The effect of sewage effluent on the physico-chemical and biological characteristics of the Sand River,Limpopo, South Africa |
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| Institution: | 1. Guangdong Institute of Microbiology, Guangzhou 510070, China;2. State Key Laboratory of Applied Microbiology Southern China, Guangzhou 510070, China;3. South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;4. University of Chinese Academy of Sciences, Beijing 100039, China;5. Department of Agriculture and Environmental Sciences, Cooperative Research Programs, Lincoln University in Missouri, Jefferson City, MO 65101, USA;1. Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa;2. National Health Laboratory Service, Tshwane Academic Division, Pretoria, South Africa;3. Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa |
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| Abstract: | 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 sewage treatment plant along the urbanised area of Polokwane, whilst sites 3, 4, 5, 6, 7 and 8 were downstream. The physico-chemical parameters and coliform counts in the water samples were determined. The suitability of the 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. Canonial correspondence analysis (CCA) indicated the macroinvertebrates, Chironomidae, Belastomatidae, Chaoborus and Hirudinea being strongly associated with nitrogen, phosphorus, conductivity and temperature. Escherichia coli levels in the Polokwane wastewater treatment works maturation ponds, could potentially lead to contamination of the Polokwane aquifer. The Sodium Adsorption Ratio was between 1.5 and 3.0 and residual sodium carbonate was below 1.24 Meq/l, indicating that the Sand River 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. This shows that the river still has a good self-purification capacity. |
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| Keywords: | Macroinvertebrates Self-purification Suitability Sewage effluent Pollution |
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