Solid Waste Management: A Theoretical View
2.2 Types of solid waste
2.3.2 Collection and transportation of waste
space for placement. Low-rise dwelling in a commercial dwelling use light containers that are easy to handle since collection is manually. Highly loaded containers can cause injuries to collectors. These containers can be in a metal or plastic fonn depending on the homeowner. The metal container is noisy and can be damaged when emptied while ultraviolet rays can bum plastic containers (Bradshaw, et aI, 1992).
Although individual containers are used for one apartment, in areas where apartments are close to each other people share containers. So if the container is full collectors have to pick it up otherwise people will litter anywhere. Medium-size and high-size apartments use chutes; separate storage containers are not used and wastes are stored in containers on the premises between collections. These containers include the large open-top containers, enclosed storage containers and special containers used in conjunction with processing equipment. Containers are located on the sides or near the house, in alleys where alley collection is used and in garage where available. (Bradshaw et ai, 1992).
only gathering solid waste from different places but also dragging solid waste forcibly. The dragging and unloading are similar for most collection system while facilities, activities or locations determines the gathering and picking of waste.
(Bradshaw et aI, 1992).
2.3.2.1 Collection o/non- separated waste
In residential areas the collection services type varies depending on type of dwelling unit. In a low-rise dwelling the curb, alley, setout-setback, and backyard carry are mostly used collection services. In the curb services the homeowners have to empty containers at the curb and maintain their containers until next collection. Setout- setback service is where homeowner is responsible to take out the container and setback after being emptied. In the backyard carry service the crew enters the homeowners' property and removes stored waste. Most residential waste collection includes the direct lifting and carrying of containers, rolling of loaded containers or drop cloths. (Bradshaw et aI, 1992).
In the medium-and high-rise apartment the curbside collection is used where the maintenance staff is responsible for transporting containers to the curb side collection, which is emptied by collection vehicles. In the commercial industrial facilities the manual and mechanical means are used for collection. Usually waste from the commercial facilities is collected in the late evening or early morning with an aim to avoid accidents on large cities. In manual collection wastes are collected from plastic bags or any other disposable containers and placed on a curb. One of the crewmember remains in the collection vehicle to control it. Movable containers or large-capacity open top containers are used on commercial industrial facilities, and at times containers are emptied mechanically depending on its size and type (Tchobanoglous et aI, 1993).
2.3.2.2 Collection of separated waste at source
The separated waste is collected before disposal or recycling and for residential areas the curbside collection is used. In this method residents either have two containers to put recyclable and non-recyclable waste, or the crew has responsibility to separate wastes material. The recyclable wastes include waste like paper, plastic, glass, etc.
Vehicles used for the collection of source separate wastes include open-bin manually loaded (where the crew has to load the bins), open-bin manually loaded mechanically emptied (where the crew load the bin then the vehicle is used to empty the bin), container mechanically emptied (where the vehicle emptied the container), and mobile container system. (Tchobanoglous et ai, 1993).
At the commercial level the hauler has the responsibility to collect the source- separated wastes. Recyclables are stored at a separate container and collected by those responsible for it, and the city crew collects the contaminated municipal solid wastes. The collection system used can be viewed by looking at their mode of separation and be grouped into: -hauled container system (HCS) and stationary container system (SCS). The HCS is the system where the containers used for storage are hauled to the disposal site, emptied and taken to the storage point. SCS is system where containers are only moved for emptying in the curb otherwise remains at the waste storage location. The hauling container systems are used in areas where waste generation is high and usually large containers are used. These large containers save time during collection where workers don't have to collect many small containers, and these containers can be in different sIzes and shapes (Tchnobanoglous et ai, 1993)
There are three types of hauled container system-: host tmck systems, which is used with stable compactors where waste is mechanically loaded in a collection vehicle; tilt-frame container systems which used by vehicles that have the capacity to haul
and unload the large containers usually use the open-top containers and the stationary compactors; and lastly trash-trailer system where the heavy rubbish can be easily collected by this system and is usually used to collect demolition wastes at constructions sites (Tchobanoglous et aI, 1993).
The stationary container system can collect any wastes but usually vary in type and quantity of wastes to be collected. In systems with mechanically loaded collection vehicles the trip to the recovery facility or disposal area is done when the vehicle is full. This system is usually used for the collection of the residential wastes but cannot collect heavy rubbish and demolition and construction waste. A system with manually loaded collection system can be used for the collection of residential wastes or litter. This system of manual loading is used because most people could not have access to mechanized self-loading system. In the stationary container system labuors are needed. In the hauled container system only the collector driver is needed who is then responsible for all activities involved in the wastes collection (Tchobanoglous et aI, 1993).
Due to congestion and narrow streets in most town and urban areas of small vehicles are used to collect wastes from homes then transfer it to larger vehicles loaded at ground level. Then large vehicles would transport wastes to the transfer station, which lead to the concrete platforms (Rao, 1991). According to Tchobanoglous (1993) transfer station are used for economic consideration and that can be proved when small manually loaded collection vehicles are used, when large quantities of wastes are hauled for long distance, and when one station is used by different collection vehicles.
There is a need to mull over the distance waste collectors spend going to and from the waste collector truck. So due to this there are different methods that can used in
trying to decrease the burden left on the waste collector, but all these methods have negative impacts. This can include garbage grinders that reduce the amount of waste but put extra load on the wastewater treatment. Pneumatic pipes where waste is transported through underground pipes and delivered to the plant. In larger communities the transfer stations can be used for daily waste intake. Thus resulting in workers spending more time collecting and less time traveling. The green cans on wheel are also widely used methods to transport waste to trucks and this can even be done by households themselves since there are hydraulic lift that help in emptying the can. (Bradshaw, et aI, 1992)
In America the packer trucks are used to haul the wastes and are able to compress and reduce waste to volume of 60%. The drawbacks in collection waste are that it is expensive, whereby $65.00 needed just for one truck. Trash collection is hazardous and cause detrimental effect to human being and the environment. Using the packer truck makes it impossible to separate one resource from the other e.g. glass, metal, paper etc. Large trucks used in metropolitan areas usually cause traffic congestion and noise or air pollution (Owen, 1989:447). Different methods can be used in the disposal of wastes such as open dumping, sanitary landfill, incineration and recovery and recycling.