Sanitary waste disposal

The accumulation of various waste products and their indiscriminate disposal represents a grave hazard to health. Systems of waste disposal are designed to eliminate these hazards.

1. SANITARY WASTE DISPOSAL Dr. Dalia El- Shafei Ass.Prof of Occupational Medicine

2. Types of wastes

3. Solid Waste Disposal

4. Waste stream: Steady flow of varied wastes that we all produce, from domestic garbage to industrial agricultural, commercial & construction refuse.

5. 1- Open dump : Many people dispose wastes by simply dropping it to some place. Open unregulated dumps are still the predominant method of waste disposal in most developing countries. Open dump in rivers, canals, sea & oceans expose people, animals, and plants to many hazards & make water not suitable for drinking or use in irrigation.

6. 2- Landfills “ controlled dumping” S olid waste disposal is regulated & controlled. To decrease smells & to discourage insect & rodent breading landfill operators are required to compress the refuse & cover it every day with a layer of earth. C ontrol pollution, but dirt fill takes nearly 20% of the space. Oils , chemical compounds and toxic metals seep to the underground surrounding areas. Landfills are chosen to be high away from rivers & other water sources. It was inexpensive but with the increase in the cost of lands, construction and maintenance it became costly.

7. 3- Incineration: It is simply burning of waste. Another name is energy recovery or waste- to-energy because the energy that is generated is a useful resource. 2 approaches are used. Refuse-derived fuel where refuse is sorted to remove unburnable materials & Mass burn where everything is burned as much as possible. Residual ash & unburnable materials representing 20% of original size are taken to landfill for disposal. C ostly & flying ash contains dioxins of lead & cadmium which are hazardous materials. To decrease the emissions of these hazards, removal of batteries containing heavy metals, plastics containing chlorine before wastes are burned. Closed incineration is very sanitary & healthy method if done at small scale as in hospitals and big buildings.

8. 4- Recycling : R eprocessing of discarded materials into useful products. Some reuse materials for the same purpose & other turn old materials into entirely new products. Saves money, energy, raw materials & land spaces while also reducing pollution.

9. 5- Reuse : S hrinking of the waste stream. R euse of disposed materials after cleaning them in the same forms e.g. bottles & food containers.

10. 6- Reduction : P roduce less waste. B etter than reusing. What is a waste to one process may be a resource to another. Industry can produce less waste by changing their manufacturing processes .

11. 7- Fermentation : To manure in rural areas by forming heaps of refuse covered by layer of earth & left for few days, decomposition of organic materials occur & they are changed to useful manure.

12. Liquid Waste Disposal

13. Urban Liquid Waste Disposal : In urban areas liquid waste is disposed of through water carried system. After collecting liquid waste from houses, it reaches the final disposal where it will be disposed of by either dilution or treatment.

14. 1 - Liquid Waste disposal by dilution : Crude sewage & waste water may be taken as such, or partially treated & disposes in coastal countries, or rarely in rivers & streams. Potential risk to health due to the possibility of back flow to shore, causing its pollution and causing hazards to swimmers & fishing. Wind may carry smell back to city.

15. 2- Liquid Waste disposal by treatment: It is the method used in most cities of Egypt. Separation of suspended matter (sludge) from liquid part (effluent) & destruction of all micro-organisms in order to end with a safe material that can be used for economic values. Sludge as fertilizers Effluent for irrigation of farm.

16. Screening : Removal of large objects through passage of liquid waste across screens formed of tilted bars.

17. Sedimentation : velocity of the flow of waste liquid will be reduced & about 2 hours is allowed for it to stay in the sedimentation tank. It will thus be separated into 3 layers.

18. a- Sludge: About 60% of suspended solid will be settled down & form the sludge. The removed sludge can be disposed by: • Lagooning : spreading of sludge over specially prepared land & is left to dry & then took to be used as fertilizer. • Sludge digestion: Anaerobic process in special tanks, certain gases are liberated “methane” & the treated sludge is disposed of. • Sludge pressing: which is compressed into cakes & used as fertilizer .

19. Lagooning

20. Sludge digestion

21. Sludge pressing

22. b- Scum: Light substance like oil, grease &floating matter will rise to the surface and form the scum.

23. c- Effluent “tank effluent”: - Turbid liquid that is present between the scum & the sludge. - It is used for irrigation of farms. - Plantation of wood trees & not edible plants .

24. Rural Liquid Waste Disposal : There is no sewage system in all villages so latrines & cesspits are used .

25. latrine A pit in the ground (better made impermeable to avoid pollution of shallow underground water) and is covered by a slab to receive and collect human excreta. Contents are emptied periodically & taken to a suitable place for sanitary disposal. Latrines must be present inside houses to ensure: no handling of fresh stool, no contamination of surface soil, no unpleasant smell, simple, not expensive & acceptable from the community.

26. Cesspits C ommonest way to dispose the collected sewage & waste waters in mosques, schools, big houses. Sewage is collected by pipes and disposed in cesspit (it is a large pit 3 to 4 meters deep may be permeable or impermeable to be evacuated periodically. In impermeable tanks, under anaerobic conditions, feces will be decomposed by the action of bacteria. This breakdown of the complex organic matter will reduce its volume, kill pathogenic organisms and convert it into soluble material which is odorless, safe and stable product that can be reused as manure.

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28. Hazardous & toxic waste disposal

29. The most dangerous aspect of the waste stream is that it can contain highly toxic & hazardous materials that can be injurious to human health.

30. Controlling & managing hazardous waste : I- Produce less: It is the safest & least expensive way to avoid hazardous waste problems. Manufacturing processes can be modified to eliminate or reduce waste production .

31. II- Convert to less hazardous substances

32. III- Permanent storage

33. Radioactive waste management: Radioactive wastes are produced in different forms: high, low level & also solid, liquid & gaseous with various half-lives. Low level must be stored for several decades, while high level must be stored for thousands of years. Most low level comes from nuclear power plants, hospital universities, industries and others.

34. Radioactive waste disposal:

35. Electronic waste management : Electronic waste or "e-waste" is a term used to describe old, end-of-life electronic appliances & devices. Examples of "e-waste" include: computers; fax machines and copiers; televisions ….etc. Electronic waste often has hazardous or toxic components that can impact the environment once the materials end up in a landfill or if they are improperly managed and disposed. For example: Arsenic, Beryllium, Cadmium, Chlorofluorocarbon (CFC), Chromium, Lead, Mercury and many other toxic substances.

36. Management methods: