Environmental Engineering Reference
In-Depth Information
lagging behind (Gleick et al.
2009
). Even if this MDG should be reached, 1.8
billion people would still be without safe sanitation by 2015 (UNDP
2006
; Gleick
et al.
2009
). While it is already a great challenge to remove it from settlement areas,
treatment facilities for this wastewater often do not exist. This means that most of
the world
is wastewater is released into the environment without any treatment.
Obviously, there are great differences in rates of wastewater treatment between
countries with different levels of economic development: a recent study estimates
that
'
high-income countries on average treat 70 % of the generated wastewater,
followed by upper-middle-income countries (38 %), lower-middle-income coun-
tries (28 %), and low-income countries, where only 8 % of the wastewater gen-
erated is treated
'
(Satoa et al.
2013
: 1). The main reason for these low rates of
wastewater treatment is the high cost of conventional treatment facilities.
Low wastewater treatment rates imply health and environmental risks and an
enormous waste of resources.
'
The
sanitation systems being introduced in many countries in the South are
inadequate because they are based on a linear, industrial world-view in which sewage is
disposed,
'
modern
'
rather than recycled. The system involves unidirectional
flows of
food and nutrients from farms in the countryside to the city, which are then converted to
sewage and dumped, treated or untreated, into rivers or directly into the sea. The lost
nutrients are never returned to the land, and instead, combined with soluble synthetic
fertilizers running off agricultural land, result in eutrophication and the formation of toxic
algal blooms in freshwater and marine environments (Jones et al.
2010
: 5).
'
somewhere
'
Box 1: What is wastewater?
Urban wastewater can be one or the combination of the following.
Domestic ef
uent consisting of blackwater (excreta, urine and associated
sludge) and greywater (kitchen and bathroom wastewater)
Water
from commercial establishments and institutions,
including
hospitals
Industrial ef
uent
Stormwater and other urban runoff
Normal municipal wastewater consists to 99 % water with only 1 %
dissolved solids.
Sources: Mara and Cairncross (
1989
); van der Hoek (
2004
)
In this context of ever increasing volumes of wastewater on the one hand and
irrigation water scarcity and declining soil fertility on the other, an estimated 200
million farmers worldwide have been using wastewater to irrigate their
fields
(Raschid-Sally and Jayakody
2008
). This practice is thousands of years old and
exists in many parts of the world (UNEP and GEC
2004
; Raschid-Sally
2010
). In
spite of the global signi
cance of wastewater irrigation, the topic has remained
largely invisible to planners and decision-makers. This is illustrated by the
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