NF, RO and FO


NF, RO and FO


The SANI Membranes Hollow Plate™ technology is also well suited for nanofiltration, reverse osmosis and even forward osmosis applications. The key benefits of the Hollow Plate™ technology in NF and RO application is the open feed channel designs ability to handle difficult feeds without pre-filtration. A concept for Hollow Plate™ technology forward osmosis modules has also developed. The business focus is however on microfiltration and ultrafiltration applications for the time being.



Nanofiltration (NF)

The Hollow Plate™ Technology can also be used in nanofiltration applications. The current products restrict the maximum pressure to 10 bar. This means only low pressure nanofiltration applications can be handled by the current products.


Please contact us for more information.



Reverse Osmosis (RO)

The Hollow Plate™ Technology can also be used in Reverse Osmosis applications. The current products restrict the maximum pressure to 10 bar. This means only low pressure Reverse Osmosis applications can be handled by the current products.


Please contact us for more information.



Forward Osmosis (FO)

The SANI Membrane Hollow Plate™ technology was originally designed with a sanitary retentate side and a sanitary permeate side. In fact, the permeate side can be flush cleaned. This feature makes it possible to create true cross flow, where a turbulent flow is established on the outside (the feed side) of the membrane as well as on the back-side (the draw side) of the membrane. This make the Hollow Plate™ technology uniquely efficient as a base technology for forward osmosis. The present webpage was made public in October 2016 to secure freedom to operate using Hollow Plate™ technology for forward osmosis.

Forward osmosis is still only used in smaller industrial systems as industrial solution to draw-recovery is still not obvious.

Forward Osmosis Hollow Plate™ Module – true cross flow modules


The sketches below describe a Hollow Plate™ assembly using the SANI Membrane Hollow Plate™ technology, however configured for true, dual sided, turbulent, cross flow membrane filtration of two media streams.


The rigid semi-hollow sheet filter plates are made up of two identical plastic molded half plates. The outer surfaces of the filter plates comprise a number of molded “drain and flow areas” for a first media, these “drain and flow areas” are covered by a membrane that is sealed to the plate- and a channel for the first media is thus in the flow area between plate and membrane, the membrane being held up by the shape of the “drain and flow area” – even at a considerable outer pressure. In each side of the “drain and flow areas”, holes connect to channels inside the filter plates. These inside channels either connect to successive “drain and flow areas” or to the perpendicular entry and exit for the first media.

The second media passes the outside of the filter plates and so the outside of the membranes in a normally turbulent fast flow, at a pressure higher than that of the first media.


Mostly filter plates are stacked in quantities with a suitable distance – mostly 1 to 6 mm, where the first media exits and entries of the filter plate are fused to the next plate in the stack, forming a manifold for entry and exit of first media. The second media is mostly guided in between plates by a channel surrounding and containing the stack of plates.




The “drain and flow areas” are similar in function to a woven net, but are molded as part of the half-plates, saving the component and improving the function.


The filter plates are typically not more than 200mm wide and up to 1000 mm long, partly to secure rigid, cross flow stable plates and partly due to as limits to molding technology and cost of pressure sustaining half plates.

The forward osmosis Hollow Plate™ module can also be used for normal crossflow operation giving an improved drainage of permeate, however the trans membrane pressure must be controlled to avoid that the membrane is pressed deeply into the drain areas.


As for standard Hollow Plate™ Modules, both retentate and permeate side will be CIP flush cleanable, both sides easy drainable for fast and water saving CIP, and retentate surfaces can be inspected from outside at all times.


Please contact us for more information.


Pat. pending, Abstract:


A novel simple embodiment of a ridged, flat filter plate assembly, formed by an internally channeled flat filter plate (1) formed by bonding of two flat, typically identical, half filter plates (2, 3), the filter effect formed by a filter membrane (7) bonded adjacent to a filter area, said filter area being formed as a grid that can support the membrane while giving room for drain of permeate or flow of draw media, said filter area being an integral part of said filter plate, said filter area having perforation slits or holes (10A, 10B) in the surface of the plate, said perforations connecting to the channels (9A, 9B) inside the plate.


The channels inside the plates are for leading permeate or draw media to one or two or more paired exits (4, 5) perpendicular to the filter plate, the exits forming exit channels for permeate to exit the filter plate assembly.


In a configuration of the invention with two or more paired exits, it is possible to lead a draw stream contacting the inside of the membrane surface or to clean the permeate site of the filter plate by flushing draw media or cleaning media from one exit (4 or 5) to the other exit (4 or 5).


The filter area surface (6) is covered by bonding a fine filter (7), for example an organic flat sheet membrane, to the filter surface, whereby very fine micro or ultrafiltration or even molecular filtration and forward osmosis can be achieved.

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