## 3 Results and Discussion
### Removal of Organic Matter
chrysosporium_ for an OMW pre-treat by photocatalytic oxidation. The initial concentration of sBOD\({}_{5}\) was 408 mg/L, with a biodegradability index of 0.08 (See Figure 2), which means that AL effluent has very low biodegradability. In the experiments C2 and E2, the initial biodegradability index (BI) was higher (0.13), as a consequence of the glucose addition. In all cases, the sBOD\({}_{5}\) concentration decreased throughout the fungal treatment, with final values lower than 100 mg/L. Moreover, the BI decreases with the treatment since biodegradable matter was consumed. The _P. chrysosporium_ inoculated in E1 and E2 released enzymes able to break down recalcitrant organic matter into compounds more biodegradable. However, the fungus, as well as the endogenous microorganisms, consumed these compounds as they were produced, reducing the sCOD, the sBOD\({}_{5}\), and the BI. Regardless, the addition of the fungus gave final BI higher than in the controls, even though it was low. If the enhancing of biodegradability were the objective, for example, as the previous step for the biomethanization process, an alternative could be to directly use the enzymes produced by the fungus instead of inoculating the fungus strain. In this way, the recalcitrant compounds present in the AL effluent could be broken down without the fungus using this organic matter as a nutrient source [35; 36]. A sterilisation process may also be necessary to inactivate the endogenous microflora. The evolution of reducing carbohydrates has been also measured, and results are shown in Figure 3. The reducing sugar concentration of the initial sample was 563 mg/L, and the ratio sBOD\({}_{5}\)/reducing sugars was 0.7, indicating that a great part of the sBOD\({}_{5}\) measured is due to the reducing sugars. As expected, in the samples supplemented with 3 g/L of glucose, the initial concentration increased until 3662 mg/L. For the non-inoculated sample C1, the amount of reducing sugars remained practically stable during the treatment. In contrast, the inoculated samples (E1 and E2) showed a significant decrease in the reducing sugars concentration, with final values of 176 and 140 mg/L, respectively. The initial reducing sugars concentration dropped abruptly in the experiments supplemented with glucose, especially in the one that had been inoculated with the fungus. In this sense, all the glucose that was practically added to test E2 was consumed during the first 24 h, whereas in the supplemented control (C2), the amount of reducing sugars dropped from  
Figure 2: Changes in sBOD\({}_{5}\) concentration and biodegradability index for the different experiments at initial, intermediate, and final time of the treatment. Bars corresponds with sBOD\({}_{5}\) concentration for non-inoculated tests C1 (\(\blacksquare\)) and C2 (\(\blacksquare\)), and inoculated tests E1 (\(\blacksquare\)) and E2 (\(\blacksquare\)). The dashed lines shown the biodegradability index (BI) for non-inoculated tests C1 (\(\blacksquare\)) and C2 (\(\blacksquare\)), used as controls, whereas the solid lines represent the inoculated tests E1 (\(\bullet\)) and E2 (\(\ast\)). 3663 mg/L to 1772 mg/L in 24 h, and afterwards remained almost constant, indicating that the endogenous microbiota was not able to degrade all the glucose added. Although the enzymatic activities of the fungus were not measured in this study, the literature has widely reported that the addition of glucose favours the synthesis of fungal enzymes, which in turn are related to the elimination of colour, COD and recalcitrant compounds [37; 38; 39; 40]. This fact was reflected in E2, which showed a rapid degradation of reducing sugars, whereas sCOD removal was slower. Probably the fungus decomposed recalcitrant compounds that increased sCOD and, simultaneously, consumed them.