MEMBRANE FILTRATION

There are several classes of treatment processes that constitute membrane filtration. These processes include: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Each of these technologies utilizes a membrane barrier that allows the passage of water but removes contaminants. The membrane media is generally manufactured as flat sheets or as hollow fibers and then configured into membrane modules. The most common membrane module configurations are hollow-fiber (consisting of hollow-fiber membrane material), spiralwound (consisting of flat sheet membrane material wrapped around a central collection tube), and cartridges (consisting of flat sheet membrane material that is often pleated to increase the surface area). In addition to the various module configurations, there are a number of different types of membrane materials, hydraulic modes of operation, and operational driving forces (i.e., pressure or vacuum) that can vary among the different classes of membrane filtration (i.e., MF, UF, NF, RO, and MCF).

Common drawback of membrane systems is high reject rates. Using membrane systems in conjunction with other technologies can significantly lower reject rates leading to improved efficiency.