Ceramic Membrane Filtration of Ozonated Water
Membrane filtration is considered one of the best available technologies for meeting Stage 2 D/DBP requirements. However, one of the major problems with membrane processes is the decrease in permeate water flux resulting from membrane fouling. In addition, although membrane filtration of drinking water provides a barrier against pathogens and particles, disinfection after filtration is usually necessary to control bacterial regrowth on the filtrate side of the membrane. As a result, the production of disinfection byproducts (DBPs) remains a serious issue.
Description of Technology
The invention combines an improved ceramic membrane filter for water filtration along with an ozone degradation step. The filtration unit is comprised of a multi-layered nanocrystaline, sintered ceramic metal oxide catalyst and ceramic membrane filter. The invented process reduces fouling at the membrane surface and degrades the ozone remaining in the water from prior ozonation of water to kill microorganisms and break down bonds in natural organic material (NOM) in the untreated water. A relatively low ozone concentration is used on the initial water treatment stage. Ceramic membranes in combination with ozonation promise lower operating costs with self-cleaning membranes and the efficacy of ozone as a superior disinfectant for bacteria and viruses. The treated filtrate is subsequently chlorinated at a late stage just prior to distribution (this required by regulation in any event) with the result that that the levels of the residual chlorinated byproducts are acceptably low, and water quality is very high. The ozonation and membrane process produces biologically stable water, which contains low biodegradable organic carbon. Replacing chlorination with ozonation as the primary disinfectant significantly reduces the formation of trihalomethanes and other water treatment products.
- Self-cleaning membranes: This will result in cost savings.
- Benefits of ozone use: Ozone is a superior disinfectant for bacteria and viruses.
- Production of OH radicals at the catalyst surface: These radicals are very effective as disinfectants for such compounds as pharmaceuticals.
- Improved water quality: The invention process enables lower concentrations of DBPs, thereby improving water quality of the treated water.
- Use in existing plants: The technology can be used in existing water treatment facilities, after the necessary modifications are made.
- Particular application to borderline eutrophic water: This class of pre-treated water is difficult to treat with existing methods.
Municipal water treatment systems, water treatment facilities at resorts and national parks, field purification units and military applications.
US 2006/0175256 A1 (filed Dec. 6, 2005)
Susan Masten, Simon Davies, Melissa Baumann, Bhavana Karnik
For Information, Contact:
Michigan State University