An innovative greywater treatment system for urban areas ... - SuSanA

Figure 12: Technical drawing of MBR tank; (HUBER SE, 2011a)
To purify the greywater an ultrafiltration membrane from Polyethersulfone (PES) with a
nominal pore diameter of 38 nm and a filter surface of 3.5 m 2 is installed, called
MembranClearBox® (see Figure 13). The small pore size of the membrane retains all
particles including bacteria and the majority of viruses. The module is submerged in the
activated sewage sludge in the MBR tank. An aerator which is mounted on the bottom of the
tank provides oxygen to keep the biological processes of microorganisms active and ensures
continuous mixing within the container. Another aerator located directly under the membrane
module produces scouring air to clean the surface. It is an intermittent process, where the air
flows along the surface of the module, which avoids coating, clogging and fouling of the
membrane. To purify the water permeate is drawn through the membrane by underpressure
of the permeate pump. If the filling level is too low inside the tank, it is automatically detected
by a sensor which turns the permeate pump off. Thus, the membrane is prevented from
drying out, which would destroy it otherwise. Upon the occurrence of the lower level limit, the
system switches to economy mode, which supplies the biology only with oxygen. The data of
transmembrane pressure (pmax = - 350 mbar) and the flow of permeate is collected and
supervised by online remote control. The withdrawal of excess sludge takes place every 4
weeks by a pump hanging at medium-height inside the container.
Membrane module
Permeate outflow
Scouring air
Membrane plates
Scouring aerator
Spacer
Bacteria
Membrane
Viruses
Plate Permeate suction
Figure 13: Details of ultrafiltration membrane; (HUBER SE, 2011b; GEP - Freude am Wasser, 2007)
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