Operational & cost benefits with Ammonia monitoring
Following a successful trial, United Utilities has selected ATi as its preferred provider for final effluent ammonia monitoring in three of its Lancashire waste water treatment plants, saving them up to £2,000 a year in maintenance costs.
The Leyland and Chorley sites were initially selected to test two Total Ammonia Monitors on final effluent and the results were, in the words of plant manager Martin Gilday, “fantastic”.
Comparison data from Leyland over a two month period, shown in Figure 1 (FE Ammonia Comparison Data), demonstrates how manual testing on site corresponded to ATi’s online monitor. Based on these results – their most accurate ever – United Utilities have now made the installations permanent, along with further installations at a third plant, which will see them save up to £2,000 a year in maintenance costs.
To date over 30 other sites across the UK and Ireland have installed ATi’s Q46N final effluent technology, with a further 50 plants also scheduled for installation this year. These sites typically have an effluent consent of 5 mg/l or less, and any failure to comply with the discharge consent could lead to hefty financial penalties under the OFWAT performance assessment. However the Leyland and Chorley plant is a particularly well maintained site, therefore effluent is typically even lower in ammonia concentration and is difficult to detect with other technologies, such as ion selective electrodes. However the Q46N unique reaction chemistry gives a five times uplift in sensitivity, allowing measure at levels as low as 0.02ppm, 20 parts per billion.
Accurate, first class results
Continuous measurement data is crucially important to confirm treatment facilities are operating efficiently. By using the Q46N monitors, measurements can be retained on an internal datalogger, with data downloaded periodically or transmitted via GPRS to a dedicated server, which feeds a website to enable 24/7 access to live water quality information.
Figure 2 (new Q45N three week Continuous FE Measurement) shows recorded data taken during the trial. No calibration or maintenance was necessary during this period. The data shows several weeks of unattended use, with reported ammonia levels often running below 0.2ppm.
All monitors in the trials were installed with a Rotorflush submersible pump, fitted with a 150 micron filter. After three months, each site was visited to determine the extent of system fouling and to carry out maintenance. Although there was evidence of some particulate build-up (Image 1 – Particulate Build-up), this does not prevent the monitors from working and results showed how they continue to operate effectively without calibration during this time.
As part of the maintenance checks, the monitors were then validated using an ammonia standard, with the sensors responding and recovering quickly to the sample levels (Figure 3 – Ammonia Validation).
Results also demonstrated that over the three month period there had been a slight drop in the sensor calibration slopes, suggesting that on final effluent applications a calibration every six weeks would be appropriate. Calibrations can be carried out within 10 minutes and could be done at the same time as when the reagents are changed.
New product developments
Since installing the original Q46N monitors to the United Utilities plants, several developments to the original design have been incorporated following feedback from customers, which identified the need for two types of final effluent monitor. Whereas the preference of some water companies is for a monitor that requires regular manual calibration, others require a monitor that features an auto-calibration, so it both responds and calibrates automatically. Automatic validation of measurement provides the best possible confidence and calibrates against two known calibration standards to enhance accuracy and raises awareness of unacceptable performance.
Following this feedback, ATi have been offering automatic validation for the Q46N since the end of 2013. ATi has also worked closely with Rotorflush as part of these trials and recommends their self-cleaning pump for all final effluent applications.
Substantial operational and cost benefits
Martin Gilday, United Utilities Plant Manager, believes that ATi’s Q45/46N dissolved ammonia monitors offer substantial operational and cost benefits: “The low cost of operation and accuracy of results has enabled us to make a number of changes to plant performance, which has greatly reduced the risk of failure. Already the instrument has proved invaluable, providing us with crucial trending data, identifying how upstream processes may be improved and ensuring compliance with the Environment Agency permit.”
“Our instrumentation selection was influenced by the quality of support ATi offers as part of its first rate customer service package, including free training, fast response times, low maintenance costs and high quality and efficient monitors. This trial is generating a lot of interest amongst the management team and if we can prove that the lifetime costs are as low as they appear and if the unit continues to perform reliably, the low capital and maintenance costs will mean that ATi’s final effluent monitors could find application at a large number of our treatment works”.
Chris McTear, ATi Technical Support Manager, said:
“One of the main advantages of 24/7 data is that it helps to identify spikes and enables process operators to determine the cause of the problem, allowing them to adjust the treatment process.
“ATi’s Q45/46N system allows you to deploy these monitors and get months of low maintenance, reliable monitoring, including MCERTS, for all pH and ammonia monitors. The Dissolved Ammonia monitors offer a completely new and improved approach to simultaneous on-line monitoring of chloramines and ammonia in final effluent, which is simpler, cheaper and more sophisticated than conventional monitoring equipment.
“Continuous data offered by the Q45/46N monitors also helps with the identification of treatment deficiency and data for multiple parameters provides a better understanding of the whole process. Regular sampling and analysis can be lower in cost than online monitoring, which is what some of our customers prefer, however this puts you at risk of a pollution incident going undetected between sampling times.”