ENVIRONMENT AND ENERGY
43
Enhancing wastewater
collection treatment (Part 2)
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.
Extracted from United Nations World Water Development Report 2017
DEWATS and low-cost sewerage are naturally
complementary. DEWATS can also serve as a medium-
term solution pending the large-scale design of
centralised systems, and there is significant flexibility
on their use. Indeed, large-scale centralised wastewater
treatment systems may no longer be the most viable
option for urban water management in many countries,
due to high maintenance costs and resource needs.
Moreover, they often require large areas of land and are
too inflexible to meet the needs of rapidly expanding
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urban areas. This holds true for water supply and
wastewater infrastructure, rainwater collection and
drainage. DEWATS serve individual or small groups
of properties. They allow for the recovery of nutrients
and energy, save freshwater and help secure access to
water in times of scarcity. They may require less upfront
investment than larger, centrally piped infrastructures,
and are more effective in coping with the need to
scale up (or down) services to needs. However, they do
require individuals with a minimal amount of training to
take care of their operation and maintenance.
Through decentralised technologies, sustainable
neighbourhoods in cities could partly replace traditional
public systems. A challenge of DEWATS may be that local
communities need to accept that they live close to the
treatment facilities, so efforts must be made to make the
plants aesthetically acceptable. For this reason, systems
based on reed beds are often favoured.
DECENTRALISED STORMWATER MANAGEMENT
Decentralised stormwater drainage has a good potential
for ‘source control’ technologies that handle stormwater
near the point of generation. For instance, green roofs
Part of a centralised
wastewater treatment
plant in Germany.
August 2018 Volume 24 I Number 6
DECENTRALISED TREATMENT (DEWATS)
In addition to centralised wastewater treatment plants,
decentralised systems have also shown an increasing
trend. Many of the approaches to decentralised
wastewater treatment systems (DEWATS), pioneered by
organisations such as the Bremen Overseas Research
and Development Association (BORDA) and the
Consortium for DEWATS Dissemination Society, have
found their rightful place as a part of sanitation systems
for rapidly expanding urban areas and also for certain
isolated communities where conventional sewerage is
precluded on economic grounds.