An up-and-coming technology could be used to upgrade the Point Loma Wastewater Treatment Plant to federal standards at a fraction of the cost of conventional sewage treatment.
San Diego wastewater officials say it has the potential to save more than $1 billion if the city were ever forced to upgrade the Point Loma facility, its main processing plant.
"It has great advantages, and the technology is sound," said Alan Langworthy, deputy director of environmental monitoring for San Diego's Metropolitan Wastewater Department. The system serves 2 million people in San Diego and 15 other communities.
Two city employees were in France and Switzerland last week visiting sewage treatment plants that use the technology, known as biological aerated filtration.
And, beginning in January, wastewater officials want to conduct a $1.7 million test of the filtration technology.
The test is intended to show how well the technology treats 30,000 gallons a day of the region's sewage.
The 40-year-old Point Loma Wastewater Treatment plant handles 180 million gallons of sewage daily. It uses a process called advanced primary treatment to remove 85% of the solids from sewage before discharging the wastewater four miles offshore.
San Diego is one of only a handful of regions in the nation that have a waiver from the U.S. Environmental Protection Agency allowing them to treat their sewage to a level that is less than the federal standard. To meet that standard, known as secondary treatment, San Diego would have to remove 90% of the solids from its wastewater.
San Diego's waiver is the result of 40 years of battling in Congress and the courts. The city used scientific studies to convince the EPA that sewage treated to the advanced primary level and discharged far offshore does not pose a risk to human health or marine life.
The wastewater department estimates it would cost sewer customers $2 billion to upgrade to secondary treatment using the conventional method of secondary treatment, called activated sludge.
Wastewater department director Scott Tulloch said the activated-sludge method would be especially costly because Point Loma doesn't have enough room to accommodate the additional basins that would be needed, even if the city were able to use 16 acres of Navy land north of the plant. That means the city would have to build a second sewage plant elsewhere, he said.
By contrast, the new technology of biological aerated filtration needs relatively little space, sparing ratepayers the expense of constructing another plant, Tulloch said. He put the estimated cost of an upgrade to secondary treatment using this new method at $500 million.
San Diego's waiver expires in June 2008, when the city can seek a renewal for five more years.
Surfrider Foundation and San Diego BayKeeper, two environmental groups, are challenging the waiver in court, saying the city has not proved that its wastewater does not harm the environment.
"San Diego is the largest waiver holder in the entire country," BayKeeper attorney Marco Gonzalez said. "There's no real good excuse for them to have a waiver. They have to do a better job."
He said the environmental activists he represents have been pushing for the test of biological aerated filtration. "It's something on the horizon that looks like it might be doable," Gonzalez said.
More than 100 sewage plants in Europe use biological aerated filtration, which is only now beginning to catch on in the United States. Fewer than half a dozen U.S. plants use the technology.
San Diego wastewater employees earlier this year visited two of them, in Northfield, Minn., and Roanoke, Va.
"I do think what we're seeing is a potential revolution of wastewater treatment," said Scott Shirley, manager of Roanoke's sewage plant, which was the first in the United States to treat its sewage with biological aerated filters.
Like the activated-sludge method, biological aerated filtration uses microorganisms that eat small sewage solids to separate them from the wastewater.
Last week, San Diego's Public Utilities Advisory Commission voted in favor of testing the technology.
"Given the uncertainty of the waiver process, it certainly makes a lot of sense to me," board member Joseph Panetta said.
Source: Kathryn Balint
