Assessment of the impact of wastewater treatment plant discharges and other anthropogenic variables on river water quality in the eThekwini Metropolitan area.
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Date
2013
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Abstract
On a global scale the deterioration in riverine water quality is of great concern since water is
one of the most valuable and essential resources that forms the basis of all life.
For South Africa, the declining water quality is of even more importance since the country is
located in a semi-arid part of the world with scarce water supplies. The quality of water in
many rivers in South Africa continues to deteriorate at unprecedented rates, which affects its
availability and use. This situation is quite the same for rivers in the eThekwini Metropolitan
Area which is located in Kwazulu-Natal, a coastal province of South Africa.
This study assesses the qualitative impact of wastewater plant discharges from the
uMhlatuzana; Northern and KwaMashu Wastewater Treatment Works, on the uMhlatuzana
River; uMgeni River and uMhlangane River, respectively. Samples were collected from
identified points upstream and downstream of the wastewater discharges and the results were
analysed in terms of the t-test statistical technique to identify any significant change in water
quality between the upstream and downstream sites. In addition, the samples collected were
analysed for physico-chemical and microbiological parameters as respects compliance with
the Target Water Quality Guideline Range for aquatic ecosystems (DWAF, 1996); as well as
in comparison with the general requirements for purification of wastewater (DWAF, 1984).
The results from the t-test statistical analyses indicated that there was significant difference
between the upstream and downstream water quality for the following parameters and sites:
pH and permanganate value at the uMgeni River sampling sites; for dissolved oxygen at the
uMhlatuzana and uMgeni River sampling sites ; for total dissolved solids, conductivity,
chlorides, ammonia; nitrite and nitrates at all sampling sites.
In 50% of the instances there was compliance with the Target Water Quality Guideline Range
for aquatic ecosystems (DWAF, 1996). The majority of sites did not meet the general
requirements for purification of wastewater (DWAF, 1984); and the results indicate that
negative impacts from wastewater discharges occurred in 76% of the instances, while other
anthropogenic influences adversely affected water quality in 23% of instances. This study has
identified the extent; nature and source of water quality impacts on the rivers and it could
serve as a useful tool for rehabilitation and monitoring since it identifies the major source of
adverse water quality impacts.
Description
M. Sc. University of KwaZulu-Natal, Durban 2013.
Keywords
Water quality biological assessment., Water--Purification., Water treatment plant residuals--Purification., Theses--Environmental science.