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Abstract:
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Effective solids-liquid separation is the basic concept of any
wastewater treatment system. Biological treatment methods involve
microorganisms for the treatment of wastewater. Conventional activated
sludge process (ASP) poses the problem of poor settleability and hence
require a large footprint. Biogranulation is an effective biotechnological
process which can overcome the drawbacks of conventional ASP to a great
extent. Aerobic granulation represents an innovative cell immobilization
strategy in biological wastewater treatment. Aerobic granules are selfimmobilized
microbial aggregates that are cultivated in sequencing batch
reactors (SBRs). Aerobic granules have several advantages over
conventional activated sludge flocs such as a dense and compact microbial
structure, good settleability and high biomass retention.
For cells in a culture to aggregate, a number of conditions have to be
satisfied. Hence aerobic granulation is affected by many operating
parameters. The organic loading rate (OLR) helps to enrich different
bacterial species and to influence the size and settling ability of granules.
Hence, OLR was argued as an influencing parameter by helping to enrich
different bacterial species and to influence the size and settling ability of
granules. Hydrodynamic shear force, caused by aeration and measured as
superficial upflow air velocity (SUAV), has a strong influence and hence it
is used to control the granulation process. Settling time (ST) and volume
exchange ratio (VER) are also two key influencing factors, which can be
considered as selection pressures responsible for aerobic granulation based
on the concept of minimal settling velocity. Hence, these four parameters -
OLR, SUAV, ST and VER- were selected as major influencing parametersfor the present study. Influence of these four parameters on aerobic
granulation was investigated in this work |