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

Garbage on a city street

Contents Solid waste disposal Human waste disposal

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

A person walking through garbage searching for useful things

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

Methods of disposal Burning/incineration Dumping Controlled tipping Composting

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

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

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

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

Cross section of compost pit Soil Garbage Human excreta

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

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

Pictorial representation of a sewage treatment plant Primary Sedimentation Secondary Sedimentation

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

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

Pictorial representation of septic tank Anaerobic digestion Aerobic oxidation

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

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