GPS-X Technical Reference

Suspended Growth Models 188
Timer – The timer controller creates a fixed cycle of timed aerated and unaeratred
phases. The timer controller is configured by specifying the aeration
start time, the aeration end time, and the length of the entire cycle, where the
remaining time in the cycle is un-aerated.
Ammonia controller – The ammonia controller controls airflow by turning on
the air when the ammonia reaches the ammonia high limit in anoxic phase, and
turns off the air when the ammonia reaches the ammonia low limit in oxic
phase.
Nitrate controller – The nitrate controller consists of three phases: Oxic, anoxic,
and anaerobic:
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Oxic – During the oxic phase, the aeration system in the CFSR is on.
Aeration in the tank continues until the nitrate high limit in oxic phase,
nitrate concentration, is reached. Upon reaching the specified upper
concentration limit, the controller switches to the anoxic phase.
Anoxic – During the anoxic phase, the aeration system in the CFSR is
off. The anoxic phase continues until the nitrate low limit in anoxic
phase is reached. Upon reaching the specified low concentration, the
controller switches to the anaerobic phase. If the average nitrate removal
rate across the CSR drops below the minimum nitrate removal rate in
anoxic phase before reaching the low nitrate concentration, the
controller will end the anoxic phase and return directly to the oxic phase
without executing the anaerobic phase.
Anaerobic – The anaerobic phase is a time phase of specified duration,
commencing at the completion of the anoxic phase. During the
anaerobic phase, the aeration system in the CFSR is off. Once the length
of time specified in the anaerobic phase length has passed, the
controller will return to the oxic phase.
HIGH PURITY OXYGEN (HPO) SYSTEM (cnlib/cnplib libraries only)
The high purity oxygen (HPO) activated sludge object works the same way as a plug-flow tank
object, except that the aeration system uses a HPO gas feed instead of regular air. In addition, the
entire plug flow system is capped, and each reactor has a headspace. The headspaces are
connected, to allow downstream flow. The flow of gas downstream is determined from the gas
input and venting flows, and equalizes the pressure in all the reactor headspaces. Figure 6-26
shows the physical configuration of the HPO system
GPS-X Technical Reference