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PERFORMANCE OF A BIOLOGICAL PROCESS IN MEMBRANE
BIOREACTOR FOR MUNICIPAL WASTEWATER
MARIJA Vuković, MARIN Matošić*, FELICITA Briški, IVAN Mijatović*
Faculty of Chemical Engineering and Technology, University of Zagreb, Marulićev trg 19,
10000 Zagreb, Croatia
*Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000
Zagreb, Croatia
Email: [email protected]
Abstract
Biological wastewater treatment is performed by microorganisms which oxidized organic
matter from wastewater and is so-called an activated sludge process. In the application of
membrane processes for wastewater treatment, it is well known that the membrane bioreactor
(MBR) possesses numerous advantages over the traditional activated sludge process. Interest
in the membrane bioreactor technology for wastewater treatment has increased due to present
stringent legislation, the opportunity for water reuse/recycling membrane processes it
presents, and continuing advancement and decreased costs of membrane technology.
The objective of the research is to investigate the performance of a biological process in
treating municipal wastewater using a submerged hollow fiber membrane module in an
aerated basin continuously for 14 days. Continuously fed aerated MBR was used to obtain
design parameters of an activated sludge process for the municipal wastewater treatment. The
biokinetic parameters were calculated under steady state, considering a Monod-type equation.
The biokinetic parameters were found as the following: Y = 0.27 g g-1, kd = 0.03 d-1, rs,max =
5.20 g dm-3 d-1 and Ks = 0.08 g dm-3 during 14 day. The MBR process was capable of
achieving over 91 % removals for COD, on average. Microscopically, significant changes in
the structure of the flocs and of the ratio between free suspended and aggregated cells could
be observed. The sludge samples are characterized by regular formed flocs of different size
range, which varied from 59 µm to 796 µm. Mean value floc size of 14 days were 225 µm.
Most of the flocs were firm and dense. Filamentous bacteria were rare and mostly
incorporated in the flocs. Higher organisms and free swimming organisms were rare. The
obtained results suggest that microorganisms present in the flocs in the MBR use organic
fraction from wastewater for energy supply for maintenance of their metabolism and growth.
In municipal wastewater treatment, membrane filtration technologies receive great attention
because it usually produce the better quality effluent, good floc structure, generate less sludge
and require a smaller aeration tank volume.