## 3 Results and Discussion
### Comparison between the Ecotoxicological Assays  
Table 4 present the toxicity results (EC\({}_{50}\), EC\({}_{20}\) and TU) of all tests performed. Comparing the raw effluent (RE) with the treated effluents (TE1 and TE2), it seems that the treated effluents presented a lower toxicity for all the species and for almost all the parameters assessed, showing some effectiveness of the treatment system of the textile industry. The feeding rate of \(D\). _magna_ was the most sensitive parameter to the textile effluent. [PERSON] et al. [41] also found that this sublethal parameter was the most sensitive compared with the existing standardised acute tests (studying bacteria bioluminescence, algae growth and \(D\). _magna_) when assessing the toxicity of industrial effluents. However, some authors underlined the importance of considering the colour of the effluent as a inhibiting factor on the growth of algae due to physical shading, which can be reduced via dilution but not completely  
Figure 3: Average feeding rate (cells-mL\({}^{-1}\)-h\({}^{-1}\)) of \(D\). _magna_ after exposure to different concentrations of raw effluent (RE) or treated effluent 1 (TE1) compared to the control. Error bars represent the standard deviation of the mean (n = 4); asterisks indicate statistically significant differences from the control (Dunnett’s test \(p<0.05\)).  
eliminated [5; 42; 43]. In this context, it may be useful to express the toxicity not only in effluent dilutions, but also in colour units, and also the use of different organisms to correctly assess the toxicity of coloured wastewaters.  
Although the ecotoxicological assessment of the textile effluent samples is an important tool toward understanding the main effects of these types of effluents in the aquatic compartment, it is not possible to identify which specific chemical compounds cause the toxicity due to the complex mixture of the sample. [PERSON] and [PERSON] [39] evaluated the acute toxicity of a whole sample of textile effluent and their fractions on _D. magna_, trying to understand which compounds are toxic. For that purpose, these authors used the solid-phase extraction method (SPE) to extract the organic chemicals from the sample, followed by preparative high performance liquid chromatography (HPLC) to fractionate them according to their hydrophobicity. The textile effluent was fractionated using HPLC into five fractions and the authors found that the higher percentage of immobilisation of _D magna_ after 48 h (100%) was for fraction 5, which was the most hydrophobic fraction. Meanwhile, for the fractions 1, 2, 3 and 4, they recorded values of 0, 10, 10 and 30%, respectively, after 48 h. The compounds of the fraction 5 responsible for the toxicity were bis(2-ethylhexyl) phthalate, 4-nonylphenol, dibutyl phthalate and diethyl phthalate [39]. In fact, the compounds diethyl phthalate and 4-nonylphenol, were also present in our textile samples (the raw and the treated effluent) and were probably the main compounds responsible for the toxicity recorded. For the other two compounds, the bis(2-ethylhexyl) phthalate and dibutyl phthalate, although they were not present in our samples, there were other compounds from the class of phthalates which could also be responsible for toxic effects. Regarding the toxicity of the fraction 5 alone and the reconstructed mixture (with all the fractions) tested by [PERSON] and [PERSON] [39], the difference between them was not significant.