Hach-Lange RTC112 SD-Module - Manual (Page 13)

13
General information
2.5.4 Operating modes
The RTC112 SD-Module can be operated as a combined open-loop and closed-loop
controller. Several variants can be configured.
1. Configuration of a fixed polymer rate [L/h] with a fixed feed flow rate [m 3 /h].
2. Configuration of a specific polymer dosing rate [g polymer/kg TSS]. One of the
following settings is adjusted:
a. The polymer flow rate according to the TSS concentration and the feed flow rate
( Figure 3 ).
• Based on the actual feed flow rate [L/h] and TSS concentration [g/L] in the feed
flow, the polymer dosing rate [L/h] is calculated for the required specific dosing
rate.
Or:
b. The feed flow rate according to the specified polymer dosing rate and the
measured TSS concentration of the influent ( Figure 4 ).
• Based on the measurement value of the TSS concentration from the influent [g/L]
and the configurable specified polymer dosing rate [L/h], the feed flow rate [m
3 /h]
is calculated such that it corresponds to the pre-defined specific polymer dosing
rate [g/kg].
3. Both variants 2a and 2b can be combined with one of the closed-loop controllers
described below:
a. Closed-loop control of the TSS concentration in the dewatered sludge
• The specific polymer dosing rate is adjusted according to the difference between
the target and actual TSS concentration in the dewatered sludge. Higher TSS
concentrations lead to a reduction of the dose and lower concentrations will lead
to higher dose rates than preset in the open-loop part of the RTC.
b. Closed-loop control of the TSS concentration in the centrate or filtrate
• The specific polymer dosing rate is adjusted according to the difference between
the target and actual TSS concentration in the centrate. Higher TSS
concentrations lead to an increase of the dose and lower concentrations will lead
to a decrease of the dose rates preset in the open-loop part of the RTC.
N O T I C E
In a closed-loop circuit, TSS measurement is required in centrate or dewatered sludge. The
program of the RTC112 SD-Module has to be adjusted to the type of measurement location that
is being used for the closed loop part of the RTC. This is done by executing *.bat files on the CF
card of the RTC. Make_Filtrate.bat has to be executed for applications where centrate TSS is
measured and Make_Effluent for applications where dewatered/thickened sludge is measured.
Note: Never retrieve the CF-card from the RTC unit while power is on!