Analysis of the Activated Sludge Process in an MBR under Starvation Conditions

Abstract

An aerobic membrane bioreactor (MBR) at complete biomass retention was studied over a period of time under starvation conditions. Kinetic parameters were determined in a no-feed batch test. The decay rate of activated sludge, kd = 0.05 d-1, was determined by tracking the decrease of MLSS. The ratio of MLVSS/MLSS was in the range 0.76– 0.85. The pH values were between 7.02 and 8.23. As a function of different initial concentrations of MLSS, specific nitrification rates, qN, decreased from 4.23 to 0.02 mg-N/(g MLVSS d) and specific biodegradation rates, qb, increased from 0.23 to 1.90 mg COD/(g MLVSS d). From experimental data the kinetic constants for respiration, which followed Monod kinetics, were determined as qO2max = 9.8 mg O2/(g MLVSS h), Kx = 2.9 g/dm3. Additionally, a linear correlation between MLSS and mean floc size was found to exist during the biodegradation process.