Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
Toward a framework for wastewater and stormwater management
This section develops a framework for wastewater and stormwater management
by first describing the problems facing communities without adequate sanitation.
This is to provide a background for the type of management that is required
to address the problems. The concept of integrated waste management is then
introduced and the wider issues, besides those of technology, are discussed.
A framework for wastewater and stormwater management is then outlined.
1. Problems facing communities without adequate sanitation
Inadequate sanitation facing a substantial proportion of the world’s
population is well documented (recent WSSCC figures indicate that we are falling
behind in providing adequate sanitation world-wide see http://www.wsscc.org/vision21/wwf/v21flyer.html
for details). The overview on each region in the Source Book provides a summary
of conditions in the regions. Many of those without sanitation are in rapidly
growing cities in developing countries, affecting the poor in general, though
the situation is not confined to these cases. Following the considerable effort
during the UN Decade of Water and Sanitation (1981 ’E1990) much discussion and
analyses have been undertaken to find the causes for the lack of success in
providing sanitation for all, and many ideas have been put forward to overcome
the problems. The Water Supply and Sanitation Collaborative Council (WSSCC), for
example, has prepared thematic papers on the subject (WSSCC, 1999a) in
preparation for developing a framework for future action, Vision 21: A shared
vision for water supply, sanitation and hygiene (WSSCC, 1999b).
The issues involved in providing sanitation for much of the world’s
population are complex. It is difficult to cover the technical, social, economic
and environmental dimensions in a brief space. It is also difficult to
generalise the setting or circumstances of these communities. Each has its own
physical, cultural and political setting. Nonetheless it is desirable to portray
the physical setting facing communities without adequate sanitation so that we
can gain a perspective of how the problems develop, and how communities have
responded to these problems.
In general these communities are located in an environment which has a
relatively high population density. Water supply may or may not be adequate in
either quality or quantity. In cases where water is supplied through pipes,
there are not the corresponding pipes for removing the wastewater generated. The
wastewater is simply allowed to flow by gravity through the natural drainage of
the landscape ending in low lying areas, water courses, lakes, groundwater
aquifers or the sea. The natural drainage carries stormwater run-off during
rainfall events, and during flood events stormwater mixes with wastewater, and
polluted water is spread over a much wider area than the drains. In addition
solid waste is also generally dumped into the drains or natural water courses
resulting in flooding at lower rainfall events. Water-borne diseases are
therefore endemic in these communities. The environmental conditions of the area
are degraded, because water containing decaying organic substances from sewage
and garbage give foul odour, the water is depleted of oxygen and is putrid.
Groundwater in the area is also generally polluted, because of the infiltration
of polluted water to the groundwater aquifer. The general physical environment
is as illustrated as Figure 1.1.
Figure 1.1: Urban settlement with high population density, sewage disposed to
drains, pollution of drains, streams, river/sea and groundwater
If the population density is very low, the environment has the
capacity to absorb the wastes generated and environmental degradation is
negligible. Water quality of streams, rivers and groundwater in this environment
is generally excellent. Figure 1.2 illustrates a very small population in a
natural forest setting. The natural processes involved in the assimilation of
the wastes are elaborated in Section 2 (2.2).
Figure 1.2: Small settlement in a natural forest