Methods of Disposing Wastes (Refuse and Sewage)
Methods of Disposing Refuse:
- Burning in incinerators, for example, plastics, papers, textile materials.
- Land filling.
- Recycling, for example, metals scraps, glass materials, papers, plastics.
- Remains of plants and animals are thrown into farmland to decay and form compost.
Methods of Disposing Sewage:
- Pit latrine: Is simply a hole in the ground about 3 metre deep and 1 metre wide. The opening is always kept covered when not in use.
- Bucket latrine: Faeces and urine are collected inside a bucket and removed by night soil men.
- Water carriage system or water closet system (WCS): This is used where there is pipe-borne water. It is the system used in urban areas of most developed countries, and some underdeveloped countries. In this system, faeces and urine deposited in the water closet are flushed with water from a cistern. The raw sewage is conveyed by pipes to a septic tank or sewer.
Treatment of the sewage is required before it can be safely buried, used, or released back into local water systems. In a treatment plant, the waste is passed through a series of screens, chambers, and chemical processes to reduce its bulkiness and toxicity.
Stages of Sewage Treatment:
There are three general phases of treatment which are:
1. Primary Treatment: During this process, a large percentage of the suspended solids and inorganic material is removed from the sewage.
2. Secondary treatment: The main focus of this stage is reducing organic materials, by accelerating natural biological processes.
3. Tertiary treatment: This stage is necessary when the water will be revised, 99 percent of solids are removed and various chemical processes are used, to make sure that the water is as free from impurity as is possible. Chlorine is added to kill harmful microorganisms in the water.
Reasons For Treating Sewage:
1. To destroy harmful microorganisms.
2. To save the lives of aquatic plants and animals.
3. To remove offensive odour.