Nanofiltration in Process Applications

While Nanofiltration has quickly become a viable alternative to reverse osmosis in certain water treatment applications, there is a great, and largely untapped potential for expansion into process applications. Nanofiltration can significantly reduce levels of TDS, color, dissolved solids, organics, hardness, turbidity, divalent & multivalent ions while operating at much lower pressures than reverse osmosis. Given the high selectivity of NF membranes, implementation of this technology can lead to a significant savings in both capital and operating costs when compared to reverse osmosis. With this combination of selectivity and operating economics, nanofiltration naturally lends itself to water and wastewater treatment. However, there is immense potential for expansion outside of these two applications. Processors in the food, beverage, and dairy industries have already started employing nanofiltration spiral wound membranes in a variety of applications and there are many other industries that could possibly benefit from nanofiltration.

Most of the membrane industry tends to overlook process or "specialty" applications, electing to devote the vast majority of their resources towards water and wastewater treatment. While there is a strong need for effective and economical water and wastewater treatment, the potential for creating value in process applications with nanofiltration membranes is undeniable. Companies like Synder Filtration, who have focused on process applications with spiral wound membranes for nearly two decades, are helping companies optimize their processes with nanofiltration. The lower operating pressures, and unique selectivity of NF membranes have often lead to cost savings and allowed for more environmentally friendly business practices.

One of the most common applications of spiral wound nanofiltration membranes in process applications is the concentration and demineralization of lactose in the dairy industry. In conventional cheese production, only about 10 percent of the milk used in cheese production actually ends up in the cheese. The resulting byproduct contains mostly proteins, lactose, minerals, and water. This solution is typically processed through membrane filtration to either fractionate or concentrate the proteins. After the protein is concentrated and removed, the remaining solution can be sent to nanofiltration membranes for concentration or demineralization of lactose. This process allows dairies to create a concentrated lactose product that can be sold to both the food and pharmaceutical industries, or used for standardizing other products.

With multiple nanofiltration membranes available (varying by salt rejection), dairies have flexibility in their process. For example, Synder Filtration offers two nanofiltration membranes, the NFX (99% MgSO4 rejection) and the NFW (98% MgSO4 rejection). Both of these membranes are used for the concentration of lactose, but offer different degrees of salt and mineral passage. The NFX is employed where lactose yield and concentration is of great importance and the NFW, with a more open pore structure, is used where maximum salt passage, or demineralization of whey is critical. Regardless of the specific aim in lactose processing of UF whey permeate, this serves as an excellent example of the benefits of employing nanofiltration in process applications. These spiral wound membranes not only operate at lower pressures than reverse osmosis membranes, but allow the dairy industry to yield greater value from a solution previously thought to be a by-product stream. By concentrating and demineralizing lactose, the dairy industry is able to reduce liquids previously discharged to waste and also bolster their product offering.