SRTmaster™ maintains the optimum environment for
microorganisms in an activated sludge system and optimum
conditions for thickening of the wasted sludge

SRTmaster™ controls sludge retention time (SRT) also known as sludge age. It does this by using a sophisticated control algorithm that takes into account real time variations in solids inventory in the aeration tanks and in solids to be wasted. Analyzing historical patterns of sludge wasting, SRTmaster™ also provides stable solid mass loading on the wasted sludge thickening facility while filtering out any erroneous data. SRTmaster™ is custom-tuned to the customer’s specific activated sludge process. The software will inform operators of potential problems and suggest corrective action.

Unique Features of SRTmaster™ Software

  • Each control algorithm is tuned before delivery using a customized computerized model of the customer's activated sludge process
  • The unique sensor fault detection algorithm detects problems with the sensors and prevents the use of faulty data
  • A special algorithm provides stable wasted solids mass loading on the sludge thickening facility
  • The unique output data filtration algorithm guarantees that maintaining the SRT target will never have a negative effect on the performance of clarification by maintaining mixed liquor concentration within the specified range
  • By maintaining the mass of wasted sludge within the specified range, SRTmaster guarantees that a wasted sludge thickening facility will be never overloaded
  • The controller automatically notifies operators about potential problems and suggests possible solutions using fuzzy logic methodology combined with non-parametric statistics.

SRTmaster™ History

1997: As a part of a large research project, Dr. Alex Ekster develops the first prototype of the SRT control algorithm and tests it at the 167 MGD San Jose/Santa Clara Water Pollution Control Plant. The Water Environment Federation (WEF) acknowledges this project as the best research of the year and awards Dr. Ekster a Phillip Morgan Medal.

1998: Dr. Ekster launches Ekster and Associates. Ekster and Associates develops a more robust version of the SRT control algorithm using several years of experience in operating SRT control systems.

1999: Ekster and Associates enters into an agreement with Royce Instrument Corporation to market SRT controllers.

2001: The Royce SRT controller, designed according to Dr. Ekster's specifications and powered by Ekster and Associates' SRT control software, receives the 2001 WEF Innovation Award.

2002: Ekster and Associates stops licensing SRT control technology to Royce and starts direct licensing to treatment plants. Ekster and Associates increases the product line from one SRTmaster™ version to four.



  • SRTmaster™ will stabilize activated sludge and sludge thickening processes.


  • SRTmaster™ will never calculate waste flow based on faulty data.


  • SRTmaster™ will always inform operators about potential problems related to biomass and will suggest possible solutions.

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