Thesis for the Degree of Master of Science


Year 2006
Pia Kyllönen

Improving the performance of an activated sludge process using process-monitoring methods

Stricter wastewater permit conditions introduced at the beginning of 2005 have posed new challenges for integrated pulp and paper mills. Stipulations on chemical oxygen demand are particularly strict in the new conditions. The aim of this master’s thesis is to study the reasons for the high COD concentrations at UPM-Kymmene’s Tervasaari mill using process-monitoring methods.

The literature survey provides an outline of process sources of chemical oxygen demand and process monitoring methods. It also presents cases where monitoring methods have previously been used at wastewater treatment plants.

The experimental part of the thesis determined loading process sources and the impact of treatment plant variables on the COD concentrations of outgoing wastewater. The process monitoring methods utilised for this purpose were principal component analysis, regression analysis, the partial least squares method and Kohonen’s self-organizing maps.

The process data was divided into two parts: variables for incoming wastewater and treatment plant variables. The variables chosen for investigation were COD concentration after preliminary settling and COD concentration in outgoing water. Process delays were calculated for both parts and delays were taken into account in pre-processing the process data. The variables were chosen on the basis of correlation analysis and process knowledge.

Loading of both fibre lines had the greatest impact on COD concentrations after preliminary settling. The SAP fibre line, which produces bleaching pulp, caused the greatest load at the treatment plant. The load from paper machines was not significant. COD concentrations after preliminary settling had the greatest impact on the COD concentration of outgoing water. Oxygen concentrations and soluble phosphorus in aeration also had an effect. High sludge age had the greatest effect on the expansion sludge.

This info last modified 16 Jul 2018 by Jerri Kämpe-Hellenius