Membrane filtration treats drinking water by physical removal of bacteria and other particles present in
the raw water. In order to study post-filtration contamination and growth, filtered river water and
wastewater were used in a controlled laboratory-scale simulation of a batch-operated membrane filtra-
tion system. Bacterial batch growth was analyzed following intentional initial contamination with a river
water microbial community. Batch growth in the permeate was measured with online flow cytometry at
high intervals during 10 successive 24-hour operational cycles, simulating repeated daily use (filtration
followed by stagnation). Two operational mechanisms influenced the growth characteristics: (1) initial
selection of bacteria adapted to batch growth conditions, and (2) biofilm formation on the surfaces of
the permeate containers. The first mechanism contributed towards a stable and reproducible growth
behavior (lag phase of less than 4 h, maximum growth rates of 0.37–0.42 h
1
and final total cell counts
of 1.5–1.8
10
6
cells mL
1
) throughout several consecutive operational cycles. When the feed water
changed, the adapted bacterial communities grew rapidly and proportionally to the amount of substrate
in the new water source. Biofilm development in the permeate containers resulted in a 20% reduction in
the overall cell production during five operational days, suggesting this to be a potential novel strategy
towards controlling biological stability in such systems.