September 3, 2008
Filed under Uncategorized
San Diego is considering water recycling to help solve the water crisis. While Mayor Jerry Sanders is promoting conservation, City Attorney Michael Aguirre seeks a more aggressive approach to water recycling.
Aguirre isn’t satisfied with the pace and the current approach to solving the water crisis. In a recent memorandum sent to the mayor and the City Council, Aguirre challenged Sanders’ methods to combat the water crisis.
San Diego imports 90 percent of its water from the Colorado River and the San Joaquin River basin in Sacramento. The city’s dependence on water from outside the region is becoming dangerous, as supplies are not sufficient for future needs. Allocations from the Metropolitan Water District may diminish as reserves are slowly being tapped.
Part of the memorandum suggests the city move toward reclaimed water sources.. Indirect potable reuse is the recycling of wastewater and reintroducing it to our water supply. The reclaimed water is called indirect because it isn’t directly pumped into the potable distribution system. Rather, it’s mixed in with reservoir water or a ground supply like the Colorado River, then treated to meet drinking water standards.
National University biology professor Thomas Hahn says, “We must convince the public to develop these processes as soon as possible because water is the major limiting factor in the Western U.S.”
Aguirre’s findings in his memorandum to the mayor and City Council list the cost of a water recycling plant at $12 million. Funds from both the Water and Wastewater departments could be used to fund the effort.
The earth has naturally recycled water for millions of years. The recycling of wastewater would simply speed up the process.
The process of recycling water has become a natural aid to droughts and water crisis worldwide. According to the Environmental Protection Agency, treated wastewater is commonly converted to “non-potable” or non- drinkable water. It’s used for irrigation of public parks, landscaping, golf courses and industrial cooling processes.
“The least costly is use of ‘passive’ systems, which remove the solids, chemically treats them to kill bacteria, dries the material and uses it as fertilizer or as fuel for electricity generation or as landfill,” says Hahn, “Meanwhile, the liquid effluent runs through a series of ponds with both aquatic and shoreline plants to clean the water.”
Santee Lakes and Arcata Bay are local examples of these ponds. Once the pond cycle is completed, the water is as clean as water coming from the Colorado River and can be treated likewise.
Another option to reclaim water is through reverse osmosis. Hahn says the process is more expensive due to the cost of energy required to push water through membranes.
Dr. Dzung T. Nguyen, another National University professor, says, “The holes in the reverse osmosis membrane should only let water molecules or smaller molecules go through and nothing else. Most pathogens and pharmaceuticals are much bigger than water molecules. In practice, it depends a lot on the quality control processes at the reclamation plant.”
An example of success in water reclamation can be found in the Irvine Ranch Water District. Irvine’s Michelson plant sends wastewater through a complicated process of screening, filtering and adding chemicals. The end result is water suitable for irrigation and landscaping. Some high-rise buildings in the Orange County area use this water for toilets as well. This water can then be mixed with reservoir or ground water, and follow the conventional treatment process to create potable water.
Has modern science caught up with nature when it comes to water recycling? Perhaps this is a close substitute for natural means. How the city can convince its citizens that this isn’t just “toilet to tap”?
“San Diego County gets most of the water from the Colorado River,” says Nguyen, “By the time water gets to San Diego County, it has been used and reused by upper basin states several times already.”
A water recycling test project failed to convince San Diego water drinkers in 1999. Since then, Orange County has established a system and spent millions on public relations and education on the issue. So is the project simply lacking public support?
In light of education and assurances of scientists and public officials, would San Diegans be open again to exploring the option of recycled wastewater? Or will they let another good idea go down the drain?