Household and
neibourghood
Sanitation
Infrastructures:
Excreta,
wastewater disposal
in developing
countries
Doulaye Koné – Eawag/Sandec
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Structure of the presentation
Objectives of a sanitation systems
What are we talking about?
Wastewater sources and their
characteristics
Pathways of domestic wastewater
Household sanitation management
infrastructures
Realistic holistic sanitation systems
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Tasks of sanitation systems
• Prevent disease – guarantee effective barriers against
sanitation related diseases
• Protect the environment – prevent pollution, return
nutrients to the soil, and conserve water.
• Be simple - operation of the system must be feasible using
locally available resources (human and material). Where
technical skills are limited, simple technologies should be
preferred.
• Be affordable – total costs (incl. capital, operation,
maintenance costs) must be within the users’ ability to pay.
• Be culturally acceptable – it should fit local customs,
beliefs, and desires.
• Work for everyone – it should address the needs of
children and adults, of women and men.
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What are we talking about?
Blackwater
toilet wastewater
(faeces and urine with or without flushing water)
Greywater
domestic wastewater form kitchen, bath, shower (excluding
faeces and urine)
Brownwater Blackwater without urine
Yellowwater Urine
Faecal sludge
Sludge accumulating in "on-site sanitation systems"
(Latrines, Septic tanks, etc.)
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The human waste system
~ 2 billion (2004)
~ 3 billion (2025)
The Path of Excreta and
Greywater in Urban Areas
“on-site” sanitation
(excreta, black and greywater)
sewered sanitation
(black and greywater)
Septic tanks
Greywater
Wastewater treatment
plant (WWTP)
Small-bore sewerage for effluent
of interceptor or septic tanks
Latrines
Effluent to soakage
or drains
(trad., VIP, PF,
double-pit, nomix, ...)
Septage
Liquid to discharge
into receiving waters or to cotreatment in WWTP
Effluent to agricultural use or
discharged into receiving
waters
FS treatment
Plant (FSTP)
“Faecal sludgeFS”
Biosolids to agriculture for
soil conditioning and
fertilization
Products from double-pit
and no-mix latrines might
be used on-site
Eawag / Sandec 2004
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Characteristics of the different wastewater sources
Total
Greywater
Urine
Faeces
25’000 -100’000
25’000100’000
500
50
2-4 kg/cap*a
5%
85%
10%
Phosphorous
0.3-0.8 kg/cap*a
10%**
60%
30%
Potassium
1-4-2.0 kg/cap*a
34%
54%
12%
30kg/cap*a
41%
12%
47%
-
104-106
/100ml
0*
107-109
/100ml
Volume
[l/cap*a]
Nutrients
Nitrogen
COD
Faecal
coliforms
* healthy people
** can be as high as 50%, depending on washing and dish-washing powder used
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Criteria influencing the selection of sanitation systems
Economic, institutional and other aspects
•
•
•
•
•
•
regulations and standards (including
enforcement)
costs for construction, O&M
willingness to pay (initial and monthly
payments)
self-help potential and initiative of local
people and organizations
local entrepreneurs, consultants,
construction companies, ...
Existing system!
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Classification of Excreta and wastewater management
technologies
- Cesspit trucks
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Partially sewered cities
• Business centre of large cities with high water
consumption rate
• Lack of treatment sites and wastewater
treatment plants
• Discharge of wastewater into natural water
bodies and open canals
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Cities without sewers
• Represent more than 90% of cities in developing
countries
• Are very heterogeneous in urban infrastructure
• Often lack financial and human resources for
sanitation development and upgrading
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Decentralised sanitation systems
are often more suitable – why?
– Existing systems are decentralised (e.g. latrines)
– Treatment and reuse can be tailored to the specific waste
stream (e.g. urine, faeces, greywater etc.)
– Decentralised systems are easier to plan and implement (different
“independent” areas with specific needs and characteristics)
– Capital investments are generally less than for centralised
systems (reduced investments for trunk sewers and pumping
stations, lower O&M costs)
– Capacity expansion and thus capital requirements can track
demand much more closely (incremental approach)
– No reason to impose a “one size fits all” approach
– Different strategies can be employed in various parts of the
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service area.
The human waste system
~ 2 billion (2004)
~ 3 billion (2025)
The Path of Excreta and
Greywater in Urban Areas
“on-site” sanitation
(excreta, black and greywater)
sewered sanitation
(black and greywater)
Septic tanks
Greywater
Wastewater treatment
plant (WWTP)
Small-bore sewerage for effluent
of interceptor or septic tanks
Latrines
Effluent to soakage
or drains
(trad., VIP, PF,
double-pit, nomix, ...)
Septage
Liquid to discharge
into receiving waters or to cotreatment in WWTP
Effluent to agricultural use or
discharged into receiving
waters
FS treatment
Plant (FSTP)
“Faecal sludgeFS”
Biosolids to agriculture for
soil conditioning and
fertilization
Products from double-pit
and no-mix latrines might
be used on-site
Eawag / Sandec 2004
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On-site dry systems
Simple pit latrine
•
•
•
•
2 m or more in depth
covered by latrine slab
with or without
superstructure
percolation of liquids into
soil
partial anaerobic
decomposition of solids
+ cheap, easily understood
-
unstable soils (→ lining)
not good with high water
table
- hazardous and difficult
emptying (depth > 2 m)
- odor problems, fly breathing
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On-site dry systems
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On-site dry systems
VIP latrine (ventilated improved pit latrine)
• Naturally induced ventilation
with screened ventilation pipe
• removes odor
• prevents escape of flies
+ bad smell and flies reduced
- difficult to construct properly
- more expensive than simple
pit latrine
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On-site dry systems
Groundwater contamination
• If contamination potential is high -> raised pits or vaults completely
over ground
• > 2m above highest groundwater
level
• less --> at least 20 m to next well.
• But: main risk of contamination is
via dug well
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On-site dry systems
Double pit systems and raised pit (vault) systems
• Permanent pits
• Filling - consolidation emptying
• dehydration and
hygienisation --> reuse
• can be an option with
urine separation
+ “treatment” included
+ more hygienic emptying
- O&M more complicated
-/+ costs
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On-site systems
Pour flush pits
• Flushing of excreta with 2-3
liters
• Permanent pits or vaults
• Can be combined with double
vaults
+ reduced smell problem with
water seal
- water must be available
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Designing latrines
Site
• Distance and position relative to housing: depending on cultural habits
• at least 20 m from surface water sources
• easily accessible for all users (children, women, old people, disabled)
Construction materials
• local availability
• stable and durable
• esthetic considerations
Superstructure design
• depending on cultural habits (open or closed)
• protect from rain, stormwater runoff, ...
• superstructure = important factor influencing the use (essential that users
are involved in design)
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Designing latrines
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Designing latrines (cont.)
Slabs
• concrete, wood, fero-cement or
plastic (local manufacturers?)
• keyhole shape most suitable
• squat hole covers (not for VIP)
Ventilation pipes
• 15-20 cm diameter
• length of VIP pipe = 0.5m higher
than superstructure
• orientation
Pit excavation and lining
• top 0.5 m usually lined (pre-cast
concrete, bricks, cement blocks,
etc.)
No movable parts!
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Designing latrines (cont.)
• Round pits are more
suitable to distribute
evenly earth pressure
(natural arching effect)
• Hand-washing facilities
must be provided!
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Designing latrines (cont.)
Pit sizing
V = N x S x D / 1000
and
F=NxW/I
V: pit Volume (m3)
N: no. of users
S: sludge accumulation rate (litres/cap year)
D: design life (years)
2-3 years for single pits (where emptying required)
1-2 years for double pits
0.5 -1 year for double pits with urine separation
F: Infiltration area (m2); (water depth = F / pit circumference)
W: Amount of water used for flushing (liters/cap day)
I: Infiltration rates (liters/m2 day)
•
•
•
•
•
Sand
Sandy loam
Silt loam
Clay loam
Clay
40
25
20
8
unsuitable
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Designing latrines (cont.)
Sludge accumulation rates
Wastes deposited and conditions
Wastes retained in water where
degradable anal cleaning materials are
used
Wastes retained in water where nondegradable anal cleaning materials are
used
Wastes retained in dry conditions where
degradable anal cleaning materials are
used
Wastes retained in dry conditions where
non-degradable anal cleaning materials
are used
Sludge accumulation rate
"S"
(litres per capita per year)
40
60
60
90
In emergency situations (rapid accumulation) these rates have to be
multiplied by 150-200%
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Urine diversion latrines
• Faeces and urine are
separated before they
come into contact
• Urine is collected in tanks
and is reused as liquid
fertilizer
• Faeces are dehydrated in
the chambers and used
as soil conditioner
+ reduced stench problems
+ easier handling of dried
material
+ reduced chamber volume
+ no waste, but fertilizer
- special squatting pan
- 2 separate fractions
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Urine diversion latrines
•
•
•
•
2 chambers, 0.5-1 m3 each
2 doors, access normally
from outside
1 urine pipe with jerry can,
normally outside
Squatting pan with cover
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Urine diversion latrines
Operation:
•
•
•
•
Addition of ash: to increase pH
and to reduce moisture
In addition: lime, sawdust, dry
soil,...
Toilet paper separation: Toilet
paper will not decompose in the
chamber (only dehydration
process) → separate collection in
a bucket.
If the toilets are well operated
and maintained, no smell
problems will occur.
Vent pipe and
window ensure
a sufficient
aeration
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Urine diversion latrines
Processing chambers:
•
•
•
•
Always 2 chambers
Above ground level, sealed
Access to the chambers
should be possible from
outside the house
Volume according to
accumulation rate and
number of users;
→ guide value:
100-150 l/year/user and
chamber
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Emptying urine divertion toilet
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Household / neighbourhood treatment systems
Septic tank
most frequent on-site treatment
unit worldwide
sedimentation tank
settled sludge partially stabilised
by anaerobic digestion
1-3 compartments
Almost no removal of dissolved
and suspended matter
+ simple, little space required (underground)
+ high institutional acceptance
- low treatment efficiency (COD removal approx. 50%)
- O&M often neglected (desludging) or unkown!!
→ look for national design standards!
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Septic tank design
V=V1 + V2 + V3
V3=F*h
V3: scum layer
h=20-30cm
F: surface of the tank
h: height of the scum layer
V1 and V3 can also be estimated
based on existing figures:
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Household / neighbourhood treatment systems
Anaerobic baffled reactor (baffled septic tank)
•
•
•
•
•
Improved septic tank
2 to 3 chambers in series (up to 5)
Intensive contact between resident sludge and fresh influent
Treatment efficiency: 65 to 90% COD removal
HRT = 2-3 days
+ simple, high treatment efficiency, hardly any blockages
+ high removal efficiencies, also for suspended and dissolved solids
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- construction and maintenance more complicated than conventional septic tank
Septic systems
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Household / neighbourhood treatment systems
Anaerobic filter
Used for pre-settled domestic
wastewater with low SS
concentrations (e.g. greywater)
Principle: close contact of
wastewater with active bacterial
mass on filter media
filter material surface: 90 to
300m2 per m3
Treatment efficiency: 70 to 90% COD removal
Volume: 0.5-1.0 m3/cap for domestic wastewater
+ simple and durable if well constructed and wastewater properly pre-treated;
high treatment efficiency; little space requirements
- high construction costs (filter media); blockage of filter possible
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- maintenance costly and difficult
Faecal sludge – underestimated problem
e.g. Bangkok, Manila, Accra
e.g. London, Paris, Berlin
Percent of population served by
on-site sanitation
Latin America
Tanzania
Ghana
Philippines
Manila
Bangkok
0
•
•
20
40
60
80
100
2-2.5 billion urban dwellers on on-site
sanitation !
Number and share growing !
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Types of faecal sludge
Thick and yellow .......
Sludges from unsewered public or
family toilets emptied at weeks’
intervals  “unstable”
Thin and black .......
Sludges from septic tanks emptied
at years’ intervals  partially
“stable”
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