Monday, June 1, 2020

Solid waste- management and disposal.

With the development in technology, copious quantities of wastes are also generated. Such wastes are pollutants. Toxic physical, chemical or biological substance created by anthropogenic activities are known as "waste". It is known as trash or garbage in U.S.A and rubbish in Britain. Proper disposal of waste is required in order to minimize environmental pollution. 


Solid waste- management and disposal


Classification of waste:
Waste can be divided into several categories:
  • Urban waste- spoils of vegetables, fruits, plastics, bottles, chemicals etc.
  • Industrial waste- harmful toxic chemicals, by products.
  • Biodegradable waste- food waste, paper.
  • Recyclable waste- paper, cardboard,glass certain plastics.
  • Inert waste- dirt, rocks, debris, construction wastes.
  • Biomedical waste- syringe, expired drugs.
  • Toxic waste- pesticides, insecticides, herbicides, fungicides.
  • Hazardous waste- paints, chemicals, tires, batteries, lights.
  • Composite waste- toys, furnitures.
  • Electrical waste- washing machine, computers, mobiles.
Components of management:
  • Collection.
  • Handling, storage and processing.
  • Segregation, processing and transformation.
  • Transfer and transport.
  • Disposal.
  • Reusing.
Disposal methods:

Open dump
Open dumps are just the wastes in a heap in contact with the atmosphere. Such dumps are unsightly. Such dumps are home to rats, insects and other pests. The foul smell is unbearable for the residents nearby. Such rubbish may gets scattered through water and wind. Percolating rain water may leach out harmful chemicals that may carried away into surface run off or percolating into groundwater. Thus, it also gives rise to water pollution. As the trash is in direct cotact with the atmosphere, the toxic and hazardous gases also gets released in the atmosphere. Thus, open dump sites are unsatisfactory means of disposal of solid waste.


Unsighty open dump.

Sanitary landfill
Sanitary landfills are an alternate to the earlier open dumps. It has been in use since early 20th century. In a sanitary landfill the rubbish is covered with a layer of earth atleast once a day. The earth cover serves as a barrier between the waste and the atmosphere. It also confines the refuse. Such sanitary landfills are constructed at a low places such as valleys, old abandoned mines etc. The reason behind this is when the site is filled completely, a thick layer of earth is deposited and the land can be use for purposes like parks, parking lots and even gardens can be constructed over it.

 But there are some problems in reusing the land for infrastructure purposes. 
Limited excavation- as the waste material is near to the surface, it limits the depth of excavation for construction purposes. 
Stress on the infrastructure- some pollutants gets decomposed or escapes in the form of gases from the landfill site. Thus, it generates pressure on the construction above it.
Methane problem- pollutants can escape from an improper landfill site in the form of gases. As in open dumps, aerobic respiration takes place and give rise to gases like carbon dioxide and sulphur dioxide. In sanitary landfills, initially aerobic respiration takes place and forms carbon dioxide and sulphur dioxide. When the oxygen in the landfill is used up, anaerobic respiration takes place. It generates methane and hydrogen sulphide. If the surface soil is permeable, such gases may come out from it. If the surface soil is not permeable it can reduce the pollution and accumulate the methane. But this methane, builts up a pressure. Therefore, some kind of ventilating mechanisms needs to be there. Such methane can be use for economic purposes. If the quantity is insufficient for economical purpose, it is burnt at the vent only.
Leachate problem- this is problem with improperly designed landfill sites. If the water table merges with the landfill site throughout the year or during rainy season, it leads to groundwater pollution. If the layer above and below the landfill are permeable leachate may come out and can contaminate surface and ground water. However, nowadays there are certain alternatives for these problems. Both the layers above and below must be impermeable. Or before filling the site, low permeable clay must be filled. Also plastics and water proof liners are in used to prevent the problem. But, though no landfill can be an ideal site.
Bathtub effect- if the above layer is highly permeable and lower layer is impermeable, percolating water gets accumulate in the landfill site. After, a certain point the leachate may spill out and contaminates other things such as groundwater. This problem is low where precipitation is in low amount such as in regions having arid climates. Solution, for this problem is provided by pumping out the waste material but this approach generates another major issue i.e."liquid waste disposal".

Incineration


Waste incinerator.

The main disadvantage of landfill is it requires large areas and with the problem of increasing population, areas for landfill have became scarce. The partial solution to this problem is provided by the method known as " Incineration". In USA, it is a common practice for each household to have a small incinerator in their backyard. Incineration is the process of burning of refuse. It is an imperfect solution because it creates another problem known as air pollution. By burning the refuse cetain hazardous gases are released in the atmosphere. Depending on the material that is burned, gases gets released. It might be carbon dioxode, sulphur dioxide or even chlorine. Also volatile toxic elememts such as mercury and lead escapes with the gases. Refuse which is non combustible must be seperate out and needs to be dispose off in some other way. Moreover, advantages of using incinerator is:


  • It reduces the total volume of refuse.
  • It is useful in generating electricity.
Ocean dumping
Ocean dumping is also a method for disposal of waste into the ocean. It is done through shipboard incinerators and the unburned refuse is thrown into the ocean. Such a method is being used by industries and municipalities. It makes the waste out of our sight but sometimes the refuse are brought back by the ocean currents. Moreover, it is also a cause of ocean pollution. It affects aquatic life and we should not play with any creatures life. Also ocean is an economic resource. 

Waste brought back by the currents.