The benefits of using reclaimed water
By Larry Kolb, San Francisco Bay Regional Water Quality Control Board

Committee for Green Foothills hosted an environmental forum in October that explored the appropriate, safe uses of treated wastewater. Green Footnotes invited panelist Larry Kolb to describe some of these uses for our readers.

Using treated wastewater for landscape irrigation and other uses is an old idea that is getting new interest. Wastewater reclamation makes existing water supplies go further. For example, irrigating local golf courses, freeway medians and cemeteries can free up freshwater for domestic needs. In addition, because even well-treated wastewater contains more chemicals than we can measure, direct application to soils allows such pollutants to break down rather than polluting waterways where it would otherwise be discharged.

San Jose's Guadalupe River Park & Gardens showcases the use of recycled water in their Courtyard Garden on Taylor Street.

For these reasons, wastewater reclamation is widely regarded as a good thing. The State of California and its various agencies have executive orders, resolutions, and policies endorsing water reclamation, adopted under both political parties.

Concerns about using reclaimed water
Water reclamation raises two main concerns: added cost and safety considerations. Added costs include treatment that may be required to meet health standards, as well as the cost of new piping to the points of use. Safety considerations require that rigorous health-based standards for treatment are consistently met and that use restrictions are complied with. (An example of a use restriction is prohibiting irrigation of a golf course during hours of use.)

The hue and cry over reclaimed water
The cost and safety issues of reclaimed water can be addressed; however, the ultimate challenge is public acceptance. Although an old saying in the water business states that no one in California has ever gotten sick from a reclamation project, loud public outcry surrounds many reclamation proposals -- particularly those proposals that would inject very highly treated effluent using reverse osmosis (similar to distillation) into aquifers that are used for drinking water supply. The term "toilet to tap" is a potent epithet.

Of course, we more or less take for granted that the streams from which we take our surface water supplies almost always have their own waste inputs. For example, about 90 percent of the wastewater discharged into the San Joaquin River is taken out a little further downstream and reused.

The agricultural potential for reclaimed water
The really large market for reused water is in agriculture, especially for crops like cotton or alfalfa where potential direct human exposure is limited.

If we had the political will, it would be feasible to reclaim about half the wastewater generated in the state for agricultural use. Since agriculture accounts for some 80% of our water use, it could readily absorb a good part of our reclaimed water.

However, using reclaimed water for agriculture also poses some barriers. Because farmers get freshwater supplies at huge subsidies, many are afraid they might lose this benefit should they accept reclaimed water. Another problem is salt. In general reclaimed water has somewhat more salinity than river water, and its use would make the San Joaquin Valley's already-serious salinity buildup problem slightly worse.

Water reclamation brings environmental benefits, including reduced need for new dams
A new argument for agricultural use of reclaimed water is that it could alleviate some of the impacts of climate change. There is a very good chance that we will lose most of the free seasonal water storage provided by snowpack as our winters get warmer, especially at higher elevations. Instead of replacing this storage with new reservoirs, we could shift to use of reclaimed water, which is available year-round.

Today there are two trends that we can see for California water supplies. One is more use of reclaimed water. The other is increasing use of desalination to allow use of salty or brackish water for domestic use. Together these technologies have the promise of meeting our needs for additional urban water while minimizing the need for costly and environmentally harmful new dams.

Published October 2003 in Green Footnotes.
Page last updated November 13, 2003