Improving Wastewater Treatment with Digital Measurement

Developments in digital technology have presented brand new opportunities for water sensing, offering unprecedented access to a plethora of real-time, highly precise data without the pitfalls associated with many traditional sensor types. By making use of these devices in their water treatment processes, operators can rely on the greatly improved measurement of many of the vital parameters entailed in the treatment of both household and industrial effluent.

This article examines some cases of the new digital sensing technologies on offer and explains how they are already delivering tangible benefits for water utilities.

It’s said that prevention is better than cure and that’s twice as true in the wastewater industry.

The requirement to meet stringent environmental legislation and reach maximum profit through lowered operating expenses is incentivizing many operators to look for ways to better understand what’s happening in their processes.

Developments in digital water sensing technology are providing never before seen access to a raft of real-time, high accuracy data without the pitfalls associated with a good deal of conventional sensor types. By making use of these devices, operators can rely on the greatly improved measurement of many of the pivotal parameters entailed in wastewater and industrial effluent treatment.

Recent years have seen purely analog systems increasingly being pushed to the wayside by digital measurement devices which offer expanded data gathering and communications capabilities.

As well as averting incidents of pollution, the better access to timely data provided by these devices is allowing users to make considered decisions that result in a step-change in performance, efficiency and maintenance.

Continuous Measurement Cuts Costs

Continuous automatic measurement is superior to manual methods, hands down. Contrasting with traditional manual sampling methods, continuous online analyzer systems allow samples to be automatically measured and analyzed at the point of sampling, giving real-time indicators of present process conditions.

Additional positive outcomes include reduced failures and maintenance problems, unexpected shutdowns or growing plant maintenance for example. Others include fewer delays and failures that can affect treatment efficiency and regulatory compliance.

As well as lowering the necessity for operators to make sometimes expensive interventions, automatic continuous monitoring can also aid in reducing levels of sludge. The use of the most recent digital dissolved oxygen sensors in activated sludge systems, for example, can offer much stricter control of dissolved oxygen levels, matching them to actual oxygen demand and helping to make sure the right conditions needed to maximize aeration process efficiency. As aeration processes account for more than half of a plant’s energy costs,  strict control of dissolved oxygen can be ensured and also help operators in realizing significant energy cost savings.

Continuous Measurement Helps Compliance

With both Ofwat and the Environment Agency taking an increasingly strong position on the quality of wastewater discharged to the environment, it quite literally pays to use the best available technology to limit the risk of any infringements.

The necessity of measuring phosphate levels was driving Severn Trent’s decision to install 120 Aztec 600 phosphate analyzers in wastewater treatment plants throughout its operating area. With the ability to measure with precision phosphate levels down to 0.0016 ppm, the analyzers are helping to make sure that the company keeps within the increasingly strict consent limits put in place by the UK Environment Agency.

Operating as part of a dosing control system next to ammonia analyzers, iron analyzers and turbidity monitors, the phosphate analyzers have lowered the company’s dependence on manual sampling.

Linked to Severn Trent Water’s eSCADA system, the analyzers offer continuous real-time data, which includes any alarms set off by problems such as high phosphate levels. Put together with the data harvested from other instruments, such as ammonia and turbidity analyzers, Severn Trent has a comprehensive picture of its water quality at all times.

Getting real-time data on phosphate levels aids in ensuring the company never falls outside its agreed limits. The data is also of great benefit when it comes to planning investments in the future that are designed to further improve effluent quality.

React or Predict?

Analytical sensors in wastewater treatment come up against some of the hardest operating conditions of any measurement instrument.

With these devices frequently in constant contact with substances ranging from toxic liquids through to sewage sludge, it is not a shock that regular maintenance and inspection regimes are required to make sure accuracy is continued.

Until fairly recently, conducting these regimes was reliant upon a combination of manufacturer guidelines, established practice and, to an extent, guesswork. Operators could build a maintenance timetable founded on the likely operational lifespan of a device, paired with the effects of exposure to the medium being measured. What they frequently were not able to foretell, however, was the effect of any unforeseen variations, either in the performance of the device or the substance it contacted.

The effectiveness of the maintenance and inspection routines depended on having available staff to carry them out. With an increasing amount of companies faced with shrinking engineering teams spread across multiple sites, there has been a danger that these routines are not always conducted to plan.

In both instances, there is a danger of measurement performance being affected by deteriorating accuracy or total instrument failure, increasing the chance for consent levels to be breached and the likelihood of the imposition of stiff financial penalties.

With the arrival of digital sensors, these issues are being eliminated. When put together with the arrival of the latest generation of digital transmitters, plus the introduction of remote condition monitoring, digital sensors are helping to revolutionize water quality analysis, not least by allowing operators to use the data they produce to create smart maintenance routines. This data can include not only the water quality parameter being measured but also device-level diagnostics, offering new opportunities for performance assessment and identifying issues before they happen.

By making use of this data to generate tailored maintenance routines, operators can make sure that engineers are only sent to site when needed. As well as significantly enhancing the reliability of the installation, the readiness of this ‘deeper data’ can also lower the expense of operation and maintenance, allowing digital sensors to provide a greatly reduced total cost of ownership than their analog counterparts.

Simplicity is another significant factor. With skilled operators being at a premium, it is necessary to make sure that devices can be used with ease. This involves not only operation but also setting up, fine-tuning and fault-finding.

With this in mind, instrument manufacturers have worked to limit the complexity of their devices, allowing them to be used by even the least experienced operators. The most recent generation of digital transmitters feature ‘EZLink’ plug and play technology, which helps them to be speedily and easily connected to digital sensors, with all required information and settings automatically uploaded.

As these transmitters use a shared operating interface, operators trained on one device can transfer the same knowledge to program and operate any of the other instruments and analyzers with a limited need for additional training.

Summary

The opportunities provided by digital devices in people’s day to day life when it comes to instant access to live data is leading to a growing expectation of the same level of performance in the workplace.

Additional information, improved control, less expense, more focused maintenance, fewer breakdowns and a significantly reduced likelihood of pollution incidents – when it comes to wastewater treatment, the sweeping benefits provided by the most recent generation of online digital sensors and analyzer systems make them the perfect solution for water companies that require ways to keep a continuous eye on process performance and regulatory compliance.

This information has been sourced, reviewed and adapted from materials provided by ABB Measurement & Analytics.

For more information on this source, please visit ABB Measurement & Analytics.

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