Reactor performance and composition of aerobic granular sludge during different process disturbances

In an ongoing PhD project, aerobic granular sludge is used for wastewater treatment. Aerobic granules are very dense and compact aggregates of microorganisms that are formed under certain environmental conditions. In earlier studies we have investigated the impact of different environmental factors such as organic loading rate, nitrogen loading rate, feed pattern and start-up strategies on the granule formation and evolution of microbial community. It has been noticed that disturbances to the system can have a large impact on the granule formation. One sequencing batch reactor with granules have been running since February 2016 and the plan is to keep the reactor running at stable conditions and then inoculate two other identical reactors with granules from this reactor and see what happens when the granules are exposed to various disturbances. The time that granules are allow to settle at the end of each cycle is now 30 minutes. In general, granule formation is achieved when the settling time is less than two minutes. It is therefore very interesting that this reactor has got a granulated biomass in spite of the long settling time. The first perturbation that we want to do is to shorten the settling time to just two minutes and follow the reactor performance and granule characteristics such as size, settling speed and chemical composition. Also samples for the microbial community will be assessed. In the work both daily maintenance of the reactor, sampling and data assessment will be included.









Contacts: Professor Britt-Marie Wilén (supervisor),

PhD candidate Raquel Liébana,