Environmental Engineering Reference
In-Depth Information
and appropriate steps taken to reduce the impact of urbanization. The only way to avert
ecological disasters is to ensure that high quality effluent is discharged into receiving
water bodies. Activities in one area of the watershed are correlated to the environmental
imbalance of the other and such relationships are independent of administrative and
political boundaries. Considering all these factors, the scope and aims of this chapter is
to:
• Present background information with respect to diffuse pollution aspects in formal
urban areas;
• Present an example of urban storm water quality evaluation and pollution loads
estimation, and discussdifferent aspects of this procedure in the light of the existing
conditions in the region. A case study in Harare, Zimbabwe has been used for this
purpose. The study was limited in terms of time, manpower and support facilities, thus
the results obtained reflect a relatively short time period and should be regarded as a
preliminary survey, which indicates the present storm water quality status and could
serve as a basis for a further research of storm water quality and its impact in the area.
• Discuss implications of polluted urban drainage on the management practice of local
authorities andput forward recommendations for future developments in this direction.
2 DIFFUSE POLLUTION FROM URBAN STORM WATER RUNOFF
2.1
Sources of pollution
Non point source pollution and its evaluation and abatement are probably the most
pervasive and ubiquitous water quality problems. It is not the land itself or land use per se
that causes pollution. Various
boundary inputs and polluting processes and activities that occur on the land could
cause pollution. The most common inputs and processes that are the cause of urban
diffuse pollution are:
• Accumulation of dry atmospheric deposits (dust) and street dirt and subsequent wash-
off from impervious surfaces (roofs, parking slots, streets, roads, etc.). The sources of
the accumulated pollutants are:
Dry atmospheric deposition;
Streets refuse accumulation, including litter, street dust and dirt and organic
residues from vegetablesand animal population;
Traffic emission;
Erosion of pervious lands, impervious poorly maintained covers and construction
related activities;
• Discharge of pollutants, such as oil, paint, detergents and other household/commercial
solvents andchemicals, into the drainage systems;
• Application, storage and wash off of chemicals, raw materials and other pollution
containing materialsfrom industrial enterprises;
