Abstract
The study focused on evaluating the effects of effluent from Wastewater Treatment Works (WWTW’s) on the aquatic health of the Rietspruit River with the aim of establishing the current ecological integrity of the Rietspruit River between the Sebokeng Wastewater Treatment Works (SWWTW’s) and the Rietspruit Wastewater Treatment Works (RWWTW’s). The study looked at the water quality discharged from the SWWTW’s, RWWTW’s and Urban run-off, focusing on assessing the physical, chemical parameters, water toxicity and macroinvertebrates abundance and richness at three sampling points using aspects of mini-SASS 5. Water samples were taken during periods of both high and low flow climatic conditions to determine the impact of discharged effluent from WWTW’s and Urban run-off. Water quality parameters were measured in situ and these were compared to the South African Water Quality Guidelines (SAWQG) using the Target Water Quality Ranges for aquatic ecosystems (TWQR). The results for physio-chemical parameters, typical water quality and chemical analysis, indicated that, Temperature, pH and Turbidity were within TWQR and had higher values recorded for high flow compared to values recorded for low flow. Dissolved Oxygen (DO mg/L) for low flow and high flow sampling conformed to the TWQR except for Sites 3,4 and 5 during low flow sampling. During high flow, Sites 1 and 2 were within the requirements of the TWQR, similarly so was Site 2 during low flow, whereas as all the other samples were not. Electrical Conductivity (EC) during high flow conditions was greater than the low flow records, however, all five sites sampled did not meet the requirements of the TWQR. Nitrite values recorded during high flow were higher than low flow conditions. Only Nitrite values at Sites 1 and 2 during low flow conditions were within the TWQR. Nitrate, Ammonia and Phosphate values were greater during the high flow sampling period when compared to the low flow values and none were within the TWQR limits of the SAWQG. Results for water toxicity for Sites 1 to 5 for both high flow and low flow sampling recorded a percentage effect (PE) of ≤ 20% for Daphnia Pulex with zero mortality during 24, and 48 hours of exposure. Fouteen macroinvertebrate taxa were observed in this study and more species were recorded during the high flow sampling versus the low flow conditions. It can be concluded that there are positive effects from the effluents discharged from the WWTW’s as it is eliminating harmful contaminants from water discharged in to the Rietspruit river which improves the quality of water in the Rietspruit river safe and fit for human and animal consumption. The WWTW’s are an essential service in removing pollutants from wastewater that could be harmful if consumed, furthermore, the WWTW’s processes, ensures that harmful bacteria do not end up in the environment that could have damaging effects on people, animals, and plants. It is recommended that the Constitution of the Republic of South Africa, Act 108 of 1996 and the National Water Act (NWA) No. 36 of 1998 be
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enforced to assist in promoting sustainability in a setting where social, ecological, and developmental challenges are equally crucial. It is also recommended that new laws must be enacted and be transformed for water resources protection from being treated as a simple commodity to one that is of high importance which will interconnect aquatic ecosystems. These laws should also be coupled with the protecting of aquatic ecosystems habitats.