Considerable concern exists regarding the appearance and effects of trace and ultra trace pollutants in the aquatic environment. In this context, it is necessary to identify relevant hot spot wastewater - such as hospital wastewater - and to implement specific wastewater treatment solutions. Membrane bioreactor (MBR) technology seems to be a suitable pre-treatment approach for the subsequent advanced treatment by high pressure membrane systems such as nanofiltration (NF) and reverse osmosis (RO). This paper is based upon investigations on the first full scale MBR for separate treatment of hospital wastewater in Germany. In this study an NF as well as an RO module for further treatment of the MBR filtrate were tested. The removal efficiencies were assessed using the following target compounds: bezafibrate, bisoprolol, carbamazepine, clarithromycin, ciprofloxacin, diclofenac, ibuprofen, metronidazole, moxifloxacin, telmisartan and tramadol. In summary, the results of this study confirmed that MBR technology followed by an advanced treatment for trace pollutant removal is an adequate approach for specific treatment of hot spot wastewater such as hospital wastewater. In particular, it was shown that - comparing the tested NF and RO - only (a two stage) RO is appropriate to remove pharmaceutical residues from hospital wastewater entirely. The recommended yield of the 2-stage RO is 70% which results in a retentate sidestream of 9%. Our investigations proved that RO is a very efficient treatment approach for elimination of trace pollutants.

Using data from 6 full-scale municipal membrane bioreactors (MBR) in Germany the hydraulic capacity utilisation and specific energy consumption were studied and their connexion shown. The average hydraulic capacity utilisation lies between 14% and 45%. These low values are justified by the necessity to deal with intense rain events and cater for future flow increases. However, this low hydraulic capacity utilisation leads to high specific energy consumption. The optimisation of MBR operation requires a better utilisation of MBR hydraulic capacity, particularly under consideration of the energy-intensive membrane aeration. A first approach to respond to large influent flow fluctuations consists in adjusting the number of operating modules. This is practised by most MBR operators but so far mostly with variable flux and constant membrane aeration. A second approach is the real-time adjustment of membrane aeration in line with flux variations. This adjustment is not permitted under current manufacturers' warranty conditions. A further opportunity is a discontinuous operation, in which filtration takes place over short periods at high flux and energy for membrane aeration is saved during filtration pauses. The integration of a buffer volume is thereby indispensable. Overall a modular design with small units, which can be activated/ inactivated according to the influent flow and always operate under optimum conditions, enables a better utilisation of MBR hydraulic capacity and forms a solid base to reduce MBR energy demand.