Solid Waste Management

By Shreya Laddha|Updated : December 2nd, 2021

Through Champion Study Plan for GATE Civil Engineering (CE) 2022, we are providing Solid Waste Management study notes and other important materials on every topic of each subject.

These topic-wise study notes are useful for the preparation of various upcoming exams like GATE CivilIESBARCISROSSC-JEState Engineering Services examinations and other important upcoming competitive exams.

This article contains fundamental notes on the "Solid Waste Management" topic of the "Environmental Engineering" subject.

Solid Waste Management

  1.INTRODUCTION

Solid waste refers here to all non-liquid wastes. In general this does not include excreta, although sometimes nappies and the faeces of young children may be mixed with solid waste. Solid waste can create significant health problems and a very unpleasant living environment if not disposed of safely and appropriately. If not correctly disposed of, waste may provide breeding sites for insect-vectors, pests, snakes and vermin (rats) that increase the likelihood of disease transmission. It may also pollute water sources and the environment.

  1. MUNICIPAL SOLID WASTE

Common ordinary household and commercial waste, called refuse or municipal solid waste (MSW), is the subject of this chapter. Technically, refuse is made up of garbage, which is food waste, and rubbish almost everything else in your garbage can. Trash is larger items, such as old refrigerators, tree limbs, mattresses, and other bulky items, that are not commonly collected with the household refuse.

The municipal solid waste problem can be separated into three steps:

  1. Collection and transportation of household, commercial, and industrial solid waste
  2. Recovery of useful fractions from this material.
  3. Disposal of the residues into the environment                 3.SOURCES AND TYPES OF SOLID WASTE

3.1.  Sources of solid waste

In most emergency situations the main sources of solid waste are:

■ Medical centers

■ Food stores

■ Feeding centers

■ Food distribution points

■ Slaughter areas

■ Warehouses

■ Agency premises

■ Markets

■ Domestic areas

Appropriate solid waste management strategies may vary for institutional, communal and domestic sources.

3.2.  Different categories of solid waste include:

  1. Organic waste: wastes from preparation of food, market place etc.
  2. combustibles: paper, wood, dried leaves, packaging for relief items, etc. (high organic and low moisture content)
  3. Non-combustibles: Metal, tin cans, bottles, stones, etc.
  4. Ashes/dust: Residue from fires used for cooking.
  5. Bulky waste: Tree branches, tyres, etc.
  6. Dead animals: Carcasses of domestic animals and livestock.
  7. Hazardous waste: Oil, battery acid, medical waste.
  8. Construction waste: Roofing, rubble, broken concrete, etc.
  1. INITIAL STEPS

In order to establish effective solid waste management in the affected area the following process should be used:

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  1. KEY COMPONENTS OF SOLID WASTE MANAGEMENT

Solid waste management can be divided into five key components:

■ Generation

■ Storage

■ Collection

■ Transportation

■ Disposal

5.1.  Generation:

Generation of solid waste is the stage at which materials become valueless to the owner and since they have no use for them and require them no longer, they wish to get rid of them. Items which may be valueless to one individual may not necessarily be valueless to another. For example, waste items such as tins and cans may be highly sought after by young children.

5.2.  Storage:

Storage is a system for keeping materials after they have been discarded and prior to collection and final disposal. Where on-site disposal systems are implemented, such as where people discard items directly into family pits, storage may not be necessary. In emergency situations, especially in the early stages, it is likely that the affected population will discard domestic waste in poorly defined heaps close to dwelling areas. If this is the case, improved disposal or storage facilities should be provided fairly quickly and these should be located where people are able to use them easily.

 Improved storage facilities include:

■ Small containers: household containers, plastic bins, etc.

■ Large containers: communal bins, oil drums, etc.

■ Shallow pits

■ Communal depots: walled or fenced-in areas

In determining the size, quantity and distribution of storage facilities the number of users, type of waste and maximum walking distance must be considered. The frequency of emptying must also be determined, and it should be ensured that all facilities are reasonably safe from theft or vandalism.

5.3.  Collection:

Collection simply refers to how waste is collected for transportation to the final disposal site. Any collection system should be carefully planned to ensure that storage facilities do not become overloaded. Collection intervals and volumes of collected waste must be estimated carefully.

 

 

5.4.  Transportation:

This is the stage when solid waste is transported to the final disposal site. There are various modes of transport which may be adopted and the chosen method depends upon local availability and the volume of waste to be transported.

Types of transportation can be divided into three categories:

■ Human-powered: open hand-cart, hand-cart with bins, wheelbarrow, tricycle

■ Animal-powered: donkey-drawn cart

■Motorized: tractor and trailer, standard truck, tipper-truck

5.5.  Disposal

The final stage of solid waste management is safe disposal where associated risks are minimized. There are four main methods for the disposal of solid waste:

■ Land application: burial or landfilling

■ Composting

■ Burning or incineration

■ Recycling (resource recovery)

The most common of these is undoubtedly land application, although all four are commonly applied in emergency situations.

  1. ON-SITE DISPOSAL OPTIONS

The technology choices outlined below are general guidelines for disposal and storage of waste on-site, these may be adapted for the particular site and situation in question.

6.1.  Communal pit disposal

Perhaps the simplest solid waste management system is where consumers dispose of waste directly into a communal pit. The size of this pit will depend on the number of people it serves. The long-term recommended objective is six cubic meters per fifty people.

The pit should be fenced off to prevent small children falling in and should generally not be more than 100m from the dwellings to be served. Ideally, waste should be covered at least weekly with a thin layer of soil to minimize flies and other pests.

Advantages: It is rapid to implement; and requires little operation and maintenance.

Constraints: The distance to communal pit may cause indiscriminate disposal; and waste workers required to manage pits.

6.2.  Family pit disposal

Family pits may provide a better long-term option where there is adequate space. These should be fairly shallow (up to 1 m deep) and families should be encouraged to regularly cover waste with soil from sweeping or ash from fires used for cooking. This method is best suited where families have large plots and where organic food wastes are the main component of domestic refuse.

Advantages: Families are responsible for managing their own waste; no external waste workers are required; and community mobilization can be incorporated into hygiene promotion programme.

Constraints: Involves considerable community mobilization for construction, operation and maintenance of pits; and considerable space is needed.

6.3.  Communal bins

Communal bins or containers are designed to collect waste where it will not be dispersed by wind or animals, and where it can easily be removed for transportation and disposal.

Advantages: Bins are potentially a highly hygienic and sanitary management method; and final disposal of waste well away from dwelling areas.

Constraints: Significant collection, transportation and human resources are required; system takes time to implement; and efficient management is essential.

 6.4. Family bins

Family bins are rarely used in emergency situations since they require an intensive collection and transportation system and the number of containers or bins required is likely to be huge. In the later stages of an emergency, however, community members can be encouraged to make their own refuse baskets or pots and to take responsibility to empty these at communal pits or depots.

Advantages: Families are responsible for maintaining collection containers; and potentially a highly sanitary management method.

Constraints: In general, the number of bins required is too large; significant collection, transportation and human resources are required; takes time to implement; and efficient management essential.

6.5.  Communal disposal without bins

For some public institutions, such as markets or distribution centres, solid waste management systems without bins can be implemented, whereby users dispose of waste directly onto the ground. This can only work if cleaners are employed to regularly sweep around market stalls, gather waste together and transport it to a designated off-site disposal site. This is likely to be appropriate for vegetable waste but slaughterhouse waste should be disposed of in liquid-tight containers and buried separately.

Advantages: System rapid to implement; there is minimal reliance on actions of users; and it may be in line with traditional/usual practice.

Constraints: Requires efficient and effective management; and full-time waste workers must be employed.

  1. TRANSPORTATION OPTIONS

Where bins or collection containers require emptying, transportation to the final disposal point is required. As described, waste transportation methods may be human-powered, animal-powered or motorized.

7.1.  Human-powered

Wheelbarrows are ideal for the transportation of waste around small sites such as markets but are rarely appropriate where waste must be transported considerable distances off-site. Handcarts provide a better solution for longer distances since these can carry significantly more waste and can be pushed by more than one person. Carts may be open or can be fitted with several containers or bins.

7.2.  Animal-powered

Animal-powered transportation means such as a horse or donkey with cart are likely to be appropriate where they are commonly used locally. This may be ideal for transportation to middle distance sites

7.3.  Motorized

Where the distance to the final disposal site is great, or where the volume of waste to be transported is high, the use of a motorized vehicle may be the only appropriate option. Options include tractor and trailer, a standard truck, or a tipper-truck, the final choice depending largely on availability and speed of procurement.

For large volumes of waste it may sometimes be appropriate to have a two-stage transportation system requiring a transfer station. For example, waste is transported by handcart to a transfer station where it is loaded into a truck to be taken to an off-site disposal site several kilometers away.

  1. OFF-SITE DISPOSAL OPTIONS

The technology choices outlined below are general options for the final disposal of waste off-site.

8.1.  Landfilling

Once solid waste is transported off-site it is normally taken to a landfill site. Here the waste is placed in a large excavation (pit or trench) in the ground, which is back-filled with excavated soil each day waste is tipped. Ideally, about 0.5m of soil should cover the deposited refuse at the end of each day to prevent animals from digging up the waste and flies from breeding.

The location of landfill sites should be decided upon through consultation with the local authorities and the affected population. Sites should preferably be fenced, and at least one kilometer downwind of the nearest dwellings.

Advantages: A sanitary disposal method if managed effectively.

 Constraints: A reasonably large area is required.

8.2.  Incineration

Although burning or incineration is often used for the disposal of combustible waste, this should generally only take place off-site or a considerable distance downwind of dwellings. Burning refuse within dwelling areas may create a significant smoke or fire hazard. especially if several fires arc lit simultaneously. Burning may be used to reduce the volume of waste and may be appropriate where there is limited space for burial or landfill. Waste should be ignited within pits and covered with soil once incinerated. in the same manner as landfilling. The same constraints for siting landfill sites should be applied here also.

Advantages: Burning reduces volume of combustible waste considerably: and it is appropriate in off-site pits to reduce scavenging.

 Constraints: There can be smoke or fire hazards.

8.3.  Composting

Simple composting of vegetables and other organic waste can be applied in many situations. Where people have their own gardens or vegetable plots. organic waste can be dug into the soil to add humus and fiber. This makes the waste perfectly safe and also assists the growing process. This should be encouraged wherever possible, particularly in the later stages of an emergency programme.

Properly managed composting requires careful monitoring of decomposing waste to control moisture and chemical levels and promote microbial activity. This is designed to produce compost which is safe to handle and which acts as a good fertilizer. Such systems require considerable knowledge and experience and are best managed centrally. In general, they are unlikely to be appropriate in emergencies.

Advantages: Composting is environmentally friendly: and beneficial for crops.

Constraints: Intensive management and experienced personnel are required for large-scale operations.

8.4.  Recycling

Complex recycling systems are unlikely to be appropriate but the recycling of some waste items may be possible on occasions. Plastic bags. containers, tins and glass will often be automatically recycled since they are likely to be scarce commodities in many situations. In most developing country contexts there exists a strong tradition of recycling leading to lower volumes of waste than in many more developed societies.

Advantages: Recycling is environmentally friendly.

Constraints: There is limited potential in most emergency situations, and it is expensive to set up.

*****

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