Part one of this article appeared in the July issue and discussed microfiltration and utrafiltration. This article discusses nanofiltration and reverse osmosis.
Once considered a viable technology only for desalination, membrane processes are increasingly employed for removal of bacteria and other microorganisms, particulate material and natural organic material that can impart color, tastes and odors to the water.
Legionellosis, the disease caused by Legionella spc., is common, though most people would guess it is extremely rare. Outbreaks of Legionellosis, defined as a cluster of three or more cases in a single locale, occur regularly in the United States and much of the developed world. Outbreaks have been reported in Australia, Holland, Thailand, Japan, England and many other countries. In the U.S., the Center for Disease Control (CDC) receives reports of 1,000 cases of Legionellosis annually.
The application of disinfectants in drinking water treatment for controlling microbial quality has drawbacks. These include the formation of potentially harmful disinfection byproducts (DBPs) that can be potential carcinogens (e.g., trihalomethanes [THMs] when chlorine is used as a disinfectant). The general equation is:
ÊÊÊNOM + Disinfectant -> DBP
ÊÊÊWhere NOM = Natural Organic Matter
As consumer awareness grows in regard to the quality of water consumed every day from the numerous well water systems across America, the process that is gaining the most attention is that of disinfection.
The process of reusing wastewater for sprinkling at the Sugar Hill Golf Course in Gwinnett County, Georgia, was time consuming, costly and problematic. An in-line ultraviolet disinfection unit installed at the treatment plant solved the problem.
There is no question that the use of chlorine offers you a highly effective way to purify water and wastewater. The only question is: Which form of chlorine should you use?
An overview of UV disinfection and its applications.
An overview of an American Water Works Association Research Foundation project.
Membrane filtration, widely used in chemical and biotechnology processes, is already established as a valuable means of filtering and cleaning wastewater and industrial process water.