Africa Water, Sanitation & Hygiene Africa Water & Sanitation & Hygiene Nov-Dec 2017 | Page 32

Sanitation
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posing health risks to farmers and to eventual con-
sumers of the agricultural products. Available tech-
nologies allow removal of almost all contaminants
from wastewater, making them suitable for every use.
The WHO Guidelines on Safe Use of Wastewater in
Agriculture and Aquaculture and the Sanitation Safe-
ty Planning approach provides a comprehensive fra-
mework to ensure that health risks are managed to
protect public health. 9
Recovery of energy and biofuels from biosolids. The
new Sewerage Act of Japan of 2015 requires sewage
operators to utilize biosolids as a carbon-neutral form
of energy. In 2016, 91 wastewater treatment plants
recovered biogas for electricity and 13 produced solid
fuels. A leading example is the city of Osaka, which
produces 6,500 tonnes of biosolid fuel per year from
43,000 tonnes of wet sewage sludge for electricity
generation and cement production. 10
Farming in a semi-desert with water and nutrients
from sewage in Egypt. Sohag Governorate is a se-
mi-desert region in central Egypt with around 4.5
million inhabitants. A two-year experiment in a farm
outside the city of Gerga in Sohag demonstrated the
potential benefits of reusing treated sewage was-
tewater to irrigate and fertilize crops on otherwise
dry and infertile soils, simultaneously relieving pres-
sure on scarce water resources and helping to meet
growing demand for food. 11
7 million people in the state of Paraná, Brazil. Since
2002, agricultural use has been the final disposal me-
thod for the sewage sludge. The treated sludge has
been used for green manure crops, mulberries, rye,
coffee, sugarcane, barley, citrus, beans, corn, soy-
beans, grass and eucalyptus and pine reforestation.
One aspect of the treatment at the plant is disinfection
of sludge through prolonged alkaline stabilization. In
this process, the sludge’s pH is raised to 12 by adding
large quantities of lime. This means that the treated
sludge can act as a soil acidity corrector, representing
further savings for the farmers. 12
The Gulper and Vacutug, East and Southern Africa.
In densely populated urban areas, emptying latrines
safely and efficiently is a challenge. Small enterprises
often meet the demand for latrine-emptying servi-
ces, bridging the gap between household/neighbour-
hood human waste storage and municipal treatment
plants. In Dar es Salaam, Tanzania, some firms use
a manually-operated pump called ‘The Gulper’. This
is basically a hand pump that fits on top of a perma-
nent pipe rising out of a latrine pit, and lifts waste out
of the pit and into a container to be taken away for
processing. In many cases, private contractors run
collection services, taking the waste away to muni-
cipal treatment works on a regular basis. Similarly, in
Maputo, Mozambique, an engine-powered ‘Vacutug’
machine empties shallow pit latrines. 13
Reuse of sewage sludge in agriculture, Paraná Sta-
te, Brazil. . Sanitation Company of Paraná (Sanepar)
runs 234 wastewater treatment plants serving over
9 UN-Water: World Water Development Report 2017: ‘Wastewater: An untapped resource’: http://www.unwater.org/publications/publications-detail/
en/c/853650/
10 UN-Water: World Water Development Report 2017: ‘Wastewater: An untapped resource’: http://www.unwater.org/publications/publications-detail/
en/c/853650/
11 Extract from UNEP and SEI (2016): ‘Sanitation, Wastewater Management and Sustainability’: https://www.sei-international.org/mediamanager/
documents/Publications/SanitationWastewater&Sustainability-Chapter9-Case-studies.pdf
12 Extract from UNEP and SEI (2016): ‘Sanitation, Wastewater Management and Sustainability’: https://www.sei-international.org/mediamanager/
documents/Publications/SanitationWastewater&Sustainability-Chapter9-Case-studies.pdf
13 WaterAid (2014): ‘The urban sanitation business’ blog: http://www.wateraid.org/news/news/the-urban-sanitation-business
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Africa Water, Sanitation & Hygiene • November - December 2017