Microwave!! Does this ring a bell?
I bet you are well aware of microwaves! Yes, the one that we use for cooking and that reminds us of delicious cakes and pastries.
But how about if I tell you that we can also use the same microwave for inactivation of microbes.
In fact, with the help of the microwave we can reduce 100% of microbes to 99% within 1-2 minutes.
Microwave is an emerging technology for treating microbes. This technology is very popular in many industries like:
- Food processing
- Drying of tea leaves
- Inactivation of microbes from peanut butter, beef, catfish fillets
- Preservation of therapeutic drug
- Extraction of fragrance
- Extracting natural products and active ingredients from plants
- Preparation of safe drinking water
- Sewage sludge
- Treatment of biohazardous waste
Microwave Technology in Treatment of Biohazardous Waste
Did you know that we can use microwave technology for waste treatment as well? Let me tell you some key facts about this.
Microwave technology has the principle of a steam based disinfection process. Disinfection occurs due to the action of moist heat and steam generated by microwave energy. Microwaves are effective and quick technology. It’s convenient for disinfection of biomedical waste. The key purpose of this technology is waste minimization and effective treatment.
Microwave energy cycles are at a very high frequency, approx 2.45 billion times per second. These cycles cause water and other molecules in the waste to vibrate. These molecules try to align themselves to the shifting electromagnetic field. The enormous vibration causes friction which generates heat. This heat turns water from waste into steam. The heat denatures protein in the cell wall of microbes thereby, inactivating pathogens. Water is essential in microwave technique.
There is a misconception that microwaves cannot treat metals. But, microwaves can treat sharps. We avoid strong and large metals like steel plates, prosthetic pieces, because of chances for damaging shredder.
Waste Minimization and Microwave Technology
You know that minimization is the reduction to the greatest possible extent. Waste for disposal, recycle, employing reuse and other programs. Microwave helps in the role of minimization by reducing the volume of waste. They have shredding chambers. Shredding helps in volume reduction of waste. Waste minimization has many benefits for our environment. Some of the advantage of waste minimization are:
- Protection of environment
- It enhances the occupational safety and health
- It reduces the costs
- It reduce liability
- It can improve community relations
Working of Microwaves as Waste Treatment Technology
Microwaves have six steps for waste disinfection as per Sanitec Microwave system:-
1. Waste loading:
Carts with red bags containing hazardous/infectious waste are attached to the feed assembly. Then the feed assembly is filled with high temperature steam. When air is passed through HEPA filters, the handler opens the top flap of the hopper. Next, a bag of waste is lifted and inclined into a hopper.
2. Internal shredding:
After introduction of waste the flap is closed. Waste is first crumbled by rotatory feed arm. Then crumbled waste is grinded into smaller pieces by shredder.
The shredded particles are then transported by a rotating conveyor screw. There they are exposed to steam then heated to between 95° and 100°C by four or six microwave generators.
The holding section makes sure that the waste is least treated for at least 30 minutes.
5.Optional secondary shredder:
The treated waste may shred into a second shredder. That breaks them into even smaller pieces. Before operation in about 20 minutes an optional shredder can be attached. When sharp waste is treated into a microwave unit this is beneficial.
The shredded waste is then conveyed by a second conveyor screw or auger. The waste from the holding section is discharge into a rolloff-container or bin. The bin is then taken to a compactor or sanitary landfill.
Waste treated with Microwave Technology
Not all infectious wastes can be treated through this technology. Waste that is advisable to treat is similar to autoclaves and retorts. Some type of suitable waste for this technology are :
- Cultures and stocks
- Materials contaminated with blood and body fluids
- Isolation wastes
- Surgery wastes
- Laboratory wastes (excluding chemical waste)
- Soft wastes (gauze, bandages, drapes, gowns etc.) from patient care
“Human anatomical waste” treatment is possible with appropriate time, temperature, and mechanical system. But ethical, legal, cultural, and other considerations may hinder their treatment.
Some states and local authorities have allowed treatment of “trace-contaminated chemotherapy waste”. But facilities should check out the regulations.
Unsuited wastes for Microwave Technology
There are also some of the waste that cannot/should not be treated with microwave technology. Here, im mentioning some list of those waste:
- Volatile organic compounds
- Semi-volatile organic compounds
- Bulk chemotherapeutic wastes
- Other hazardous chemical wastes, and
- Radiological wastes
Efficiency of Microwave Technology
Studies shows, waste treated by microwaves has no microbe growth (approx 7 log10 kill or better). Testing has been done for the following organisms:
- Bacillus subtilis
- Pseudomonas aeruginosa
- Staphylococcus aureus
- Enterococcus faecalis
- Nocardia asteroides
- Candida albicans
- Aspergillus fumigatus
- Mycobacterium bovis
- Giardia miura
You must be thinking what are these high profile names?
Let me tell you, these are the statins/ types of microorganisms that are commonly found in our wastes. Which are responsible for causing many communicable and deadly diseases and infections.
Advantages of Microwave Technology
These are some main advantages of microwave technology:
- It’s approved and accepted by many states as an alternative technology.
- With proper precautions while handling biohazardous waste, emission is minimal.
- Among all the biomedical treatment technologies this is most environment friendly.
- There is no liquid effluent discharge.
- Volume of waste can be reduced to 80% by shredder.
- Microwave Technology is automated and easy to use.
- This technology requires only one operator.
- It enhanced chemical reactivity.
- It has the ability to treat wastes in-situ.
- It has a rapid and flexible process which can be handled remotely.
- It is energy efficient.
- It reduces the overall costs and helps in savings
Disadvantages of Microwave Technology
Every coin has two sides, this is no different. Some considered disadvantages of microwave technology are :
- Toxic remains of chemical waste can be transmitted into air with steam. This can contaminate landfills.
- Secondary shredder for sharps is noisy.
- There may be bad odors around the microwave unit.
- It has high initial capital cost
- Hard, large metal objects can damage the shredder.
Types of Microwave Units
There are two main designs of advanced microwave technology based on principle.
- Batch processes
- Semi-continuous microwave systems
Let me tell you some details on these two types.
An example of batch process microwave technology is the Sintion waste disposal system. Waste is place in steam permeable bags. No double double bags or closed containers. Puncture-proof sharps containers should not be airtight sealed.
Operator places one bag per cycle by opening the flap of the disinfection chamber. Outside of the waste is in contact with steam while within the waste microwave energy works. The disinfection chamber operates at 121°C (250°F) but at time of need it can go as high as 134°C (273°F). Treatment cycle can be set for 10 to 30 minutes. It’s expected to be 20 minutes.
After treatment waste is conveyed to an optional shredder. Then it is transferred to the compactor or removed.
Sintion has a self controlled computer based program. It has wheels so it’s easily movable. CMB offers staff training and installation. They also sell plastic bags and containers for internal transport. They install shredders on demand.
An unit of Sintion can handle upto 60-70 liters of waste per cycle (about 12 kg/cycle) or 2.1-2.5 cu ft per cycle (26 lb/cycle), corresponding to about 78 lbs/hr most.
Approximate Energy Consumption:-
The approximated energy consumption of one unit is about 1.5 kWh per cycle. It can produce 8.7kW at the peak demand.
Approximate cost can fluctuate from an operational point of view. The approximate cost for these are around $45,000.
The Meteka Batch microwave technology is also a good example.
2.Semi-continuous microwave systems
The example of this including shredder is the Sanitec waste disposal system. This is ideal for large amounts of biomedical wastes. This lead to collection of at the point of generation, transport and treatment of waste at one site.
Sanitec has been working since 1990. It was a division of Asea Brown Boveri (ABB), a major multi-national engineering company. But now part of Sanitec International Holdings. There are over 70 units installed in some 20 states and in six other countries. Most units are in hospitals, but about 20 are in commercial treatment centers.
It consists of hopper, conveyor screw, steam generator, shredder, microwave generators, discharge screw, secondary shredder, automatic charging system and controls. Sanitec offers help in permitting, in-service training, siting, and engineering design. Besides selling, Sanitec can also offer tailored leasing and financing and operation for large waste streams.
Two model are widely used over the globe and their capacities are:-
- Model #HG-A 100 – 220 to 400 lbs/hr
- Model #HG-A 250 – 550 to 900 lbs/hr
Approximate Energy Consumption:-
Approximate energy consumption for one unit is 0.1 kWh per pound of waste treated. It can be about 70 kW on peak demand.
Approximate cost can fluctuate from an operational point of view. The approximate cost for these are:-
Model #HG-A 100 – about $500,000
Model #HG-A 250 – about $600,00
For less amount of waste with shredders many other technologies are in the market. Bertin are among the supplier companies.
Microwave technology is an effective emerging tool for inactivation treatment of biohazardous waste. One of the major problems in the waste treatment process of waste is transportation. Relocation from generation point to disposal/treatment site in closed containers is an issue. Dispersal inactivation is very convenient for microwave technologies.
It’s quite useful in developing countries where control transport of waste is a challenge. In comparison to more widely used autoclave technology, microwaves have some upperhand. Microwave irradiation uses less energy so has a possibility to save energy costs. Lurking effects of reducing carbon footprints are also there.
So, why not use microwave technology? Think and decide for your betterment and gain. If you have something to say on the topic please comment or say hello in the comment box below. I love to hear from you all. If you want more informational blogs please do subscribe to us. Goodbye until next time and be safe.