ASIM User Forum - [O2 set point in ASIM 4.0]

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From: Laila Bahgat
Date: 04/04/2007

What is exactly meant by O2 set point in an uncontrolled
system? As far as I remember this set point is the means to
calculate the error in a PI controller for example or the
deviation of the actual concentration from a pre-set level.

Please comment whether this parameter (the O2 set point) is
used correctly in the following situation or not:

In the simulation of an oxidation ditch system using ASIM
4.0: influent enters at the middle zone exactly before the
aerator & oxygen conc. = 3 mg/ litre, in the following zone
O2 conc. decreases to 1 mg/l while it approaches zero in
zone 1 that may be considered as an anoxic zone. 
The aeration process is not controlled. 

Is it correct to represent the aerobic/ anoxic state of the
different zones of the ditch via the O2 set point of the
reactors (zones) i.e. By setting O2 set point of zone 1 = 0,

zone 2 = 3 mg/ litre and        zone 3 = 1 mg/l.

What about the initial values of O2 in all reactors?

Thanks in advance for your feedback.

Reply #1
From: Rolf Fankhauser
Date: 04/12/2007
If O2 setpoint is not zero, then aeration is controlled to
keep the O2 concentration to the value set by O2 setpoint.
If O2 setpoint is zero, aeration is constant according to
the kla value set under 'Edit Flowscheme / Reactors and
secondary clarifiers'. 

Please note that an english tutorial is now available at the
ASIM homepage.

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