Medics accept the necessity to protect themselves and all us from infectious wastes. One of the main causes is disease transmitting microbes. If such waste is left untreated, it can cause diseases. To prevent deadly disease wise treatment of infectious waste is compulsory. It’s estimated that 80% of medical waste is outright segregated in different bins. The Remaining 20% of waste is technologically treated. In treatment of infectious waste these technology most preferred technology are:
- Incinerators
- Autoclaving
- Steam sterilization
- Microwaving
- Chemicals
From ancient times, human excreta has led to disease outbreaks. Some of these diseases are cholera, dysentery, typhoid and poliomyelitis. Such waste may bear pathogens in concentrated form that can pollute water and food. These are the reasons that Biomedical Waste Management has become of utmost importance.
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The Ministry and related groups issued a set of guidelines for local laws to state aid sanitations. By our grasp we have evolved some simple approaches for potent handling of medical wastes.
The EPA (Environmental Protection Agency) published the Draft Manual for Infectious Waste Management in 1986. Published as the final version — EPA Guide to Infectious Waste Management
In this blog, I’m going to tell you some details of infectious waste and their treatment technique. First of all I’ll start from some basic understanding of infectious waste.
Infectious Waste
According to the EPA infectious waste is a waste that is capable of producing infectious disease. According to this definition there are some factors responsible for causing disease. Some of these factors are:
- Presence of a pathogen of sufficient virulence
- Dose
- Portal of entry
- Resistance of host
Thus not all the waste is infectious waste. For a waste to be infectious, presence of pathogen with enough virulence and quantity is must. So, exposure to a host with waste could result in infectious disease.
Besides, the ministry has identified an optional waste category that contains miscellaneous contaminated waste.
The terminology problem is a major concern. As the term infectious, biohazardous, biomedical, medical, toxic, pathologically hazardous are all used to define infectious waste.
According to statista, CPCB’s mentioned amount of medical waste has approximately doubled from 2007 to 2018. That shows that in 2007 it’s estimated to be about 288 metric tons per day which exceeds to 530 metric tons per day.
Techniques for treatment of Infectious wastes
According to the EPA, treatment is any method/technique/process designed to change biological character/composition of waste. Since landfill methods may cause limitations and dispersal of waste. It’s recommended to treat the waste prior to its disposal. Also the treatment and disposal should be under the disposal guidelines set by authorities.
Recommended treatment techniques for treatment of infectious waste are mention in detail below:
Incinerators
Incineration is a high temperature dry oxidation process. Which converts organic and combustible waste into inorganic, non- combustible matter. In turn it results in a significant reduction of quantity and volume of waste. This process is used to treat the waste that can not be reused, recycled, and disposed of in a landfill site. Incinerators also used to generate energy from waste.
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Incinerators for treatment of medical waste should operate between the 900 to 1200 degree C temperature. For low heating value:
Above 2000kcal/kg (8370kJ/kg) is for single-chamber incinerators. Above 3500kcal/kg (14640kJ/kg) is for pyrolytic double-chamber incinerators.
Unsuited waste type
- Pressurized gas containers.
- Large amounts of reactive chemical waste.
- Silver salts and photographic or radiographic wastes.
- Halogenated plastics such as polyvinyl chloride (PVC).
- Waste with high mercury or cadmium content like broken thermometers, batteries and lead-lined wooden panels.
- Sealed ampoules or ampoules containing heavy metals.
Suitable waste types for Incineration
- Isolation waste
- Contaminated animal carcasses, body parts, and bedding
- Pathological waste
- Human blood and blood product
- Cultures and stocks of infectious agents and associated biologicals
Advantage of Incinerators:
- Adequate for all infectious wastes, most pharmaceutical and chemical waste.
- Good disinfectant efficiency.
- Reduces the volume and weight of waste.
- No need for trained personnel
- Residues can be disposed of in landfills without worry.
- Some types have relatively low investment and operating cost.
Disadvantage of Incinerators:
- Significant emission of atmospheric pollutants.
- Incomplete destruction of cytotoxic.
- Some types have relatively high investment and operating costs.
- Need for periodic removal of slag and soot.
- Inefficiency in destroying thermal resistant chemicals and drugs such as cytotoxics.
- Emission of fly ash.
- Release bad odour in the environment.
Operating cost
An incinerator is operated and maintained by a well trained technician. Operating cost of the current incinerator plant is considered expensive. The cost of an incinerator depends on many technical factors like burning capacity, size of incinerator, chimney etc.
In contrast with companies and e-shops, it’s estimated that you can buy a hospital waste incinerator with minimum Rs 125000/Piece to a maximum range of Rs 2200000/Piece.
| Incinerator equipment | Investment costs (in 1000 US$) for capacities (tonnes/day) | ||||
| 0.4 | 1 | 2 | 4 | 8 | |
| Without energy recovery or gas cleaning | 50 | 100 | 120 | 150 | 230 |
| With energy recovery but without gas cleaning | 100 | 180 | 230 | 340 | 570 |
| With energy recovery and gas cleaning | 300 | 400 | 480 | 600 | 780 |
Chemical Disinfection
Chemical disinfection is commonly done in healthcare facilities with routine to kill microbes. It is used to clean floors, walls etc. Nowadays it is done commercially to disinfect wastes.
This method is most fit for treating liquid waste. Like blood, stools, hospital sewers, etc. But it is also used for solid waste and even highly hazardous wastes with some limitations. Shredding of solid waste is necessary to increase the extent between waste and disinfectant.
Factors which affect quality of chemical disinfection
- The kind of chemical used
- The amount of chemical used
- The contact time between disinfectant and waste
- The extent of contact between disinfectant and waste
- The organic load of the waste
- Operating temperature, humidity, pH, etc.
Unsuited waste type
- Human body parts, waste
- Animal carcasses
Suitable waste type
- Cultures and stocks of infectious agents and associated biologicals
- Blood and blood products
- Contaminated sharps
Advantage of chemical disinfection
- Very efficient for disinfection under good operating conditions.
- Some chemicals are cheap
- Drastic reduces in quantity because of shredding.
Disadvantage of chemical disinfection
- Requires well trained personnel for operating the process.
- Use hazardous substances that need comprehensive safety measures to handle.
- Inadequate for pharmaceutical, chemical, and some types of infectious waste.
Operating costs
According to a report by W.H.O. For the disinfection of waste, investments are in the range US$ 50000–100000. Operating costs, which are generally in the range US$ 100–120 per tonne. That is particularly dependent on the price of chemical disinfectants. Price of chemicals may vary from country to country. Where cheap chemical disinfectants are available, this process seems very attractive. Yet, it is not very popular in developing countries.
Wet Thermal Treatment
Wet thermal is based on exposure of shredded hazardous waste to high temperature, high pressure. It is similar to autoclaving. It kills most types of microorganism if temperature and contact time is appropriate.
Shredding of waste is advisable prior to disinfection. For sharps, crushing is prefer to increase disinfection efficiency.
Unsuited waste type
- Anatomical waste
- Animal carcasses
- Liquid waste or waste containing high organic content
- Chemical and pharmaceutical waste is not disinfected efficiently
Suitable waste type
- Contaminated sharps
- Contaminated animal carcasses, body parts, and bedding
- Isolation waste
- Cultures and stocks of infectious agents and associated biologicals
- Human blood and blood product
- Pathological waste
Advantages of Wet Thermal Treatment Technique
- It is very convenient for the environment
- It wastes volume due to shredding.
- Low investment and operating cost.
Disadvantages of Wet Thermal Treatment Technique
- Shredders are prone to frequent breakdown and poor functioning.
- Operation requires qualified technicians.
- Inadequate for anatomical, pharmaceutical, and chemical waste
- And for waste that is not considered as steam-permeable like solid waste.
Operating cost
According to a report published by W.H.O. Investment costs range from US$ 50000 to US$ 200000 for the full equipment. Equipment has
- Tank capacities between 20 litres and 8m3
- Operating temperatures between 120°C and 160°C.
As for the sketch, the cost of equipment with the capacity to treat 50 tonnes of waste/year is about US$ 100000 on the European market. Operating costs are about US$ 400 per tonne of waste (less in developing countries).
Autoclaving
Autoclaving is an efficient wet thermal treatment. Autoclaving is used for infectious waste like microbial cultures, sharps etc. It is recommended to all hospitals to have an autoclave. Researches convey that, for potent inactivation of microbes and most bacterial spores in a small amount of waste (about 5– 8 kg). It requires a 60-minute cycle at 121°C (minimum) and 1 bar (100kPa). This allows for full steam penetration of the waste material.
Factors affecting
- The moisture content of the waste
- Ease of penetration of the steam.
Unsuited waste type
- Pathological
- Cytotoxic
- Radioactive waste
Suitable waste type
- Contaminated sharps
- Contaminated animal carcasses, body parts, and bedding
- Isolation waste
- Cultures and stocks of infectious agents and associated biologicals
- Human blood and blood product
- Pathological waste
Advantages of Autoclave
- It doesn’t have adverse effects on the environment.
- It reduces enormous waste volume.
- Easy to handle.
- Weight is also reduced by 20-35%.
Disadvantages of Autoclave
- It is not used for pathological, toxic, radioactive waste.
- Exhaust air should be filtered.
- Water generated during the process should be treated before discharge.
Operating cost
Operating autoclaves and their associated repairs can be a costly affair. Autoclaving expenses are not only limited to the cost of an autoclave machine. But it includes:
- Equipment cost
- Laundry cost
- Water cost
- Electricity cost
- Consumable costs (sterilization indicators)
- Packaging materials
- Instrument cleaning solutions
- Human resource cost
- Depreciation cost of equipment
- Cost of equipment maintenance contracts
The total electricity cost calculated using a cost of INR 10 (US$0.17) for 1 kWh. The total cost associated with the autoclave was INR 6,077,977 (USD 91,191). Plus a comprehensive maintenance contract of INR 200,000 (USD 3,000) per year. The cost per cycle of the autoclave is based on a total cycle:calculation of 24,000 cycles: 8 cycles per day ×25 days per month ×12 months per year ×10 years.
Depreciation cost was calculated using depreciation over 10 years for capital equipment (ie, steam sterilizers, washer disinfector, drying cabinet costs). Human resource cost calculated for the total manpower cost/month for 1 scientific officer, 4 technologists, 7 attendants, and 2 housekeepers.
Microwave technique
Microwave technology is an emerging tool for biohazard waste treatment. Most of the microorganism is removed by using a microwave. Microwave of frequency of about 2450 MHz and a wavelength of 12.24cm is used. The water present in the waste is quickly heated, destroying infectious components by heat conduction.
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In a microwave unit waste is first transferred into a shredder, then waste is humidified. Waste is then transferred into an irradiation chamber that is equipped with microwave generators. Then we irradiate it for 20 minutes.
Factors affecting
- Quality of shredder
- Shredding tendency
- Quality of irradiation chamber
- Number of microwaving units fitted
Unsuited waste type
- Pressurized gas containers.
- Large amounts of reactive chemical waste.
- Photographic or radiographic wastes.
- Halogenated plastics such as polyvinyl chloride (PVC).
- Waste with high mercury or cadmium content like broken thermometers, batteries, lead-lined wooden panels.
- Sealed ampoules or ampoules containing heavy metals.
- Waste that can react or blast by high temperature.
Suitable waste type
- Contaminated sharps
- Pathological waste
- Beddings
- Isolation waste
- Cultures and stocks of infectious agents and associated biologicals
- Human blood and blood product
Advantage of microwave technique
- Environment friendly.
- Reduce the volume of waste.
- Good disinfection efficiency under appropriate operating conditions.
Disadvantage of microwave Technique
- Relative high maintenance and operating cost.
- Maintenance and operation problem.
- Need a trained technician to operate.
Operating cost
Microwave is an irradiation equipment with a capacity of 250kg/hour (3000 tonnes/year). It includes:
- Loading device
- Shredder
- Steam humidification tank
- Irradiation chamber
- Microwave generators
- Plus a waste compactor
That may cost about US$ 0.5 million. More compact systems have recently been developed to treat healthcare waste at point of production. They are of considerably lower capacity, but are much cheaper.
Land disposal for treatment of infectious waste
It is dumping of the waste into sanitary landfills or municipal waste dumps. Dumping of medical waste in open dumps are the least advisable treatment of infectious waste. Open dumps are symbolized by uncontrolled scattering of wastes. It leads to excess pollution, fires, disease transmission. Health care waste should not be dumped into an open dump.
Sanitary landfills have some advantage over open dumps. It divides the waste from the environment. Proper engineering is done before the site is ready to accept waste. Staff are present to ensure the proper process. Routine coverage of waste is practice.
Using landfill for medical waste disposal is least advisable. Yet, if you are going to use this option it is recommended you proceed with encapsulation. Below I have done the encapsulation method in detail.
Encapsulation for treatment of medical waste
Disposal of waste is less advisable before treatment. One good alternative is encapsulation, for pretreated waste. Encapsulation involves filling containers with waste, adding an immobilizing material and sealing the containers.
The process is done by cubic box/ high density polyethylene or metallic drums. Boxes should be three fourths filled with waste and then filled with mediums. Mediums are like plastic foam, cement mortar, bituminous sand or clay materials.
After the medium is dried the boxes should be sealed and transferred to landfills. Encapsulation is not advisable only for sharps but can be done when mixed with non sharp waste.
Advantage of Encapsulation technique
- This technique is simple, low cost and safe
- It can also be used in case of pharmaceutical and chemical waste.
Disadvantage of Encapsulation
- The process is not for non- sharp infectious substances.
Safe burial of infectious waste on hospital premises
Healthcare units in very remote places, refugee camps or areas where other techniques are not available. This technique is acceptable.
Factors affecting
- Access to the site should only be permitted to authorized persons, not everybody.
- Only hazardous waste should be dumped. If every type of waste is buried there, the site will fill in less time.
- Chemical waste (>1kg) should not be buried at one time as it harms the environment.etc.
Advantage of safe burial technique
- It is safe, low cost.
- Safe if access to the site is restricted for locals.
- Safe if natural infiltration is in limit.
Disadvantage of safe burial technique
- Safe only if access to the site is limited and certain precautions should be taken.
Conclusion
Techniques mentioned in this blog, effectively reduce the hazards of infectious wastes. Improper treatment can give rise to other health and environmental problems. Toxic emission and/or pollution of groundwater is one of the major problem.
When deciding on a treatment method we should always carefully check it in the light of local circumstances. It is not necessary that any preferred technique is also preferable to you.
Safe and correct disposal method choice is mandatory. As a responsible citizen everyone should practice the correct disposal method. If you want to say something about this subject please let me know in the comments. I would love to hear from you. Please subscribe to us for more informational blogs.
