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4.4 Reuse (Topic d)

Wastewater reuse is an issue in arid regions, and in other areas where water costs are high. In 1993 the USEPA developed a guide for wastewater reuse. Many states and provinces now have specific guidelines for reuse of reclaimed wastewater, with the standards and criteria set in California being considered the most stringent and progressive.

A standard reuse of wastewater is as utility water for the wastewater treatment plant which produced it, especially for larger plants. The chlorinated effluent water is used for washdown and for irrigation of the treatment plant grounds, to save city water charges.

Irrigation methods are discussed under topic e, as they are also a disposal method. Irrigation of golf courses, grassed playing fields, and highway medians using treated wastewater is common in many arid and semi-arid areas of North America.

Large scale groundwater recharge is practiced in California, New Jersey and Georgia. Orange County in California injects reclaimed water to prevent saltwater intrusion to the local aquifer. Los Angeles has practiced surface spreading to recharge local aquifers since the 1960s. The City of Perth Amboy, NJ, operates two open water recharge reservoirs to supplement the local drinking water aquifer and to prevent salt water intrusion. Clayton, County in George applies reclaimed wastewater to its potable water watershed.

Wastewater is also reused by industries. In Texas, the Southwestern Public Service Company of Amarillo Texas, operating gas fired steam generation electric power stations, has used treated wastewater in its cooling towers since 1971. Blowdown water from the cooling towers is used on local grazing land for irrigation.
Dual plumbing systems reuse treated wastewater for non-potable purposes. At the Las Vegas Treasure Island Resort Hotel, graywater mixed with groundwater is treated with activated carbon, straining, preliminary disinfection, polymer dosage, pressure filtration, reverse osmosis and UV disinfection before being used to supply the hotel's "pirate sea". In Toronto, Ontario, the Healthy House, a demonstration project, treats septic tank effluent with a Waterloo Biofilter, multi-media sandfilters and ozonation and reuses the product for laundry, toilets, baths and showers. At the Sandy Hill cooperative housing project, part of the communal greywater is screened and treated with ozone for reuse for toilet flushing in apartments. (Jowatt and Pask 1997). Many states and provinces now have Plumbing Codes that permit dual plumbing (potable and non-potable) systems that enable wastewater to be reused for flushing toilets and urinals.

There are also instances of reuse as drinking water. Since 1978, Upper Occaquan Sewage Authority in Alexandria, Va., has been blending 75.7 million L/d of repurified water into a reservoir before being converted to potable water.

In San Diego, California, a wastewater effluent project was conceptually approved for construction by the California State Department of Health Services, which would discharge reuse treated wastewater into the City’s watershed for use as drinking water. A water reclamation plant presently provides up to 10.7 million m3 /year of reclaimed wastewater for landscape irrigation and other non-potable uses. By 2004, up to 18.5 million m3 you would have been further treated in a water repurification plant for human consumption. The process included micro-filtration, reverse osmosis, nitrate removal by ion exchange, and ozonation. (Richman 1997). However, the City Council suspended the project in January, 1999 and is now looking at other alternatives.

Another reuse project in Tampa Bay, Florida, which was also carefully researched and pilot tested, was recently shelved in March, 1998 due to difficulty building public consensus in several political jurisdictions, and the availability of new desalination technology.

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