Monitoring & metering
Hesketh explains. “In this example, the ESNET measures final effluent turbidity and transmits the data to MeteorCloud, and if the value is too high, MeteorCloud sends an instruction to the dosing unit via the ESNET. Similarly, when turbidity is low, dosing is unnecessary and therefore halted.”
The same mechanism is applied for other dosing mechanisms. For example, pH measurements are used to control the dosing of caustic soda (sodium hydroxide). It has been suggested that final effluent monitoring might be too late for dosing control, but in Hesketh’s experience the key is the judicious selection of the set-point.
By automating dosing control, Scottish Water is negating the need for the installation and maintenance of additional process management hardware, all of which improves the sustainability of operations.
LOOKING FORWARD range of diverse locations.
ESNETs are available in two formats - kiosk and portable. The kiosks are designed for permanent installation and the portable units are used for short-term deployment. Scottish Water, for example, have 7 portable ESNETS that are used primarily for process investigations. Each of the Scottish Water ESNETs has a multiparameter water quality sonde fitted with sensors for measuring dissolved oxygen, temperature, pH, conductivity, turbidity and ammonium. Each sonde is located within an integrated flow chamber, through which sampled water is pumped. Water quality data is automatically transferred to the MeteorCloud® platform, which provides secure data visualisation, analysis and alarms. One of the most important features of ESNETs is the ease with which they can be installed, usually requiring no capital works or pre-existing communications infrastructure. They are also designed to run with a very low power requirement, and are able to operate from a solar charged battery – even in Scotland.
Instrumentation Monthly August 2025
Meteor Communications initially trained Scottish Water staff on how to install, service and calibrate ESNET systems, and this team of trained individuals now manages the network themselves. Their work involves routine visits to each site every 4-6 weeks to clean the pump and sample line, and to swap in a pre-calibrated sonde. Hesketh’s team also log in to MeteorCloud every morning to check for any data anomalies that might mean swapping a sonde before its allotted date.
ENABLING PROCESS EFFICIENCY The wastewater process team at Scottish Water are able to log in to the MeteorCloud platform to view both historical and live water quality data, and to set up text alarms and email alerts to inform wastewater operations. One of the most remarkable benefits to be gained from the ESNET systems is their ability to control dosing units. “We have started to hardwire some of the ESNETs to our dosing units, so that set points for, say, turbidity, can trigger coagulant dosing with PAC,” Hesketh
In addition to the water quality sonde, it is also possible to connect other sensors to ESNETs. For example, some users also connect water level or meteorological sensors. In addition, a multitude of different data feeds can be connected to ESNET systems, including analogue, digital and serial protocols. This lowers data infrastructure costs and reduces the need for manual checks. Scottish Water has exploited the ESNET’s connectivity by attaching traditional final effluent ammonia monitors at some locations. “This has enabled us to compare the data from ESNET sondes with that from their (much more expensive) predecessors,” Hesketh says. “The results have been very pleasantly surprising, because we have found that the data from the two different instruments trend in similar ways. However, there is still a justification for deploying a dedicated ammonia analyser where levels are particularly low.” The program of ESNET installations is progressing well, delivering real-time multiparameter final effluent water quality data to enable prompt process management. Initial work to connect dosing units to the ESNETS has shown enormous potential to reduce the volume and cost of dosing chemicals, so Scottish Water plans to expand this capability across the whole country, with concurrent environmental and cost benefits.
The ESNET-based automatic dosing control mechanisms have only recently commenced operation, so it is probably too soon to draw any firm conclusions. Nevertheless, early indications are showing savings in chemical costs of around 20 per cent. The Scottish Water wastewater process team is therefore optimistic about potential future improvements.
Meteor Communications
www.meteorcommunications.co.uk 67
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