Environmental Engineering Reference
In-Depth Information
BNR plants operation, while the waste stabilization ponds are very scarcely tested,
mainly in terms of effluent quality.
• Potable water from the city's consumer points - this program has the aim to control the
potable waterat the consumer end and to ensure that no signs of pollution are present
in the distribution network. It is executed on a regular basis at selected locations along
the distribution network and tests basic parameters.
• Urban drainage runoff (storm water drainage channels) - this program aims at the
evaluation of urbandrainage water quality at two main discharge channels in the city.
The frequency of sampling is relatively low and is not event orientated. More details
regarding this program are given in point 5.
• Surface water pollution control - this program aims at determining the natural water
quality at locationsrelated to effluent and storm water discharges. It has the purpose to
control the impact of such discharges independently from DWR, and includes about
36 sampling stations. In terms of number and location (network design), the sampling
stations cover the basin well, within the city of Harare urban areas. The frequency of
sampling is not high and the data collected could be used as indicative information
regarding the status of water quality, rather than reliable information for supporting
the decision-making process.
In general, the city's monitoring sub-programs are covering all aspects of the water
quality spectrum. In terms of network design, they are well developed, except for
industrial effluent discharges, where the capacity is not enough in order to control all
major polluters. The parameters observed cover basic pollutant constituents only. There
is an urgent need to upgrade the city's laboratory, in order to include in the monitoring
process the testing of toxic elements as well as blacklisted parameters.
The DWR monitoring program, with respect to the Lake Chivero basin concentrates
on surface water quality only, and forms part of the national grid for water quality
assessment. It contains about 20 sampling points at characteristic locations, the vast
majority of which coincide with sampling point locations of the municipal program. It
should be noted that the scope of the DWR monitoring program provides information
regarding the general status of the water quality of the basin. These objectives need to be
reformulated in the light of the requirements of the recently adopted strategy of pollution
control - the “polluter pays” principle. It is advisable to update the existing program, so
that it provides room for the implementation of auditing functions of DWR, with respect
to permit provision and control of its implementation. It would require a much wider
scope in terms of sampling point locations, corresponding to the number of permits
issued, but the frequency of sampling could be lower, depending on each specific case.
During the year 2000, the program included a rather large number of parameters tested,
which might not be so relevant to the data analysis process. At the same time, ammonia
was not included in this list. The importance of this parameter could not be
overemphasized in view of the eutrophic conditions in Lake Chivero and the massive fish
death reported by Moyo (1997). This fact shows the need of the regular overview and
revision of existing programs in order to have an optimum solution at an economically
effective and sustainable cost.
A common drawback of both programs is the lack of reference points for each
separate river, which could also be used for the periodic evaluation of background
