Recovery of resources from wastewater is a step waiting to be taken on the road towards greater sustainability. Not only the water content of wastewater streams is to be recovered, but attention must also be paid to the recovery of the energy and nutrients present in it. In this context, the crucial technology for energy recovery from liquid waste streams is anaerobic digestion. The main problem with energy recovery from municipal wastewaters by means of anaerobic digestion, though, is its dilute nature, which makes the process inecient. There is therefore a real advantage to be gained from the development of separation processes which can upconcentrate municipal wastewater in a thorough but also, and crucially, energy- ecient manner. Such an upconcentration would then allow for economical and
sustainable energy recovery from the produced concentrate through anaerobic di- gestion and for reuse of the claried water fraction, either directly or after another treatment step such as reverse osmosis.

This thesis deals with the search for an eective upconcentration technique. The techniques which were investigated are chemically enhanced primary treatment, centrifugation, primary membrane ltration and so-called bio-adsorption or bio- occulation in a highly loaded membrane bioreactor.
In addition, the eciency of the anaerobic digestion of concentrates produced by upconcentration techniques was looked into, in order to be able to get an insight into the energy eciency of the combination of an upconcentration technique and anaerobic digestion. Digestion tests were performed upon concentrates obtained by means of bio-adsorption and centrifugation. Three dierent digester types were
tested in order to investigate which can achieve the best possible energy recovery:
completely mixed tank reactors, anaerobic sequencing batch reactors and a temperature phased reactor.

It was found that the most eective up-concentration techniques were chemically enhanced primary treatment and bio-adsorption in a highly loaded MBR, but the goal of achieving an energy positive treatment train could not be met.
The anaerobic sequencing batch reactor was found to be a suitable reactor for digesting the concentrate produced by bio-adsorption processes, allowing for a 50% reduction in reactor volume compared to completely mixed reactors. Temperature phased digestion did not add any signicant benets.