Functional Elements of Solid Waste #1

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Functional Elements of Solid Waste

  1. Waste generation
  2. On-site Handling, Sorting, Storage, and Processing at the Source
  3. Collection
  4. Transfer and transport
  5. Resource recovery and Processing
  6. Disposal

1. Waste Generation

Waste generation encompasses those activities in which waste, be it solid or semi-solid material, no longer has sufficient economic value for its possessor to retain it.

The processing of raw materials is the first stage when wastes are generated and waste generation continues thereafter at every step in the process as raw materials are converted into final products for consumption.

The characteristics, quantities, volume and composition of solid waste generated may differ from one country to another and between urban and rural areas. It depends mainly upon the customs, climate, living conditions and economic standard of the area.

Functional Elements of Solid Waste

2. On-site handling, sorting, storage, and processing at the source

On-site Handling

  1. On-site handling methods and principles involve public attitude and individual belief and ultimately affects the public health.
  2. It is an activity associated with the handling of solid waste until it is placed in the containers used for its storage before collection.
  3. This may take place at any time before, during or after storage.

Importance

  1. Reduce Volume of waste generated
  2. Alter physical form
  3. Recover usable materials

Methods

  1. Sorting
  2. Shredding
  3. Grinding
  4. Composting

Functional Elements of Solid Waste

On-site Storage

  1. Waste storage is an important component of a waste management system.
  2. Waste storage encompasses proper containers to store wastes and efficient transport of wastes without any spillage to transfer stations/disposal sites.
  3. The design of an efficient waste collection system requires careful consideration of the type, size, and location of containers at the point of generation for storage of wastes until they are collected.
  4. The first phase to manage solid waste is at the home level. The individual householder or businessman has responsibility for the onsite storage of solid waste.
  5. It requires temporary storage of refuse on the premises.
  6. There are four factors that should be considered in the onsite storage of solid waste. These are
    • The type of container to be used
    • The location where the containers are to be kept
    • Public health
    • The collection method and time

Storage containers

  1. Garbage and refuse generated in kitchens and other work areas should be collected and stored in properly designed and constructed water-proof garbage cans (waste bins).
  2. The cans or receptacles can be constructed from galvanized iron sheets or plastic materials.
  3. They should have tightly fitting covers.
  4. They must be of such size that, when full, they can be lifted easily by one man.
  5. They should be located in a cool place on platforms at least 30 cm above ground level.
  6. After putting in the garbage, they should be kept covered.
  7. The bins must be emptied at least daily and maintained in clean conditions.

Containers

  • There is 2 types of containers:
    1. Stationary Containers
    2. Hauled Containers

Stationary Containers

In this system, containers used for the storage of waste remain at the point of collection. The collection vehicles generally stop alongside the storage containers, and collection crews load the waste from the storage containers into the collection vehicles and then transport the waste to the processing, transfer, or disposal site.

Stationary Container System

Functional Elements of Solid Waste

Hauled Containers

An empty storage container (known as a drop-off box) is hauled to the storage site to replace the container that is full of waste, which is then hauled to the processing point, transfer station or disposal site.

Hauled Container System

Container Size (capacity)

  1. Consideration should be given for the size of the loaded container that must be hauled to the collection vehicle or to the disposal site.
  2. Therefore, container size for: –
    • ash: up to 80 to 128 liters
    • mixed refuse should not exceed 120 to 128 liters
    • rubbish up to 200 liters
    • kitchen waste is 40 liters
    • garbage is 48 to 80 liters
  3. Plastic liners for cans and wrapping for garbage reduce the need for cleaning of cans and bulk containers and keep down odors, rat and fly breeding.
  4. Galvanized metal is preferable for garbage storage because it is resistant to corrosion.
  5. Plastic cans are light in weight but are easily gnawed by rats.
  6. Bulk containers are recommended where large volumes of refuse are generated such as at hotels, restaurants, apartment houses, and shopping centers.
  7. A concrete platform provided with a drain to an approved sewer with a water faucet at the site facilitates cleaning.

Functional Elements of Solid Waste

3. Collection

  1. The waste collection does not mean the gathering of wastes but the process includes gathering of wastes as well as the transporting of wastes to transfer stations and/or disposal sites.
  2. This is the removal of refuse from collection points to the final disposal site.
  3. It is the most expensive as compared with other operation and management procedures because it demands special vehicles, experienced people to manage, more manpower, hand tools and more funds for fuel, salary, maintenance, gathering or picking up of solid waste from the various sources, taking the collected wastes to the location where it is emptied and unloading of the collection vehicle.
  4. The factors that influence the waste collection system include the following
    • Collection points
    • Collection frequency
    • Storage containers
    • Collection crew
    • Collection route
    • Transfer station

1.    Collection points:

Collection system components such as s crew size and storage: Control the cost of collection.

Note: The collection points depend on locality and may be residential, commercial or industrial.

2.    Collection frequency:

Climatic conditions and requirements of a locality as well as containers and costs determine the collection frequency.

3.    Storage containers:

  • Proper container selection can save collection energy, increase the speed of collection, and reduce crew size.
  • Containers should be functional for the amount and type of materials and collection vehicles used.
  • Containers should also be durable, easy to handle, and economical as well as resistant to corrosion, weather, and animals.
  • In residential areas, where refuse is collected manually, standardized metal or plastic containers are typically required for waste storage.
  • When mechanized collection systems are used, containers are specifically designed to fit the truck-mounted loading mechanisms.

Functional Elements of Solid Waste

4.    Collection crew:

  • The optimum crew size for a community depends on labour and equipment costs, collection methods and route characteristics.
  • The size of the collection crew also depends on the size and type of collection vehicle used, space between the houses, waste generation rate and collection frequency.

5.    Collection route:

  • The collection programme must consider the route that is efficient for collection.
  • An efficient routing of collection vehicles helps decrease costs by reducing the labour expended for collection.
  • Proper planning of collection route also helps conserve energy and minimise working hours and vehicle fuel consumption.
  • It is necessary therefore to develop detailed route configurations and collection schedules for the selected collection system.
  • The size of each route, however, depends on the amount of waste collected per stop, distance between stops, loading time and traffic conditions.
  • Barriers, such as railroad, embankments, rivers and roads with heavy traffic, can be considered to divide route territories.

6.    Transfer station:

  • A transfer station is an intermediate station between the final disposal option and collection point in order to increase the efficiency of the system, as collection vehicles and crew remain closer to routes.
  • If the disposal site is far from the collection area, it is justifiable to have a transfer station, where smaller collection vehicles transfer their loads to larger vehicles, which then haul the waste long distances.
  • In some instances, the transfer station serves as a pre-processing point, where wastes are dewatered, scooped, or compressed.

Functional Elements of Solid Waste

Collection process

Involves five different phases.

  • Phase 1 – House to the dustbin
  • Phase 2 – Dustbin to truck
  • Phase 3 – Truck from house to house
  • Phase 4 – Truck to transfer station
  • Phase 5 – Truck to disposal

4.    Transfer and Transport

  1. Transfer stations are used to collect the refuse at a central location and to reload the wastes into a vehicle where the cost per kilogram-kilometer ton-mile will be less for the movement of the ultimate waste to the disposal site.
  2. Transfer stations are employed when the disposal site is situated at a significant distance from the point of collection.
  3. A transfer station can reduce the cost of transporting refuse by reducing manpower requirements and total kilometers.
  4. When a collection vehicle goes directly to the disposal site, the entire crew, driver plus laborers, are idle.
  5. For a transfer vehicle, only one driver is needed. As the distance from the centers of solid waste generation increases, the cost of a direct haul to a site increase.

5.    Resource Recovery and Processing

  1. Resource recovery is partial solid waste disposal and reclamation process. It can be expected to achieve about 60% reductions in future landfill volume requirements.
  2. Resource recovery must recognize what is worth recovering and environmental benefits.
  3. Resource recovery and processing is a complex, economic, and technical system with social and political implications, all of which require critical analysis and evaluation before a commitment is made.
  4. They demand capital cost, operating cost, the market value of reclaimed materials and material quality, potential minimum reliable energy sales, assured quantity of solid wastes, continued need for a sanitary landfill for the disposal of excess and remaining unwanted materials and incinerator residue, a site location close to the center of the generators of solid wastes.

Obstacles to resource recovery

  1. heterogeneity of the waste
  2. putrescible of the waste
  3. location of the waste
  4. the low value of the product
  5. uncertainty of supply
  6. unproven technology
  7. administrative and industrial constraints
  8. legal restriction
  9. uncertain market

Functional Elements of Solid Waste

6.    Disposal

  1. Once collected, municipal solid waste may be treated in order to reduce the total volume and weight of material that requires final disposal. Treatment changes the form of waste and makes it easier to handle. It can also serve to recover certain materials, as well as heat energy, for recycling or reuse.
  2. There are many methods of disposing of the solid waste-
  3. Open burning
  4. Dumping into the sea
  5. Sanitary Landfills
  6. Incineration
  7. Composting
  8. Plowing in fields
  9. Hog feeding
  10. Grinding and discharging into sewers
  11. Salvaging
  12. Fermentation and biological digestion

Functional Elements of Solid Waste

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