"After the chemical addition, the waste water still has hydrogen sulfide (which is responsible for) that rotten-egg odor or organic smell neighbors complain about," Crosse said. "But it would be much worse if we didn't add the ferrite chloride."
Sand and grit, settling to the bottom of the tanks, are removed. Then the remaining sewage is pumped into a covered tank for what is referred to as primary treatment. In this phase, waste water is filtered through a sedimentation tank, where solids settle to the bottom or are skimmed from the top.
Before 1986, Crosse said, Hyperion was removing only about 60% of solids during this phase. But with the addition of new chemicals, the record has improved to about 85%, he said.
The removed solids become sludge, a smelly black soup that spends 16 days concentrating and drying in digestion and centrifuge tanks. Until 1987, the city of Los Angeles was pumping untreated sludge about seven miles off the coast of Santa Monica, in what scientists agree was an ecological catastrophe.
Hyperion has since found new ways to dispose of sludge. Much of it is converted into methane gas or "sludge powder" and burned to generate electricity for the plant, Crosse said. Some dried-out sludge is used to make Topgro, a city-sponsored fertilizer available at local nurseries.
The current controversy at Hyperion involves so-called secondary treatment, in which the remaining solids are oxygenated, converted into bacteria and then removed. Visitors can see part of this process in action at the plant's 300-foot-long uncovered aeration tanks, a witch's brew of bubbles and foam.
Currently, about half of the waste water at Hyperion receives secondary treatment. The effort to upgrade the plant so it can provide such treatment for all its sewage would result in what is known as "full secondary" treatment.
The current construction project will enable Hyperion to improve the quality of sewage treatment, including building covered aeration tanks, according to Crosse. This is important because in 1987 the city of Los Angeles--under pressure from environmental groups and federal agencies--committed to advanced treatment of all ocean-bound waste water by 1998.
"The move to full secondary is the driving force" behind the expansion, Crosse said.
Some politicians and scientists, however, wonder if the benefits of advanced treatment are worth the billions of dollars in expense.
U.S. Rep. Steve Horn (R-Long Beach) introduced a bill that would relax requirements for advanced treatment of sewage discharged into Santa Monica Bay--and, officials say, save water customers in Los Angeles several hundred million dollars. The full House is expected to vote on the legislation soon, possibly as early as this week.
Until recently, Ron Deaton, the chief legislative analyst for the city of Los Angeles, was lobbying for the so-called Horn Amendment on the grounds that the city has a longstanding policy against "unfunded mandates"--federal or state requirements that saddle local communities with the expense of implementation. According to Deaton, the clean-water rules constitute such a mandate.
What especially concerned Deaton and others was that San Diego has for years been arguing for an exemption from stiffer sewage treatment rules. San Diego currently provides what it calls "advanced primary" treatment of sewage, which according to officials there removes nearly as large a percentage of solids from waste water as secondary treatment.
"My concern, and the city's concern, was that we had spent a lot of money complying with the mandate, and other people haven't," Deaton said in an interview.
Deaton has stopped lobbying for the new legislation, apparently because of environmental and legal concerns raised by members of the Los Angeles City Council. But the issue is far from over. Scientists are also debating the necessity of full secondary treatment.
Paul Dayton, a professor of oceanography at the Scripps Institution of Oceanography in San Diego, argues that San Diego's "advanced primary" treatment has only minimal effects on a handful of marine species in a half-mile radius of the ocean floor where the waste water exits the sewage plant's pipe.
Furthermore, the marine communities in Southern California are so "robust" that the waste water poses no serious threat to the worms, crustaceans and clams that live in them, he said.
"Full secondary may not be necessary (in Los Angeles); it's certainly not necessary in San Diego," Dayton said. "Ecologically, it's insane to say (we need to) spend billions of dollars for one-half to two miles of crustaceans. These animals are extremely abundant. . . . This is not an ecologically serious problem in Southern California."
An aide to Rep. Horn said the congressman drafted the provision because current clean-water rules have cost the city and Los Angeles County hundreds of millions of dollars and do not help the environment. Horn himself was not available for comment, aides said.