Combining submerged membrane technology with anaerobic and ...

Chapter 2eq. 2.10eq. 2.11eq. 2.12The experimental procedure to determine each resistance value was as follows: (a)R m was estimated by measuring the permeate flux of tap water; (b) R t was evaluated bythe flux of biomass microfiltration; (c) the membrane surface was then flushed with tapwater and cleaned with a sponge to remove the cake layer. After that, the tap water fluxwas measured again to obtain the resistance of R m + R pb. From steps (a)–(c), R t, R m, R pband R c could be calculated. The resistance of the colloidal fraction of the cake was alsodetermined using a new filter according to equation 2.13:eq. 2.13where J col is the flux of the supernanatant after centrifugation of biomass at 4000 gduring 10 min.Using the Carman-Kozeny equation to calculate the pressure drop of a fluid flowingthrough a packed bed of solids in laminar flow and taking into account that the filtrationtakes place at constant pressure, the specific resistance to filtration (SRF) (α, m·kg -1 ) canbe calculated after linearization according equation 2.14:eq. 2.14where P is the pressure applied [Pa], A the filtration area [m 2 ], w the total suspendedsolids [kg·m -3 ], η is the dinamic viscosity of filtrate [Pa·s] and b is the time-to-filtration ratio[s·m -6 ], which is the slope of the curve that is obtained by plotting the time of filtration to thevolume of filtrate ratio (t/V) versus the filtrate volume (V). From the conventional constantpressure filtration equation, a plot of t/V vs. V is expected to yield a linear relationship forthe entire filtration data. The linearity of t/V vs. V plot is observed only when the value of V(or time) or the cake thickness is sufficiently large.78