What is Solid Wastes II Solid Wastes

What is Solid Wastes 

Solid waste can be defined as the residues of vegetables, ash, waste paper,  broken glasses and plastics. When these are mixed with some other particles, they  become solid waste . Solid waste is produced through our daily activities. The sources of solid waste are market area, business centers, industry, offices, educational institutions and houses. Wastes pollute our surroundings . It makes our environment unhealthy . Therefore, the wastes should be managed properly. 

Sources of Solid Wastes

i. Domestic Wastes

The wastes produced from everyday households activities are called domestic wastes. It includes kitchen wastes, plastic wrappers, bottles, old and rusted metals, papers and dust.

ii. Industrial Wastes

Industries use several kinds of raw materials for manufacturing their products. When machines and factories run, there is production of useless bi-products as well. Some industries produce huge amount of chemicals and pollutant substances in the environment. It increases solid waste in the environment.

iii. Wastes from the Market Area and Streets

Market area mainly produced wastes like plastics, wrappers, fruit-peels, vegetables wastes, etc.

iv. Wastes from the Offices

Waste materials produced from the official activities mainly include paper pieces, plastics, furniture wastes, dust and broken official materials. Wastes from the offices pollute the environment by getting mixed into the environment components.

v. Waste from the Construction Sites

Construction sites produce wastes like pieces of metals, instrumental wastes, wooden wastes, pebble, dust , iron nails etc.

vi. Waste from the Hospitals

Hospital wastes are often contaminated with disease germs. Therefore, such wastes should  be managed separately. Hospital wastes mainly include blood contaminated swabs, syringe, needle, date-expired and unused medicines, x-ray films, plastering materials. etc.

Classification of Solid Wastes

Solid waste can be classified into organic and inorganic wastes.

a) Organic wastes (Biodegradable wastes): Degradable wastes produced from the residues of biotic substances are known as organic wastes . This category of waste is decomposed by certain bacteria and protozoa and complex compounds are spat into simpler ones. The examples of organic wastes are kitchen waste, vegetable residues, and the residue of plant and animal bodies. These wastes are decomposed by microscopic organisms, mix in the soil and get consumed by plants again.

b) Inorganic Wastes:  (Non-biodegradable wastes):  The waste which is not degradable is known as inorganic waste. The examples of inorganic waste are plastics, metals,. polythene, glasses, etc. This kind of waste does not mix in the soil so easily and can have negative impacts if it enters into our body. 

Methods of Managing Solid Wastes

a) Methods of Management of Biodegradable Solid Waste

i. Landfill Method

This is a popular method in city area. In this method, wastes are collected in a particular area, carried by carrier vehicles, and thrown in a dumping site which is generally far from the residential areas. It is widely practiced in the town areas like Kathmandu, Pokhara, and Dharan in Nepal. This method requires a dumping site, which is very difficult to get as it should be far from residential area and water resources.

ii. Pit Method

In this method, the biodegradable wastes are kept safely in a pit of appropriate size. After a pit is filled, the wastes are allowed to be decomposed inside the pit. As the wastes are biodegradable , it is ultimately get mixed into the soil.

iii. Burial Method

If the wastes are foul-smelling and harmful, the burial method is used . In this method, the wastes are collected and buried under the land.

iv. Incineration Method

The process of managing solid wastes by burning is called incineration .  This method is more useful in those places where there is no land fill site. It is better to dispose more harmful wastes like the wastes of hospital, pharmaceutical, chemical industry, etc. by incineration because it kills the germs and worms responsible for diseases.

v. Composting Method

It is common practice from the beginning of agricultural age. Farmers use the waste materials produced from herbs, animal dung and other degradable organic substances for preparation of compost manure. Decaying bacteria helps to decompose the wastes and convert them into compost in the process. For this purpose, pits of different sizes can be made to prepare compost. There are major three methods of preparation of compost manure. They are;

Aerobic method: The prefix "aero-" means air or oxygen. Thus, aerobic method depends on presence of oxygen. It is a method of preparation of compost manure in which the aerobic bacteria decomposes organic matters in the presence of oxygen or air. Aerobic bacteria are those bacteria which respire in aerobic method. In this method the organic solid wastes are collected in  a pit of suitable size. The wastes are turned repeatedly after 4-7days. This helps in supplying oxygen for the bacteria and accelerates the process of waste decomposition. The manure becomes ready in about one month period. 

Anaerobic method: The prefix "an-" means no or without and "aero" means air or oxygen. Thus, anaerobic method means the method without air or oxygen. It does not depend on the presence of oxygen. It is a method of preparation of compost manure in which the anaerobic bacteria decomposes organic matters in the absence of oxygen. Aerobic bacteria are those bacteria which respire in anaerobic method. In  this method the organic solid wastes and mixture of organic sludge are placed alternately one after other in a suitable pit of about 4 to 5 feet depth . The thickness of waste and sludge layer is made about 9 and 2 inches respectively. After the pit is filled, the pit is covered with a layer  of soil or sludge at its top to prevent any leakage of heat from the pit. It is, then, left undisturbed for about 4-6 months for its anaerobic decomposition. The manure can be used after the decomposition.

Differences between aerobic and anaerobic methods of compost manure preparation 

Aerobic Method		Anaerobic  Method
1.	There is need of air or oxygen in this method.	1.	There is no need of air or oxygen in this method.
2.	Aerobic bacteria are the active decomposers.	2.	Anaerobic bacteria are the active decomposers .
3.	It needs turning of wastes after about 4-7 days.	3.	It does not need turning of waste.
4.	The layers of wastes are not made.	4.	Layers of wastes and sludge are made.
5.	The pit  should not be covered.	5.	The pit should be covered with soil and sludge.
6.	It takes short period of about one month.	6.	It takes longer period of about 4-6 months.

Vermicomposting method: It is a method of converting organic wastes into compost manure with the help of certain species of worms like wrigglers and earthworm. In this method, the organic wastes are collected in a safe container and the worms are kept there for composting. Worms consume the organic wastes and produce vermicast or the manure. They reproduce and multiply in number in the container. The time taken by the wastes to be converted into manure depends upon the volume of the wastes and number of worms kept. 

b) Methods of managing non-biodegradable solid wastes 

Wastes should be managed in the some place from where it is generated. Otherwise, it should be collected and carried to a fixed area where management is possible. There are different ways of managing the solid waste. Among them 3R method of management of solid waste is popular 3R stands for Reduce, Reuse, and Recycle. 

i. Reduce 

Reduction of waste is the process of production of solid wastes in minimum amount as far as possible. Wise use of resources help to reduce waste. People are mainly responsible for generating and managing waste. Reduction of waste helps us to maintain environmental cleanliness which prevents several kinds of diseases. The use of proper bags and baskets in the market instead of polythene bags can be very helpful in this task. We should be minimize the use of such materials which are to be thrown after use. 

ii. Reuse 

Using the same materials with slight-or no-modification time and again is called reuse. Repeated use of plastic bags and baskets is one example of reuse. Similarly, use of old newspapers as wrappers by shopkeepers is widely practiced example of reuse in our markets. 

iii. Recycle 

Recycling uses old wastes to make new products. It is the process of making new useful product by processing waste materials. It cuts down the amount of rubbish and saves natural resources by reducing the need for new materials. Items which are most suitable for recycling are the organic matters (plant and animals) which can be composted and used as fertilizers. Similarly, some metals (such as aluminium cans), paper, and plastics are also recyclable. 

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