Activated Sludge Process Optimisation – DO control via Ammonium measurement: ISE vs. Wet Chemistry.
INVESTMENT REAPS REWARDS
A recent trial of a WTW VARiON Ammonia ISE against a competitor’s wet chemistry analyser on the inlet to a major ASP on a flagship works in the UK revealed just how far the ISE technology has come through the intensive investment in R&D that Xylem has made. 6 weeks of data is presented across the plots below.
Two ISE sensors were installed: one with additional air cleaning and one “straight out of the box”. These sensors were calibrated to the liquor matrix during the initial commissioning and then remained untouched for the remainder of the trial.
DATA ANALYSIS
As can be seen from the data in the full report, it is the ISE sensors which have proven to be the most reliable, the difference between the two ISEs by the 6 week mark highlighting the importance of the air cleaning to the installation location. The wet chemistry analyser required two emergency service visits to correct major issues in week 2 and week 4 of the above data, and repeatedly produced data that could not be actioned when operating in the intervening times, and during the first two weeks of the trial struggled to measure the diurnal load variation.
This data challenges the historical preference for wet chemistry analysers to assess the Ammoniacal loading of an ASP. Due the cost (both capital, installation and operational) of these instruments, a single measurement point at the inlet to the ASP has been the only commercially viable solution, with the assumption that the feed to each of the lanes in the plant will have the same hydraulic characteristics and therefore the loading will be identical. This is rarely the case and the differences between lanes can become more severe as the size of plant increases. These differences limit both the treatment efficacy achieved through control via a single measurement point and limit the efficiency savings which can be made through the availability of a larger volume of reliable and actionable data.
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Xylem Analytics UK manufactures environmental monitoring instruments and systems with a reputation for high levels of accuracy and reliability.
WTW, a Xylem brand, brings 75 years of knowledge and technical expertise in waste water instrumentation coupled to continuous innovation in performance and reduction of cost of ownership. This customer focused drive has resulted in market-leading sensors and systems for ammonium, nitrate, nitrite, turbidity, suspended solids, pH, conductivity, UVT, SAC and COD.
Xylem Analytics’ experience in instrumentation, optimisation, system development and control enables them to select the best solution for your challenge, be it simple and discrete single sensor systems or a plant wide multi-parameter network. Local installation, commissioning, service support and training is also available through our dedicated engineering and projects teams.
To read full article on Activated Sludge Process Optimisation and see the results – Click here
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