54
Version 2.1
Update: April 2016
PONSEL Mesure
– Aqualabo Contrôle
35 Rue Michel Marion
– 56850 CAUDAN, FRANCE
Tel.: +33(0)2 97 89 25 30
– Fax: +33(0)2 97 76 55 72
7.2.7 VB5
– MES 5 sensor: Sludge blanket detection – Sludge blanket detection/Suspended
Solid/Turbidity.
Description
Optical IR (870 nm) based on IR absorption
Temperature: NTC.
Materials
DELRIN, Nickel-plated brass, EPDM ; Polyurethane jacketed cable
Safeway
The optical windows are vulnerable to:
chemicals (organic solvents, acids and strong bases, peroxide, hydrocarbons),
mechanical treatments (impact, abrasion).
Measure/
Interfering
Bubbles on optical parts can interfere with the measurement.
On environment change, wait se
nsor’s temperature stabilization before proceeding with
measurement.
Operating
temperature
0°C to 50°C
Maintenance
After each use, rinse meticulously the sensor with clear water.
If deposits like biofilm or mud persist, clean the sensor with soapy water and wipe the
head with a soft cloth or an absorbent paper.
Storage
Place the protection case on the head of the sensor with a bottom of water to maintain
the hydrated optical windows.
Temperature of
storage
- 10°C to + 60°C
Turbidity
calibration in FAU
On a clean sensor, check once in a while the 0 NTU value by dipping sensor in bubble
free clear water. If the 0 point is shifted, proceed with the complete sensor calibration
(on 1 or 4 ranges).
For this procedure, a Formazin solution, with concentration matching the middle
of the measurement range, will be necessary. This solution will be prepared from
a 4000 NTU main solution.
For the preparation of solutions, take a flask of 200 mL. Introduce the necessary
volume of Formazin (cf. table below) and fill up to 200 mL with distilled water.
The formazin solutions of concentrations lower at 1000 NTU deteriorate quickly, so do
not preserve a solution during several days.
The solution at 2000 NTU can be preserve in the refrigerator for 2 or 3 weeks in a
opaque flask.
Measurement range
Concentration Formazin
solution
Volume of Formazin
(mL)
0.0-50.0 FAU
25 NTU
1,25 mL
0.0-200.0 FAU
100 NTU
5 mL
0-1000 FAU
500 NTU
25 mL
0-4000 FAU
2000 NTU
100 mL
Suspended Solid
calibration in g/L
Turbidity in g / L, it is necessary to calibrate the sensor on a real sample.
The calibration is achieved in 2 steps :
- Step 1 (offset) : immerse the sensor in distilled water (0 mg / L),
- Step 2 (slope) : immerse the sensor into a sample of sludge, maintained under
agitation, and validate the theoretical value measured by the sensor. Analysis the
sample dry weight in the laboratory according to the NF standard T 90 105 2.
Sludge blanket
detection in %
For a use of the sensor in mode Sludge Blanket detection the sensor is tested on 1
point:
- 1 offset with some distilled water (100 %)
Temperature
calibration
Refer to section 7.2.1
