Gravity Driven Membrane Filtration

The principle of GDM (Gravity Driven Membrane filtration) has been developed at Eawag in 2009. In contrast to conventional ultrafiltration, no flushing or cleaning is required and a biofilm is allowed to develop on the membrane. This leads to a stabilization of flux at a value of 4 – 10 L/m2.h, depending on the feed water quality (see Figure 4).

Figure 4: Stabilization of flux during Gravity-Driven Membrane filtration (GDM) of several types of surface waters and diluted wastewater
Figure 5: Field test of a GDM-based household filter in Kenya

For the GDM process, relatively low pressures can be used (25 – 60 mbar) which can be easily obtained by gravity, so that no additional pumps are required in case a water head is available.

Since its discovery in 2009, numerous applications of GDM have been explored. This includes the development of a household water treatment system (See Figure 5), community-scale water treatment, pretreatment of sea water 10Toilet (see http://www.bluediversiontoilet.com/). Within the SELF project, GDM is used for two different purposed:

  • Treatment of rainwater (disinfection)
  • Treatment of grey water: a gravitational, aerated submerged membrane reactor is used for the treatment of grey water.  This reactor is comparable to the GDM reactor as applied in the Blue Diversion toilet (http://dx.doi.org/10.2166/washdev.2015.116)