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World’s Leading supplier in Precision Dissolved Oxygen Measurement and Respirometry

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Winner of WEX – Water and Energy Exchange

– Global Innovation Award

Madrid 2014



ASP-CON can be installed permanently into several different areas in the Secondary Wastewater Treatment Plant to provide feed-forward or feed-back control for plant operation and optimisation. The ASP-Con carries out several continuous measurements, and also analyses discrete batch samples of the product to give the following parameters on a frequency which the plant operator can set:


This continuously provides the Dissolved Oxygen level, and in conjunction with the other measured variables, provides a higher level of automation than is currently achieved by using this parameter alone.

The temperature of the Mixed Liquor Suspended Solids is provided, as this affects this performance of the bacteria in the activated sludge process.

This parameter is reported continuously, which in combination with the critical oxygen concentration point, will assist in dynamically set the plants DO set-points.

This measurement is necessary to ensure the Ammonia result is not being impacted by high levels of potassium.

This parameter is reported continuously so that any dosing required to maintain a neutral pH can be determined ensuring that nitrification is not inhibited.


This parameter is reported continuously Oxidation-Reduction Potential,can be used as an alternative to dissolved oxygen depletion in anoxic and aerobic processes.

This batch measurement is used in the control of wasting rates and to determine the F:M ratios of the plant.

The settlement of the sludge is determined and reported so that the anticipated performance through the final clarification can be predicted.

TSS (predicted)
On the completion of the settlement test the supernatant is tested for turbidity and to indicate whether the process can provide the required settlement during the final clarification stage.

RAS Concentration
When measured this parameter, in combination with the MLSS, will enable the plant to determine and automate the wasting of excess sludge.

Nitrification Levels*
This measurement will allow the fine-tuning of the aeration system to ensure that the system will achieve its ammonia consent.

Oxygen Uptake Rate
This parameter indicates how active the bacteria are, and thus the load on the plant, as an indicator as to the optimum MLSS level.

Specific Oxygen Uptake Rate
Using the MLSS data this parameter is used to provide comparative performance of the bacteria over time to determine whether the health of the bacteria is being maintained or if there are problems within the plant. This is the first parameter to be analysed to give an indication of any toxicity problems that the plant may be experiencing.

Critical Oxygen Concentration Points
This analysis provides both the minimum DO level required for full Carbonaceous biodegradation and also the DO required for maximal ammonium depletion by the nitrifying bacteria. This provides the key to allowing the operator to dynamically set the DO set points within the plant to optimise aeration and minimise energy consumption.

Toxicity Management
This measure is provided by comparative measurements of the OUR, nitrification status, and MLSS levels and compared with a decision matrix, which indicates where toxicity is a likely source of poor bacterial performance.

The ASP-CON achieves these measurements by a combination of mechanical and analytical methods that forms the basis of controlling the secondary treatment process. This also removes the need for manually completed tests, releasing time for other priority tasks.

The ASP-Con instrument uses an innovative system for cleaning and calibrating that extends the service interval time and the design of the sample capture process, which negates problems associated with ragging that afflicts some wastewater treatment plants.

The outcome of an ASP-Con controlled plant will be to achieve compliance for the optimum costs in energy and the reduction of significant CO2 emissions, and liberating labour for other priority tasks.

There are 3 electrode options – Ammonium and a choice of the following:-

  • Potassium or Nitrate
  • pH or ORP

                     The Next Step Change in the Activated Sludge Treatment Process

Frank Rogalla – Director of Innovation & Technology, Aqualia

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Strathkelvin Instruments Limited,

Rowantree Avenue,

North Lanarkshire, ML1 5RX,


01698 730400
Fax: 01698 730401
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