USEFUL for MBBS students

2. DISPOSAL OF WASTES

3. DISPOSAL OF WASTE
 Disposal of waste is now largely the
domain of sanitarians and public health engineers.
However health professionals need to have basic
knowledge of the subject since improper disposal of
waste , constitutes health hazard.

4. Wastes that can cause health
problems are
 Human and animal feces, solid wastes
 Domestic wastewater (sewage)
 Industrial wastes, and agricultural wastes
 appliances in disuse wastes like cars, computers,
household appliances, electronic appliances(bulbs,
regulators)

5. HEALTH HAZARDs
 The output of waste depends upon daily habits,
lifestyle , living standard and degree of
urbanization and industrialization.
The per capita daily solid waste ranges 0.25 to 2.5
kg in different countries.
 Favours fly breeding
 Attracts rodents
 Infects man’s food
 Water and soil pollution
 Unsightly appearance and nuisance from bad
odours.

6. Impacts of solid waste on health
Faecal-oral (mainly Diarrhoeal disease)
 2 million deaths/year from diarrhoea, mostly under
5
◦ One billion cases/year
◦ 4.3% of Burden of Disease DALYs
 1/3 of developing world pop’n carry intestinal
worms
 200 million infected by schistosomiasis

7. Transmission of faecal borne
diseases
Faeces
Water
Fingers
Flies
Soil
New hostFood

8. Sanitation barrier
The disease cycle
may be broken
at various level :
 Segregation of
faeces
 Protection of water
supplies
 Protection of foods
 Personal hygiene
 Control of flies
Faece
s
Water
Fingers
Flie
s
Soil
Food
Sanitationbarrier
Protecte
d host

9. Sanitation
 the hygienic means of preventing human contact
from the hazards of wastes to promote health

10. Groups at risk
from the unscientific disposal of solid waste include :
 Population in areas where there is no proper
waste disposal method, especially the pre-school
children
 Waste picker workers;
 workers in facilities producing toxic and infectious
material..
 population living close to a waste dump and those,
whose water supply has become contaminated
either due to waste dumping or leakage from
landfill sites.
 Uncollected solid waste also increases risk of
injury, and infection

11. Solid waste
 garbage, rubbish, demolition product, sewage
treatment residue, dead animals and other
discarded materials.
 It should not contain nightsoil.

12. What is refuse?
 Refuse is a general term applied to solid and semi
solid waste materials other than human excreta.
TYPES/SOURCES of refuse
 Garbage: left-over vegetables, animal and fish
material from kitchens and food establishments.
 Rubbish: waste material such as bottles, broken
glass, tin cans, waste papers, discarded
porcelainware, pieces of metal, wrapping papers
etc.
 Ashes: left-over from burning of wood and coal.
 Dead animals/ carcasses
 Stable manure

13. Types of refuse
 Street sweeping: dust, manure, leaves, cigarette
butts, waste paper and other materials
 Night soil: human waste wrapped and thrown into
sidewalks and streets
 Yard cuttings: leaves, branches, grass

14. What is sewage ?
 Waste water from a community, containing solid
and liquid excreta, derived from houses, street and
yard washings, factories and industries.
 Resembles dirty water with an unpleasant smell

15. What is Sullage ?
 Waste water which does not contain human
excreta, e.g., waste water from kitchen and
bathrooms.

16. Refuse - Storage
 Should be collected in BINS(Domestic
or Public)
Domestic Bins:
 Galvanized steel with closed cover of
0.5 C.ft height for 5 members family of
Indian setups. It can be more
facilitated by paper sack
Public Bins:
 Larger than domestic bins
 Without covers
 2-3 inch above the ground level
Bins are handled and emptied mechanically
by lorries fitted with cranes.

17. Refuse - collection
 Best method - house to house collection. Not much
practiced in India
 Refuse is disposed all along the street and around the
house and this refuse is transported in refuse collection
vehicles to the place of ultimate disposal.

18. Refuse - collection
1. Frequent collection of refuse, specially garbage
2. A longer interval between collection creates
problem of storage and foul odor for the
homeowner
3. cover the refuse in the vehicles during
transportation to final disposal sites to prevent
flies, minimize odors or remove traveling “eye
sores”.
4. adequate and properly maintained collection
carts, trucks and other vehicles to eliminate
collection delays and complaints from residents.
5. The route to the final disposal should be as direct
as possible from the point of origin. It should
preferably not pass busy streets.
6. It is preferrable to have collection done at night

19. Methods of Disposal of
Waste
19

20. COMMUNITY REFUSE DISPOSAL
METHODS
I. DUMPING
II. CONTROLLED TIPPING
III. INCINERATION
IV. COMPOSTING
V. MANURE PIT
VI. BURIAL

21. Refuse disposal methods for
households
 BURIAL
 BURNING
 FEEDING TO ANIMALS
 COMPOSTING
 GRINDING AND DISPOSAL TO SEWER

22. METHODS OF DISPOSAL
a) Dumping –
 Refuse is dumped in low lying areas.
 Due to bacterial action refuse decreases in
volume and converted gradually into
humus.
 Drawbacks –
 refuse is exposed to flies and rodents
 source of nuisance
 pollution of surface and ground water
WHO condemned “ most insanitary method
that creates public health hazards.”

23. METHODS OF DISPOSAL
b) Controlled tipping or sanitary landfill –
Material is placed in a trench or other prepared area,
compacted and covered with earth. Three methods are
available
.

24. Controlled tipping or sanitary
landfill
1. Trench method –Where level ground is available.
The refuse is compacted and covered with excavated earth.

25. Controlled tipping or sanitary
landfill
2. Ramp method –
Where the terrain is moderately sloping

26. Controlled tipping or sanitary
landfill
3. Area method –
For filling land depressions, disused quarries and clay
pits. The refuse is deposited and consolidated in
uniform layers up to 6-8 ft deep.

27. METHODS OF DISPOSAL
c) Incineration –
 Method of choice where suitable land is not available.
 Mainly used for hospital refuses and large cities of
industrialize countries where there is lack of suitable
land.
 Not a choice in India as it contains fair amount of fine
ash which makes burning difficult.
 It also involves loss of much needed manure.

28. METHODS OF DISPOSAL
d) Composting –
 Combined disposal of refuse and nightsoil or sludge. It
is a process of nature where by organic matter breaks
down under bacterial action resulting in formation of
stable humus like material called compost which has
considerable manurial values.
 By product : CO2 , water and heat

29. COMPOSTING
 There are two methods commonly in practice:
1- Bangalore method (anaerobic method)
2- Mechanical method (aerobic method)
1 Bangalore method:
 Trenches are done depending upon amount of refuse and
nightsoil to be disposed off.
 It is filled with alternate layers of refuse and night soil, the
top layer should be of refuse, atleast 25 cm thickness.
 Then the heap is covered with excavated earth. Within 7 days
, due to bacterial action, material decomposition starts and
after 4-6months decomposition is completed yielding manure.

30. COMPOSTING
1 Bangalore method:

31. COMPOSTING
2. Mechanical method:
• Compost is manufactured on large scale.
• Refuse is first cleared off salvageable material like
rages, bones, metals, glass and other items.
 It is then pulverised to reduce the size of particle < 2
inches which is then mixed with sewage , sludge or
nightsoil in rotating machine and incubated.
 Time : 4-6 weeks
 Not commonly practice in India

32. METHODS OF DISPOSAL
e) Manure pits –
 In rural India – no system for collection and disposal of
refuse, thrown around the house indiscriminately.
 Problem is solved by digging manure pits: garbage,
cattle dung, straw and leaves dumped in to the manure
pits and covered with earth after each day’s dumping
 Within 5-6 months the all refuse materials converted to
manure which later then sprinkled on the field.

33. METHODS OF DISPOSAL
f ) Burial:
 This method helps for small camps.
 Trench should be made and all refuse material dumped
in and when the trench level is 40 cm of the ground , it is
filled with the earth and compacted and then new trench
made.
 The contents taken out after 4-6 months and used on the
field.

34. Public education
By pamphlets, newspapers, broad casting , films etc.
 The public education is must needed in waste disposal as
it avoids many communicable diseases and mosquito
borne diseases.
 Heavy funding is needed to implement all levels of
disposal methods.
 For waste disposal
International organization – International solid wastes
and public cleansing association (ISWA) is working
since 1970.
 A WHO international reference centre : collect, evaluate
and disseminate information in waste disposal practices
and to foster research.

36. EXCRETA DISPOSAL
Public health importance :
Imp source of infection
Imp cause of environmental pollution
Health hazards: soil pollution, water pollution,
contamination of foods, propagation of flies.
The resulting diseases are typhoid, paratyphoid,
dysenteries, diarrheas, cholera, hookworm
disease, parasitic infestations and other intestinal
infections.

37. Extent of the problem in India
 Nearly 74 % of India’s population live in to
rural areas : Majority of them “ go to the
fields” for defecation.
 Not more than 15 % of urban Indian
population had the amenity of a sewerage
system.
 Prevalence of intestinal group of diseases
around 50 million per year.
 Enteric fever quit common in rural areas :
annual incidence from 102 to 2119 per lakh.
 The solution to the problem is only through
hygienic disposal of human excreta.

38. Methods of excreta disposal
I. Unsewered areas :
A. Service type latrines (Conservancy system)
B. Non service type (Sanitary) latrines
1) Bore hole latrine
2) Dug well or pit latrine
3) Water-seal type of latrine
4) Septic tank
5) Aqua privy
C. Latrine suitable for camps & temporary use
1) Shallow trench latrine
2) Deep trench latrine
3) Pit latrine
4) Bore hole latrine

39. Methods of excreta disposal
(contd.)
II. Sewered areas :
1) Water carriage system and sewage treatment
1) Primary treatment
 Screening
 Removal of grit
 Plain sedimentation
2) Secondary treatment
 Trickling filters
 Activated sludge process
3) Others
 Sea outfall
 River outfall
 Sewage farming
 Oxidation ponds

40. Bore hole latrine
 Special equipment “auger” is required to dig a bore
hole.
 For a family of 5-6 peoples a bore hole serves for
over a year.
Merits :
 No need for the services of a sweepers
 Pit is dark and unsuitable for fly breeding
 Must be located 15 meter away
from source of water supply then
no danger of water pollution.

42. Dug well latrine
 It is an improvement over the bore hole latrine.
Advantages :
 Easy to construct & no special equipment required
 The pit has longer life span than bore hole : will last for
above 5 years for 4-5 persons.

43. Water seal type latrine
Two types :
 P.R.A.I. , evolved
by the Planning,
Research and
Action Institute,
Lucknow (Uttar
Pradesh)
 RCA Research
cum Action
Projects in
Environmental
Sanitation of the
Ministry of Health
and Family
Welfare,
Government of

44. Water seal type latrine
The water seal performs two important functions : -
1. It prevents access by flies. That is, the nightsoil is sealed from flies, by a
small depth of water contained in a bent pipe, called as water trap,
2. it prevents escape of odours and foul gases thereby eliminates the
nuisance from smell. Once the latrine is flushed, nightsoil is no longer
visible.
These merits have rendered the water seal type of latrine more acceptable to

45. SEPTIC TANK
 satisfactory means of disposing excreta and liquid
wastes from individual dwellings, small groups of
houses and institutions which have adequate water
supplies but do not have access to a public
sewerage system.

46. WORKING OF A SEPTIC TANK
 two stages are involved in the purification of
sewage.
1. anaerobic digestion takes place in septic tank
proper,
2. aerobic oxidation, takes place outside the septic
tank, in the sub-soil.

47. Sulabh shauchalaya
 The invention patna based firm, is al low cost pour
flush water seal type latrine – now being used in
many parts of India.
 Improved version of standard handflush latrine.
 Excreta undergoes bacterial decomposition and
converted in to manure – requires very little water.
 Sulabh international build and maintain the system
of Sulabh community latrines with minor amount of
charge for utility.

48. Sulabh shauchalaya
 pan with a steep slope of 25°-
28° and an especially designed
trap with 20 mm waterseal
requiring only 1 to 1.5 litres of
water for flushing
 It does not need scavengers to
clean the pits.
 There are two pits.The capacity
of each pit is normally designed
for 3 years’ usage.
 Both pits are used alternately. In
about two years, the sludge gets
digested and is almost dry and
pathogen free, thus safe for
handling as manure.

49. Latrine suitable for
camps & temporary
use
 Shallow trench latrine(for a
short period (up to one
week):The trench is 30 cm
(1 ft.) wide and 90-150 cm
(3-5 ft.) deep.
 Deep trench latrine(for
camps of longer duration,
from a few weeks to a few
months).
The trench is 1.8 to 2.5 m(6-8
ft.) deep and 75-90 cm (30-35
in.) wide

50. WATER CARRIAGE SYSTEM(or
sewerage system)
 collecting and transporting of human excreta and
waste water from residential, commercial and
industrial areas, by a network of underground
pipes, called sewers to the place of ultimate
disposal.
 There are two types in water carriage system -
1. the combined system, the sewers carry both the
sewage and surface water.
2. In the separate system, surface water is not
admitted into sewers. The separate system is
considered the system of choice today.

51. WATER CARRIAGE SYSTEM(or
sewerage system)
Elements---
 1. Household sanitary fittings (plumbing system of
buildings)
 2. House sewers
 3. Street sewers or trunk sewers
 4. Sewer appurtenances : manholes, traps, etc

52. Composition of sewage:
 99.9% water and rest 0.1% solid
 Organic and inorganic
 Suspension and solution
 Living organism

53. SEWAGE PURIFICATION???
 one gram of faeces may contain about 1,000
million of E coli,10 to 100 million of faecal
streptococci, and 1 to 10 million spores of Cl.
perfringens besides several others. The average
adult person excretes daily some 100 grams of
faeces.
Aim of sewage purification:
 Stabilize the organic matters so it can be dispose
of safely

54. SEWAGE PURIFICATION
 A standard test which is an indicator of the organic
content of the sewage is biochemical oxygen
demand (BOD).
1. Biochemical oxygen demand (BOD):
 It is the amount of oxygen absorbed by a sample of
sewage during a specified period, generally 5 days,
at a specified temperature, generally 20 deg.C for
the aerobic destruction or use of organic matter by
living organisms.
 The value ranges from 1 mg/L to 300 mg/L. If the
BOD is 300 mg/l and above, sewage is said to be
"strong"; if it is 100 mg/I, it is said to be "weak"

55. SEWAGE PURIFICATION
 Other indicators:
2. CHEMICAL OXYGEN DEMAND (COD)
3. Suspended solids: 100 to 500 mg/L.
100 mg/I :weak
500 mg/l : the sewage is said to be strong.

56. Decomposition of organic
matter
 by two processes : aerobic and anaerobic
processes.
(1) Aerobic Process ; the most efficient method
• organic matter is broken down into simpler
compounds namely CO,water, ammonia, nitrites,
nitrates and sulphates by the action of bacterial
organisms including fungi and protozoa.
(2) Anaerobic Process : Where the sewage is highly
concentrated and contains plenty of solids,
 The end-products of decomposition are methane,
ammonia, CO, and H20.
 These reactions are slower.

57. MODERN SEWAGE
TREATMENT

58. MODERN SEWAGE
TREATMENT
 PRIMARY TREATMENT:
1. Screening
2. Grit chamber
3. Primary sedimentation
 SECONDARY TREATMENT: Effluent is subjected
to aerobic oxidation by one of the following method
1. trickling filter method
2. Activated sludge process
 Secondary sedimentation:

59. MODERN SEWAGE
TREATMENT
 Sludge digestion:
 One greatest problem associated with MST
treatment and disposal of resulting sludge
1. Digestion: If sludge is incubated under favourable
condition of temperature and PH --- anaerobic
auto-digestion in special tank “sludge digestion
tank”
2. Sea disposal:
3. Land disposal:

60. MODERN SEWAGE
TREATMENT
Disposal of effluent:
 Disposal by dilution
 Disposal on land
 Sea outfall
 River outfall
 Land treatment
 Oxidation pond
 Oxidation ditches

61. OXIDATION POND-Waste disposal
ponds/ redox pond / sewage lagoons
 Useful for small communities
 There must be presence of:
1. Algae
2. Certain types of bacteria feed on decaying organic
matters
3. Sun-light

62. OXIDATION POND
The effluent may be use for growing vegetable
crops
May be discharge in rivers or other water courses
after appropriate treatment

63. MCQ 1
Q. Which of the following is considered an adequate
water supply/capita/day in urban areas
(a) 50-100 L
(b) 100-150 L
(c) 150-200 L
(d) 200-250 L

64. MCQ 2
Q. Which one of the following is not a waterborne
disease :
(a) Kala azar
(b) Poliomyelitis
(c) Giardiasis
(d) Cholera

65. MCQ 3
Q. Hardess of drinking water should be
a) <1 mEq / L
b) 1-3 mEq / L
c) 3-6 mEq / L
d) >6 mEq / L

66. MCQ 4
Q. Which of the following compound gives permanent
hardness to water
a) Magnesium bicarbonate
b) Calcium sulphate
c) Calcium bicarbonate
d) Magnesium chloride

67. MCQ 5
The vital layer of the slow sand filter is also known
as :
(a) Superficial layer
(b) Sand bed layer
(c) Biological layer
(d) Chemical layer

68. MCQ 6
The disinfecting action of chlorine is mainly due to
(a) Chloride atom
(b) Hypochlrous acid
(c) Chloride ion
(d) Hypochlorite ion

69. MCQ 7
Action of chlorine is maximum when water pH is
around
(a) 3
(b) 5
(c) 7
(d) 9

70. MCQ 8
Chlorination does not affect in normal doses
(a) Salmonella
(b) Polio
(c) Shigella
(d) Vibrio

71. MCQ 9
Minimum recommended concentration of free
residual chlorine is
(a) 0.1 mg/L
(b) 0.5 mg/L
(c) 1 mg/L
(d) 1.5 mg/L

72. MCQ 10
‘Problem Village’ is all except
(a) no safe water is available within distance of
1.6 Km
(b) no safe water is available up to depth of 15 m
(c) no water harvestation is available
(d) drinking water contains toxic elements

73. MCQ 11
Q. Globe thermometer is used to measure
(a) Air Temp
(b) Cooling power of Air
(c) Humidity
(d) Mean Radiant Temp.

74. MCQ 12
Q. Kata thermometer was devised to measure
(a) Air Temp
(b)Cooling power of Air
(c) Humidity
(d) Air movement.

75. MCQ 13
Q. Body temperature may rise to 110°F in case of
a) Heat exhaustion
b) Heat stroke
c) Heat syncope
d) Heat cramp

76. MCQ 14
Q. Air velocity is measured by
(a) Anemometer
(b) Psychrometer
(c) Globe thermometer
(d) Stevenson screen.

77. MCQ 15
Q. The main greenhouse gas which is largely
contributing to Global warming is
(a) Carbon dioxide
(b) Methane
(c) Nitrous oxide
(d) Fluorocarbons

78. MCQ 16
Q. Soiling index is an index to measure
(a) Radioactive pollution
(b) Soil pollution
(c) Air pollution
(d) water pollution

79. MCQ 17
Q. Permanent hearing loss is caused by noise
above
a) 110 dB
b) 130 dB
c) 160 dB
d) 180 dB

80. MCQ 18
Q. As per the Housing standards recommended by the
Environmental Hygiene Committee, height of the roof should
not be less than (in feet)
a) 2
b) 5
c) 10
d) 20

81. MCQ 19
Q. The minimum Floor area in a house required for
one person should be
(a) 100 sq. ft
(b) 200 sq. ft
(c) 250 sq. ft
(d) 50 sq. ft

82. MCQ 20
Q. The minimum Cubic space in a house required
for one person should be (in Cu ft)
(a) 100
(b) 200
(c) 250
(d) 500

83. MCQ 21
Q. In a House, window area should be
_________ of floor area
(a) 1/5th
(b) 2/5th
(c) 1/3rd
(d)1/2

84. MCQ 22
Q. The recommended number of air changes in
living room should be ______ (per Hour)
(a) 1-2
(b) 2-3
(c) 3-4
(d)4-5