In non-chlorinated deep bed filters for drinking water treatment, besides particles, biodegradable organic carbon (BDOC) is removed by microorganisms. This work aimed at the improvement of BDOC degradation in deep bed filters, which may be operated in front of GAC adsorbers by the application of permeable synthetic collectors (PSC). First PSC and different GAC were investigated experimentally for their BDOC and turbidity removal performance and pressure drop as well. A model was developed to find an expected optimum combination of PSC and GAC.
The following pilot scale investigations showed that a PSC-layer on top of adsorptively exhausted GAC relieves bacteria sessile on the bottom media from deposition of particles which may be toxic to the bacteria and increase mass transfer resistance. In general the PSC/GAC combination performs considerably better with respect to turbidity and BDOC-removal than a conventional two-media filter.