Use of image analysis in the study of competition between filamentous and non-filamentous bacteria

• Published in: Water research (Oxford) 2004-06, Vol.38 (11), p.2621-2630
• Main Authors: Contreras, Edgardo M., Giannuzzi, Leda, Zaritzky, Noemı́ E.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bacteria; Biological and medical sciences; Biological treatment of waters; Biotechnology; Environment and pollution; Exact sciences and technology; Filamentous bulking; Floc-forming bacteria; Flocculation; Fundamental and applied biological sciences. Psychology; General purification processes; Image analysis; Industrial applications and implications. Economical aspects; Kinetics; Mathematical modeling; Microscopy; Models, Theoretical; Pollution; Sewage - microbiology; Sphaerotilus natans; Waste Disposal, Fluid - methods; Wastewaters; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2004.03.022

One of the most common problems in the operation of activated sludge plants is the inability to separate solids from treated effluents in the clarifiers caused by the overgrowth of filamentous micro-organisms (FM) with respect to floc-forming bacteria. In order to develop kinetic models that help to predict bulking events, growth kinetics of the FMs and non-filamentous bacteria (NFB) should be known. This paper addresses the competition of a FM and a NFB in a continuous stirred tank reactor. Experimental observations of the effect of the dilution rate on the composition of the mixed culture were compared to simulated results. Image analysis was used to measure NFB and FM fractions in order to evaluate the proposed mathematical model. Experimental results and numerical simulations showed that low D values favored the growth of FM; on the contrary, when high D values were applied a rapid overgrowth of the NFB were observed. Thus, high D values favored the growth of NFB minimizing the risk of filamentous bulking.