The LFNano™ membrane system is a nanofiltration system providing osmotic water quality with a simple, unique system to mitigate the effects of membrane fouling. The system combines three features:
1) Proprietary open architecture NF membrane element
2) Anti-fouling particulate coating/injection
3) Feedwater circulation
This system drastically reduces the impacts of membrane fouling. Fouling is where the contaminants in the water plug up the ‘pores’ in the membrane. Fouling is the limiting factor to the adoption of membranes today as most methods of dealing with it are mechanically complex and expensive. The membrane cartridge uses thin film composite (TFC) nanofiltration membrane in an open configuration, eliminating the dead spots common to standard elements today. The system is designed to circulate the feedwater continuously in order to eliminate the velocity/recovery relationship (limitation) while maintaining a high velocity. This maintains a consistent feed concentration which gives consistent performance or removal (avoids concentration polarization) and limits the buildup of foulants on the membrane surface.
The LFNano™ membrane element has an open configuration that imparts an extremely low headloss allowing a low energy circulation of the feed water. The photos below show a close up of a cross section of the LFNano™ membrane element with the unique feed spacer along with a photo of the element that looks almost identical to traditional spiral elements today.
LFNano™ Spiral Element (cross section close-up and element)
The system also uses anti-fouling particles that protect the membrane from organic fouling and inorganic scaling. These anti-fouling particles can be based on standard high surface area particles like diatomaceous earth or activated carbon. The particulate feed stock is modified for use in the LFNano™ and is injected into the feed stream to bind up the very fine particles that would otherwise imbed into the membrane. These injected particles can be easily removed when they accumulate in the vessel or on the membrane surface. Below are microscopic views of some possible particulate stocks that can be used in the LFNano™ (diatomaceous earth, granular activated carbon and bentonite).
High Surface Area Anti-Fouling Particles
The use of these particles greatly extends the fouling intervals and protects the membranes from the smallest of the foulants which can imbed into the membrane and impede the flow of water through it. The coating of these particles on the membrane also allows for an online flux reset by the DXV ‘rest cycle’ whereby the membrane is rested between one (1) and five (5) times per day. The rest lets the system restore most of the flux lost in the treatment process.
