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

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, k_d = 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 q_N, decreased from 4.23 to 0.02 mg‐N/(g MLVSS d) and specific biodegradation rates q_b 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 q_O2max = 9.8 mg‐O₂/(g MLVSS h), K_x = 2.9 g/dm³. Additionally, a linear correlation between MLSS and mean floc size was found to exist during the biodegradation process.