as water within a closed

41、circuit with shared treatment. 3.17 cooling tower program team (Team): One or more persons to whom the owner delegates authority and responsibility for the actions required by this Protocol. 2017 NSF NSF P453-2017 3 3.18 corrective actions: Procedures that must be implemented within a specified time

42、 period when the parameters associated with control measures applied at a control location deviate from control limits. 3.19 cycles of concentration: The ratio of make-up water volume to blowdown water volume. Cycles of concentration can be approximated from the ratio of the conductivity of the blow

43、down water to the conductivity of the make-up water. 3.20 dead leg: An unused pipe or section of pipe with no flow in which the length is greater than six times the inner-diameter of the unused pipe. This also includes redundant or backup equipment with only periodic flow during system operation. 3.

44、21 dissolved solids: Soluble materials in the water, either formed from constituents of the water itself (hardness, salts, etc.) or from the local environment (airborne particles, insects, salts, etc.). The amount of dissolved solids is expressed as mg/L. 3.22 DPD: N,N-diethyl-p-phenylene diamine is

45、 a chemical indicator used in the colorimetric determination of the concentration of oxidizing biocides. DPD reacts with oxidizing biocides, including chlorine and bromine. The DPD method can be used to determine free and total halogen concentrations; combined halogen residual is the difference betw

46、een total and free halogen. 3.23 drift: Drift is the aerosolized water in droplet form carried out of the tower with the air. Microorganisms, such as Legionella, can be transmitted in the droplets which can be inhaled by and infect humans. Drift is different from vapor, the pure gas phase of water t

47、hat is liberated by evaporation. 3.24 drift eliminator: A drift eliminator is a device used to catch and coalesce aerosolized water droplets that are discharged from the cooling tower as drift. Drift eliminators are designed to change the direction of airflow abruptly, imparting centrifugal force to

48、 separate water from the air and cause small droplets to coalesce into large droplets that fall back into the tower basin. 3.25 emergency treatment: (See: off-line remedial treatment) 3.26 FIFRA: The Federal Insecticide Fungicide Rodenticide Act is the law that provides for federal regulation of pes

49、ticide distribution, sale, and use in the United States. All pesticides, including anti-microbial biocides that are distributed or sold in the United States must be registered by EPA under FIFRA. Most States have pesticide regulations that are comparable to FIFRA and also require compliance for products sold, distributed, or used in such State. 3.27 fill: The component of the cooling tower that causes the circulating water to spread out over a large surface area, in order to increase the evaporation rate by exposing the water to a greater vol