By Greg Reyneke, CWS-VI
The purpose of this series is to discuss factors to consider when developing and implementing an effective disinfection protocol. It includes chemicals used for disinfection, their advantages and limitations; steps for developing an effective disinfection protocol; and procedures for maintaining ongoing system cleaning and disinfection. Part 4 of this series deals with developing a disinfection action plan.
There are several important areas to be addressed in an effective disinfection action plan.
Threat assessment
Assessing the level of bacterial contamination includes observing odor and appearance of contact surfaces, as well as plate culture, to determine presence of pathogens.
Physical cleaning
After the initial assessment, cleaning is the next step and must be thoroughly performed before applying disinfectant. Experts agree that cleaning alone can remove over 90 percent of bacteria from surfaces, significantly enhancing the efficacy of disinfectant compounds and minimizing chances of regrowth/colonization.
This initial cleaning step involves scrubbing, brushing and scraping to physically remove as much gross dirt, biofilm, debris and organic material as possible from all contact surfaces. Cleaning is also important since many disinfectants may be inactivated or ineffective in the presence of organic debris or waste.
Disposal of debris into dumpsters should only occur if there is no zoonotic risk of disease transmission. All personnel should wear appropriate protective clothing and footwear. If a zoonotic disease is suspected, enhanced personal protective equipment should be used according to National Institute for Occupational Safety and Health (NIOSH) protocol.
Surfactant wash
Washing or sanitizing further reduces the number of microorganisms in the area to a safer level. Educt an anionic or non-ionic surfactant into treatment equipment, allow sufficient contact time and then rinse vigorously to remove organic and other material. Although cleaning may appear to remove all debris, microscopic biofilm may remain on surfaces and interfere with disinfection efficacy.
Biofilm is a complex aggregation of bacteria adhering to surfaces in an exopolysaccharide matrix, resulting in a thin residue that could remain after cleaning. These bacteria are highly resistant to disinfection. Surfactant detergents, mechanical scrubbing, brushing and scraping during cleaning help reduce biofilm. Adding phosphoric acid to the surfactant mixture can be quite efficacious in reducing biofilm accumulation.
Multiple bed volumes of fresh water should be rinsed through the system to ensure complete removal of surfactants and contaminants. Some disinfectants can be inactivated by soaps and detergents.
Disinfection
Selection of the proper disinfectant will depend on the microorganism suspected, as well as environmental factors and safety issues. Always read the entire product label and follow dilution instructions explicitly to ensure the safest, most effective concentration is applied.
To achieve effective disinfection, surfaces must be thoroughly wet and clean; properly mixed disinfectant should be applied at a rate of 0.1 to 0.4 L/minute (0.1 to 0.42 quarts) or according to manufacturer specifications. Dilution ratios of disinfectant will vary according to type of disinfectant and the specific application.
Disinfectant should remain for the appropriate contact time, which will vary with the product and particular application. Equipment should be thoroughly rinsed before returning the system to service.
Evaluation
To verify that all pathogens have been destroyed or reduced to acceptable levels, a follow-up evaluation of the equipment should be conducted. While visual inspection of cleanliness is important, bacteriological samples should be obtained to determine the true effectiveness of the cleaning and disinfection protocol.
Failure of a disinfection program usually results from the selection of an ineffective disinfectant, careless use of an effective disinfectant or environmental factors, such as water hardness, heavy metals, pH, additional contaminants and water temperature. The timing of sample collection is important.
The best time to sample is two to three days after disinfection. Surface samples for small, smooth areas, can be collected by wiping or swabbing a sterile swab across a non-porous surface. Commercially available methods include RODAC™ and Petrifilm™ Plates (3M).
These small, flat, sample-ready plates allow on-site microbial testing and are commonly used for food processors. They are available for a variety of specific microorganisms or classes (aerobic count plates, coliform count, environmental Listeria, etc.) as well as yeast and mold counts and can also be used for direct-contact or swab applications.
Other methods of environmental sampling include surface samples collected by ultrafilter membrane. Each step of the disinfection action plan (assessment, cleaning, washing/sanitizing, disinfection) should be evaluated for problems encountered and usefulness or efficiency of the cleaning or disinfection techniques.
Sample disinfection protocol # SP-5000
Every location is different, with varying water-usage patterns and expectations of water quality. The annual service and disinfection model is clearly deficient, so service intervals should be based upon the aggregate amount of hardness and other inorganics processed by the system.
Many industry experts agree that a system should be serviced and completely disinfected after processing approximately 1,000,000 grains or at least every 12 months, whichever is sooner. Disinfection frequency should be increased if there is any suspicion that the influent water supply is not microbiologically safe.
Industry standard employee safety precautions should always be taken before implementing this or any other disinfection protocol.
While every possible effort has been made to ensure the efficacy of this protocol, you are still ultimately responsible for the microbiological safety of the equipment in your facility. You should completely familiarize yourself with the advantages, disadvantages and liabilities of this or any other protocol before applying it. Proceed with caution at your own risk.
References (for all four parts of the series)
- US EPA. Pesticides: Regulating Pesticides – Registering Pesticides. www.epa.gov/cgi-bin/epaprintonly.cgi
- US EPA. Disinfectants for use on hard surfaces – Efficacy data requirements. www.epa.gov/oppad001/dis_tss_docs/dis-01.htm
- US EPA. Read the Label First. www.epa.gov/pesticides/kids/hometour/label/read
- National Institute for Occupational Safety and Health. Comprehensive Procedures for collecting environmental samples for culturing Bacillus anthracis. http://www.cdc.gov/niosh/unpenvsamp.html
- Antec International Ltd. Emergency disease control: The critical need for modern formulated disinfectants. http://www.antecint.co.uk/main/basichem.htm
- Health Canada. Environmental sampling for the detection of microorganisms. www.hc-sc.gc.ca/foodailment/mh-dm/mhe-dme/compendium/volume_3/e_mflp41
- Grow AG. “Writing guidelines to require disinfection.” Rev. sci. tech. Off. int. Epiz. (Scientific and Technical Review of the Office International des Epizooties) 1995:14(2);469-477. http://www.cfsph.iastate.edu
- Tamasi G. “Testing disinfectants for efficacy.” Rev. sci. tech. Off. int. Epiz. (Scientific and Technical Review of the Office International des Epizooties) 1995:14(1):75-9.
- Joklik WK (editor). Ch. 10. Sterilization and disinfection. Zinsser Microbiology. 1992. Appleton and Lange, Connecticut. pp. 188-200.
- Kennedy J, Bek J, Griffin D. Selection and use of disinfectants. University of Nebraska Cooperative Extension G00-1410-A. November 2000.
- Maris P. Modes of action of disinfectants. Rev. sci. tech. Off. int. Epiz. (Scientific and Technical Review of the Office International des Epizooties) 1995:14(1):47-55.
- Jeffrey DJ. Chemicals used as disinfectants: Active ingredients and enhancing additives. Rev. sci. tech. Off. int. Epiz. (Scientific and Technical Review of the Office International des Epizooties) 1995:14(1):57-74.
- Envirocheck® Rodac plates for surface testing. http://service.merck.de/microbiology/tedisdata/prods/49761_07084_0001.html
- 3M Petrifilm Plates. Environmental Monitoring Procedures. http://multimedia.mmm.com/mws/mediawebserver.dyn?nnnnnnX7fzBnHRon0RonnnLjxZiqY1Un-
About the author
Greg Reyneke, CWS-VI, is currently General Manager at Intermountain Soft Water in Lindon, UT and serves on the WC&P Technical Review Committee. He also serves on the advisory board of the Smart Dealer Network, a trade association dedicated to helping independent water treatment dealers succeed in today’s changing world and reach their full potential.