Water & Wastewater Treatment Magazine
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24 | AUGUST 2019 | WWT | www.wwtonline.co.uk Trent's decision to install 120 Aztec 600 phosphate analysers in wastewater treatment plants throughout its operating area. With the ability to accurately measure phosphate levels down to 0.0016ppm, the analysers are helping to ensure that the com- pany keeps within the increas- ingly stringent consent limits set by the Environment Agency. Operating as part of a dosing control system alongside am- monia analysers, iron analys- ers and turbidity monitors, the phosphate analysers have reduced the company's reliance on manual sampling. Connected to Severn Trent's eSCADA system, the analysers provide continuous real-time data, including any alarms generated by issues such as high phosphate levels. Com- bined with the data obtained from other instruments, such as ammonia and turbidity analysers, Severn Trent has a complete picture of its water quality at all times. Obtaining real-time data on phosphate levels helps ensure the company never strays outside its consented limits. The data is also a boon when it comes to planning future in- vestments designed to further improve effluent quality. React or predict? Analytical sensors in waste- water treatment face some of the toughest operating condi- tions of any measurement instrument. With these devices o„en in constant contact with substanc- es ranging from toxic liquids through to sewage sludge, it is not surprising that regular maintenance and inspection regimes are needed to ensure continued accuracy. Until relatively recently, car- rying out these regimes relied on a combination of manufac- turer guidelines, established practice and, to some extent, guesswork. Operators could put together a maintenance schedule based on the likely operational lifespan of a device, coupled with the effects of expo- sure to the medium being meas- ured. What they o„en couldn't predict, however, was the The Knowledge Wastewater sensors impact of any unforeseen varia- tions, either in the performance of the device or the substance it was in contact with. Furthermore, the effective- ness of the maintenance and inspection routines relied on having the staff available to carry them out. With a growing number of companies increas- ingly faced with shrinking engi- neering teams stretched across multiple sites, there has been a risk that these routines are not always carried out to plan. In both cases, there is a risk of measurement performance being affected by deteriorating accuracy or complete instru- ment failure, increasing the potential for a breach of consent levels and the likelihood of stiff financial penalties being imposed. With the advent of digital sensors, these challenges are being overcome. When coupled with the arrival of next genera- tion digital transmitters, plus the arrival of remote condition monitoring, digital sensors are helping to transform water quality analysis, not least by enabling operators to use the data they generate to create smart maintenance routines. This data can include not just the water quality parameter be- ing measured, but also device- level diagnostics, opening new possibilities for assessing performance and pinpoint- ing problems before they can develop. By using this data to create tailored maintenance routines, operators can ensure that engineers are only dispatched to site when necessary. As well as greatly enhancing the reliability of the installation, the avail- ability of this 'deeper data' can also reduce the cost of operation and maintenance, enabling digital sensors to offer a much lower total cost of ownership than their ana- logue counterparts. Another important factor is simplicity. With skilled operators being at a premium, there is a need to ensure that devices can be used easily. This includes not just operation, but also setting up, finetuning and fault-finding. For this reason, instru- ment manufacturers have worked to minimise the complexity of their devices, enabling them to be used by even the least experienced operators. Another development is the use of plug-and-play technolo- gies that allow digital transmit- ters and sensors to be quickly and easily connected, with all necessary information and set- tings automatically uploaded. By helping to take the complex- ity out of setting up an anlyser system, such features can help to reduce the risk of potential measurement errors caused by incorrect installation. Summary The possibilities offered by digital devices in people's everyday lives when it comes to immediate access to live data is increasingly leading to an expectation of the same level of performance in the workplace. More information, bet- ter control, less cost, more focused maintenance, fewer breakdowns and a substan- tially reduced chance of pollution incidents – when it comes to wastewater treat- ment, the all-round benefits offered by the latest genera- tion of online digital sensors and analyser systems make them the ideal solution for wa- ter companies needing to find ways to keep a continuous eye on process performance and regulatory compliance. WASTEWATER QUALITY Analytical sensors in wastewater treatment face some of the toughest operating conditions of any measurement instrument