UNIT IV ENVIRONMENTAL TECH
Municipal solid waste (MSW)
Municipal solid waste is a collection of different kinds of debris in solid forms from different types of household activities within towns or cities (Nziazi and Wang, 2016). Such wastes usually emanate from households, industries and the market places. The scraps range from food, plastic, metal, yard, leather, rubber, battery, papers, textile, paints, construction material wastes, among others ( Hussein & Mansour, 2018). These can be found in the environment in the form of old newspaper thrown on the streets, used food packaging material like coffee tins, waste food from the cafeteria, bogus by a factory, old torn clothes, used wrappers, and many others.
Users of MSW
Even though they are considered as waste, some users find them useful. These users include gas and electricity production firms who produce energy to be used in households, plastic manufacturers who recycle scraps plastics as raw material and the people in the community who collected the waste materials for reusing in different ways. Other users are the farmers who make solid waste to produce organic fertilizer for their plants. Chemical manufacturers can also use solid wastes.
Garbage is the kind of waste that is mainly produced from the kitchen and is associated with wetness. For example, foodstuffs that have gone bad. On the other hand, rubbish can be classified as wastes that are dry like paper, leaves from a tree or items swept out of the house while trash can be referred to as wastes from production processes that are considered useless.
Optimum routing
Optimum routing involves the identification of paths followed by trucks that collect garbage from the source to final destinations. The primary purpose why routing is necessary is so that costs are reduced concerning transport, labour, operation and health mitigation. The major characteristics of optimum routing include. One of them is the use of shortest routes possible whereby the trucks usually follow the shortest route available to reduce the distance covered and hence transportation cost is reduced. They apply mathematical algorithms to obtain the best optimization costs. This helps to know the optimum number of trips to be covered by a truck. There is also the use of specialized software in managing the waste collection and use of GIS to help new truck drivers to easily located waste points.
Transfer station
Transfer stations are areas set aside by the municipal authority where solid wastes collected from the city or town are temporarily kept and sorted well before being transferred to the last stage of management. The main function for the transfer stations is to allow for sorting so that wastes are correctly dealt with in the final stage. Those that are recyclable are taken to recycling centres for use, the hazardous material is separated to avoid their way into landfills, and other wastes are made to the incinerator for energy production.
Incineration
At the incineration point, organic wastes from the transfer stations are burnt through a process known as thermal treatment. The two advantages of the incinerator are that it produces enough heat that can generate electricity. It also contains filters that prevent pollution by trapping pollutants. The two disadvantages of using incinerator is that it is quite expensive to put up the infrastructure. It also may emit some toxins from burning plastics that are cause long-term harm to health.
Composting
Other wastes from the transfer stations may be taken to compost sites. Composting comprises of putting organic wastes like kitchen refuses to decompose. The reason for composting is to produce fertilizer that is essential for the growth of plants. It aids in soil aeration, nutrient supply and improved texture. In general, the main purpose of composting is to decrease the volume of waste pile in the area. As the matter decomposes, they are absorbed in the ground and hence reduction in the pile volume.
Dumps and landfills
Dumps and landfills are always confused to mean the same thing, but below are some illustrations that helps us understand the differences. A dump is an area dug to allow people to deposit wastes and is not usually authorized by the government. A landfill on the other hand is also an area excavated for waste disposal but it is control by governing power. A dump does not have any waste treatment sections but landfill usually is well constructed with areas where wastes are treated and also have leachate.
Another major differentiating feature is that a dump do not have any way of controlling liquids produced from the wastes while a landfill usually has a liner fitted at its bottom to hold liquid produced. Finally, the last difference is that dumps can produce foul smell and even contain pests while landfills are usually managed in such a way that they are daily covered with soil to prevent bad smell from being exposed to the air and the pests inside are trapped from moving to the surface.
City one
If each person produces 5 pounds in a day, then in one month the same person can produce approximately (5×30) pounds per month.
5 x 30 = 150 pounds per month
Calculating in terms of a year will be ( 150 x 12)= 1800 pounds of waste
To get the total production of wastes in pounds for that city,
(1800x 20000) = 360000000 pounds
City 2
One year = 300000m3 with depth of 15 m
Volume = surface area x depth
300000=surface area x 15
300000= 15( surface area)
Area = 20000m2
References
Nzianzi, N. K., Wang, H( 2016). Environmental materials and wastes. Science direct retrieved from https://www.sciencedirect.com/environmental-materials-and-wastes
Hussein, A., Mona, S.M., Mansour (2018) solid waste issue: sources, composition, disposal, recycling and valorization. Science direct. Retrieved from https://doi.org/10.1016/j.epe.2018.07.003