environmental hygiene
environmental hygiene
By Richard Dixon and David W . Koenig , PhD
Water Quality and Conservation
Taken together water is critical for life , critical for pathogen transmission and survival , and critical for infection control . Therefore , it is important to understand water as it enters the healthcare facility and all the forms it can be encountered in that facility .”
Water is vital for life on this planet . Some organisms have up to 90 percent water by body weight . Humans contain up to 60 percent water . Water is also critical in the survival and transmission of pathogens in the healthcare environment . Microorganisms require water to grow and reproduce .
Water requirements for growth are best defined in terms of water activity , aw , of the substrate rather than as water concentration . The water activity of a solution is expressed as aw = P / Po , where P is the water vapor pressure of the solution and Po is the vapor pressure of pure water at the same temperature . Addition of a solute to an aqueous solution in which a microorganism is growing will have the effect of lowering the aw , with a concomitant effect upon cell growth .
Every microorganism has a limiting ‘ aw ’ below which it will not grow , e . g ., for streptococci , Klebsiella spp ., Escherichia coli , Clostridium , and Pseudomonas spp . the value is 0.95 . Staphylococcus aureus is the most resistant and can proliferate with an aw as low as 0.86 . Some fungi can grow with an aw of 0.7 . Therefore , wet environments favor the survival and therefore transmission of pathogens .
Water is also key to the cleaning and disinfection of these surfaces . Cleaners and disinfectants are mostly water-based , either being used as a ready-to-use ( RTU ) or diluted with water at the point of use . Taken together , water is critical for life , critical for pathogen transmission and survival , and critical for infection control . Therefore , it is important to understand water as it enters the healthcare facility and all the forms it can be encountered in that facility .
Water Quality
In the United States , potable water or drinking water is regulated by the Environmental Protection Agency ( EPA ). The EPA sets the legal limits on more than 90 chemical and microbial contaminates for drinking water . The EPA mandates that any water treatment technology must meet a disinfectant standard and that the resulting product is free of pathogens .
Although potable water standards ensure safe drinking water , the water is not sterile . Following EPA standards ensures that drinking water has a low probably of containing at risk organisms . The disinfectant is added at the treatment facility and is at a level that allows for preservation of the drinking water through the potable water distribution system to
point of use . The level of disinfectant can be relatively low at the point of use , dependent on the demand in the distribution system . The disinfectant added is not sufficient to control contaminates that may be introduced into the distribution system due to breaks in the system . Once the water is removed from the distribution system , that level can decrease rapidly due to demand . Importantly for infection control measures , the design of the building ’ s water distribution system can significantly alter water quality . The water in the building can pass into water heaters , heat exchangers , faucet aerators , and lie stagnant in dead legs before use . Ice machines can be a challenge for microbial control . Furthermore , in older buildings , mixed metals and plastics used in the distribution system due to renovations and building additions can impact mineral build-up and biofilm development . Water systems that are not managed appropriately allow waterborne pathogens to increase in types and numbers resulting in infections in susceptible individuals .
Innovations for optimizing water quality , safety and conservation in a healthcare facility are insightful , forward-thinking , and necessary . By employing a holistic approach to water management , facilities can not only enhance operational efficiency and reduce the cost of the water supply from the local municipality but also contribute to environmental sustainability and , most importantly , patient , staff , physician , and visitor safety . The next sections will review those processes and provide insights in optimizing water usage while reducing pathogen transmission risk .
Water Microbiology : The main risk of bacteria in drinking water is usually due to contamination events that introduce human fecal organisms to the water distribution system . The most common problem organisms associated with drinking water are Vibrio cholerae , Vibrio parahaemolyticus , Salmonella enterica , Shigella dysenteriae , Shigella flexneri , Shigella boydii , Shigella sonnei , Escherichia coli , and Campylobacter sp . Problem viruses include adenovirus , astrovirus , hepatitis A and E viruses , rotavirus , norovirus , and enteroviruses , including coxsackieviruses and polioviruses . Other bacteria associated with water and infection include Mycobacterium , Legionella , Burkholderia , Klebsessia , and Ralstonia . Fungi can be isolated from tap water distribution systems , but their types and numbers are poorly defined . The most detected fungi are Aspergillus , Cladosporium and Penicillium . Giardia and Cryptosporidium are the most problematic protozoans found in water systems . www . healthcarehygienemagazine . com • december 2023
27