Environmental Engineering Reference
In-Depth Information
Just upstream of point E, a few small-scale industries are located, including a dairy
processing plant and a meat cold-storage facility. The last two have their local wastewater
treatment plant consisting of waste stabilization ponds system (WSPS). It is poorly
maintained, the screens and grit chambers are clogged, and aquatic vegetation is invading
the ponds, in addition to a large amount of sludge accumulated. Dzalanyama Forest
Reserve The abstraction point for the LWBWSTP is located about 1 km downstream of
this area. The plant consists of a conventional treatment scheme, where coagulation by
alum is provided, followed by sedimentation, rapid sand filtration and disinfection by
chlorine.
2.4
Methodology
Sampling points were established at several locations along the Lilongwe River and its
tributaries in places where the conditions allowed accessibility for sample collection. The
locations are shown in Figure 11.3 and were given identification symbols from A to G.
Pont A was located downstream the confluence of the Lilongwe and Katete Rivers and
was selected as a control point. Points F, D and G were located at the bridges on the
corresponding rivers, and point E was located near the abstraction structure, collecting
the river water to be treated in the LWBWTW. The choice of sampling locations was
related to suspected sources of pollution. Sampling was carried out twice a month on a
fortnight basis for four months from the month of November to February 2001. Several
additional samples were collected during January 2002. Three grab samples were
collected at different depths to form a depth-integrated representative sample at each
sampling point. Samples were collected and preserved as required and recommended in
the Standard Methods (1994). During sampling, efforts were made to avoid areas that
showed evidence of localized stagnation, erosion and other visible disturbances.
Lilongwe Water Board provided equipment for the
