Controlling Contamination in Water Treatment Equipment—Part 1
By Greg Reyneke, CWS-VI
All water treatment systems are susceptible to bacterial contamination. Benign bacteria like HPCs can lurk in safe city water supplies and slowly colonize traditional water treatment equipment. Heterotrophic plate count (HPC) bacteria are a generally benign family of chlorine-resistant bacteria that inhabit most plumbing systems. HPCs are evident as part of the slimy coating that can be found on drinking filters and inside water softeners known as a biofilm.
A biofilm is a collection of organic and inorganic material, as well as living and dead organisms, responsible for numerous water quality and distribution problems such as loss of residual disinfection levels, odors, color, microbial-induced corrosion, reduced material life and a reduction in dissolved oxygen content. While HPCs themselves are generally not harmful to human health, they provide nutrition and protection for pathogenic organisms.
Pathogenic organisms can be introduced into a water quality management system through a variety of ways, including through the influent water supply, during regeneration, or through outside action. For this reason, biological risk management (BRM) protocols are necessary to prevent, contain and eliminate the colonization of pathogenic and non-pathogenic entities within water treatment equipment.
Properly implemented disinfection protocols can be a cost-effective means of reducing both benign and pathogenic organisms. Prevention of contamination is obviously easier and more cost-effective than addressing an incident after colonization has occurred. The development and implementation of a step-by-step disinfection protocol for the control and prevention of bacterial contamination in water treatment equipment is essential for all installations, whether residential, commercial or industrial.
Disinfection protocols may vary depending on the needs of a specific site. No single disinfectant or protocol is ideal for all situations. Always consult your local Certified Water Specialist (CWS) for location-specific guidelines.
The purpose of this four–part series is to discuss:
• Factors to consider when developing and implementing an effective disinfection protocol
• Chemicals used for disinfection, their advantages and limitations
• Steps for developing an effective disinfection protocol
• Procedures for maintaining ongoing system cleaning and disinfection
After the development of a disinfection protocol, it is equally important to train personnel on the proper procedures to use and safety issues involved as well as to have the procedures posted in prominent locations throughout the facility to serve as a reminder of proper disinfecting techniques. The first part of this series will focus on disinfectants and labeling.
Disinfecting agents are registered by the US EPA as antimicrobial pesticides and are substances used to control, prevent, or destroy harmful microorganisms (bacteria, viruses, or fungi) on inanimate objects and surfaces. These antimicrobial products have traditionally included sterilizers, disinfectants and sanitizers. (Data on a product’s chemistry, efficacy, toxicity to humans, animals and plants and other parameters are submitted to the US EPA prior to the marketing of the chemical after comprehensive testing).
Antiseptics and germicides are used to prevent infection and decay by inhibiting the growth of microorganisms. Since these products are used on or inside living humans or animals, they are considered drugs and are regulated by the US Food and Drug Administration (FDA); those products are outside the scope of this document.
Chemical disinfectants can have various effects against microorganisms. Therefore, a basic understanding of the different chemical agents is important.
Biocide or germicide refers to chemical agents that kill microorganisms. These general terms includes disinfectants, antiseptics and antibiotics. Germicides and biocides generally react with proteins, specifically essential enzymes of microorganisms. Actions may include oxidation, hydrolysis, denaturation or substitution. When a killing action is implied, the suffix ‘–cide’ (biocide, bactericide, virucide, sporicide) is used, while ‘–static’ (biostatic, bacteriostatic, virostatic, sporostatic) is added when an organism’s growth is merely inhibited or it is prevented from multiplying.
Sanitizers do not destroy or eliminate all bacteria or microorganisms, but reduce the amount of microbial contamination on inanimate surfaces to levels that are considered safe from a public health standpoint. Many sanitizers are a formulation of a detergent and disinfectant.
Disinfectant describes a product applied directly to an inanimate object. It destroys or irreversibly inactivates most pathogenic microorganisms, some viruses, but not (usually) spores. In comparison, antiseptics are applied to the surface of living organisms or tissues to prevent or stop the growth of microorganisms by inhibiting the organism or by destroying them.
Sterilization refers to the process, either physical or chemical, that destroys or eliminates all forms of life, especially microorganisms.
Detergents serve to disperse and remove soil and organic material from surfaces, allowing a disinfectant to reach and destroy microbes within or beneath the dirt. These products also reduce surface tension and increase the penetrating ability of water, thereby allowing more organic matter to be removed from surfaces.
Some disinfectants have detergent properties (chlorine compounds, iodophors and quats, which are ammonium compounds that are cationic detergents and are attracted to the negatively charged surfaces of microorganisms). Detergents are classified in three categories: cationic, anionic and non-ionic.
Cationic detergents are positively charged solutions; with the exception of quaternary ammonium compounds, they are seldom used as cleaning ingredients. Anionic detergents, or soaps, are negatively charged alkaline salts of fatty acids. They are less ideal for cleaning because they can be excessively foamy, creating a residue that may allow soil and microorganisms to accumulate.
Nonionic (uncharged) detergents are very good emulsifiers, have good penetration and dispersion, are effective at lowering surface tension and have reduced foaming properties. These products do not typically complex the metallic ions typically found in hard water. Most commercial detergents are a combination of anionic and non-ionic surfactants.
Product labels contain important information on the proper use and potential hazards of a chemical. Strict attention must be given to the proper use of a product with regard to its application, effectiveness and associated hazards (human, animal and environmental).
Disinfectants may have a range of uses and label claims, such as cleaner, deodorizer, sanitizer, disinfectant, fungicide and Viricide or for hospital, institutional and industrial use. Label claims are primarily determined by the product’s efficacy against three test microorganisms: Staphylococcus aureus, Salmonella cholerasuis and Pseudomonas aeruginosa.
Limited efficacy is a claim of disinfection or germicidal activity against one specific microorganism group (e.g., gram-negative or gram-positive). Gram-positive designation comes from effectiveness against Staphylococcus aureus, while gram-negative bacteria claims must be effective against Salmonella cholerasuis. The label must specify the group against which the product is effective.
General-purpose or broad-spectrum is a claim of effectiveness against gram-positive and gram-negative bacteria. This claim must be supported by efficacy testing against Staphylococcus aureus and Salmonella cholerasuis.
Hospital or medical environment claim must be supported by efficacy testing against S.aureus and S. cholerasuis but also efficacy against the nosocomial bacterial pathogen, Pseudomonas aeruginosa. Claims against pathogenic fungi or other microorganisms are permitted, but not required, on the label following standardized testing procedures.
Important label information
Effectiveness of product under certain conditions. Product testing for the US EPA requires testing under ‘hard water’ conditions up to 400 ppm hardness (CaCo3) in the presence of five-percent serum contamination to simulate the product’s effectiveness under field conditions. If the product is tested under additional conditions, it may be listed on the label.
Active ingredients. The active ingredients of the product are listed as percentages and are the chemicals responsible for the control of the microorganisms.
Inert ingredients. Biologically inactive ingredients are often lumped into one statement and include items such as soaps or detergents, dyes or coloring agents, perfumes and water.
Precautionary statement(s). These describe the potential hazards of the product (to people or animals) and actions to take to reduce those hazards (wearing gloves or goggles). Specific signal words are used to indicate the degree of hazard. Descriptors used (from least harmful to most harmful) are: Caution, Warning, Danger and Danger-Poison.
First Aid. This is a section lists the actions to take in the event of accidental swallowing, inhalation or contact with the product.
Notes to physicians. Specific medical information needed by medical professionals may be listed in this area.
Additional precautionary statements. Also contained on the label, they may include additional safety and precautionary information such as environmental hazards, physical or chemical hazards (corrosiveness or flammability) and storage and disposal information.
Directions for use. This section describes what the product controls, as well as where, how and when to use it. Some products may have multiple uses, require different dilutions and/or contact times for such specific actions (-cidal versus –static). The best application method to use with the product will also be listed.
Next Issue: Part 2–Disinfection action plan.