SOLID WASTE MANGEMENT
PROCESS OF CLEANING THE DRY WASTE
DISPOSAL OF SOLID WASTE
The principle methods of are:
Controlled tipping or sanitary landfill
- In this method, refuse is dumed in low lying areas.
- Easy method of disposal of dry refuse and suitable for reclamation of land.
- As a result of bacterial action, refuse decreases considerably in volume and is converted gradually into humus.
- Most unsanitary method of waste disposal.
CONTROLLED TIPPING(sanitary landfill)
- Most satisfactory method of refuse disposal where sutable land is available.
- Material is placed in trench, adequately compacted, and covered with earth at the end of working day.
3 methods-trench method, area method, ramp method
- Trench method-used where level ground is available
- Area method- used for filling land depressions
- Ramp method-used where terrain is moderately sloping
- Chemical, bacteriological and physical changes occur in burial surface.
- Temperature rises to over 60°C within 7 days and kills all pathogens and hastens the decomposition process
- Refuse can be disposed off hygienically by burning or incineration.
- It has limited application in refuse disposal as it is a loss to community in terms of manure and mainly used for health care waste disposal.
It is a process of nature where matter breaks down under bacterial action resulting in formation of a relatively stable humus-like material, called the compost.
Principle by products are carbon dioxide, water and heat.
- Methods of composting are-Bangalore method(Anaerobic method)
-Mechanical method(Aerobic method)
Bangalore method(hot fermentation process)
- Developed by Indian Council of Agriculture Research at the Indian Institute of Science, Bangalore
- Trenches are dug depending upon the amount of refuse and night soil to be disposed off.
- First layer of refuse is spread at the bottom of the bottom of the trench. Over this nightsoil is added
- Then alternate layers of refuse and nightsoil are added till the heap rises 1ft above the ground level.
- The top layer should be refuse, at least 9 inches in thickness
- Then the heap is covered wih excavated earth compacted
- At the end of 6months, decomposition is completed and resulting material is a well decomposed, odourless, innocuous material with manurial value.
- Mechanical composting
In this aerobic method, compost is manufactured on a large scale
- one or more closed tanks or digesters equipped with rotating vanes that mix and aerate the shredded waste. Complete digestion of the waste takes about one week
- The waste is shredded into minute particles
They are dug by individual householders to dump the garbage, cattle dug, straw and leaves.
They are covered with earth after each days dumping
In 5 to 6 months time the refuse is converted into manure which can be returned to the field
The trench is excavated and at the end of each day the trench is filled with earth and compacted.
Suitable for small camps.
- DISPOSAL OF HEALTH CARE WASTE /BIOMEDICAL WASTE
Treatment and disposal options are:
Wet thermal treatment
High temperature dry oxidation process that reduces organic and combustible waste to inorganic incombustible matter
Reduces waste volume and weight
Used to treat waste that cannot be recycled, reused or disposed off in a landfill site.
Types of incinerators
- Double-chamber pyrolytic incinerators
- Single-chamber furnaces with static grate
- Rotary kilns
Pyrolytic incinerators(controlled air incineration)
-comprises of pyrolytic chamber and post-combustion chamber
-waste is thermally decomposed through an oxygen deficient medium temperature combustion process producing solid ashes and gases
Single chamber incinerator
-treat waste in batches
-loading and de-ashing operations are done manually
-drum or field incinerator is the simplest form of a single chamber incinerator.
-drawback is that it will cause emission of black smoke, causes air pollution
-comprises of rotating oven and post-combustion chamber
-used for:infectious waste and pathological waste, all chemical and pharmaceutical wastes including cytotoxic waste
-disadvantage is energy consumption is high
- Chemicals are added to waste to kill or inactivate the pathogens.
- Most suitable for treating liquid waste such as blood, urine, stools, or hospital sewage.
- Types of chemical disinfectants are: formaldehyde, ethylene oxide, glutaraldehyde, sodium hypochlorite, chlorine dioxide
Wet thermal treatment(steam disinfection)
- Based on exposure of shredded infectious waste to high- temperature, high-pressure steam
- Inactivates most types of microorganisms
- Advantage: low environmental impact, relatively low investment and operating costs.
- Most microorganisms are destroyed by the action of microwaves of a frequency of about 2450MHz and a wavelength of 12.24cm
- Procedure involves filling containers made of high density polyethylene or metal drums, with waste.
- These containers are then filled up with medium of immobilization material such as plastic foam, cement mortar or clay.
- After the medium has dried the containers are sealed and disposed off in landfill sites.
- Used only when this is only viable option available especially in establishments which use minimal programs for health care waste management
- Involves mixing waste with cement and other substances before disposal in order to minimize the risk of toxic substances contained in the waste migrating into surface water or ground water.
- Suitable for pharmaceuticals and for incineration ashes with a high metal content.
Color coding of hospital waste
- GARBAGE-Genral waste after domestic usage includes household/kitchen waste.
- SULLAGE– This is a term that describes the wastewater. Often, it is also called ‘gray water’ and in simpler terms, sullage is the leftover water that humans use inside their homes except for the toilet.
- SEWAGE-Almost same as sullage but contains human excreta