Thesis (M.Sc. (Aquaculture)) -- University of Limpopo, 2014 / Population growth in urban areas is putting pressure on sewage treatment plants.
The improper treatment of sewage entering the aquatic ecosystems causes
deterioration of the water quality of the receiving water body. The effect of sewage
effluent on the Sand River was assessed. Eight sampling sites were selected, site 1
and 2 were upstream of the of the sewage treatment plant along the urbanised area
of Polokwane, whilst sites 3, 4, 5, 6, 7 and 8 were downstream. The physicochemical
parameters and coliform counts in the water samples were determined.
Macroinvertebrate abundances and diversity (H') was determined at the different
sites during the dry and rainy season. The water quality status of the Sand River with
respect to the South African scoring system (SASS) scores and average score per
taxon (ASPT) was determined. A linear regression was performed to test the
correlation of the SASS scores with abundance and H'. Heavy metal concentrations
in water, sediment, grass (Ishaemum fasciculatum) and fish (Oreochromis
mossambicus) at the sites were evaluated. The suitability of the Sand River and
surrounding borehole water for irrigation was also determined.
Hierarchical average linkage cluster analysis produced two clusters, grouping two
sites above the sewage treatment works and six sites downstream of the sewage
effluent discharge point. Principal component analysis (PCA) identified total nitrogen,
total phosphorus, conductivity and salinity as the major factors contributing to the
variability of the Sand River water quality. These factors are strongly associated with
the downstream sites. Canonical correspondence analysis (CCA) indicated that
Chironomidae family was found on the nitrogen gradient during the dry season.
However during the rainy season, Chironomidae was found in the centre of the
ordination which indicated that it was ubiquitous. Escherichia coli levels (1463.73
counts/100ml) in the maturation ponds of Polokwane wastewater treatment works
could potentially lead to contamination of the Polokwane aquifer. High diversity was
recorded at the sites before discharge and the sites further downstream. There was
significant correlation (P<0.05) between the SASS scores and macroinvertebrate
diversity during the dry season (R2=0.69) and the rainy season (R2=0.77). Fish
samples had significantly higher (P<0.05) iron and copper concentrations, while the
vi
sediment had significantly higher lead concentration (P>0.05). The United States
salinity laboratory (USSL) diagram indicated that the sodium hazard (SAR) and
alkalinity hazard (conductivity) was low and the Sand River and borehole water was
suitable for irrigation. The residual sodium carbonate (RSC) was below 1.24 meq/l,
also indicating that both the Sand River and borehole water is still suitable for
irrigation. The total phosphorus concentrations fluctuated across the different site.
Total nitrogen concentrations showed a gradual decrease downstream from the point
of discharge. The coliform levels also showed a gradual decrease downstream. This
shows that the river still has a good self-purification capacity.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/1329 |
| Date | January 2014 |
| Creators | Seanego, Koena Gloria |
| Contributors | Moyo, N. A. G. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xv, 148 leaves |
| Relation | Adobe Acrobat Reader, version 8 |
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