1991 Volume 27 Pages 45-54
For a rational design and operation of a biofilm reactor for the treatment of water and wastewater it is necessary to clarify the mechanism of biofilm formationand detachment and to estimate the biomass hold-up retained within the reactor. In this study the biofilm development was recorded on video tape and the relationships between the biofilm detachment rate, the content of extracellular biopolymer (ECP) and the area of cavity, which was formed at biofilm/substratum interface, was quantified to investigate the type of biofilm detachment and what factors govern the phenomenon. Experimental biofilm which consisted of denitrifying microorganisms was established on the surface of the polyvinyl chloride plate. Three types of large biofilm detachment were observed. The first type showed that about 30% of the biofilm detached cleanly from the surface of the substratum after about 40 days. It was considered that this type was caused by the formation of the cavity and the decrease of the ECP content. The second type was revealed that a part of the biofilm detached from the middle of the biofilm in the course of 60-90 days. This phenomenon seemed to be attributable to the gas production within the biofilm. The third type displayed a combination of the first and second types after about 100 days.
