The application of filterability as a parameter to evaluate the biological sludge quality in an MBR treating refinery effluent

Membrane bioreactors (MBR) have been extensively employed at industrial effluent treatment plants; however the membrane fouling has restrained its more extensive application. Filterability is an important parameter to evaluate sludge properties and the potentiality of membrane fouling in MBR, nevertheless the lack of standardization of its assessment method has made it difficult to understand its actual role on MBR performance and compare its results. In this context, this work aims to compare three filterability assessment methods described in the literature (TTF, FT, and SFI) regarding its capability to sense sludge quality variation and reproducibility, and evaluate the application of this parameter as a tool to monitor and control fouling in MBR treating petroleum refinery effluents. This study showed that, among the methods evaluated, time to filter was the most effective to assess the filterability, both in terms of its capability to sense sludge quality variation and reproducibility. The results have also shown that filterability is directly related to the membrane fouling potential, and can be used as a tool to monitor and control fouling process in MBR. Significant filterability correlations among total colloidal organic carbon (colloidal COT), extracellular polymeric substances, and floc average size were found, for which Spearman coefficients determined were 0.71, -0.63, and -0.63, respectively. Therefore, filterability has the potential to forecast and control fouling so that its use, together with other parameters, allows for process optimization and reduction of power consumption, while increasing the membrane lifetime.