In comparison to the other high-rate anaerobic processes, Anaerobic Fluidized Bed Reactor(AFBR) has several advantages, such as higher retention capacity of active biomass, production of sludge granules of fair settlability, less accumulation of inert materials, better mixing, and degassing property. However, an extended start-up period needed for biofilm development and some other operational problems are known as drawbacks of this process. Hence, in this research, the influence of hydraulic characteristics on the biofilm development and COD shocks on the stability was investigated in an attempt to improve process performance.
Three AFBRs of effective bed volume of 1.57L(total volume 3L) and of the height/diameter ratio of 16 were used. As a support material, each reactor contained 1.2L, 0.98L, and 0.83L of sand of 0.2~0.3mm in diameter and 2.65g/㎤ in density. Synthetic wastewater of glucose was fed and the upflow velocity in each reactor was adjusted to acheive a bed expansion of 30%(AFBR I), 60%(AFBR II), and 90%(AFBR III).
From this limited experimental study, an optimal start-up and a most active biofilm development could be obtained, when the upflow velocity was maintained so as to expand the bed by 55-65% and when the additional inoculation procedure was applied.
The COD removal efficiency of AFBR II was more than 90%, and gas production and organic emoval rates increased in proportion to COD loading rate untill 27g COD/㎥/d and the volume of fully developed biofilm occupied upper 70% of the effective bed volume.
For influent COD shocks during 1/4 and 1/2 HRT, the system exibits little disruption and continues to provide a high degree of treatment.