Environmental Engineering Reference
Designing Sustainable Wastewater Reuse
Systems: Towards an Agroecology
of Wastewater Irrigation
Philipp Weckenbrock and Graham Alabaster
1 Introduction: The Nexus of Wastewater Irrigation
Water is one of the major elements on our planet ' is surface and inextricably linked
with life. Of all the earth
is water, only 1 % is accessible as groundwater (0.7 %) or
surface water (0.3 %) (Gleick 1996 ). Even today, many regions of the world, in
particular parts of subSaharan Africa, south and southeast Asia and Latin America
are facing water scarcity (Molden 2007 ). And in a global context of industrial
development, changing dietary patterns, rising incomes and climate change, pres-
sure on these accessible freshwater sources is increasing (UNDP 2006 ; Bates et al.
2008 ; Pachauri and Reisinger 2008 ; McIntyre et al. 2009 ).
Agriculture is by far the sector with the highest water requirements accounting
for approximately 70 % of the global freshwater withdrawals (Rosegrant et al.
2009 ). However, in a competition about scarce freshwater resources with house-
holds and industry, farmers often lose out (World Resources Institute 2000 ; Jia et al.
2006 ; Molle and Berkhoff 2006 ).
While many sources of irrigation water are declining, wastewater availability is
more likely to increase. According to the United Nations Population Division, most
future population growth is going to take place in urban areas of developing
countries, both large and medium-sized cities and the smaller urban centres (UNPD
2007 ). One of the implications of this growth is increasing volumes of wastewater.
Dealing with this wastewater presents planners with a great challenge. Although
progress has been made with regard to the Millennium Development Goal (MDG)
on providing safe drinking water, progress on the MDG on safe sanitation has been