Toxicity Evaluation of Wastewater Treatment Plant of Textile Effluent Using Fish: Nile tilapia <i>Oreochromis niloticus</i>

Abstract

The experiment was conducted to evaluate the acute toxicity level of effluents from inlet and outlet of the biological lagoons of Hawassa Textile waste treatment plant using Nile tilapia, Oreochromis niloticus as test organism. Data for 24hrs, 48hr, 72hrs and 96hrs were recorded, and were analysed to determine the effects of toxicants of the effluent on behavioural responses and survival rate of Oreochromis niloticus. The results revealed that normal swimming behaviours were observed on the fish stocked at lower effluent concentration, while erratic swimming, gasping and frequent surfacing behavioural responses were observed on the fish stocked at higher effluent concentration. There was no fish mortality in control and 10% (v/v) outlet effluent concentration. The highest percentage mortality was observed at 100% (v/v) inlet effluent concentration followed by 100% (v/v) outlet and 40% (v/v) inlet effluent concentrations. The 96hrs fifty present lethal concentration (LC 50 ) and acute toxicity unit (ATU) values for inlet and outlet wastewater were 30.5% (v/v), 3.279, 71.5% (v/v) and 1.399, respectively. The safe effluent concentration for both inlet and outlet wastewater is set to be 3.05% and 7.15%, respectively. As a whole the present results revealed that the total efficiency level of the treatment plant to remove toxicants was 57.33% (v/v). However, efficiency of the treatment plant should be improved to use the water for irrigation and other domestic purposes; otherwise, the use of the wastewater at present condition is unsafe.

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“…Similarly, other previous research by Ezeonyejiaku et al [ 62 ] mentioned that Catfish ( Clarias gariepinus ) was resistant to toxicity than that of tilapia. Furthermore, according to Kassaye [ 61 ], Oreochromis niloticus is less resistant to the toxicity of textile effluent than Clarias gariepinus which is consistent with the current study.

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“…Liu et al [ 30 ] also mentioned that untreated wastewater in their work is more toxic to the test organisms than treated effluent. Kassaye [ 61 ] also reported absence of mortality in control and 10% (v/v) outlet effluent concentration and 100% (v/v) inlet effluent concentration. The highest percentage mortality was noted at 40% (v/v) inlet effluent concentration and 100% (v/v) outlet effluent concentration on Nile tilapia ( Oreochromis niloticus ).…”