**4.1 Characterization of effluents of selected WWTPs**

As it has been mentioned previously, the characterization of WWTPs effluents is carried out by several physical-chemical parameters, among them, turbidity and suspended solids concentration, which are parameters whose maximum admissible values are indicated in the Spanish legislation related to water reclamation (Royal Decree 1620/2007). Characterization results of WWTPs effluents are shown in the table 4.


Table 4. Results of the characterization of studied effluents

As well as this characterization, a bibliographic study was carried out. This study was done in order to confirm that the results of the selected WWTPs obtained are between typical values regarding characteristics of WWTPs effluents. In accordance with this study, habitual values of analyzed parameters in WWTPs effluents are shown in the table 5 (Imai et al., 2002; Mendoça et al., 2007; Hassanli et al., 2008; Kalavrouziotis et al., 2009; Santos et al., 2009).

In accordance with the obtained results it can be observed that the characterization values of the selected effluents are within usual intervals to effluents of WWTPs.


Table 5. Usual values of physical-chemical parameters in WWTPs effluents according to other references
