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ENVIRONMENT AND ENERGY
Enhancing wastewater
collection treatment
(Part 1)
Examining a number of options and responses for
enhancing wastewater collection and treatment, with
a special emphasis on the advantages of low-cost
decentralised systems.
Reed beds are often
included in both centralised
and decentralised
treatment systems.
Extracted from United Nations World Water Development Report 2017
SEWERS AND WATERBORNE SANITATION
The importance of sewerage as a means of transporting
waste materials away from human sources and other
economic activities is well documented, as are its impacts.
Despite more ecologically acceptable alternatives,
waterborne waste disposal remains the prevalent method
for sanitation and for evacuating wastewater from
domestic, commercial, and industrial sources.
Other sanitation options, such as on-site systems, are
perfectly suited to rural areas and low population density
settings, but are expensive and nearly impossible to
manage in dense urban environments, aside from the
most developed economies. In many cases, significant
challenges still exist in the collection and transport of
faecal sludge from on-site facilities.
According to a study in the city of Kampala, more
than 80% of the users of such facilities had no
experience with emptying personal latrines and over
60% of the collected septage came from institutional
and commercial sources. The number of households
connected to sewer systems correlates (to a greater or
lesser extent) with the connections to a water supply,
although always in much lower proportions.
Various reports clearly show that, globally, the
July 2018 Volume 24 I Number 5
proportion of people connected to a sewer system
(60%) is higher than had been previously assumed.
Even in rural areas where the number of connections is
typically low, there is a significant share of people with
a connection to a sewer system (16%). This contradicts
previously published estimates which quoted 10%.
Many large cities in developed and transitioning
economies have extensive sewerage systems, some of
which are still functioning effectively some 100 years
after construction. London still relies on trunk sewers
constructed in the Victorian era as part of the reticulation
used today. Complications arise with increasing
urbanisation and excessive connections to sewer
systems that surpass their original design capacity.
Ageing wastewater collection systems generate a
number of problems, including corroded concrete,
cracked tile, collapse, and clogging. Addressing these
problems can be expensive.
LOW-COST SEWERAGE
Driven by the high costs of conventional sewerage,
methods of low-cost sewerage were conceived in
response to the challenges faced by most
developing countries: low tariffs combined with
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