Master’s thesis proposal autumn 2017 – Ozone treatment for reducing bulking sludge selects for a new type of filamentous bacteria

Klagshamn Wastewater Treatment Plant (WWTP) has, as many activated sludge plants with long solids retention times treating municipal wastewater, problems with bulking sludge caused by filamentous microorganisms, mainly by Microthrix parvicella. Ozonation of a part of the activated sludge is a good way of reducing filamentous sludge bulking, and is performed in full-scale at Klagshamn WWTP. The growth of M. parvicella has decreased, however, a new type of filamentous bacteria, type 0041, dominates instead. The bulking problems are not as severe as with M. parvicella, but still a problem making it necessary to find new operational strategies for ozonation as a control method for all filamentous bacteria types.

The main aim of this Master’s thesis project is to investigate how type 0041 is affected by different ozone dosages and reaction times, and thereafter propose new ozonation strategies at Klagshamn WWTP.

A literature survey should be performed to increase the knowledge about filamentous bacteria type 0041 and possibly other filamentous microorganisms that is favored by the absence of M. parvicella. Also people at other WWTPs that have used ozonation to prevent bulking sludge should be contacted and interviewed about their experiences. Full-scale tests at Klagshamn of different ozone dosages and reaction times should be evaluated by activity tests and microscopic characterisation of the ozonated sludge.

Autumn 2017

Karin Jönsson, senior lecturer, Lund University (
Ivelina Dimitrova, process engineer, VA SYD (
David Gustavsson, research leader, Sweden Water Research (