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Nanofiltration and Ultrafiltration

Nano (NF) and ultrafiltration (UF) are implementations of membrane filtration technology (like reverse osmosis) that are used for example in potable water treatment and various industrial processes. Nano filtration can be used, for example, for the removal of arsenic from groundwater (potable water or industrial processes) and it also removes hardness salts, thus making water softer. Ultrafiltration is used for the removal of microbes from potable water and raw water treatment before reverse osmosis.

In membrane filtration processes, water is always divided into permeate (filtrated water) and concentrate (residue water stream that includes the filtrated substances). In some cases, the concentrate can be collected and re-used by feeding it into the beginning of the process. There are also applications where concentrate is the final product instead of permeate. With nano and ultrafiltration, the yield is typically between 70–90%.

Equipment and system principle

A nano or ultrafiltration system (like all membrane applications) consists of a pre-treatment stage (defined based on raw water quality), high-pressure pump(s) and housings/vessels with membranes inside. In nanofiltration, the membranes are typically spiral-wound as in reverse osmosis. Ultrafiltration membranes are usually hollowfibre. The process is usually controlled with a separate control system (programmable logic controller) which allows for a customised user interface, monitoring features and integrations with other systems.

Required information for system design

To complete a water treatment system design, a raw water analysis is needed together with information about the required water flow/capacity of the system and the required water quality after treatment or information about the use of the water produced. If the equipment is being installed in an existing space, information about the available drainage and room dimensions is also good to know.