Waste disposal

1. SOLID WASTE,
HUMAN EXCRETA
&
SEWAGE DISPOSAL
Dr. Neelam Kumar
Professor & Unit Head
Department of Community Medicine
Pt. B.D Sharma, PGIMS, Rohtak

2. SOLID WASTE

3. The definition…………
■ Produced by the United Nations Statistics Division
(U.N.S.D.):
"Wastes are materials that are not prime products (that is
products produced for the market) for which the generator
has no further use in terms of his/her own purposes of
production, transformation or consumption, and of which
he/she wants to dispose. Wastes may be generated during
the extraction of raw materials, the processing of raw
materials into intermediate and final products, the
consumption of final products, and other human activities.
Residuals recycled or reused at the place of generation are
excluded."

4. Kinds of Wastes
Solid wastes: wastes in solid forms, domestic, commercial and
industrial wastes
Examples: plastics, styrofoam containers, bottles,
cans, papers, scrap iron, and other trash
Liquid Wastes: wastes in liquid form
Examples: domestic washings, chemicals, oils, waste
water from ponds, manufacturing industries
and other sources

6. Classification of Wastes according to
their Properties
Bio-degradable
can be degraded (paper, wood, fruits and others)
Non-biodegradable
cannot be degraded (plastics, bottles, old machines, cans,
Styrofoam containers and others)

7. Classification of Wastes according to
their Effects on Human Health and the
Environment
Hazardous wastes
Substances unsafe to use commercially, industrially,
agriculturally, or economically and have any of the following
properties- ignitability, corrosivity, reactivity & toxicity.
Non-hazardous
Substances safe to use commercially, industrially, agriculturally,
or economically and do not have any of those properties
mentioned above. These substances usually create disposal
problems.

8. Classification of wastes according to their origin and type
■ Municipal Solid wastes: Solid wastes that include household
garbage, rubbish, construction & demolition debris, sanitation
residues, packaging materials, trade refuges etc. are managed
by any municipality.
■ Bio-medical wastes: Solid or liquid wastes including
containers, intermediate or end products generated during
diagnosis, treatment & research activities of medical sciences.
■ Industrial wastes: Liquid and solid wastes that are generated
by manufacturing & processing units of various industries like
chemical, petroleum, coal, metal gas, sanitary & paper etc.
■ Agricultural wastes: Wastes generated from farming
activities. These substances are mostly biodegradable.

9. Classification of wastes according to their origin and type
■ Fishery wastes: Wastes generated due to fishery
activities. These are extensively found in coastal &
estuarine areas.
■ Radioactive wastes: Waste containing radioactive
materials. Usually these are byproducts of nuclear
processes. Sometimes industries that are not directly
involved in nuclear activities, may also produce some
radioactive wastes, e.g. radio-isotopes, chemical sludge
etc.
■ E-wastes: Electronic wastes generated from any modern
establishments. They may be described as discarded
electrical or electronic devices. Some electronic scrap
components, such as CRTs, may contain contaminants
such as Pb, Cd, Be or brominated flame retardants.

10. Global Solid Waste Generation
■ Around the world : waste generation rates are rising.
■ In 2012, the worlds’ cities generated 1.3 billion tonnes of solid
waste per year, amounting to a footprint of 1.2 kilograms per person
per day.
■ With rapid population growth and urbanization, municipal waste
generation is expected to rise to 2.2 billion tonnes by 2025.
Reference: www. worldbank.org

11. SOLID WASTE MANAGEMENT RULES

17. 5 R of Solid Waste Management

18. EXCRETA DISPOSAL

19. Public Health Importance
■ Human excreta is a source of infection
Important cause of environment pollution
Responsibility of society to dispose it
safely
■ Failure to dispose safely leads to
severe threat to public health

20. Health hazards
Improper excreta disposal causes
Soil pollution
Water pollution
Contamination of foods
Propagation of flies
Burden to community in terms of sickness,
mortality & low expectation of life
Deterrent to social & economic progress

21. Diseases-improper disposal
Bacterial: typhoid, dysenteries
Viral: hepatitis, diarrhoeas
Helminths: hook worm, ascariasis

22. Extent of problem-India
74% of population is rural and majority of
them go to fields for defecation
Situation in urban area is equally worse
The solution to the problem is only through
hygienic disposal of human excreta which is
a corner stone of all public health services

23. HOW THE DISEASE IS CARRIED FROM EXCRETA
FAECES
FINGERS
FLUID/WATER
FLIES
FIELD/SOIL
FOOD NEW HOST

24. Transmission of diseases to the human host is
prevented by segregation of faeces, protection
of food, personal hygiene, control of flies.
Transmission of faecal born diseases

25. FAECES
FINGERS
WA
TER
FLIES
SOIL
FOOD
PROTECTED HOST
S
A
N
I
T
A
T
I
O
N
B
A
R
R
I
E
R
Sanitation barrier –
transmission of faecal-borne diseases

26. SANITATION BARRIER
Segregation of excreta by imposing a
barrier is called Sanitation barrier. This is
the most effective step so that the disease
agent can not reach the new host directly
or indirectly

27. METHODS OF EXCREATADISPOSAL

28. Unsewered areas
Service type (conservative)
Non service type (sanitary latrine)
Bore hole latrine
Dug well or pit latrine
Water-seal type of latrines
PRAI
RCA
SULABH
Septic tank
Aqua privy
Latrine suitable for camps & temporary use
Shallow trench/deep trench/pit/bore hole latrines

29. Sewered areas

30. Water carriage system & sewage
treatment
Primary treatment
Screening/removal of grit/plain sedimentation
Secondary treatment
Trickling filters/activated sludge process
Other methods
Sea outfall
River outfall
Sewage farming
Oxidation pond

31. SERVICE TYPE
Night soil is collected from pail or bucket
type of latrines by human agency, and later
disposed by burying or composting.

32. DRAWBACKS
Water pollution
Soil pollution
Access to flies
Corrosion of buckets and pans
Recruitment of staff is difficult,
should be replaced by sanitary latrine

33. Sanitary latrine
Excreta should not contaminate the ground
or surface water
Excreta should not pollute the soil
Excreta should not be accessible to flies,
rodents, animals & other vehicles of
transmission
Excreta should not create a nuisance due to
odour or unsightly appearance

34. WATER SEAL LATRINES
It has water seal which prevent access to
flies and escape of odour.
There are two types
P.R.A.I evolved by planning research and
action institute lucknow.
R.C.A. type by research cum action projects
in environmental sanitation of ministry of
health.

35. FEATURES
LOCATION: It should be away from source
of water supply to prevent contamination.
SQUATTING PLATE or SLAB: It is made
up of an impervious material to keep it clean
and dry. So that it will not facilitate the growth
of hook warm larva.
Dimensions 90cms square, 5cms thickness,
slop ½ inch for drainage of water with
footrests

36. SEPTIC TANK
■ It is a water tight masonry tank
used for individual dwelling,
small groups of houses and
institutions.
■ DESIGN: Single chambered or
double chambered.
■ CAPACITY: 20 to 30 gallons per
person for household with a

37. SEWAGE

38. Introduction
• Sewage is a waste water from a community, containing
solid and liquid excreta, derived from houses, streets,
factoriesandindustries.
• ‘Dry weather flow’ : average amount of sewage which
flows through the sewerage system in 24 hours

39. Composition of Sewage
• Sewagecontains
– 99.9 percentwaterand
– 0.1percentsolids(partlyorganicandpartlyinorganic).
• The strength of the sewage may be expressed in
termsof:
 Biochemicaloxygendemand,
 Chemicaloxygen demandand
 Suspendedsolids.

40. Biochemical Oxygen Demand (BOD)
• The amount of oxygen absorbed by a sample of sewage
during a specified period (generally 5 days) at a specified
temperature(usually20°C)for aerobic digestion.
• Themost importanttestcarriedouton sewage.
• Sewage with a BOD valueof:
– 300mg/l(300ppm)oraboveistermedasstrong
– 100mg/l(100ppm)orbelowistermedasweak.

41. Chemical Oxygen Demand (COD)
• The amount of oxygen required to oxidize the organic matter by
use of dichromate in an acid solution and to convert it to carbon
dioxideandwater.
• ThevalueofCOD isalwayshigherthantheBOD
– many organic substances can be oxidized chemically but not
biologically.
• COD is used to test the strength of wastewater that is either non
biodegradable or contains compounds that inhibit activities of
microorganisms.
– Commonly, BOD is used to test the strength of untreated and treated
municipaland biodegradable industrial wastewaters.

42. Sewage Purification
• Theaim of sewage treatmentis:
– to convert an offensive and potentially dangerous mixture into an
inoffensive effluent andsludge
– which can be disposed off safely and without causing nuisance
intoriver,seaoron land.
• The conversion of complex organic matter in the sewage to
simpler substances takes placeby two processes:
– aerobicand
– anaerobic.

43. • Theaerobic process:
– requires a continuous supply of free dissolved oxygen for the
aerobic microorganisms to break the organic matter into simpler
substances such as carbon dioxide, ammonia, water, nitrite, nitrate,
sulphateetc.
• Theanaerobic process
– more effectivewhere thesewage is highly concentrated and
contains plentyofsolids.
– Hence, this method is usually gainfully utilized for
digestion of sludge in sewageworks.
– The end products of anaerobic decomposition are
methane,ammonia,carbon dioxide,hydrogenetc.

44. Modern Sewage Treatment
• The sewage treatment undergoes through many
stages.
– Primary,secondary and tertiarytreatmentstages.
• Primary treatment :
– Thefirststage is the physicaltreatmentto remove solids (from the
liquid).
• Secondary treatment :
– Theprimary treatmentis followed by biologicaltreatment brought
aboutbyaerobicandanaerobicbacteria.

45. • Tertiary treatment :
– Treatment rendered in addition to the conventional secondary
treatment for improving further the quality of effluent is termed
‘tertiarytreatment’or advanced waste treatmentprocess.
• Chemical treatment by the addition of coagulants may be
used to assist sedimentation and sludge treatment.

46. Flow diagram of a Modern Sewage Treatment Plant

47. Activated Sludge Process

48. Sludge Treatment
• The sludge from primary or final sedimentation tanks
contains 90 to 95percentwater.
• This high water content needs to be reduced for converting
the sludge to a solid condition in which it may be used or
disposedoffharmlessly.
• Anaerobic digestion is the most preferred sludge treatment
method.