Better filters

For many years, engineers have worked to efficiently filter valuable bio-process products on an industrial, economic scale.

The challenge has been to push rates up without incurring high shear rates and resultant cell lysis, which would cause loss of yield. High shear can destroy delicate and valuable biological materials such as proteins, blood, algae and yeasts, and also brings with it a requirement for higher flow rates, which in turn raises pumping costs.

Inventors at the University of Oxford have now developed two very elegant solutions to this dilemma. Both are improvements upon the existing practice of using ceramic block or tubular membrane filters, allowing users to obtain an increase in performance without incurring massive disruption.

The first solution, an insert, could be applied to existing tubular membrane filters (TMF) as an add-on. The second would be a suitable replacement for an existing ceramic block filter element.

The insert helps achieve excellent mixing at low rates of flow, and with a laminar flow pattern, thus minimising cell damage. High filtration fluxes are obtained at much lower feed flow rates than are used in conventional TMF modules. The new technology consists of a moulded insert centrally located in each membrane tube. The insert fits loosely within the tube and takes the form of a coarsely threaded rod with a helical groove of semi-circular cross section.