Underground storage of reclaim water on the increase

Use of reclaimed, or grey water, is a major part of the US effort to conserve water, by reducing the amount of drinking water consumed in non-essential uses. But in south west Florida, existing reclaim systems are not able to cope with the dry season shortages leading to new solutions such as underwater reclaim wells.

Across the region, there are currently around 12 aquifer storage projects, valued at more than $150 million, in various stages of development. These are expected to handle 30 million gallons/day once commissioned. At St. Petersburg, which has the oldest and largest urban reclaimed water system in the country, reclaimed water supplies now run out during the dry season. However, the city is hoping to solve the problem with the commissioning of an $800,000 underground scheme.

Elsewhere, the Southwest Florida Water Management District, Swiftmud, has proposed a $9.5 million project for the cities of Clearwater and Largo, which could reclaim nearly 2 billion gallons/year. This would help both cities solve the problem of a predicted shortage of reclaimed water in the dry season that would leave the majority of residents unable to access any reclaimed water supplies. Unlike earlier schemes, the Clearwater/Largo project could have a pipeline link to the wetlands area of Pasco, so that excess reclaimed water could be used to stop the wetlands drying out. Pasco is close to the region’s main drinking water supplies and an earlier proposal to permit the use of reclaimed water to replenish the wetlands had been opposed on health grounds.

Investment in reclaim water can also relieve pressure on the Floridan aquifer, which was designated as a ‘water use caution area’ in 1992, because its water resources were seen “to be, or likely to become critical in the next 20 years”. This region of around 5000 square miles, takes in the counties of Manatee, Sarasota, Hardee and DeSoto, and portions of Hillsborough, Charlotte, Polk and the Highlands.

The major concern in the caution area is to halt the decline of lake levels along the Highland Ridge, where most Floridan aquifer recharge occurs, and stop the advance of coastal saltwater intrusion in the aquifer. Regional water supply plans and a determination of minimum flows and levels across the caution area are due to be adopted no later than December 2001.