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. However, when applying disinfection to surfaces the spores of some microorganisms are not destroyed and re- appearance of those populations is probable. When sterilizing a sample or a surface all species are killed and in addition the spores are also destroyed. Both disinfection and sterilization can be a chemical or a physical process meaning that chemical agents can be used or not. In the case of chemical disinfection and sterilization the situation becomes more complicated in comparison to physical treatment.

Equipment and facilities can be treated with chemicals to provide disinfection and sterilization Chemicals work in various ways to kill bacteria and microorganisms, including:

  • starvation of the microorganisms by eliminating access to nutrients
  • oxidation of their membrane
  • creation of toxic environments towards them
Different chemical agents work better in different operating conditions, including
  • the pH of the solution/ sample/ surface
  • ttemperature
  • presence of other agents such as organics, inorganics, aggregates of pollutants and nutrients.

In addition to those performance conditions most microorganisms exhibit tolerance towards some groups of disinfectants and thus the disinfection procedure becomes more demanding and complicated.

Industrial disinfection and sterilization commonly is divided into food and non-food applications. Food applications require stricter microbial and bacterial control and according to EPA sterilization in those applications should achieve at least 99.999% efficiency in harmful microorganism removal. For comparison, non-food applications require 99.9% removal. ‘Food applications’ requirements are also applied in other segments of services and industry such as health care, pharmaceuticals, biomedical applications, artificial transplants and other similar ones.

Types of Industrial Disinfectants

Quaternary Ammonium Compounds

Also called QACs or Quats. These compounds have a Nitrogen atom located at the center of their structure, bonded to four organic chains. The chains can be tailored in terms of length, crosslinking and branching resulting to different efficiency against different microorganisms. Their main functionality is to keep microorganisms and nutrients apart, thereby starving the microoragnisms.

Oxidizing agents

This is the broadest category of disinfectants because so many different agents (and approaches) can induce oxidation of cell membranes of microorganisms and bacteria. Old style oxidation agents can be combined with novel materials often to create new opportunities for disinfection applications and combinations. Oxidizing agents include Sodium Hypochlorite, hydrogen peroxide, chlorine, Chlorine dioxide [1], Iodine, electrolyzed water, copper nanoparticles, Potassium permanganate, Ozone [2], silver nanoparticles [3], and Paracetic acid. This category is based on functionality and not on chemical classification like the rest of the categories. Hydrogen peroxide can be used as an antiseptic as well. It exhibits additional advantages like low irritation and allergies possibilities and it can be combined with nano particles of metals (like Silver and Copper) to enhance its efficiency. Chlorine dioxide is used mainly with water application (water treatment, sanitation, even with 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 wooden surfaces and in food packaging. Iodine is also a disinfectant agent 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 and has proven very effective.

Ozone is a very efficient disinfectant agent which when combined with energy sources such as light or heat can initiate a free radical decomposition mechanism of organics that affects bacteria and microorganisms in very short times. Due to its high reactivity it should be applied close to the final use point of water, food, packaging or other application. Paracetic 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 that is exceptionally rare.

Alcohols

Pure alcohols and concentrated aqueous solutions of alcohols are widely used as disinfectants in health care facilities . Various alcohols solutions have been employed as both disinfectants and antiseptics - the disinfectant properties depend on the content of water because pure alcohols can only be effective on surfaces (no diffusion into porous membranes)

Phenolic compounds

Phenolic compounds have been used more than any other category by the industrial manufacturers of disinfectants. Popular ones include Phenol, Thymol and Chloroxylenol. Caution is advised when using these compounds (especially in pure forms) as some of them have shown extreme toxicity towards infants.

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. Recent research has shown that graphene oxides are extremely effective towards gram negative and sufficiently effective towards gram positive species [4, 5]. Significant advantages of these novel materials are their superb mechanical and electronic properties as well as their tailored porosity that can operate in dual fashion: starvation and killing of harmful species.

Physical disinfection

Techniques include heat application, sound treatment [6], and irradiation [7]. Those approaches have proven effective towards resistant microorganisms and they often are used in combination with chemical treatment. Physical disinfection targets the mechanical, biological and chemical structure of microorganisms - not the nutrients. 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 irrespective of the chemical environment present; by-products can sometimes form when physical disinfection methods are employed, but their own efficiency remains stable.

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