Settlometer IWT PhD Scholarship Alexis Vanderhasselt

Monitoring and control of sludge sedimentation

The separation of sludge and effluent is of paramount importance for the good operation of an activated sludge wastewater treatment plant. Installations are confronted with variations in the sludge settling properties as well as in the influent flow. These dynamic conditions legitimate the permanent surveillance of the sludge sedimentation. This work aims at using the information provided by an automatic settlometer to the best extent to create a system that guarantees effective separation of sludge and effluent. In order to reach this goal, several steps need to be taken:

1) The short and long term evolution of the settling properties at full-scale installations has to be observed. The former must be done in order to get a perspective on the magnitude of the short-term dynamics in the sludge settling properties. These data have to be compared with other on-line data in a search for those parameters that have a major impact on the settling properties.

2)The dosage of additives is an on-line control system by far the most straightforward way to influence the settling properties. Therefore, it has to be evaluated to which extent and under which conditions the settling properties can be modified by the use of additives. Attention has to go to the influence of the measuring device on the observed effects.

3) The settling curves provided by the sensor have to be evaluated and a way has to be found in which this information can be dealt with. Here the fitting of a mathematical sedimentation model to the observed sedimentation curves could be an interesting issue. This way of operation could be beneficial as it would allow to translate the curves into specific quantitative parameters.

4) Finally, a system has to be created that is able to determine wheather the settler is prone to the massive washout of sludge. This system can be based on the actual settling properties and/or the hydraulic loading. When an overloaded situation prevails appropriate on-line control actions will be taken as e.g. the dosage of additives ot he use of stepfeed.

Project duration: 1996-09-01 - 1998-12-31

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Bob De Clercq
Department of Applied Mathematics, Biometrics and Process Control
Coupure Links 653
9000 Gent
Tel: +32(9) 264.59.35
Fax: +32(9) 223.49.41

Last update: 01 december 2008,

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