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Final Settlement Tanks (FST)

Final settlement tanks (FSTs) are similar in design to primary settlement tanks and are an integral part of the activated sludge process. They are used to settle out the biological material flowing from the secondary treatment plant producing supernatant that has low levels of organic material and suspended matter that is suitable for additional tertiary treatment or discharge into a water course. They also enable the site to collect the microorganisms produced during treatment so that they can be re-used to seed the incoming settled sewage at the front end of the process. The flow returned to the start of the aeration process is called ‘Returned Activated Sludge’ (RAS).

Humus tanks perform a similar function in conjunction with the more traditional percolating filter type plants that are still in common use. On these plants the settled solids are normally removed for treatment in a sludge processing plant.

The terms Humus Tanks and Final Settlement Tank (FST) are often interchanged and can be taken to perform either of the function above.

Measurement of the position of the sludge blanket location is an important part of automating and optimising the control of the plant and of preventing pollution incidents, further details are provided by following the links below.

For specialist advice call:

+44 (0)1726 879800

Online Enquiry

Related Applications, Measurements and Products

SludgeWatch 715

SludgeWatch 715 Sludge Blanket Detector

The SludgeWatch 715 provides a simple, low cost method of spot checking the sludge blanket level in a wide variety of settlement tanks

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8100 Monitor

8100 and 8200 Sludge Blanket Detectors

The 8100 and 8200 Monitors provide an exceptionally simple and reliable method of detecting the sludge blanket level

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ASLD2200

ASLD2200 Sludge Blanket Monitor

The ASLD2200 is a fully automatic sludge blanket level detector designed for the water and waste water industry

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SludgeWatch Ultra Monitor

SludgeWatch Ultra Sludge Blanket Monitor

Highly sophisticated Sludge Blanket Monitor using an ultrasonic transducer to track the sludge blanket interface

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7200 Monitor

7200 Monitor

The 7200 Monitor combines with the Partech range of Suspended Solids and Turbidity Sensors

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IL55BV2 Suspended Solids and Sludge Density Sensor

Inline Sensor for Sludge Density, Suspended Solids and Turbidity Monitoring

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ASLD2200 On Site

Sludge Blanket Monitoring

Continuous monitoring of the sludge/water interface or sludge blanket is central to the efficient operation of clarifiers, thickeners and settlement tanks

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8100 Monitor with Radio Transmitter

Sludge Blanket Detection

Detecting the presence of the Sludge Blanket at a fixed level is one of the simplest ways of carrying out this control measurement

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Sludge Density

Sludge Density measurement allows automatic control of the de-sludging of settlement tanks and control of the return rate of activated sludge to the secondary treatment process.

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To speak with one of our specialist advisors, call

+44 (0)1726 879800


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