Decentralized Faecal Sludge Treatment (DEFAST) and Reuse

Kampala Sanihub project
Decentralized Faecal Sludge
Treatment (DEFAST) and
Reuse
Like many other developing countries, faecal sludge
management in Uganda has been given less attention by
researchers and authorities. The first and largest faecal
sludge treatment plant in Uganda is less than 8months in
operation and still cannot handle all the collectable faecal
sludge in Kampala. Some areas are still quite distant from
the treatment plants which leads to high emptying costs.
The high traffic density on roads leads to loss of time in
transportation which is an economic loss to entrepreneurs.
The situation is worse in
other fast growing towns
with limited space left
for constructing new pit
latrines and yet there
are no faecal sludge
treatment options. Some
municipal authorities
with Waste Water (WW)
stabilisation ponds do
not accept dumping of
faecal sludge (about
10-100 times more
polluted than WW)
due to fear of failure
of some mechanisms.
Some growing towns
with no treatment
plants resort to illegal
dumping in dug pits.
Loading sludge with a diaphragm pump
Compiled by: Osbert Atwijukye, Sanitation Engineers Water For People.
Reviewed by: Cate Zziwa Nimanya, Country Director Water For People Uganda, Achiro Brenda Muthemba, Programme Manager
To solve the problem of overloading the existing plants, illegal dumping, long distances and
saving on the capital costs of other new plants, there is need to manage waste close to source i.e
communities and households. This may be possible by introduction of Decentralised wastewater/
Faecal Sludge Treatment System (DEWATS/ DEFAST) in different divisions of the city.
THE DEFAST MECHANISM
Units
• Inlet/screening: to remove non biodegradable
solid substances passing through gulper screens
• Sedimentation: For dewatering, separation and
bio digestion.
• Anaerobic Baffled Reactor: made up of two
tanks and will have a sludge layer to support
growth of anaerobic microorganisms which degrade
organic pollutants. At this stage we expect highest
removal efficiency of the organic pollutants.
• Anaerobic Filter: Will have two tanks all packed
with filtration media to about 2/3 full. The media
is expected to support the growth of biological film/
layer that will trap some pathogens, Suspended
Solids and other remaining pollutants.
• Aerobic Planted Gravel Filter: The flow will
be lateral and the unit removes smell and color
plus some pollutants both organic and inorganic.
• Holding tank: This is for polishing the effluent
and temporary storage before discharge.
• Other accessory parts will include; the sludge
drying bed and biogas collection.
• Drying bed: For further dewatering of digested
sludge from the biodigester and ABR. Its roofed
with clear plastic material to prevent rain.
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KAMPALA SANIHUB PROJECT
The pilot plant has a capacity of 500l of
faecal sludge per day and has been in
operation for 8 months. The efficiency in
terms of BOD, COD removal among others
is over 85%, though final effluent has not
yet met the discharge requirements for
Uganda.
Table Showing Results from first sampling compared to national discharge standards.
National
Discharge
Standards
1.IF1
2. BD1
3. ABR1
4. AF1
5. PGF1
7.89
7.59
7.77
8.1
8.13
6.0-8.0
TDS (mg/L)
13950
13250
10600
8650
4590
1200
TSS (mg/L)
35967
20305
4489
1877
792
100
COD (mg/L)
20570
19580
5748
3535
1886
100
BOD (mg/L)
12100
11250
3500
2150
1180
50
NO3-N (mg/L)
20.5
45.8
38.7
33.8
13.2
10
T-PO4 (mg/L)
342.8
326.3
95.8
58.9
31.4
10
Faecal Coliforms
(CFU/100L)
46,400
29,600
11,200
34,300
1,930
Sample source
Parameter
Ph
3-
10,000
1IF-influent,2 BD1-Biodigester, 3ABR1-Anaerobic baffled reactor, 4 AF-Anaerobic Filter, 5.PGF1-Planted gravel filter.
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KAMPALA SANIHUB PROJECT:
NO3-N (mg/L)
20.5
45.8
38.7
33.8
13.2
10
T-PO43- (mg/L)
342.8
326.3
95.8
58.9
31.4
10
Faecal Coliforms (CFU/100L)
46,400
29,600
11,200
34,300
1,930
10,000
1IF-influent,2 BD1-Biodigester, 3ABR1-Anaerobic baffled reactor, 4 AF-Anaerobic Filter, 5.PGF1-Planted gravel
filter.
COD
sampling location
TSS
Concentration (mg/l)
Sampling location
concentration (mg/l)
concentration(mg/l)
BOD
sampling location
This will be the area of concentration in theyear 2014/2015. We will basically focus on producing
animal feeds through breeding of black soldier flies in faecal sludge, vermicompost using tiger
worms and lastly will be energy recovery.
Experiment Introducing Tiger worms to FS
Expected Benefits, Threats, Target market and problem solution;
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For more information:
Contact, Water For People Uganda
Plot 9 Olumi Close, Kitante, www.waterforpeople.org, www.sanihub.blogspot.com, cnimanya@waterforpeople.org
KAMPALA SANIHUB PROJECT