Disinfection of Medical Waste Management Facilities


Disinfection, sanitation, and sterilization refer to degrees of cleaning and killing microorganisms. In general, disinfection attempts to eliminate bacterial and microorganism populations by killing all harmful species. Disinfection of a surface does not destroy the spores of some microorganisms, leading to eventual reappearance of those populations. Sterilization of a sample or a surface, on the other hand, kills all species; the spores are also destroyed. Both disinfection and sterilization can be accomplished by chemical or physical processes such as radiation and heat.

Chemicals can kill bacteria and fungi through one or more of these processes:

  • Starving the microorganisms by eliminating access to nutrients
  • Oxidizing the cellular membranes and viral envelopes
  • Creating a toxic environments towards the organisms
  • The efficacy of chemical disinfectants depends on operating conditions, including

    • the pH of the solution/ sample/ surface
    • temperature
    • presence of other materials such as organic compounds, inorganic salts, aggregates of pollutants, and nutrients

    Most microorganisms exhibit tolerance towards some types of disinfectants.

    Types of Industrial Disinfectants

    There is no ideal disinfectant, and the best choice depends on the needs of the facility and the situation. Waste managers often find themselves balancing the antimicrobial effectiveness with the toxicity of the disinfectant solution as stronger disinfectants are often toxic to people and animals.

    Relationship to Antiseptics

    Medical facilities also use antiseptic preparations on patients. These are more or less disinfectants, but the word antiseptic is used when a body part is being cleaned. The familiar alcohol swab before a shot is an antiseptic. Unlike disinfectants used to clean floors and surfaces, antiseptic preparations should act quickly and have efficacy against bacterial flora normally found on the skin. Although the term might be used by lay people, waste management professionals should not refer to liquids used to clean buildings or equipment as antiseptics. Use the word disinfectant.

    Quaternary Ammonium Compounds

    Also called QACs or Quats, quaternary ammonium compounds have a Nitrogen atom located at the center of their molecular structures, bonded to four organic chains. The chains can be tailored in terms of length, crosslinking, and branching. Quats work by disrupting the structures of proteins and lipid membranes. Preparations are typically 200 ppm to 400 ppm active ingredient. Quats have surfactant properties like detergents.

    Oxidizing agents

    This is the broadest category of disinfectants because so many different agents can induce oxidation of bacteria and fungi cell membranes. This category is based on functionality rather than chemical structure . Oxidizing agents include

    • sodium hypochlorite (NaClO)
    • formaldehyde (CH2O)
    • hydrogen peroxide (H2O2)
    • chlorine (Cl2)
    • chlorine dioxide ClO2
    • Iodine
    • electrolyzed water (a solution of hypochlorous acid and sodium hydroxide)
    • copper nanoparticles
    • potassium permanganate KMnO4
    • ozone (O3)
    • silver nanoparticles
    • peracetic acid (CH3CO3H)

    Some industrial disinfectants combine conventional oxidation agents and novel materials.

    Hydrogen peroxide is widely available and can be used as a disinfectant. It does not irritate the skin and few people are allergic to it, and it can be combined with nanoparticles of metals (like silver and copper) to enhance its efficiency. Chlorine dioxide is used mainly in water applications (industrial water treatment, sanitation, drinking water) due to its better performance for bacteria and microorganism killing and very low by product formation.

    Silver nanoparticles are a disinfection agent that is also used in preservation of wood and in food packaging. Iodine is also a disinfectant that is widely used as an antiseptic as well; iodine is most commonly used in aqueous solutions as a wound treating agent or water additive. Electrolyzed water is an acidic solution (pH in the range 3.5-6.5) that contains hypochlorous acid and sodium hydroxide.

    Ozone is a fast-acting disinfectant agent which when combined with light or heat can initiate free radical decomposition of organic compounds. Due to its high reactivity it should be applied close to the final use point of water, food, packaging or other application. Peracetic acid is another important disinfectant especially for food applications as it combines the efficiency of strong oxidizing agents with a constant stability in chemical environments. combines the efficiency of strong oxidizing agents with a constant stability in chemical environments.

    Alcohols

    Pure alcohols and concentrated aqueous solutions of alcohols are widely used as disinfectants in health care facilities. Alcohol solutions are employed as both disinfectants and antiseptics. Ethanol (ethyl alcohol) and isopropanol (isopropyl alcohol) are the most widely used alcohols at 60 to 90 percent concentration, although other types of alcohol sometimes find their way into disinfectants. Mixtures of alcohols and formaldehydes are also used. Pure alcohols sometimes have limited diffusivity, so they work on surfaces but do not penetrate materials like slightly diluted alcohol solutions do.

    Phenolic compounds

    Phenolic compounds have been used more than any other category by the industrial manufacturers of disinfectants. Popular ones include Phenol (carbolic acid, C6H5OH), Thymol (2-isopropyl-5-methylphenol, C10H14O) and Chloroxylenol (para-chloro-meta-xylenol, C8H9ClO). Caution is advised when using these compounds (especially in pure forms) as some of them have shown toxicity towards humans.

    Novel materials

    Carbon allotropes have been a field of active research for the development of novel disinfectant agents. Such allotropes include graphene, graphene oxides and functionalized forms of graphene. Research has shown that graphene oxides are extremely effective towards gram negative and sufficiently effective towards gram positive species [4, 5]. Advantages of these materials are their hardiness and resistance to degredation as well as their tailored porosity that can operate in dual fashion: starvation and killing of harmful species.

    One way to establish if something is an effective disinfectant is if it passes the AOAC Use Dilution Test. This test dates back to the 1950s. It tests a disinfectant solution or liquid under certain conditions: a piece of stainless steel is exposed to bacteria and then immersed in the purported disinfectant. The EPA has more.

    Physical disinfection

    Techniques include heat application, sound treatment [6], and irradiation [7]. Physical approaches are effective against hardy microorganisms, and they often are used in combination with chemical treatment. Physical disinfection targets the mechanical, biological and chemical structure of microorganisms - not access to nutrients or the microenvironment around the pathogens. High frequency sound waves, for example, can break down the cell walls of microorganisms. Their greatest advantage over chemical methods is that they can function in all chemical environments.

    Which Disinfectant Should I Use?

    The waste manager or industrial hygienist gets paid to make these decisions. There is no answer from a textbook or website. The best disinfectant should be chosen from commercially available options. Don’t try to create your own disinfectant unless you have a thorough knowledge of chemistry. And you want the disinfectant to be available in the future. Selection factors include:

    • Antimicrobial activity against the range of pathogens of interest.
    • Impact to environment (important if disinfectant is used in large volume).
    • Toxicity to people, including risk of toxicity from trace disinfectants.

    Never combine two disinfectants or two cleaning solutions. Use them sequentially if needed, with a rinse of the floor or equipment in between applications.

    Staged cleaning

    If you clean with detergent prior to disinfection, it is likely the disinfection will be more effective. Some preparations combine detergents with disinfectants, and there is nothing per se wrong with that. But cleaning in more than one stage is both theoretically superior and in real life shows better results than single-stage washing.

    Switching Disinfectants

    Although there is no firm industry practice here, managers should consider changing disinfectants used for a given application occasionally. This reduces the chances of resistant pathogens forming and it increases the overall spread of organisms being attacked. Commercial preparations tend to be unique - no two companies make the exact same formulation - but the active ingredients are often the same.

    Validating disinfection

    Antiseptics

    Another cleanliness term used in healthcare is antiseptic which is both a noun (e.g. a liquid solution applied to the skin that kills microbes) and an adjective - surfaces that have been treated with antiseptic. Industrial hygienists don’t use this word as it overlaps in meaning with sanitized and disinfected. Alcohol is a common antiseptic, applied to a person’s skin before an injection is given or catheter is introduced. There are also antiseptic cleansers sold for use in medical facilities so healthcare professionals can wash their hands. Normal bar soap or liquid soap is not considered antiseptic. Some are sold as “antibacterial” which is partly a marketing gimmick as all detergents are antibacterial to some extent. Antibacterial soap used to contain triclosan or triclocarban or another chemical, but the FDA outlawed triclosan and many other chemicals in 2016. These can no longer be put into soap or detergent for human use: cloflucarban, fluorosalan, hexachlorophene, hexylresorcinol, 6 iodophors (iodine-containing ingredients), methylbenzethonium chloride, phenol, secondary amyltricresols, sodium oxychlorosene, tribromsalan, triclocarban, triclosan, and triple dye. Source.

    Antiseptic preparations include alcohols, chlorhexidine, chloroxylenol, and quaternary ammonium compounds as active ingredients.

    References

    1 C.J. Volk, R. Hofmann, G. Ranger, R.C. Andrews, C. Chauret, G.A. Gagnon, Implementation of chlorine dioxide disinfection: effects of the treatment change on drinking water quality in a full-scale distribution system, J. Environ. Eng. Sci. 1 (2002) 323-330

    2 P. Xu, M.L. Janex, P. Savoye, A. Cockx, V. Lazarova, Wastewater disinfection by ozone: main parameters for process design, Water Res. 36 (2002) 1043-1055

    3 S.S. Birla, V.V. Tiwari, A.K. Gade, A.P. Ingle, A.P. Yadav, M.K. Rai, Fabrication of silver nanoparticles by Phoma glomerata and its combined effect against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, Lett. Appl. Microbiol. 48 (2009) 173-179

    4 S. Gurunathan, J.W. Han, A.A. Dayem, V. Eppakayala, J.H. Kim, Oxidative stress mediated antibacterial activity of graphene oxide and reduced graphene oxide in Pseudomonas aeruginosa, Int. J. Nanomed. 7 (2012) 5901-5914

    5 Biao Song, Chang Zhang, Guangming Zeng, Jilai Gong, Yingna Chang, Yan Jiang, Archives of Biochemistry and Biophysics 604 (2016) 167-176

    6 Huasheng Zou, Lifang Wang. Ultrasonics Sonochemistry, Volume 36, May 2017, Pages 246-252

    7 Ji Zheng, Chao Su, Jianwen Zhou, Like Xu, Yanyun Qian, Hong Chen. Chemical Engineering Journal, Volume 317, 1 June 2017, Pages 309-316