Water monitoring

of chlorine through to the EDI, which it can also damage. Furthermore, the customer wanted to avoid any flow of chlorine back into the river system. A carbon filter can now be used upstream of the RO to prevent the inbound flow of chlorine. For detection accuracy, Bürkert’s 8905

water analysis system and chlorine sensor has a t90 time, the duration that it takes the sensor to measure 90 per cent of the chlorine concentration, of less than 30 seconds, whereas typical industry standards for chlorine sensors have a t90 time from 60 to 180 seconds. The fast reaction time also means that the

8905 sensor is unaffected by polarization, whereby a sensor measuring zero chlorine for long periods of time can take several hours to react and measure with reliability when small amounts of chlorine are reintroduced. Typical sensors can therefore be unable to measure trace chlorine levels, which can pass through the system before they are able to react. Instead, Bürkert’s 8905 sensor is able to accurately and reliably measure chlorine even at µg/l trace level. Faster reaction is a result of the chlorine sensor design, which features only a single membrane compared to a typical chlorine sensor which incorporates a membrane pair surrounding an electrolyte buffer. The single membrane of the 8905’s chlorine sensor means that the ions buffer through reduced resistance before chlorine trace is detected by the sensor, creating the faster response rate. The accuracy of the Type 8905’s additional

sensors also identified new data that would be useful to the plant, including pH levels up to pH12, which can be used to pursue further improvements in performance and reliability across the water treatment plant. The sensors also detected a caustic solution used as part of the cleaning process, the results of which will be used to assess the long term impact to the RO system. Cost was also reduced in system

installation. The 8905 system can be installed into a single compact panel, approximately one meter square, as opposed to utilising several larger boards, complete with transmitters. This reduces wiring costs and installation time, as well as footprint. The potential for Ethernet connectivity for plant automation will also reduce the cost of sensor outputs and increase the ease of system integration. The system can be operated by the seven-inch touch display or remotely using Bürkert’s Communicator PC tool. The results of the trial have identified accurate, repeatable and reliable readings across the analytics, which have identified potential for a more effective water treatment system. These results can then be utilised to deliver improvements across the plant for better reliability and reduced downtime.

Bürkert Fluid Control Systems

Instrumentation Monthly April 2021 Water managers demand better, faster data

2020 was an unusual year in many respects, but for OTT Hydromet, one of the more remarkable features of the year was an unprecedented level of orders for water level and flow monitoring equipment. Amid increasing pressure from climate change and urbanisation, OTT’s UK managing director Nigel Grimsley explains the growing demand for monitoring technology that enables more effective water management.


n 1978 OTT launched the Allgomatic – a large desktop device for ‘data measurement, storage and transmission,’ – it was not even called a

datalogger. Prior to the Internet and mobile phones, OTT’s customers were monitoring water level in boreholes and stilling wells with dip tapes or sensors such as shaft encoders and compressed air bubblers connected to displays, dataloggers or chart recorders. Discharge calculations were based on stage measurements, possibly with a point and hook gauge, combined with manual measurements of velocity with a rotating element current meter. Raingauges were mostly operating with a collection vessel or with a tipping bucket mechanism; recording tips with a connected datalogger. Inevitably, this provided a retrospective view of water resources that was mainly useful for detecting trends and informing models. Flood protection measures at this time were

often designed to increase channel capacity and/or divert water away from sensitive areas. This may have involved engineered flood defence infrastructure with higher flood defences and straighter channels. Flood plains were increasingly used for agricultural, commercial or residential development, and the creation of ever-growing areas of impervious concrete and asphalt increased flood risk at a time when climate change was starting to increase the frequency and severity of severe weather.

LOOKiNG fOrwArd Jump forward to today and flood management has changed dramatically - Natural Flood Management (NFM) is now regarded as a more effective and sustainable strategy. Flood risk is now addressed on a wider catchment scale so that upstream initiatives do not have negative effects further downstream. This catchment based approach has meant that water managers are increasingly looking for solutions that employ techniques which work with natural hydrological and morphological processes and features to manage flood waters. These NFM techniques include the restoration, enhancement and alteration of natural features such as flood plains. However, there are many other ways in which NFM can help to lower peak flow and decrease flood risk. Tree planting for example, intercepts rainfall and overland flow, increases water infiltration into soil, and provides important connective habitat for wildlife, as well as providing increased carbon storage.

TOmOrrOw’s TecHNOLOGy In addition to the provision of baseline data, monitoring systems are also necessary for measuring the effectiveness of mitigation measures and providing timely warnings when

alarm conditions arise. In order to better understand catchments, groundwater and surface water levels should be correlated with upper catchment monitoring which includes the measurement of meteorological parameters. The demand for high intensity monitoring is

growing rapidly, as water managers demand lower levels of uncertainty in their monitoring data, and seek to exploit the advantages of networks of continuous monitors. The high volumes of orders that OTT received in 2020 featured many networkable sensors such as the OTT ecoLog 1000; a self-contained surface and groundwater level logger with two-way communication for smart phones and tablets. Remote sensors were also highly popular, including the OTT SVR 100 surface water velocity radar and the OTT RLS non-contact radar level sensor. The volume of dataloggers with satellite communications capability is also increasing as network managers seeks to exploit the benefits of reduced data transmission costs. The demand for better monitoring is driving

the development of OTT’s latest hydrometeorological technologies, which can be summarised in four categories:

Accurate, reliable, low-power, smart sensors Flexible, intelligent, easy-to-use dataloggers

Reliable, appropriate, cost-effective telemetry with multiple transmission options and redundancy capability

Customisable, easy-to-use, insightful, web- enabled, data management software

With the benefit of insights from

comprehensive real-time monitoring networks, collecting high intensity data from multiple points, water managers will be able to make better informed, defensible decisions.

OTT Hydrometry 57

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