Hach-Lange RTC103 N-Module - Manual (Page 12)

12
General Information
Figure 2 Design of the analog and digital input and output modules
Note: The number of LEDs indicates the number of channels.
2.5 Theory of operation
2.5.1 Theory of operation of the RTC103 N-Module
The RTC103 N-Module (Real-Time Controller for Nitrification) optimises nitrification
processes in waste water treatment plants which are continuously aerated (e.g. plug flow
nitrification tanks or pre-denitrification).
The RTC103 N-Module consists of an open-loop controller, based on NH
4
-N influent
concentration, flow rate, and the temperature in the aeration tank. Optionally, the Total
Suspended Solids concentration in the aeration tank (MLSS) can be taken into account.
Based on that information, a DO set-point is calculated which is required to reach the
desired NH
4
-N set-point at the effluent of the aeration tank. In addition to open-loop
control, there is also a closed-loop PID based on the NH
4
-N concentration at the end of
the nitrification zone that can be applied to improve control performance. The PID-output
values are combined with the open-loop output to calculate the required DO set point
(
Figure 3 ).
1 Analog or digital input or output module 
or bus termination module
2 LED area with installed LEDs or free LED installation
spaces.
2
1