Management of sewage and waste water disposal

DR. OTAIGBE O. I.
Department of Community Medicine
Irrua SpecialistTeaching Hospital
29th June 2016

 Introduction
 Definitions
 Classification of Sewage
 Excreta Disposal
 Methods of Excreta Disposal
 Improved and Unimproved Sanitation
 SewageTreatment
 SludgeTreatment
 Disposal of Effluent
 Applications of Sewage Management
 Sewage Management and SDG
 WorldToilet Day
 Conclusion
 References
2
29/06/2016 OTAIGBEO.I. Management of Sewage andWastewater Disposal

 My short confession
 An ugly and smelly part of our lives that we rather not
talk about
 We pretend it does not exist
 Very few people ever think of what happens to their
waste once it has been flushed down the toilet
3

 The hard truth:
 IT EXISTS!!!
 It exists because we produce it
4

 A safe environment is fundamental to health.
 Air and water precede even food and shelter in a
hierarchy of health and survival needs.
 Safe water supplies and waste management
(including liquid waste) are important in
ensuring a safe environment.
5

 As at 2015, it was estimated that 2.4 billion
people did not have improved sanitation.
(WHO/UNICEF JMP 2015)
 An estimated 946 million people worldwide still
defecate in the open. (WHO/UNICEF JMP 2015)
 This constitutes a source of infection and an
important cause of environmental pollution.
6

 Also, waste water from bathing and domestic
washing, if not properly drained, can accumulate
and create a conducive environment for the
proliferation of vectors.
 Therefore management of sewage and waste
water disposal are very vital public health
activities.
7

 Sewage is waste water from a community,
containing solid and liquid excreta, derived from
houses, street and yard washings, factories and
industries. (Park, 2011)
 Sullage is waste water which does not contain
human excreta e.g. waste water from kitchens
and bathrooms. (Park, 2011)
8

 Sewage Management refers to the various processes
involved in the collection, treatment and sanitary
disposal of liquid and water-carried wastes from
households and industrial plants. (Oloruntoba, 2010)
 Sewers are the pipes through which sewage flows.
 Sewerage is the network of such pipes through which
sewage flows.
9

1. Domestic (human excreta and sullage)
2. Industrial orTrade
3. Runoff (storm water or flood water)
10

 Health hazards of improper excreta disposal include:
▪ Soil pollution
▪ Water pollution
▪ Contamination of foods
▪ Propagation of flies
11

 How is disease carried from excreta?
12
FAECES
WATER
FINGERS
FLIES
SOIL
FOOD
NEW HOST

 Sanitation barrier
13
FAECES
SANITATION
BARRIER
WATER
FINGERS
FLIES
SOIL
FOOD
PROTECTED
HOST

Qualities of a sanitary latrine
1. It must not pollute the surface of the soil.
2. It must not contaminate or pollute surface
water or ground water.
3. It must not make sewage accessible to flies and
other animals.
14

4. There must be no handling of fresh sewage.
5. It should not be unsightly or smelly.
6. It must be simple, affordable and culturally
acceptable to the community.
15

1. Unsewered areas
▪ ServiceType (Conservancy) e.g. bucket latrine
▪ Non-serviceType e.g. pit latrine, trench latrine,
chemical toilet, septic tank, aqua privy etc
2. Sewered areas
▪ Water-carriage system (sewerage system)
16

Bucket Latrine (Conservancy)
 Night soil is removed by a human agency using a
bucket
 Disposed of by burying or composting
 Bucket latrine and open defecation are discouraged
as methods of excreta disposal
17

1. Pit Latrine
 Consists of the pit, the floor and the
superstructure
 The pit should be at least 2m deep.
 The floor should be made of reinforced concrete
slab to ensure it is strong and safe.
18

 The superstructure is usually made from local
materials such as mud and wattle, bamboo and
sugar palm thatch or timber and tin sheeting.
 A pit latrine should be sited 6m from houses and
30m away and downhill from a water source.
 The pit must be provided with a tight lid.
19

20

 Advantages of Pit Latrine
▪ Cheap
▪ Quick to construct
 Constraints of Pit Latrine
▪ Foul smell
▪ Large numbers of disease vectors
21

 Modifications of the pit latrine include:
▪ Ventilated Improved Pit (VIP) Latrine
▪ Borehole Latrine
▪ Pour-Flush Latrine (Water Seal Latrine)
22

Ventilated Improved Pit (VIP) Latrine
 It is a modification of the pit latrine
 Aims to eliminate the common problems
associated with the simple pit latrine
 Addition of a vent pipe with a flyscreen
23

24
VENTILATED IMPROVED PIT LATRINE
flyscreen

25

26

27

28

 Advantages ofVIP Latrine
▪ Reduced odour & flies
 Constraints ofVIP Latrine
▪ Expensive
▪ Difficult and time consuming to construct
properly
29

Borehole Latrine
 Most appropriate in situations where a large number of
latrines must be constructed rapidly
 Also useful where pits are difficult to excavate, either
because of ground conditions or the lack of a labour force
 Typical diameter of 400mm and a depth of 5-10m
30

31
depth
5
–
10m
0.5m
Cover slab
Typical diameter
400mm
Borehole Latrine
Solid accumulation

32
Borehole Latrine

 Advantages of Borehole Latrine
▪ The borehole can be excavated quickly
▪ Suitable in hard ground conditions
▪ Appropriate where only a small workforce is
available
33

 Constraints of Borehole Latrine
▪ Drilling equipment is required
▪ Greater risk of groundwater pollution
▪ Short lifespan
▪ Sides are liable to be fouled, causing odour and attracting flies
▪ High likelihood of blockages.
34

Pour-Flush Latrine (Water Seal Latrine)
 Water acts as a hygienic seal and helps remove
excreta to a wet or dry disposal system
 The simplest types use a latrine pan
incorporating a shallow U-bend which retains
the water (water seal)
35

 After defecation, a few litres of water must be
thrown into the bowl in order to flush the
excreta into the pit or sewerage system below
 May be constructed directly above a pit or may
be offset whereby the waste travels through a
discharge pipe to a pit or septic-tank
36

37
POUR-FLUSH LATRINE
DIRECT OFFSET

38
POUR FLUSH LATRINE

 Advantages of Pour-Flush Latrine
▪ Reduced odour
▪ Relatively less water is used up
▪ Ideal where water is used for anal-cleansing
▪ Easy to clean
 Constraints of Pour-Flush Latrine
▪ Solid anal-cleansing materials may cause blockages
▪ More expensive than simple pit latrines
39

2. Trench Latrine
 Consists of shallow trenches
 Dug in such a way that excavated soil is left close to
the trench for the purpose of covering the excreta
after use
 Useful for temporary sites such as refugee camps,
work camps, picnic sites, holiday and festival camps
40

41
TRENCH LATRINE

42
TRENCH LATRINE

 Advantages ofTrench Latrine
▪ Rapid to implement
▪ Faeces can be covered easily with soil
 Constraints ofTrench Latrine
▪ Limited privacy
▪ Short lifespan
▪ Requirement of considerable space
▪ Fly breeding if excreta is not covered with earth
▪ Often odour problems
43

3. Composting
 Excreta and refuse are mixed and allowed to
decompose in a corrosion-resistant container
 Household systems for composting nightsoil and
other organic material (e.g. ash, sawdust, organic
household waste etc)
 Usually used when there is an urgent need for organic
fertilizer
44

45
COMPOSTTOILET

46
COMPOSTTOILET

47
COMPOSTTOILET

 Advantages of Composting
▪ Cheap
▪ Humus is produced which can be used as organic
fertilizer
 Constraints of Composting
▪ Breeding of flies
▪ Odour
48

4. ChemicalToilet
 A toilet not connected to a sewage system but has a
compartment/tank in which waste is treated with
chemicals for temporary storage
 Tank usually contains a chemical solution (e.g.
formaldehyde) to aid digestion and reduce odour
 Suitable for mobile communities, caravans, boats,
buses, trains and aircrafts
49

50
CHEMICALTOILET

51
CHEMICALTOILET

52

53
29/06/2016 Most mobile toilets are chemical toilets
OTAIGBEO.I. Management of Sewage andWastewater Disposal

 Advantages of ChemicalToilet
▪ Portable
▪ Hygienic
▪ Minimized odour
▪ Can be mobilized rapidly
 Constraints of ChemicalToilet
▪ High cost
▪ Unsustainable for long periods
▪ Regular servicing and emptying required.
54

5. SepticTank
 Ideal where there is availability of water
 Consists of the flushing device (water closet), the
inspection chamber and the short pipe (sewer)
which leads into the septic tank
55

 The night soil discharges from the house through
the sewer to the septic tank
 Solids settle and are digested anaerobically
 Clear effluent leaves to the soakaway pit where it is
absorbed by the surrounding soil
56

 Aerobic oxidation takes place in the surrounding
subsoil
 Sludge in the septic tank is removed when the
tank is filled
 Desludging usually done once every 1 – 5 years
57

58
SEPTICTANK

59

60
DESLUDGING A SEPTICTANK

 Advantages of SepticTank
▪ Can be built and repaired with locally available materials
▪ Has a long service life
▪ No problem of flies and odour, if properly used
 Constraints of SepticTank
▪ Only applicable for water-dependent sanitation systems
▪ Treatment is partial, the effluent may still contain pathogens
▪ Sludge must be removed periodically
29/06/2016 OTAIGBEO.I. Management of Sewage andWastewater Disposal 61

6. Aqua Privy
 Consists of a water-tight tank made up of concrete and a
floor which carries an inlet drop pipe
 Faeces are stored in the tank which is kept at a constant
water level
 A soakaway pit is also provided for the effluent
62

63
AQUA PRIVY

 Advantages of Aqua Privy
▪ Reduced odour
▪ ideal where water is used for anal-cleansing
▪ easy to clean
 Constraints of Aqua Privy
▪ Increased quantity of water required
▪ solid anal-cleansing materials may cause blockages
▪ more expensive and difficult to construct than simple pit
latrines.
64

 Collecting and transporting of human excreta
and wastewater from residential, commercial
and industrial areas by a network of
underground pipes (sewers) to the place of
ultimate disposal
 Method of choice in cities and towns with high
population density
65

 A sewerage system consists of the following
elements:
▪ Household sanitary fittings (plumbing system)
▪ House sewers
▪ Street sewers or trunk sewers
▪ Sewer appurtenances eg manholes
66

 A different categorization by theWHO/UNICEF
Joint Monitoring Programme (JMP) for water
supply and sanitation
▪ Improved Sanitation – one that hygienically separates
human excreta from human contact
▪ Unimproved Sanitation – one that does not do so
67

 Flush or pour flush to:
✓ piped sewer system
✓ septic tank
✓ pit latrine
 Ventilated improved pit latrine
 Pit latrine with slab
 Composting toilet
WHO/UNICEF JMP 2015
68

 Flush/pour flush to elsewhere
 Pit latrine without slab/open pit
 Bucket
 Hanging toilet or hanging latrine
 Shared facilities of any type
 No facilities, bush or field
WHO/UNICEF JMP 2015
69

Composition of Sewage
 Water 99.9%, solids barely 0.1% (organic and inorganic)
 Offensive odour mainly due to the organic matter
 Numerous microorganisms are also present, some of which
are pathogenic
70

 It is estimated that 1 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 C.
perfringes besides several others. (Park, 2011)
 The average adult person excretes daily some 100
grams of faeces. (Park, 2011)
71

Strength of Sewage
 Can be expressed in terms of:
▪ Biochemical Oxygen Demand (BOD)
▪ Chemical Oxygen Demand (COD)
▪ Suspended Solids
72

Biochemical Oxygen Demand (BOD)
 It is defined as the amount of oxygen absorbed by a sample
of sewage during a specified period, generally 5 days at a
specified temperature, usually 20°C for aerobic digestion.
(Bhalwar, 2009)
 Sewage with a BOD value of 300 mg/l or above is termed as
strong while that of 100 mg/l or below is termed weak.
73

Chemical Oxygen Demand (COD)
 Chemical oxygen demand is the amount of oxygen
required to oxidize the organic matter by use of
dichromate in an acid solution and to convert it to
carbon dioxide and water.
74

 Commonly, BOD is used to test the strength of
untreated and treated municipal and biodegradable
industrial waste waters.
 COD is used to test the strength of wastewater that
is either non-biodegradable or contains compounds
that inhibit activities of microorganisms.
75

Suspended Solids
 If the suspended solids are 100 mg/l or more,
it is termed strong.
76

 The aim of sewage treatment is to convert an
offensive and potentially dangerous mixture into an
inoffensive effluent and sludge which can be
disposed off safely and without causing nuisance
into river, sea or on land.
77

 Treatment of sewage can be divided into 3 main stages:
▪ PrimaryTreatment
▪ SecondaryTreatment
▪ TertiaryTreatment
(Bhalwar, 2009)
78

29/06/2016 79
Raw sewage Screening
Grit
settling
Primary
sedimentation
Aerobic
oxidation
Secondary
sedimentation
Treated
effluent
Activated
sludge
Disposal
A schematic representation of the various stages in sewage treatment
6 – 8 hours @ a
velocity of 1 – 2 ft/min
2 – 3 hours
OTAIGBEO.I. Management of Sewage andWastewater Disposal

1. Screening
 The raw sewage is first passed through bar-screens with
openings of 5 to 10 cm between the bars placed across the
inflow channels.
 The screens intercept large floating objects such as pieces
of wood, rags, masses of garbage and dead animals.
 The screenings can be manually raked from the screens
and buried.
80

2. Grit Removal
 Sewage is then passed through a long narrow
chamber – grit chamber
 The chamber is approximately 10 to 20m in length.
 It allows settlement of heavier solids such as sand and
gravel while permitting the organic matter to pass
through.
81

3. Primary Sedimentation
 Sewage is now admitted into a huge tank –
primary sedimentation tank.
 Sewage is made to flow very slowly across the
tank at a velocity of 1 – 2 feet per minute.
 Sewage spends about 6 – 8 hours in the tank.
82

 Sedimentation of suspended matter takes place
during this period.
 The organic matter which settles down is called
sludge.
 It is removed by mechanically operated devices,
without disturbing the operation in the tank.
83

 Microorganisms present in the sewage attack
complex organic solids and break them down
into simpler soluble substances and ammonia.
 Lighter solids including grease and fat rise to the
surface to form scum.
 Scum is removed from time to time and
disposed off.
84

 The effluent from the primary sedimentation tank still
contains a proportion of organic matter in solution or
colloidal state, and numerous living organisms.
 It is thus subjected to further treatment, aerobic
oxidation, by one of the following methods:
▪ Trickling filter method
▪ Activated sludge process
85

 The trickling filter method makes use of beds
of broken stones or gravels as percolating
filters.
 As the effluent percolates through the filter
bed, it gets oxidized by the bacterial flora
present in the filter.
86

 The activated sludge process is a more modern
method than the trickling filter.
 Sufficient quantity of sludge obtained from the final
settlement tank (called activated sludge) is added to
sewage that is to be treated (the effluent from the
primary sedimentation tank).
 Activated sludge contains active aerobic bacteria vital
for decomposition of sewage.
87

 This mixture (called the ‘mixed liquor’) is
mechanically aerated in an aeration chamber
to facilitate bacterial decomposition.
 In the presence of ample oxygen the aerobic
bacteria utilize the raw sewage and convert it
into stabilized, odourless compounds.
88

 The oxidized sewage from the trickling filter
or aeration chamber is led into the secondary
sedimentation tank where it is detained for 2
to 3 hours.
 The sludge that collects here is called aerated
sludge or activated sludge.
89

 Following secondary treatment, two types of
substances are left - the semisolid sludge and
the watery effluent.
 The sludge is a thick, black mass containing
95% of water and it has a revolting odour.
90

 There are a number of methods of sludge
disposal:
▪ Digestion
▪ Sea disposal
▪ Land disposal
91

Disposal by dilution
 Disposal into water courses such as rivers and streams
 The effluent is diluted in the body of the water and
the impurities oxidized by the dissolved oxygen in
water
 Effluent must be rendered free from pathogenic
organisms by adequate chlorination
92

 The effluent limitation guidelines in Nigeria set
the limit for discharge of effluent into surface
water as follows:
▪ a 5-day BOD of not more than 30mg/l
▪ total suspended solids of not more than 30mg/l
(Federal Environmental ProtectionAgency Act, 1988)
93

Disposal on land
 If suitable land is available, the effluent can be
used for irrigation purposes.
 Reuse of treated effluent for the irrigation of
crops and urban ‘green spaces’ (such as parks
and golf courses) has expanded significantly in
many countries.
94

 However, the risk of transmission of
infections (especially enteric viruses) through
sewage farming remains alive.
 The risk increases if the sewage had not been
treated adequately, prior to its discharge for
sewage farming.
95

 Other methods of sewage disposal include:
▪ Oxidation pond (waste stabilization pond, redox
pond, sewage lagoons)
▪ Oxidation ditches
96

 Any other treatment rendered in addition to
the secondary treatment to further improve
the quality of the effluent e.g. ultraviolet light
irradiation, microfiltration etc.
 Also called advanced waste treatment
process

 Agriculture
 Aquaculture
 Recreation
 Power generation
98

 Sustainable Development Goal (SDG) 6 aims to
‘Ensure availability and sustainable management of
water and sanitation for all’
 It comprises six technical targets relating to drinking
water, sanitation and hygiene, wastewater
management, water efficiency, integrated water
resource management and protection of aquatic
ecosystems.
99

 Target 6.2
▪ By 2030, achieve access to adequate and
equitable sanitation and hygiene for all and end
open defecation, paying special attention to the
needs of women and girls and those in vulnerable
situations
100

 Target 6.3
▪ By 2030, improve water quality by reducing
pollution, eliminating dumping and minimizing
release of hazardous chemicals and materials,
halving the proportion of untreated wastewater
and substantially increasing recycling and safe
reuse globally
101

 Nigeria has not made much progress with
respect to reducing open defecation.
 Worldwide, Nigeria has seen the largest increase
in numbers of open defecators since 1990, with
39 million people defecating in the open in
2012,compared with 23 million in 1990.
(WHO/UNICEF JMP 2014)

 Nigeria has the 4th highest number of people
practicing open defecation (39 million),
coming behind only India, Indonesia and
Pakistan. (WHO/UNICEF JMP 2014)

 November 19 isWorldToilet Day
 It is a day to take action
 A day to raise awareness about all people
who do not have access to a toilet – despite
the human right to water and sanitation
104

 Did you know?
▪ more people in the world have a mobile phone
than have access to a toilet!
105

 The United Nations GeneralAssembly in 2013
officially designated 19 November asWorld
Toilet Day.
 It is coordinated by UN-Water in
collaboration with Governments and relevant
stakeholders.
106

107

 All sewage ends up back in the environment, whether
treated or untreated.
 Therefore, effective management of sewage and
wastewater disposal is vital for the health of every
community.
 It is also an area with great prospects for power
generation, agriculture and aquaculture among
others.
108

 Consequently, there is also significant
untapped potential for wealth generation.
 WE MUSTTHINK BIG SO NOWASTE IS
WASTED!
109

110

 Bhalwar, R., 2009. Textbook of Public Health and Community Medicine. New Delhi. Department of
Community Medicine, AFMC, Pune in collaboration withWHO, IndiaOffice, New Delhi.
 Obionu, C.N., 1999. Synopsis of Occupational and Environmental Health. Enugu. Delta
Publications Nigeria Limited.
 Oloruntoba, E.O., 2010. Overview of Environmental Health. WACP Part 1 Revision Course (August
2010). University of Ibadan.
 Park, K., 2011. Park’sTextbook of Preventive and Social Medicine. 21st Edition. Jabalpur. M/s
Banarsidas Bharnot Publishers.
 UNICEF, WHO, 2014. Progress on sanitation and drinking water – 2014 update. Geneva. WHO
Press.
 UNICEF, WHO, 2015. Progress on sanitation and drinking water – 2015 update and MDG
assessment. Geneva. WHO Press.
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Management of sewage and waste water disposal

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