Severn Trent Water is one of the first utility companies to use YSI Hydrodata’s new multiparameter intake protection system, the ‘HydroSAM’. The HydroSAM is designed to replace older water quality monitoring systems that draw samples through a network of pipes which feed a series of in-line sensors.

Until now, these wall mounted systems have been installed to monitor water quality upstream of river abstraction points, so that plant managers are provided with data that can inform water treatment decisions. However, such systems require a high level of maintenance and frequent calibration.  In contrast, the HydroSAM has been designed for minimum maintenance and long-term deployment. The heart of the HydroSAM is a multiparameter probe known as a ‘sonde’, thousands of which are in use all over the world as insitu water quality loggers in both freshwater and marine applications.   Water quality monitoring sondes are often left in remote and difficult to access locations and it is for this reason that YSI has, over many years, developed sensor technology that is able to take accurate readings without the need for frequent site visits.

The sondes have also been designed to be compact, thus providing a further benefit to the HydroSAM. River water is pumped through a single sample chamber in which the sonde is located, so that all of the sensors are exposed to the same sample.

The HydroSAM employed by Severn Trent Water monitors pH, temperature, conductivity, turbidity, dissolved oxygen and ammonia. However, it would be possible to add sensors for chlorophyll and blue/green algae.



The sequence of events that ended with the installation of the HydroSAM began with Works Manager, Natalie Horton becoming increasingly frustrated with the problems and high maintenance requirements associated with traditional monitoring systems. However, she had heard that the Environment Agency deploy multiparameter sondes in rivers and approached YSI Hydrodata to discuss the possibility of their use for intake protection.

As a result, a sonde was installed directly in the river Severn upstream of the Shelton WTW near Shrewsbury on a 3-month trial.

Prior to the trial, Natalie Horton admitted to a fair degree of scepticism over the sonde’s ability to cope with occasional high levels of fouling. However, after visiting the site, she said that she was “Delighted to discover that, as a result of the inbuilt sensor wiping mechanisms, the sensors were completely free from fouling and the readings correlated very closely with [their] own calibrated equipment.”

Following the success of the trial, Severn Trent Water ordered a full HydroSAM which has been permanently installed ten miles upstream of the water intake.

The system provides almost continuous monitoring data to the Shelton works and operators have been provided with the facility to dial into the unit from anywhere or to visit the site and collect data with a portable computer. Alarm conditions have been set and the unit will issue alarms via the PCMS should those conditions arise.



Natalie Horton has since become Risk and Safety Manager for Water Supply at Severn Trent Water. Looking back over the HydroSAM trial she says “It is vitally important for our water treatment works to be provided with advance knowledge of water quality and trends so that we can manage the treatment process as effectively as possible. It is always our aim to maintain stability in the plant because unforeseen changes in the intake could necessitate a need for reduced flows to maintain water quality.

For example, turbidity can range from 1 NTU to over 200 NTU, but this can be accommodated quite easily if we have an accurate and reliable intake protection system.

However, the main benefit for us has been the reduced requirement for calibration and maintenance; site visits used to be necessary every week, but now a simple 6-weekly calibration check is all that is needed. We have been delighted with the HydroSAM - it was simple to install and operate, it has proved to be reliable, and it saves labour costs.”

Natalie Horton concludes; “The performance of the new water quality monitor has been absolutely brilliant.”