The
330 km3 of municipal wastewater produced globally each year is enough
to irrigate 40 million hectares – equivalent to 15 per cent of all
currently irrigated land – or to power 130 million households through
biogas generation, concluded a UN report released on October 22.
The
report, titled "Sanitation, Wastewater Management and Sustainability:
From Waste Disposal to Resource Recovery," published by the United
Nations Environment Programme (UNEP) and the Stockholm Environment
Institute (SEI), gives an overview of current knowledge and practice in
wastewater management and demonstrates the opportunities for recovery
and reuse of the resources found in domestic waste flows: in
agriculture, energy production and other applications.
Globally
produced municipal wastewater contains the equivalent of 25 percent of
the nitrogen and 15 per cent of the phosphorus applied as chemical
fertilizers. It can also carry large amounts of iron, chloride, boron,
copper and zinc. In just one day, a city of 10 million flushes enough
nitrogen, phosphorus and potassium to fertilize about 500,000 hectares
of agricultural land. A more circular approach to wastewater would
significantly contribute to achieving the recently adopted 2030
Sustainable Development Agenda. In addition to accelerating progress
towards the Sustainable Development Goal 6 of ensuring water and
sanitation for all, reusing and recovering wastewater resources could
bring vast economic and social benefits, advancing many other goals. For
example, in India, the World Bank estimated that adequate sanitation
could bring savings of US dollars 54 billion annually through cutting the costs
of healthcare and water provision. In the Lao capital of Vientiane
enough biogas could be produced from wastewater to allow 10,000 km of
bus drives per day. The daily value of nutrients in wastewater produced
by Indian coastal cities has been estimated at US dollars 17.5 million. Another
study calculated that elements found in urban wastewater in the United
States, including silver and gold, had an economic value of US dollars 280 per
tonne of sludge.
The UNEP/SEI report recommends that sustainable
sanitation and wastewater management systems be created that are
technically, culturally and institutionally appropriate, economically
viable and resilient to disasters. The study also demonstrates how
cultural and emotional challenges including the "yuck factor" - can be
resolved. For example, in Ouagadougou, Burkina Faso, urine was renamed
and repackaged after storage, in order to clearly show that the product
had changed from a waste product to a safe fertilizer. In El Alto,
Bolivia, herbs were added to the treated urine as a colouring and
reodorizing measure. In Hölö, Sweden, low population-density has made
centralized wastewater treatment financially unfeasible, so a unique
cooperation between the utility, the local authorities, the research
society and the farmer community developed a cost-effective recycling
policy that produces fertilizers and reduces pollution using a mix of
infrastructure, patented black water technology, social awareness and
certification.
Other innovative solutions of reusing wastewater,
highlighted by the report, include using duckweed to clean water in
Niger, using sludge as construction filler material in Sweden and even a
proposal to use the organic waste matter for producing protein feed for
livestock through the controlled harvesting of insects.
UNEP – United Nations Environment Programme
SEI – Stockholm Environment Institute