Transcript C2U2_Conventional_onsite_sanitation - Unesco-IHE

Course 2 Unit 2
Conventional on-site sanitation
Lecturer: Mariska Ronteltap
[email protected]
Part A – Overview
Part B – Description of commonly used low-cost on-site
excreta management systems
Part C – Comparison with UDD toilet
To be really precise, this presentation is about “Conventional low-cost
excreta management systems”
This Unit has been made entirely by Elisabeth von Münch without
editing; you can hear her on the audiofiles also on the platform.
2
Course 2 Unit 2
Course 2 Unit 2
Part A: Overview
Clarification of terms:
Latrine is used interchangeably with the term “toilet”
Pit = Hole in the ground (not water tight)
Vault = Container above ground (water tight)
What do we mean by “conventional” and “on“On-site” means:
site”?
“Conventional” means here:
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Currently widely known and used
Accepted by decision makers as a
potential option
Usually it still often means little
consideration for sustainability
(unfortunately)
UDD toilets could become part of
conventional options in the future
(this would be a good thing!)
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Not connected to sewer
Treated “at the site where people
live”
– but this is not always strictly
true, e.g. septic tanks
eventually need removal of
faecal sludge to a centralised
treatment plant
“Decentralised” is often used
interchangeably with “on-site”
The opposite of on-site is called:
– off-site; or
– centralised systems; or
– sewer-based sanitation (the
only other alternative could be
to tanker the wastewater
away)

Reasons for having on-site sanitation
systems rather than a sewer system
To save construction and maintenance costs
– Because people cannot afford a connection to a sewer
– Many municipalities cannot afford construction and maintenance of an
expensive sewer system and a wastewater treatment plant
Municipalities face huge costs to rehabilitate aging sewer infrastructure
older than 150 years (e.g. in Germany, UK)
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To save water (or because water is scarce or not reliably available);
however, not all on-site sanitation systems have low water use (e.g.
septic tanks)
To serve remote locations (long distances)
– e.g. in Australia and in the US (in the US 50% of new houses use on-site
sanitation - I heard this at the conference in Aachen in 2007 but have no
exact reference for this figure)
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Because housing is only temporary or illegal (slums, refugee camps)
Because it is more flexible with respect to population growth and decline
Because people prefer not to mix excreta with water in order to make
containment of pathogens easier (in the case of a waterless on-site
sanitation system)
Can you think of other reasons?
Reminder: Sanitation consists of 4 components
1. Excreta management
Many people think of only excreta
management when they talk
about sanitation
2. Greywater management
Most often just dumped into the
street or gutter (mixing with
rainwater, soil infiltration)
Less critical from public health point
of view compared to item 1 but
still needs consideration
3. Solid waste management
4. Rainwater drainage
The remainder of this presentation will deal
with low-cost excreta management
Greywater = wastewater from kitchen, bath/shower, sinks, laundry (minimal excreta content)  See
Course 2 Unit 1 for greywater treatment aspects
Course 2 Unit 2
On-site sanitation is quite easy if…
…Population density is low
(e.g. rural areas)
…or if money is not an issue!
But big problems for:
High population density
and low income
(peri-urban areas,
slums)
My rules of thumb:
Low density: < 100 people/ha
Peri-urban areas: 100 – 240 people/ha (e.g. Lusaka, Zambia case)
Slums: > 800 people/ha (e.g. Dhaka, Bangladesh)
1 ha = 10,000 m2 = 0.01 km2 (1 soccer field = 0.7 ha)
What is the population density in your city?
this is the
focus of this
lecture: lowcost on-site
sanitation in
urban areas
Course 2 Unit 2
Conventional low-cost excreta management methods (in
approximate order of increasing system cost)
Excreta disposal method
Needs faecal
sludge mgmt.?
Can accept
greywater?
Human dignity
Public health
risk
Open defecation
No
No
Very low
Very high
Flying toilet
No
No
Very low
Very high
Bucket latrine
Yes
No
Low
High
Simple pit latrine
Yes
No
Can be OK
Medium
Ventilated improved pit (VIP) latrine
Yes
No
OK
Low
No but faecal
matter collection
No
OK
Low
Pour-flush latrine with pit, aqua privy
Yes
No
OK
Low
Water-flush or pour-flush toilet with
septic tank
Yes
Yes
OK
Low
Water-flush toilet with holding tanks /
cess pits
Yes
Yes
OK
Low
Urine-diversion dehydrating toilet*
* Not (yet) conventional but included for comparison
More about costs: see Course 4 Unit 1 “Financial aspects”
Course 2 Unit 2
Course 2 Unit 2
Part B: Description of commonly used low-cost on-site
excreta management systems
(this part is excluding UDD toilets; UDD toilets are covered in detail
in Part C)
Commonly-used on-site excreta management
systems described in Part B
1. Open defecation
2. Flying toilet
3. Bucket latrine
Remember: these are not counted as
basic/improved sanitation in the
MDGs
4. Simple pit latrine
5. Ventilated improved pit latrine
6. Pour-flush latrine with pit or septic tank
7. Aqua privy with septic tank
8. Water-flush toilet with septic tank
9. Water-flush toilet with holding tanks / cess pits
These can be counted as
basic/improved
sanitation in the MDGs
if no open pit but pit
with slab, not shared,
not public toilet and
adequate treatment of
faecal sludge (see
Course 1 Unit 1 Part C
on MDGs)
UDD toilets are not (yet) commonly used – so they are not listed in this table here,
but described in detail in Part C
1. Open defecation
 About 2.4 billion people have no
access to basic sanitation
(WHO/UNICEF, 2006) and
many of these use open
defecation (or bucket latrines,
flying toilets)
 Great public health risks unless
population density is very low
 Rain events flush faeces into
receiving water bodies
– Example: Diarrhoea incidences
increase during rainy season in
peri-urban areas in Lusaka,
Zambia
Open drain used as public toilet in Ouagadougou, Burkina Faso
(Oct. 06)
2. Flying toilet
 Defecate into plastic bags
and throw these away
 Main problems:
– Little human dignity and
comfort for the user
– Plastic bags can block open
drains
– Plastic bags can break and
spill their content  animals
and children can get in
contact with fresh faeces
3. Bucket latrine
 Defecate and urinate into a
bucket which is regularly
emptied manually
http://www.millennium-ark.net/News_Files/NBC/shelter.in.place.html
Course 2 Unit 2
What does faecal sludge from bucket latrines
look like?
A worker in Kumasi
(Ghana) is
transferring faecal
sludge from a
manhole, which is
used to store faecal
sludge from bucket
latrines, to a bucket
and then to a
transport vehicle
(Source: Vodounhessi
(2006))
Note the lack of boots (but
he does wear gloves which
is good)
Faecal sludge
4. Simple pit latrine
 User urinates and defecates into a toilet
placed over a hole (pit) in the ground
 Pit depth: 2 m or more, covered with
latrine slab
 Diameter of pit: 1 – 1.5 m (round or
square)
 The hole may be lined around the top to
prevent collapsing
 The pit is designed so that the liquid pit
content seeps into the ground
 Can be squatting (top photo) or sitting
(bottom photo)
 Very common for:
– Rural areas
– Peri-urban areas, slums, schools
– Emergency sanitation, refugee camps
Ouagadougou, Burkina Faso
(from Course 1 Unit 3)
Reminder: How can pit latrines affect the
groundwater?
Pit latrine
Groundwater
(clean)
Shallow
drinking water
well
Groundwater
(polluted)
Nitrate
Pathogens
Based on: Werner, Ch., Mang H.-P., Klingel, F. Bracken, P. (2004): General overview of ecosan.
PowerPoint-Presentation. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ)
GmbH ecological sanitation programme.
Question: so why don’t we build fully lined pit
latrines?
 If a pit latrine was fully lined, it would no longer be a pit latrine
but a holding tank
 The pit would fill up very quickly with all the urine (remember:
about 1.5 L/cap/d of urine)
 Pits are only lined at the top and perhaps the side to prevent
collapsing but never at the bottom
5. Ventilated Improved Pit (VIP) Latrine
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VIP latrine is the same as
simple pit latrine but has a
vent pipe and fly screen
(reduces odour and fly
breeding)
Toilet room and pit should be
dark to not attract flies
Some VIPs are built as a
double-pit structure (see next
slide)
Air flow
Superstructure
Fly
screen
Vent pipe
Substructure / pit:
Liquid seeps into the
ground
liquid
(urine)
Pits are not water tight as they
would otherwise fill up too
quickly
Source: Harvey et al. (2007)
Double Pit VIP Latrine
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Pit in use
(drying)
Double pit improves
conditions for pit emptying
and potential for reuse
compared to single pit
Pits are alternated every 6
months or (better) every 12
months
But lack of faecal sludge
management and potential
for groundwater pollution are
still problems
Pit: Liquid seeps into the
ground (no separate urine
collection)
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Pit latrines in peri-urban areas of Lusaka, Zambia
Raised pit latrine due to rocky
soil (note leaking on the side)
Source: Mayumbelo (2006)
More photos from pit
latrines in peri-urban
areas of Lusaka
Photos by Kennedy Mayumbelo
(Lusaka Water and Sewerage
Company), March 2007: “The pit
latrine is being used by three
households, all on the same plot.
There are a total of 14 people
currently using it and it is leaking
very badly from the sides (problem of
construction). It is also full and the
users said they only use it because
they have no choice; as expected all
the three households are tenants and
the landlord lives elsewhere.”
Typical problems with pit
latrines in peri-urban areas
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High odour levels
Fly breeding
Overflowing
Collapsing of pits
No space to dig new pits
Difficult to dig new pits if ground is
rocky
No systems to empty pits (lack of
faecal sludge management)
Pit latrines have to be outdoors
Pollution of groundwater which is
used for drinking water by using
shallow wells (e.g. Lusaka, Zambia)
Pits are also used to dump rubbish
Have you ever used a pit latrine?
A collapsed pit latrine (photo by Linus Dagerskog, CREPA, taken in Ouagadougou,
Burkina Faso)
Linus said: “the most disgusting thing I have ever seen; a bubbling sludge, flies
everywhere, and the house owner did not really know how to cover or fill it.”
Course 2 Unit 2
A pit latrine where the hole is
in the process of collapsing
(seen in Maseru, capital of
Lesotho (a small country
inside of by South Africa),
December 2006)
Photo: E. v. Münch
Despite their “popularity”:
pit latrines are actually not sustainable if…
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The groundwater table is shallow
Karst geology or ground that is underlain by pervious rock leading
to:
– a rapid rate of groundwater movement
– potential for groundwater contamination (in combination with shallow
wells being used as a water supply source)
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Area has a potential for flooding
Soil type is rocky (hard to excavate)
No space to dig new pits or no means to empty full pits and to treat
faecal sludge
Population density is high
Situation has lack of security (since pit latrines have to be built in
some distance from the settlements)
Pit emptying
 After some months or years of use
(depending on the number of users
and the size of the pit), a pit latrine
fills up. It then needs to be either
abandoned or emptied.
 Note: water needs to be added to
make faecal sludge from pit latrines
pumpable!
 Methods for emptying:
– Manual emptying with buckets
(extremely high health risks!)
– Mechanised emptying with vacuum
tankers (see Course 2 Unit 3
“Storage and transport logistics”)
Vacuum tanker collecting
faecal sludge from septic tank
Course 2 Unit 2
Why are pit latrines so wide-spread in low
income areas?
 Cheap and easy to construct and maintain
 “Drop-and-forget” mentality
 Can be appropriate solution if:
– population density is low; and
– soil conditions are suitable (not rocky, not sandy, easy to dig
but also stable); and
– area not prone to flooding; and
– groundwater table not shallow but rather deep; and
– good general security (no harassment for women and
children at night)
Course 2 Unit 2
6. Pour-flush latrine with pit or septic tank
Pit under toilet
Pit offset from toilet
•
•
•
Source: Harvey et al. (2007)
After defecation,
a few litres of
water must be
poured into the
bowl to flush the
excreta into the
pit or septic tank
Water acts as a
hygienic seal
(reducing odour
and flies)
(The toilet’s
squatting pan
could be modified
to include urine
diversion as a
first step towards
ecosan)
7. Aqua Privy with septic tank
•
•
•
•
Source: Harvey et al. (2007)
Simple latrine
constructed over a
septic tank
Tank must be
watertight to
maintain constant
liquid level in the
tank
Tank can receive
greywater
Nowadays less
common (I have
never seen one –
have you?)
8. Water-flush toilet with
septic tank
Septic tanks:
 Underground tanks, usually one per
household
 Work in conjunction with water-flush
toilets
 Combined settling, skimming and
anaerobic digestion
 Solution for the wealthy in developing
countries (requires water for flushing)
 Pre-treated, settled effluent usually
infiltrated into ground (“soakaway”)
 Tanks need emptying  Faecal
sludge management often lacking
 For an ecosan concept, septic tanks
could be used just for greywater or
just for blackwater (urine, faeces and
small amount of water)
See “Introduction to Anaerobic Treatment” (Course 2 Unit 4) and
“Conventional Faecal Sludge Management” (Course 2 Unit 7)
Underground septic tanks in Maseru,
Lesotho (Dec. 2006)
Septic tank effluent discharged to soakaway or small-bore sewer
(see Course 2 Unit 8 “Small-bore sewer systems”)
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Typical problems with septic tanks (particularly, but
not only, in developing countries)
 Effluent quality low and often not enough space for sustainable soil
infiltration
– Tank is undersized (little anaerobic treatment occurring)
– Population density has become too high  capacity of soil to absorb
and treat liquid effluent is exceeded
– Pollution of groundwater is possible (effluent soak-aways most common)
 Tank may be leaking (faecal sludge is leaking out); maintenance is
neglected
 Need regular emptying (typically every 5-10 years, depending on
size and number of users)
– Faecal sludge is overflowing together with the effluent
 Capacity for faecal sludge treatment lacking (resulting in illegal
dumping anywhere in the environment)
 Relatively expensive (not affordable for the poor)
 Need access roads for emptying trucks
Course 2 Unit 2
Do you have your own experiences with septic tanks
(e.g. at home or at work)?
 How often is it emptied (faecal sludge removed)?
 How do you know when to empty it?
 What is the effluent quality of your septic tank like? Is it good?
How do you know?
 Is it ever giving you odour problems?
 Where is the faecal sludge taken to and how is it treated?
Such individual soil-based systems are difficult to monitor!
9. Water-flush toilet with holding tank (also called cess pit or conservancy tank)
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Needs watertight tank and
frequent emptying
Sometimes cess pits are
(illegally) converted into a
leaching pit by breaking
through the base of the
tank - so that the cesspit no
longer fills up!
 This may be
convenient for the owner
but may lead to
groundwater pollution
In the US, the word
“cesspool” is used, but this
is not a water-tight tank but
allows infiltration
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Faecal sludge management (FSM)
 The following on-site systems result in the production
of faecal sludge:
– Household pit latrines, bucket latrines
– Unsewered public toilets, e.g. aqua privies, pour flush, VIP,
cess pits
– Septic tanks (households, institutions, hotels,…)
 Faecal Sludge Management = FS transport,
treatment, reuse
 See separate lecture on FSM (Course 2 Unit 7
Some
handysludge
rules of
thumb:
“Faecal
management”)


Specific faecal sludge production (Heinss et al., 1998):
1.0 L/cap/day from septic tanks
0.2 L/cap/day from toilets without water use
Typical FS total solids content 25 g/L (Steiner et al.,
2002)
Faecal sludge management overview
Proposed scenario
Current situation
= Faecal sludge crisis:
(need to add
water to
empty pit by
pumping)

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
’’Closing
the loop’’
But how to deal
with liquid
effluent?
uncontrolled
disposal
illegal dumping
no beneficial
reuse
Course 2 Unit 2
Course 2 Unit 2
Part C: Comparison with UDD toilet
For cost comparisons see Course 4 Unit 1 (“Financial aspects”)
UDD toilet details are given in Course 1 Unit 3 and Course 1 Unit 4
Example: Single vault urine-diversion dehydrating (UDD)
toilet
 This type of toilet is
often wrongly called
“composting toilet” or
“ecosan toilet”
 Ecosan is not limited
to a specific
technology, hence
UDD toilets or other
toilet types could be
used in an ecosan
project
Removal of dried
material
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
(Double vault UDD toilet
would normally have two
vent pipes)
Course 2 Unit 2
Advantages of a UDD toilet compared to a pit latrine
 Can be indoors, because:
– No pit required (the pit would normally allow liquid to seep into
the ground)
– No odours (because urine and faeces are not mixed)
 Suitable for areas with:
– High-density settlements
– Difficult soil conditions
– A danger of groundwater pollution
 Easy to recycle excreta
 Does not require faecal sludge management (vacuum
tankers for pit emptying)
 Does not require regular digging of new pits
 Can be more portable (e.g. the Separett foldable UDD toilet
shown in Course 1 Unit 3 Part E)
Course 2 Unit 2
Disadvantages of a UDD toilet compared to a pit
latrine
 Requires user training and awareness, e.g. must not urinate
into the faeces compartment (one should also provide
waterless urinals for men)
– Can produce odours if not used correctly
 Still relatively new concept amongst NGOs, municipalities,
universities, consultants, manufacturers, etc.
 Dried faecal matter must be removed once or twice per year
 Anal washing with water (if practised) must take place over a
drain which is separate from the faeces vault
 Urine must be collected, stored, transported and used as
fertiliser, or infiltrated into the ground or otherwise dealt with
– Urine collection container could be stolen
– Even the collected urine itself is known to have been
stolen once people appreciate its value as a fertiliser
(experience of CREPA in West Africa)!
How to select best on-site sanitation option?
 Compare sustainability of available options (use sustainability
criteria, see Course 1 Unit 1) – this includes: social, technical,
economic, environmental, public health and institutional aspects;
and/or
 Use selection criteria based on local conditions (example on
next slide)
Example: Short-listing of options for
peri-urban areas in Lusaka, Zambia (slide 1 of 2)
Selection criteria:
1. Not pollute groundwater (groundwater is used as
drinking water)
2. Not require water to transport waste (water is scarce
and expensive)
3. Sanitise excreta to destroy pathogens (protect public
health)
4. Cost effective – low capital and O&M (people have low
income)
Source: Mayumbelo (2006)
Short listed options:
 Option 1: VIP latrine and downstream
processing
 Option 2: Single-vault UDD toilet and
downstream processing
Note: Option 1 does not meet selection criterion 1 but is included to serve as a
reference point in the cost analysis
Course 2 Unit 2
Example cont’d: Decide on the implementation
level (slide 2 of 2)
 Household facility
– One toilet for 4 people
 Plot facility
– One toilet for all people living on one plot (12 in this case)
 Communal facility
– One toilet block that is shared by a number of plots
Good compromise
between convenience
and cost
And at the end: Summary of conflict between
(conventional) onsite sanitation and urbanization…
References for this presentation (slide 1 of 2)
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Harvey, P., Bastable, A., Ferron, S., Forster, T., Hoque, E., Morris, L., Piano, E., and Smith,
M. (2007) Excreta Disposal in Emergencies: A Field Manual, WEDC, Loughborough
University Available: http://wedc.lboro.ac.uk/projects/new_projects3.php?id=15 *
Heinss, U., Larmie, S. A., and Strauss, M. (1998) Solids separation and pond systems for the
treatment of faecal sludges in the tropics. Lessons learnt and recommendations for
preliminary design. EAWAG/SANDEC, Dübendorf, Switzerland.
http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_ewm/downl
oads_ewm/solids_sep_and_pond_treatm.pdf *
Steiner, M., Montangero, A., Koné, D., and Strauss, M. (2002) Economic aspects of low-cost
faecal sludge management. Estimation of collection, haulage, treatment and disposal /reuse
cost, EAWAG/SANDEC, Dübendorf, Switzerland.
http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_ewm/downl
oads_ewm/FSM_cost_report.pdf *
WHO/UNICEF (2006) Meeting the MDG Drinking Water and Sanitation Target – The Urban
and Rural Challenge of the Decade. WHO/UNICEF Joint Monitoring Programme (JMP) for
Water Supply and Sanitation. Available:
http://www.who.int/water_sanitation_health/monitoring/jmp2006/en/index.html (provided
under Course 1 Unit 1 Assigned Reading)
* Provided on the I-LE for this course unit (Extra materials)
References (slide 2 of 2)
recent MSc theses at UNESCO-IHE
 Mwase, H. (2006) The potential of ecosan to provide
sustainable sanitation in emergency situations and to achieve
“quick wins” in MDGs, MSc Thesis, UNESCO-IHE Institute
for Water Education, Delft, The Netherlands
 Mayumbelo, K. M. K. (2006) Cost analysis for applying
ecosan in peri-urban areas to achieve the MDGs - Case
study of Lusaka, Zambia, MSc Thesis MWI 2006-10,
UNESCO-IHE Institute for Water Education, Delft, The
Netherlands.
 Vodounhessi, A. (2006) Financial and institutional challenges
to make faecal sludge management integrated part of ecosan
approach in West Africa. Case study of Kumasi, Ghana. MSc
Thesis WM 2006.05, UNESCO-IHE Institute for Water
Education, Delft, The Netherlands.
The first two are also available from the GTZ literature database:
http://www.gtz.de/en/themen/umwelt-infrastruktur/wasser/9835.htm