Patent ID: 6586172
Filing Date: 2003-07-01
Classification: A61L,C02F

Abstract:
A method of UV-irradiation of a biological fluid containing a desired component and a contaminating micro-organism, which method comprises the steps of:a) providing an apparatus comprising a longitudinally extending vessel having wall means of a UV-transparent material disposable, in use of the apparatus, in close proximity to a UV radiation source within an irradiation area and having an inlet and outlet and a passage means formed and arranged so as to define a flow path extending therebetween which is substantially free of substantial discontinuities so as to avoid substantially turbulence in fluid flowing therealong in use of the apparatus, and having an irradiation zone adjacent said UV-transparent wall means for receiving UV radiation from said UV radiation source, in use of the apparatus, said passage means having a static flow mixing means with a multiplicity of mixer elements for repeatedly subjecting the fluid flow to a mixing operation comprising dividing and re-mixing of the fluid flow, in use of the apparatus, which static flow mixing means extends along said flow path along at least said irradiation zone, said vessel having an internal diameter, d, of at least 4 mm, and said apparatus including fluid flow supply formed and arranged for passing fluid through said vessel, in use of the apparatus; and b) passing said fluid through said vessel so that said fluid is subjected to at least 20 said mixing operations, at a fluid flow rate not less than a minimum flow rate corresponding to a maximum fluid residence time within said irradiation area required for efficient mixing as indicated by the maintenance of a substantially close relation between actual log kill and log kill as predicted by the below indicated relationship, with increasing residence time which obtains above said minimum flow rate and at a fluid flow rate not greater than a maximum fluid flow rate corresponding to a minimum residence time in said irradiation area required for effective inactivation of said contaminating micro-organism by providing a desired log kill of said micro-organism, and not greater than that at which significant degradation of said desired component occurs, wherein said minimum residence time in said irradiation area is defined in accordance with the following relationship: log 10 kill=KÃ—FluxÃ—Residence timeÃ—Z/ODÃ—Tube Diameter wherein Flux indicates the amount of UV radiation incident on the passage containing the fluid flow in the irradiation area immediately inside the passage wall, in mW cmâˆ’2, wherein OD is the Optical Density of the fluid at the wavelength in the region where substantial virus inactivation takes place; K is an empirically derived constant; Tube Diameter is the internal diameter, d, of the vessel in the irradiation area, in cms; and Z=u(&rgr;/&mgr;)/Rem wherein u is fluid flow velocity in cm/sec, &rgr; is fluid density in kg/m3, &mgr; is fluid viscosity in cp, Re is the Reynolds number of the fluid whose value is defined by the formula Re=du&rgr;/&mgr; where d, u, &rgr; and &mgr; have the same meaning as before, and m is a characteristic of the static mixer system whose value is determined experimentally, whereby substantially the whole of the fluid may be exposed to a similar micro-organism inactivating level of UV-irradiation while minimizing damage to the desired component(s) of the fluid.