We are always on the lookout for applications of ozone in water treatment. One area that is gaining a lot of attention is water recycling. Ozone is an excellent choice for water recycling since it is short lived breaking down to oxygen after use. It can also be produced on site from air eliminating the need to purchase, store or transport chemicals. Finally, ozone can play many roles in water treatment, sometimes simultaneously, like disinfection or color/odor removal. Color removal was the main application in the application below.
New England Patriots Gillette Stadium uses a wastewater recycling system to conserve water for the town Foxborough, MA. The treatment system employs biological, chemical and physical processes for removal of contaminants. The plant computer controlled.
The biological portion of the plant employs membrane bio reactors (MBR). The permeate stream from these reactors is pumped to Ozone and Ultraviolet units. Ozone is injected into the wastewater stream to eliminate residual color and UV is used to disinfect the wastewater.
The water is then directed to the final effluent tank. This fully treated water is either pumped to a remote storage tank for reuse or to the designated leach field for disposal. Approximately 80 percent of treated water is pumped back to the facilities and 20 percent goes to subsurface disposal. This saves an estimated 12 million gallons of water per year.
Malibu, while famous for the scenic beauty of its coastline also has to deal with heavy tourist traffic and the water pollution associated with the tourist population. The City of Malibu has begun construction of Legacy Park, one of the biggest projects in the city’s history to address the storm water issue. The project is a water treatment plant, to clean up polluted water in the Malibu area, as well as a park.
The facilities in Legacy Park will remove 90 percent of the storm water through the water treatment plant, improving ocean water quality and restoring the local habitat. The facilities within the park will eliminate most of the runoff into the Malibu Lagoon, Surfrider Beach and Malibu Creek.
Water flows will be redirected from three major storm drains to Legacy Park’s storm water treatment facility, where it will be cleaned and disinfected. The clean water can then be stored and reused for park irrigation or deposited into Malibu Creek, if a large amount of rainfall has occurred and there is a surplus of water.
Pump stations located at the Malibu Road, Cross Creek drain and the Central Treatment Facility allow up to 1400 gallons of runoff per minute to be collected by storm drains and pumps, processed and then disinfected by an ozone treatment. This lessens the amount of harmful components such as phosphorus, ammonia and nitrogen in the water.
Nova Scotia’s proposed provincial guidelines to protect municipal drinking water systems from the harmful parasite cryptosporidium will affect many communities. The changes to the province’s treatment standards for municipal drinking water systems come after many municipalities have built or renovated multimillion-dollar water treatment facilities as part of the Nova Scotia water protection strategy. Both the federal and provincial governments have been instructing municipalities to use more effective and expensive technologies such as ultraviolet rays, ozone or chlorine dioxide against the harmful micro-organism. Ozone and UV are used extensively both in the US and Canada for treating cryptosporidium.
The provincial legislation enacted in 2002 gave municipalities six years to provide residents with fully treated water. The guidelines were put in place following the deaths of seven people in Walkerton, Ont., in 2000 after drinking water was contaminated with E. coli bacteria. Cryptosporidium can cause severe headaches and diarrhea and can’t be eliminated by chlorinating the water supply.
Municipalities have until March 31, 2010 to offer comment on the proposals. Compliance will likely be required by 2013.