Essay Example on Street Refuse: Composition & Sources of Pollution

Introduction

Street refuse is composed of a variety of substances depending on the type of road surface and also manufacturing processes carried out in a particular locality. Some of the substances include but not limited to; dust rising from road surface wearing out, the residue of chippings, sand and other materials spread by the local authority. It also includes bus tickets, cigarette endings, cartons, papers, straw and materials falling from vehicles. Other substances are matter falling from the air as a result of manufacturing, soot, and carbon from industries.

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Save 25%

Methods of Street Cleaning

Gritting and Sanding

This method is usually carried out to prevent the road from becoming slippery. Sand and grit are spread to prevent skidding under certain conditions. It should be spread sparingly because the street is cleaned afterward.

Sweeping, Washing and Watering

In this method, a sweeping and collecting machine is used and in some cases, it is fitted with a water container and spray jets for washing or watering. The mechanical sweeper damps channels in front of the sweeping brushes and watering with forced jets.

Sweeping and Tiding of Roads

Tiding by hand. Tiding in secondary streets is done by the beat system. An individual is given a certain number of roads to keep tidy and thus continually engaged in sweeping these roads. In more important city streets, however, tidying is carried out by street orderlies. Each individual is given a segment of the street and is expected to keep his or her segment free of litter and waste. He or she is equipped with the tools for cleaning such as a shovel, a broom, and a handcart. Bins are also placed in an orderly regular interval for the reception of litter.

Use of mechanical road sweepers. Cleaning of streets in the central area of the city is done by means of mechanical sweepers. These are motor vehicles equipped with a diagonally mounted rotary brush, which is driven through gearing form a power taken off connected to the gearbox. The use of modern collecting sweeper costless compared to hand sweeping.

Gully Emptying

The method involves the removal of a large amount of silt and foreign substances from the gullies. In some towns or cities which are well equipped; this process is carried out with a special gully-emptying machine. The machine comprises of a large tank mounted on a heavy motor chassis. The tank is fitted with a balanced flexible pipe. During the cleaning process, the pipe is lowered into the gulley the content of the gulley sucked into the tank as a result of a vacuum caused by a rotary air exhauster that is in the tank. After sucking off the content of the gulley, the gully is flushed out with clean water from the vehicle and the trap is then sealed. Smaller towns with no gulley empties use long-handled scoops. The scoops are used in getting sludge and solids out of the gulley. Vehicle carrying water then flushes out the gulley after which it is resealed with clean water.

Disposal of Refuse

Separation

This is the first step in disposing of refuse. This is mainly done in order to salvage useful materials that can be sold. The process of refuse disposal include screening, magnetic separation and handpicking.

Pulverisation

After separation the next step is pulverization. This process involves the mechanical breakdown of refuse into a finely divided product of uniform consistency, this makes it useful for sale as fertilizer. The modern method is that no separation is done before pulverization.

Incineration

After useful materials and salvageable materials have been recovered the remaining combustible substance is made harmless by burning in an incinerator. An incinerator is an installation for the burning of combustible refuse. Incinerators can be classified into three depending on the method of firing. Thus it can be top- feed, front- feed or back-feed.

Controlled Tipping

This involves dumping of refuse under adequate supervision and following the correct practice. If done properly it is both cheap and hygienic. Uncontrolled tipping can be both unhygienic and also cause a nuisance. Besides causing nuisance from being a breeding ground for flies and vermin, it can also cause a fire as a result of emission of foul smell. It can also lead to pollution of water sources nearby thus becoming hazardous to the public health.

Need for Pulverisation and Incineration

Pulverisation

Apart from pulverization making refuse useful for sale as a fertilizer, it is also readily composted with sewage sludge. It can thus be packaged and sold in small quantities for garden use. The downside of this is the increasing cost of transport, which is making it hard to access the market for such a huge amount of fertilizer. The pulverized refuse has high calorific value; this enables it to give off constant heat when being burnt in an incinerator and thus facilitates mechanical charging and clinkering. Pulverisation before tipping is essential in reducing bulk and make tipping more hygienic.

Incineration

This process which involves burning of refuse is very effective in making the refuse harmless. Apart from that, the heat generated as a result of burning combustible materials can be used to raise steam and the incombustible materials can be converted into clinker. Clinker can be sold or used for other purposes by the local authority. The steam generated cannot be piped over a long distance without heat loss. Hence, the undertaking requiring the heat should be located near the disposal plant.