WATER MANAGEMENT
Controlling WASTEWATER TREATMENT
Michael Dooley reports on the best approach to managing the activated sludge process that’s used in water treatment plants
T
he activated sludge process is by far the most important method for treating both domestic and industrial wastewaters. Improving the control and visibility of this biological process, which consumes
over 2% of the world’s produced electricity (of which energy consumption for aeration is by far the biggest contributor), is key to meeting every tightening compliance requirements as well as reducing energy costs.
Instrumentation used in advanced real-time control
(ARTC) of the treatment process should be self- cleaning, self-calibrating and measure or predict the following:
n Critical measures of load such as BOD and ammonia
n Critical treatment control parameters including dissolved oxygen, pH, MLSS, nitrate, phosphate, F:M ratio, ORP
n Predictors of performance such as % settlement (SVI/SSVI), supernatant turbidity, % nitrification, toxicity
n Ideally such instrumentation can provide both feed- forward and feed-back data to the treatment works control system
AN IDEAL SOLUTION FOR THIS APPLICATION One such system is the activated sludge plant controller (ASP-Con), which measures all the above parameters, is self-cleaning and self-calibrating and can be fully integrated with site PLC/SCADA control systems, cloud-based reporting and incorporates GSM-based remote access for monitoring and maintenance. The system also incorporates the capability to
control plant equipment without the need for a separate PLC-based control system. The image below shows a typical installation for the ASP-Con system. The customer can program which parameters are measured and also the frequency of sampling, auto-calibration and auto-cleaning routines. Measurement of influent ammonium load and
mixed liquor suspended solids (MLSS) were validated on a UK-based treatment works. The validation data detailed above was verified by the Water Research Council (WRc), which confirmed the instruments’ accuracy under these test conditions. Based on this
data the ASP-Con system can make an assessment of the required plant operating parameters (such as DO set point, blower operating pressure, valve positioning, etc.) and adjust them within
A typical ASP-Con installation in North America
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