|
Sequencing batch reactors (SBR) are mainly characterized by sequential
process phases of fill, react, settle, decant and idle periods that
allow considerable flexibility in the design and operation in different
conditions. This flexibility and the unique features of SBRs used to
wastewater treatment by activated sludge systems operated in laboratory
scale, allow not only conducting experiments for the standard conditions
but also testing extreme situations during various processes. The design
of an SBR bioreactors for nutrient (N,P) removal is mainly based upon
the selection of some relevant parameters (e.g. sludge age, volume
exchange ratio, cycle time, SVI) as described in, for instance, the ATV
guidelines. Mathematical modeling and computer simulation of the
existing WWTP provide an opportunity of introducing to the software
present technology and examine many modifications, which do not require
great financial costs and do not cause disturbances in the on-going
processes. The computer model used for simulation could be calibrated
and validated using data obtained from the experiment conducted with
the use of laboratory scale device. This approach has the advantage that
allows to reach important data, which cannot be achieved with technical
full-scale WWTP.
The aim of this study was to simulate the processes occurring in the SBR
removing nutrients under varied aeration conditions. Within the study
was presented the computer model simulating the operation of the SBR
type reactor together with the results of the simulation concerning
municipal wastewater treatment processes. The computer simulations
results were used to evaluate the adaptation period of the biomass and
biological wastewater treatment processes in SBR, as well as the period
of breakdown of treatment process caused by the stoppage of raw
wastewater inflow and turn off the aeration and/or mixing system. The
biological processes described in the model were found to occur
simultaenously under limited aeration conditions. A low oxygen transfer
properly differentiates the system behaviour from systems under
traditional design calculations. As a result, the oxygen transfer should
be strictly incorporated in the calibration of biological nutrient
removal to visualize the individual contributions of each process.
|
