Reverse Osmosis Applications in Microfiltration to Purify Water

ROMF

Microfiltration and reverse-osmosis are both used commonly in the purification of water. Combining microfiltration and reverse-osmosis can enhance the strengths of each method. In particular, microfiltration can be used prior to a reverse-osmosis system to create a higher quality, more purified final product. Moreover, the microfiltration as a pretreatment of the water extends the life of reverse-osmosis membranes. This paper addresses the background of both microfiltration and reverse-osmosis systems, before exploring current and future applications of the combined microfiltration and reverse-osmosis systems in water treatment.

Reverse-osmosis is "a high-efficient technique for dewatering process streams, concentrating/separating low-molecular-weight substances in solution, or cleaning wastewater," ("Reverse Osmosis, Nano, Ultra & Micro Filtration," n.d.). The name of the process describes what it entails: it reverses natural osmosis. Osmosis is the movement of water through a membrane, motivated by the search for equilibrium in the chemical potential. During the osmosis process, a solute would be retained on either side of the membrane. To reverse this process with the goal of removing the solute, pressure must be exerted. When pressure is exerted, the natural flow of water is reversed so that the solute remains on one side of the membrane. One of the most common uses of reverse-osmosis is in desalination, but it can also be used for wastewater treatment.

Microfiltration does not depend on pressure to the extent that reverse-osmosis does. Instead, the membrane itself is the key. Microfiltration membranes are in the range of 0.05-10 microns and can be used to separate specific particles ("Reverse Osmosis, Nano, Ultra & Micro Filtration," n.d.). Microfiltration enhances reverse-osmosis when it is used as a pre-treatment. One of the reasons microfiltration enhances reverse-osmosis is that the microfiltration prevents the buildup of organic and biological contaminants on the reverse-osmosis membrane. Thus, when a microfiltration system is used in conjunction with reverse osmosis, the result is a purer end product and a more cost-effective water treatment system.

Outline

I. Background and introduction

A. History of Water Treatment Methods

B. History of use of Reverse-Osmosis and Microfiltration