Use of membranes for municipal wastewater treatment
Substituting the secondary settling tank with submerged
micro- and ultrafiltration membrane has far reaching consequences for the
activated sludge process: the membrane represents an absolute barrier to all
microorganisms (also non-floc-forming), sludge age is significantly increased
(>20 days instead of <15d), sludge concentration is normally run at 10 –
15 gTSS L-1 (instead of 3 – 5) allowing to design smaller reactor volumes, also
the fact that no secondary settling tank is needed reduces the required
construction space, membranes are costly in purchase and in operation (energy
requirement). While the first full scale plants went into operation in the late
‘90s, a potential for optimisation and process improvement is still expected
with increasing process knowledge.
In order to help filling this gap Eawag is operating a
membrane bioreactor pilot (100 population equivalent) since 10th July 2001. The
following aspects are approached:
- Design, modelling and operation of biological N and P removal at different sludge ages (15, 30 and 60 days)
- Optimisation of the operation and chemical cleaning of the membrane modules
- Comparing the operation of 3 standard modules operated in parallel (Kubota, Mitsubishi and Zenon)
- Assessment of the micro-pollutant removal capacity and comparison with the conventional activated sludge process with sedimentation (see EU project POSEIDON
Further information only in German [pdf, 110 KB]