E-Andrew Sindt Creative Component S11.pdf

Figure 4.11 - Demonstration of layered method in modified Vesilind settler model (BioWin user’smanual)V S,i = V 0 e -KXi [7]Where V s,I = the velocity in a given layer i, V 0 = maximum settling velocity (m/d), K = settling parameter(m 3 /kg TSS), and X i = the TSS concentration (kgTSS/m 3 ) in layer i. (BioWin user’s manual)When the maximum settling velocity is reduced, the settling velocity in each layer will be reduced. If thesettling velocity in the top layer is reduced (where decant water is taken from), the effluent TSSconcentration will increase because the solids are not progressing down into the tank as far as theypreviously were for the same duration of settling period.4.2.1.6 Maximum Vesilind Settling VelocityA decrease in the maximum Vesilind settling velocity results in a significant increase in effluentconcentrations of TSS, cBOD, COD, NO 2 - -N, NO 3 - -N, and TN (Figure 4.12). On the other hand, increasesto the maximum Vesilind settling velocity result in relatively minor changes in effluent concentrationsfrom default operating parameter settings. This means that the default settling velocity is currently setat a rate where no further significant gains in effluent quality can be achieved through increasedmaximum settling velocity parameter at the 1 hour 48 minute SBR settling and decant phase duration.51