Descriptive and multivariable analysis of the water parameters quality of Sfax sewage treatment plant after rehabilitation

This study detailed the effect of simultaneous multiple intrinsic and extrinsic factors on the characteristics of Sfax activated sludge wastewater treatment plant (WWTP), located in Southern East Tunisia. The plant performance was evaluated through descriptive and statistical analysis of quantity and quality data of both raw wastewaters and treated effluent over a period of three years (2008 – 2010). Despite the rehabilitation, poor performance was shown to be attributed to raw wastewaters quality, civilization populations, bad functioning of the aerators and the industrial fallouts and deposits. Therefore, the downstream values of BOD5, COD, SS, FC, FS, TKN and TP are enough to achieve a final effluent that would meet the Tunisian standards limit. Multiple regression analysis showed that removal efficiencies of BOD5, COD and SS can be predicted to reasonable accuracy (R 2 = 0.973, 0.946 and 0.925, respectively). Goodness of the model fit to the data was also evaluated through the relationship between the residuals and the model predicted values of BOD5r, CODr and SSr. The advantage of this model is that it would allow a better process control.