About 95% of the water that South West Water supplies to Devon, Cornwall and small areas of Dorset and Somerset comes back to them for treatment and disposal (South West Water: Code of Practice on our Wastewater Service). Once wastewater has been treated, it can be released back into the environment, providing it has been treated to safe and acceptable levels.
Wastewater sampling is a process which must be
carried out by all UK Water Companies in order to monitor the
performance of wastewater treatment plants.
David Thomas is responsible for coordinating
the collection of Regulatory Waste Water Samples for South West
Water from over 600 sampling sites in the South West of England.
Each sample that is collected has to be transported to South West
Water's laboratory in Exeter, where the wastewater is tested to
determine that it has been treated properly at one of the company's
In order to comply with Operator Self Monitoring
(OSM) regulations (overseen by the Environment Agency),
which require that operators monitor samples and ensure sample
stability prior to testing, sample temperatures are monitored
through all phases of collection and transportation using Tinytag
A supply of over 100 Tinytag data loggers
powers South West Water's wastewater sample monitoring programme.
The company use three different models of Tinytags across their
operation: Tinytag Extra TGX-3020 (now obsolete), Tinytag Plus 2 TGP-4020 and Tinytag View 2 TV-4020. Both
the Tinytag Plus 2 TGP-4020 and Tinytag View 2 TV-4020 are used
with thermistor probes for
monitoring internal temperatures.
The data loggers have proved versatile for South West Water, and
are used across three separate tasks within water sampling:
1) Monitoring product temperature during
The temperature of the wastewater samples is measured from the
point of collection until the time they are transferred to
refrigeration units or vehicles. The data loggers'
thermistor probe is placed at the bottom of the
collection vessel, monitoring sample temperature as the autosampler
collects a composite sample over the 24 hours sample period,
spot-checks of product temperature are also carried out
2) Monitoring static fridge temperature.
Static fridges are strategically placed across the South West to
be used as drop-off points for samples before they are collected by
a courier and transferred to the laboratory in Exeter. Data loggers
measure/record the internal temperatures of these fridges to
evidence that the samples have been kept within the exacting
temperature constraints for the regulations.
3) Monitoring temperatures in transit.
When a Tinytag is being used to record the environment in which
samples are transported (be it in refrigerated vehicles or portable
fridges), the lowest portion of a logger's probe is placed into a
'dummy sample'. The 'dummy sample' being used to replicate the
temperature deviations caused within a sample when the fridge might
be open during the courier run i.e. when adding more samples to the
Using Tinytag data loggers has helped South West Water run a
tight, transparent operation. Automatic monitoring
of samples during collection and transportation using Tinytags
allows South West Water to create contiguous profiles of the sample
temperatures, which is used to demonstrate exemplary
compliance with OSM regulations. Complete datasets also
allow South West Water to identify any breaches of the specified
sample temperature limits and duly notify the Environment Agency
that any sample effected would be 'non-compliance' and a
re-schedule would be forthcoming as per regulations.
Tinytags were initially chosen by South West Water because
Gemini provides a certificated calibration service,
which reassures the company that their Tinytags are measuring with
the utmost accuracy.
David Thomas says that he has been consistently pleased with
Gemini's calibration service: "With Gemini having a
calibration service which is traceable to National Standards that
is quick and easy to use, it shows that they and we take our
Ease of use was not on the agenda when the Tinytags were
initially purchased, but has proved to be a happy bonus.
"Without a fully portable temperature logging
device," David concludes, "we as a
company would not be able to fulfil the regulatory requirements set
by the OSM regulations."