Today, the textile industry is considered as a leading economic sector in Tunisia. However, this sector demands a huge volume of water and a wide spectrum of chemicals, which is converted into potentially toxic wastewater leading to environmental perturbation and human health toxicity. Assessment of the environmental risks associated with textile wastewater becomes a necessity. In this study, textile dyeing wastewater samples were collected before and after the physico-chemical treatment carried out by textile companies located in Monastir-city-Tunisia and subjected to chemical analyzes in order to determine their physicochemical characteristics and the content of metals and textile dyes. The ecotoxicological assessment was performed using four organisms, namely Selenastrum capricornutum, Vibrio ﬁscheri, Daphnia magna and Lepidium sativum, to represent diﬀerent trophic levels. Based on chemical data, some physicochemical parameters (e.g. TSS, COD and TSS levels) and metals (e.g. Cr, Hg and Sb) in the textile dyeing effluents were revealed not in compliance with the Tunisian standard. Moreover, high quantities of three disperse dyes have been detected even in the textile dyeing wastewater samples before and after treatments. The ecotoxicological data conﬁrmed that the textile dyeing influents displayed toxic effects to all the test organisms, with Selenastrum capricornutum being the most sensitive organism. While, the above toxic effects were decreased slightly when evaluating the treated effluents. Metals and textile disperse dyes could be associated with the observed toxic effects of the textile influents and effluents. In fact, the treatment process applied by the evaluated companies was only partially efﬁcient at removing metals, disperse dyes and efﬂuent ecotoxicity, suggesting potential risks to aquatic biota. These findings emphasize the importance of applying integrated chemical and biological approaches for continuous evaluation of the toxicity of the treated eﬄuents to predict hazards on the environment.
Authors: Nosra Methneni, José Antonio Morales González, Ahlem Jaziri, Hedi Ben Mansour, Mercedes Fernandez-Serrano
; Full Source: Environmental research 2021 Mar 3;110956. doi: 10.1016/j.envres.2021.110956.