Study On Granulation Of Filamentous Microorganisms

Filamentous microorganisms are common in the activated sludge system.Filamentous bulking caused by the abundant growth of filamentous bacteria is one ofproblems occurring in wastewater treatment plants, which should be solved urgently.Although aerobic granules possess of better compactness, sludge bulking caused byfilamentous microorganisms still appears in aerobic granular sludge system. And thecurrent control strategy of sludge bulking is to inhibit filamentous growth. However,some filamentous fungi are particularly useful for the removal of pollutants.Accordingly, the granulation of filamentous microorganisms has been studiedpreliminarily in the seminar’s research. The basic idea is to make filamentousmicroorganisms grow compactly though the technology of granulation. Based on theachievement of the seminar, types of filamentous bacteria and the spatial structure andthe strength of different kinds of particles were studied.Content of this study include:The formation process of granulation of filamentous microorganisms and itswinding characteristics and the succession law of filamentous fungus were researched.Then, the similarities and differences of granulation of filamentous microorganisms,and general aerobic granular sludge were studied in the aspects of particle size, density,settling velocity, matrix switching and porosity etc. At the same time, three kinds ofgranular sludge including black, white and yellow were broken by ultrasonic disruption.According to the ultrasonic power, the number of broken and the flakes, the strengthand the formation mechanism of three kinds of granular sludge can be estimated. Anin-depth analysis of the succession and interrelationship of different sludge forms wastaken. The granulation of filamentous microorganisms in hardening condition was studied, then, the reason why filamentous microorganisms are unsustainable in a longrun was analyzed. Finally, by means of granulation, transforming the divergent growthmode of filamentous fungus so as to improved sludge structure, may be a newapproach for filamentous bulking control.Achievements of this study:(1)Results show that filamentous fungus has some kind of selectivity for theforms of aggregation of microorganisms and the structure of the filamentous funguswhich is easy to be reconstructed is also related to the type of filamentous fungus.Additionally, shear force and mesh size both have a great influence on the process ofgranulation. A relational graph between microbial strain of filamentousmicroorganisms and agglomeration degree established in this study can provideimportant reference value to the selection of microbial strain of filamentousmicroorganisms for the granulation.(2) The COD removal efficiency by black and white granular of filamentousmicroorganism is70%, which is better than aerobic granular sludge. And their removalefficiency of nitrate reaches100%, it indicates that denitrification of black and whitegranular of filamentous microorganism is shows excellent than aerobic granular sludge.But the filamentous granulation turns in a poor performance on ammonia oxidation.(3)Particles ultrasound broken research indicates that: when the grain diameter ofblack particles is larger than4mm, the black particles are composed of filamentous andnon-filamentous bacteria into alternating layers of growth; when the grain diameter isless than4mm, the black particles are entirely composed of almost filamentousbacteria. On the contrary, the larger granule size of white particles needs more brokentimes, and the smaller particles needs less times. Moreover, in the broken process ofwhite particles, filamentous bacteria can be found every time. The white particles bystaggered growth of filamentous bacteria were formed by the hole to catch particles orsludge floc., and gradually forming higher particle settling performance.