Temporal and Spatial Physicochemical Water Quality in Blantyre Urban Streams

Abstract

Water samples collected from the five major streams in Blantyre city, viz., Limbe, Naperi, Mudi, Nasolo and Chirimba, were analysed for phosphates (PO₄^3-), nitrates (NO₃^-), sulphates (SO₄^2-), biochemical oxygen demand (BOD), suspended solids (SS), pH, oil and grease, and electroconductivity (EC). The samples were collected in both dry and rainy seasons of 2006 and analysed using standard methods. Results showed that the impairment of water quality in a stream depended on the type of industry in its vicinity and state of sewerlines which conduit the wastewater from the source to the designated Blantyre City Assembly wastewater treatment plants. pH, EC, SO₄^2-, oil and grease were within the acceptable limits set by Malawi Bureau of Standards and World Health Organization for drinking surface water. However the concentrations of PO₄^3-, NO₃^- and BOD were above the maximum allowable limits set by the regulatory bodies. The results suggested that effluents from industries in the city had high potential of polluting the water bodies and could result into gross impairment of water quality in the receiving streams. It is therefore recommended that Blantyre City Assembly and other environmental regulatory bodies such as Environmental Affairs Department and Water Resources Board should be more aggressive and effective in environmental monitoring, assessment and enforcement of environmental laws and regulations so as to preserve the water resource from further degradation.

Keywords: Physicochemical water quality; Blantyre