1. Dr Paul T Francis, MD Community Medicine College of Medicine, Zawia
Waste disposal
Dr Paul T Francis, MD
Community Medicine
College of Medicine, Zawia

2. Garbage on a city street

3. Contents
Solid waste disposal
Human waste disposal

4. Solid waste disposal
Solid waste includes food waste, paper, plastics, wood, metal, glass, bricks, concrete and any discarded material
Usually human excreta is NOT included in this

5. A person walking through garbage searching for useful things

6. Health hazards of waste
Fly breeding
Attracts rats
Soil and water may get contaminated
Produces bad smell
Bad to look at

7. Methods of disposal Burning/incineration Dumping Controlled tipping
Composting

8. Burning/incineration
All combustible material can be burned
Materials like glass, metal, concrete will not burn
Hospital waste is burned in incinerators

9. Dumping A simple method is to dump the waste in low lying areas
It will fill the area and the waste will over a period of time turn to manure (السماد)
However open dumping will attract birds, flies, rats etc.
Must be done far away from the cities

10. Controlled tipping Is a good method
Pits or trenches are dug and one layer of waste is deposited and is covered with earth.
Then another layer is added till the pit is filled
Over a period of time the waste will turn into manure

11. Composting Is a method of combined disposal of waste and human feces
A pit or trench(خندقه) is dug
A layer of human feces is spread and over it a layer of waste is spread and then human excreta and so on till it reaches the surface level
A final layer waste is added and covered with earth.
After 4-6 months it will be converted to manure

12. Cross section of compost pit
Soil
Garbage
Human excreta

13. Disposal of human excreta
Human excreta is infected material containing many pathogenic organisms
Contamination of soil, water and food can lead to many diseases
‘Sewage’ is waste water containing human excreta and industrial wastes
Sewage is taken to treatment plants to make it safe

14. Important stages of purification of sewage are:
Filtration – to remove large solid waste like stones, glass, metal pieces etc.
Primary sedimentation
Aeration and oxidation
Secondary sedimentation
Sometimes untreated sewage is directly discharged into sea

15. Pictorial representation of a sewage treatment plant
Primary Sedimentation
Secondary Sedimentation

16. Sewage treatment
The effluent is harmless and can be used for irrigation
The sludge can be disposed of by composting or dumping

17. Excreta disposal in ‘unsewered’ areas – villages, small settlements
Pit latrines – for temporary camps/emergencies
A large pit is dug and people defecate into it.
When it is 2/3rd full it is covered with earth and a new pit is dug
Septic tanks – for individual homes, public latrines
Chemical toilets – used in planes and boats-
Excreta is sterilized by the chemical and disposed off

19. Pictorial representation of septic tank
Anaerobic digestion
Aerobic oxidation

20. Summary
Garbage and human excreta have to be disposed off properly to prevent health hazards
Garbage can be disposed off by – dumping, controlled tipping and composting
Human excreta can be disposed by sewage treatment on a large scale

21. Summary
Other safe methods of disposal of human excreta are – septic tank, pit latrine and chemical toilets
It is very important to keep the environment clean to prevent diseases and keep the community healthy