Table 1 clearly shows that the wastewater samples had a higher electric conductivity (EC) ranging from 5.26 to 8.72 ms/cm as a sign of presence of salts and impurities.
The sample obtained from the oxidation pond exhibited the highest concentration of organic matter, as represented by the chemical oxygen demand (COD), reaching 2 to 3 fold the levels of influent and effluent samples, respectively.
On the other hand, the ratio of BOD5 to COD for both the influent and the effluent attained 80%.
This is explicit a relatively high biodegradability for the treatment system. Nevertheless, the removal rate of organic content did not exceed 35%. Thus, the residual levels of COD and BOD were broadly above the Tunisian guidelines (Table 1).
Overall, the suspended sludge (SS) for all the samples was lower than the guidelines.