Hach-Lange UVAS sc - Manual (Page 8)

8
General information
2.2 Applications
UVAS plus sc:
immersed directly in the medium, without pumping or preparation of a sample, the
sensor measures the content of dissolved organic compounds in activated sludge
tanks in municipal sewage treatment plants, surface water, untreated water and
treated drinking water. The system can also be used for checking the outlet of
waste water treatment plants.
Bypass accessories for UVAS plus sc:
the through-flow variant of the high-precision UVAS plus sc sensor is used
wherever direct measurement in the medium is not possible for construction-
related reasons or the medium load makes it necessary to measure a filtered
sample (very high TS contents, sewage treatment plant inlet, waste dump
seepage,...).
2.3 Measuring principle
Organic compounds dissolved in water in general absorb UV light, for this reason
the measurement of UV absorption represents an independent total parameter for
dissolved organic substance water load. In drinking water treatment this method
of determination of the quality of water without chemicals using laboratory
photometers and filtered samples has a long tradition.
DIN 38402 C2 stipulates for the measurement of the UV absorption, the
measuring wavelength of 254 nm and characterises the measured value for a
filtered sample as a spectral absorption coefficient at 254 nm (SAC254 for short),
which is to be converted to extinctions per metre. In this way straightforward
comparability of the measured results from photometers with different cuvette
intensities is achieved and the units 1/m or m
–1 are obtained.
The UVAS immersed probe comprises a multiple beam absorption photometer
with effective turbidity compensation. The related controller controls the process
of the measurement using a flash lamp photometer, the mechanical cleaning of
the measuring window by a wiper, and also displays the measured values as
SAC254 in 1/m.
For other total parameters such as COD or TOC etc. there is a correlation for the
SAC254 of the same quality as, e.g., between COD and TOC. Very high
This symbol may appear on the product and identifies the connection point for the protective ground.
When this symbol appears on the product, it identifies the location of a fuse or a current limiter.
Electrical equipment marked with this symbol may not be disposed of in European domestic or public disposal
systems after 12 August 2005. In conformity with European local and national regulations (EU Directive
2002/96/EC), European electrical equipment users must now return old or end-of life equipment to the
manufacturer for disposal at no charge to the user.
Note: For return for recycling, please contact the equipment manufacturer or supplier for instructions on how
to return end-of-life equipment, manufacturer-supplied electrical accessories, and all auxiliary items for proper
disposal.
35 cm
für den
Ausbau
der Sonde
freilassen!
N O T I C E
Any use other than use in accordance with requirements defined in the user manual
leads to the loss of the warranty claims and can lead to personal injury and property
damage, for which the manufacturer assumes no liability.
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3
4
2
Substance groups measured
1. COD 3. SAC
2. BOD 4. TOC