## 5 Toxicity of Dye Effluents
### Toxicity Tests  
The wastewater generated from the textile industries after treatment is generally released into water resources for irrigation of agricultural lands. Therefore, it is obligatory to test the toxicity of textile effluents before and after treatment on the crop-seeds. For this purpose, the usual methods to study phytotoxicity are through the monitoring of germination of crop-seeds and, later, the growth of seedlings into plants. These studies are important to assess the toxic nature of dye molecules released into irrigation water. [PERSON] et al. [34] studied the germination of three plant seeds irrigated with untreated and treated textile wastewater. A 100% inhibition in seeds germination was noticed in _Lens orientalis_ and 50-60% in _Tritcium beoecium_ with the use of untreated effluent at 30 ppm, while 100% inhibition occurred at 50-150 ppm in _T. beoecium_. The least sensitive seeds were from _Tritcium aestivum_, which showed 30% and 50% inhibition at 30 and 50-150 ppm, respectively. In the study of bacterial bioremediation employing _Bacillus_ sp., after the treatment process, the effluent was 100% decolourised and found less toxic, showing 10% inhibition in _T. beoecium_ seeds and 0.0% on _L. orientalis_ and _T. aseitsitum_ seeds. This toxicity test resulted in the assumption that due to the consumption of biodegradation products formed by _Bacillus_ sp. or transformation to non-toxic metabolites, the germination of seeds was not adversely affected.  
[PERSON] et al. [35] have studied the toxic effects of an azo dye, Reactive Black B (RBB), on the cultivation of a freshwater algae _Chlorella vulgaris, which_ is a microalgae mainly used as a dietary supplement or protein-rich food additive. The studies showed that a growth medium containing azo dye RBB was toxic for the growth of algae toxicity with EC\({}_{50}\) calculated as 48 mg L\({}^{-1}\). [PERSON] et al. [36] have studied the toxicity effect of untreated and treated dye mixture and textile effluent using a bacterial consortium (_Glandularia pulchella+Pseudomonas monteilii_ ANK) on germination and growth of seeds of two crops, _Phaseolus mungo_ and _Sorghum vulgare._ The outcome of their experiment showed a higher percentage of seeds germination in experimental-sets irrigated with distilled water and treated textile effluents and treated dye mixture, whereas the growth of seedlings was inhibited in sets of untreated effluents and dye mixture. This study confirmed the toxicity of untreated dyes wastewater, while the treated samples produced similar results for the germination of seeds as with the use of distilled water.  
In comparison to bacterial treatment for dye colour removal, the fungal treatment of textile dyes is an economical and effective alternative for bioremediation. The main mechanisms involved are biosorption, bioaccumulation, and biodegradation [37]. Therefore, myo-remediation is a natural and low-cost process [38]. In this case, endophytic biodegradation occurs because of the activity of fungal enzymes, lactose, lignin peroxidase, Mn peroxidase, reductase, and tyrosinase [39]. Moreover, the breakdown process takes place in a confined environment as in soil-conditioning and composting, as compared to the discharge of toxic effluents and treated effluents into water resources after bacterial treatment in liquid systems [4; 12; 13].