Newsletter and Technical Publications
<Sourcebook
of Alternative Technologies for Freshwater Augumentation in Africa>
2.3 WASTEWATER TREATMENT TECHNOLOGY AND REUSE
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Waste Stabilization Ponds
Technical Description
Waste
stabilization ponds consist of
(i) preliminary treatment stages
which include a screening chamber for the removal of large solids, a
grit chamber for the removal of grit and other inert materials, and a
flow recording system;
(ii) facultative ponds, which are
responsible for the removal of BOD5 largely through sedimentation and
biological degradation; and,
(iii) maturation ponds, which are
responsible for the removal of pathogens through exposure of the
pathogens to conditions inhospitable to the microorganisms.
Where
the ponds are expected to treat "strong" wastes, anaerobic
pretreatment ponds may be installed upstream of the facultative ponds.
Extent of Use
Ponds are extensively used in
Africa for the treatment of urban waste.
Operation and Maintenance
At the pond edge, maintenance
involves the removal of grasses to limit mosquito breeding habitat,
plugging holes caused by birds and rodents, and maintaining pumps were
necessary.
Level of Involvement
Municipal artisans or technicians
of similar qualification and/or experience are required to operate and
manage these facilities.
Costs
This technology
is low in cost in comparison with other treatment systems. Suitability
Ponds are suitable in most countries of Africa.
Effectiveness
of the Technology
Ponds are effective in removing BOD and
suspended solids.
Environmental Benefits
This technology is not capable of
removing nutrients, which may lead to the enrichment of the receiving
waters (eutrophication).
Advantages
The
technology is effective in removing BOD at low cost.
Disadvantage
Ponds demand a large land area and cannot remove nutrients.
Cultural Acceptability
Residents complain of smell
if homes are built too close to a poorly operated and maintained
plant.
Further Development of the Technology
Ponds
work well but need more research to improve design efficiency and
enhance nutrient removal capabilities.
Information Sources Standard textbooks and more
specifically work by Marais (South Africa) and Mara (Zambia). |
Wastewater recycling and reuse technologies fall into three major
classes:
- Direct reuse
- Indirect reuse
- Internal reuse (described under "Mining and Industry",
below)
These three classes have different technical descriptions, extents of
use, and operation and maintenance requirements, but are otherwise
similar. The technical descriptions for the different wastewater treatment
systems are given in the text boxes below. Because these are well-known
technologies, numerous engineering texts exist which detail aspects of
their design, construction and operation. Standard text books should be
referenced for such detailed descriptions.
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