Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
1.2.2 Problems with sewers
The total cost of operating a water-flushed toilet is nearly 8 times that of
a pit latrine ($5,885 to $750) in Botswana. Endemic sewer blockage could result
because guidelines for sewer operation usually call for 50 l/c/d to keep waste
flowing. This sums up to 7.5 m3 per month, just to keep the sewer flowing. That
amount alone is more than most families consume in a month in Gaborone (national
per capita water use is 175 litres /day, and the poorest half of the families
use about 60 l/c/d). By Africas standard this is a high level of service, yet
it is hardly adequate to operate water-bone sewage system for half of the
population. It is perhaps obvious sewerage systems may not be generally
sustainable in most African cities. In South Africa some 31% of the urban
population have inadequate sanitation. Most of its communities desire raw
waterborne sewage systems as their first choice, but adequate funds are not
available to provide this system to all in need of sanitation facilities. The
country has therefore developed increasing interest in alternative technologies,
e.g. settled sewerage systems that provide for flush toilets but have lower cost
In Africa about 80% of water consumption of those connected to the sewer ends
up discharged into the municipal sewer, but in Gaborone, the return flow is
50-65%. This is why it is feared that if poor people are added in great numbers,
the resultant reduced sewer flows could upset the operation of the sewer system
because of too little water to keep waste flowing. The ultimate solution perhaps
lies in the pursuit of lower cost alternative technologies that suit this water
short Region which is much drought prone.
A full waterborne sewerage system was installed by Ghana Water Sewerage
Corporation in central Accra with World Bank assistance and completed in 1973,
covering 1000 ha and involving 28.5 km of sewers. It is a classic example of
unaffordable services by prospective beneficiaries. The system never worked
well, because of narrow and crooked streets and below standard housing and
plumbing that exist predominately in central Accra hampered connection to the
system (Poster et al., 1997). Table 1.11 shows that only 6.5% of the available
connections were utilized. The old agenda of supply driven sanitation system
wasted immense investments. Inappropriate designs, neglect of user requirements,
inadequate maintenance, and ill-equipped operating agencies create continuous
drain on government resources, and a disincentive to governments and donors
contemplating further sector investment. Users become disillusioned when
promised improvements fail to materialize, and refuse to pay for inadequate
services which leads to further deterioration.
Table 1.11: Sewerage systems not adequately patronized by intended
||No of year since commissioning sewerage
|| No. or % of connections made
||System capacity (No. of available
||130 nos.( 6.5%)
||10 years (16 years in 1997)
|| 10% (60%)
|Source: Wright, A.M. (1997)
The existing waterborne sewerage schemes in Greater Lagos are in various
states of disrepair and operational conditions and are of three categories:
- Housing estates - have the larger systems - Festac, Abesan, Oke-Afa, Amuwo
Odofin, Iponri, Alausa Secretariat, Victoria Island, Lagos Island.
- Institutional and commercial schemes - generally much smaller and a total
number of 65 separate schemes have been constructed.
- Only a small number of industries have sewerage schemes and treatment
plants although the Federal Regulations require this provision: Lever
Brothers, Apapa, WEMABOD plant, Ikeja.
Festac (Festival of Arts and Culture) Town, a satellite of Lagos municipality,
is a "new" town built to house the participants in the World Black
Arts Festival which Nigeria hosted in 1977. Thereafter it was settled. It is
situated on the Lagos-Badagry road which links Nigeria with the Republic of
Benin, on a land are of 770 ha. There were three communities with 4220, 4053
and 2052 dwelling units, while 1000 units were added later. Some 68% of the
inhabitants belong to the low-income group (by designation, but many of them
are anything but low-income group), 11% middle- and 21% high-income group. The
revised plan for the town provided for a total of 61,600 persons.
The sewerage system was designed to serve the whole population of the town.
Altogether there are 72 km of sewerage pipes, 24 km of open drains, 81 km of
storm sewers (drain pipes), while 112 km constitute the water supply network.
There are 7 pump stations, and the wastewater from the whole town is conveyed to
a nearby settlement known as Sattellite Town where the treatment plant is
Abuja, the new Federal Capital of Nigeria is designed to be served entirely
by sewerage system. On account of sharply varying topography, however, there
would be some four central sewage systems (Pers. comm. Emmanuel I. Ovbiebo,
1999). The system in place now is the one serving the central city of 200,000,
in the Wupa drainage basin. It is designed to have 5 treatment plants, which are
under construction. The temporary plant now in use has capacity to serve only
50,000 people. Wastewater design flow is 210-230 l/c/d, but the actual flow is
Topography favoured gravity flow at Abuja with an elevation of 495 m. The
landscape slopes gently towards Abaji, one of the satellite towns at 300m, such
that a lift station is required only near the plant. The sewer pipes are laid
along the lowest river valleys, parallel to the main river course, and such
valleys were designated green belts. But already, developers are encroaching on
the green belts and tampering with the manhole and sewer pipes.
The satellite towns of Gwagwalada, Sheda, Abaji and Yanyan of the Federal
capital of Abuja have central sewerage systems designed but not yet constructed.
At the moment they use septic tanks which would be disconnected, and filled up
with laterite when the sewerage system is ready. The question is why cant the
septic tanks be sewered instead of wasting such huge investments?
Only 5% of the inhabitants of Lagos Metropolis is connected to sewerage and
associated sewerage treatment plants which do not treat the sewage to acceptable
standards, and are poorly maintained and operated. The Federal Government 1004
Housing Estate sewerage system is served by a package treatment plant. Breakdown
of various electrical and mechanical components and lack of funds for adequate
maintenance, sees the bulk of the wastewater that enters the plant by gravity
sewers or discharges from vacuum trucks, bypass the treatment units and
discharge untreated direct to the lagoon.
The district has one of the largest existing sewerage schemes within metropolitan
Lagos, the Victoria Island sewerage scheme' though it has never been commissioned
or used. It was designed in the early 1970s to cover most of Victoria Island.
The following data summarize the stage of its completion as at December 1978
when all works appear to have ceased as the contractor abandoned site without
notice, and never returned.
- total length of sewers laid (100 mm, 150mm 200mm, 250mm, 300mm diameter
asbestos cement sewer) representing 40% completion : 23,780 metres
- total number of manholes constructed : 341
- total depth of manholes constructed representing 31% completion: 476
Total wastewater flows to Lagos lagoon in 1995 and by 2010 have been
estimated as in Table 1.12.
Table 1.12: Estimated wastewater flows from metropolitan Lagos to
the lagoon in 1995 and 2010
|Total wastewater (m3/dy)
||811,300 (115.7 l/c/d)
|Source: Lagos State Ministry of Environment
and Physical Planning (1996)