Environmental Engineering Reference
In-Depth Information
CHAPTER 11
Diffuse pollution of urban rivers - case
studies in Malawi and Swaziland
R. Hranova, S. Nkambule & S. Mwandira
ABSTRACT: Diffuse pollution of two urban rivers has been presented in
the light of two independent case studies executed during the rainy season
of 2001. The first examines and evaluates the spatial river water quality
variation (pH, EC, TC and TDS, BOD and COD) of Lilongwe River and
tributaries, in its upper reaches, before it enters the capital city of Malawi
- Lilongwe. The river is the major source of potable water supply of the
city. Different types of land use patterns have been associated with the
sampling locations chosen. Results show a considerable level of pollution
with respect to TC only, associated mainly with informal settlements
along the riverbanks and, possibly, with effluents from food industries.
The second case study examines the spatial water quality variation
(BOD
5
, ortho-P, nitrates, sulfates, ammonia, chlorides, DO, EC, pH, T,
TSS, TC and FC) of Mbabane River and tributaries, which flows along
the capital city of Swaziland - Mbabane. It collects the runoff and
municipal effluents of the City, and provides water for direct domestic and
agricultural use of the rural population, living downstream of the city.
Results show that the major source of diffuse pollution is associated with
municipal effluent discharges due to the malfunctioning of the treatment
plant. The major parameters of concern are nutrients, organic and
bacteriological pollution. However, 20 km downstream the city, the water
quality improves due to additional discharges by tributaries mainly, and
partial self-purification.
1 INTRODUCTION
Urban development patterns in the Southern African region, and in many other
developing countries, are characterized by rapid population growth and the formation of
informal or semi-formal settlements without the necessary provisions for adequate
infrastructure, and often without a basic water supply and sanitation structures. In
numerous cases the existing wastewater treatment facilities are neglected and suffer from
chronic deficiencies in the operation and maintenance practice, due to insufficient
funding and lack of trained personnel. All these, create conditions for severe public
health hazards, which are usually recognized by official authorities. However, the hazards
associated with the pollution of the environment and the available water resources are not
widely recognized and addressed. In numerous cases, informal settlements are formed in
