Effects of chemical additives on filtration and rheological characteristics of MBR sludge

The main goal of this study was to control the fouling phenomena in MBR using chemical additives. In the first phase of the study, SMP removal and bound EPS formation capacity of chemical additives were determined. Highest SMP removal (72%) was achieved by the Poly-2 additive. In the second phase of the study, short term filtration tests were conducted. Poly-1 exhibited highest performance based on membrane resistance, permeability and average TMP. According to the results obtained from constant shear rate tests in fourth phase, no significant change in viscosity with time was observed. Studies for the adaptation of rheograms to common flow models showed that chitosan and starch was not able to fit to Ostwald de Waele and Bingham models. At a shear rate of 73.4 s−1 viscosities of all samples were close to each other. Chitosan and starch achieved highest viscosity values at the shear rate of 0.6 s−1.

► Poly-1 and -2 additives recommended due to their good filtration characteristics.
► PACl and chitosan showed average performances compared to the other additives.
► Starch exhibited the worst filtration results.
► Rheology and particle size data showed correlations with other fouling parameters.
► Results at low shear rates were important due to possible effects on cake transport.