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.
Though both the cation and the anion resin are responsible for the quality of a deionization (DI) system effluent, it is the cation resin that is the big contributor to leakage. Improving the leakage characteristics of DI cation will reduce effluent conductivity, drop the pH and ultimately lead to better silica performance from the system.
Off the coast of Washington, 32 families on Guemes Island were faced with an aging well that was drawing salt water into its system. Because groundwater is scarce on the island, residents had to rely on what little rain water soaks into the ground.
The increasingly broad range of requirements for water quality has motivated the water treatment industry to refine existing techniques, combine methods and explore new water purification technologies including desalination.
Reverse osmosis plants increasingly are being installed in outlying and remote areas. By providing water they can sustain life and/or provide irrigation to previously remote areas without readily available fresh water sources.
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.
As competition for limited water supplies increases, sea water treated by reverse osmosis will become more viable.
Culligan International Company has been providing services to small municipalities since the 1970s, but in February of 1997 the company signed a $1.9 million contract with the city of Abilene, Kansas, to remove nitrates from the city's water system.
The overall cost of the project was estimated at $6 million. This marked the largest domestic municipal project for Culligan and led to the creation of a municipal markets division within the company.
Fertilizers used in this farming area raised nitrate levels in the water beyond those allowed by state law.
"In four years, half of San Diego may be filling its glasses with tap water that once ran through its toilets."