Assessment of activated sludge stability in lab-scale experiments.
The majority of activated sludge research is conducted in a laboratory environment with, most often, the start-up sludge being taken from a large-scale wastewater treatment plant. Inoculating this sludge in a lab-scale set-up induces a transient period, which, evidently, has a direct impact on the experimental results during this period of acclimatization. In the currently published literature, the acclimatization period is either neglected or fixed to two or three times the sludge age, without any guarantee that stable conditions are indeed reached. To develop a strategy that assesses the stability of activated sludge, three experiments were performed during which the activated sludge was extensively monitored through a series of physical, microscopic and biochemical analyses. It is demonstrated that it is possible to objectively quantify activated sludge stability through the monitoring of the total averaged filament length per image, the sludge volume index and the maximum specific oxygen uptake rate. Hereto, a moving window approach is adopted: within a 7 days interval the mean slope and the gap between the maximum and minimum value has to be smaller than a pre-specified threshold value. Once stability is reached, the true impact of test conditions can be studied without interference of adaptation phenomena.
Van den Broeck
Rob M R
RM
BioTeC - Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, Katholieke Universiteit Leuven, Leuven, Belgium.
Van Impe
Jan F M
JF
Smets
Ilse Y M
IY
D018533:Biomass; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods*; D004867:Equipment Design; D005427:Flocculation; D008853:Microscopy; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid; D018508:Water Purification
D012722:Sewage