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San Diego Magazine /  December 2007 /  A Sewer Runs Through It /  Treatment and Lawsuits

Treatment and Lawsuits

PRIMARY TREATMENT removes large solids, sand and grit from sewage water and then allows it to sit for a period of time while the suspended solids settle to the bottom. Scum, oil and fats are also screened out. Advanced primary treatment adds a chemical to the water to enhance the settling of solids. The primary process rids wastewater of about 75 percent of contaminants.

Secondary treatment works on the biological level. Bacteria are introduced that feed on sugars, organic materials and the remnants of human waste, and oxygen is added to promote growth of the bacteria. The bacteria then settle to the bottom of tanks and become sludge. The system can be much more elaborate, using aerobic and anaerobic processes to promote consumption of the waste, but in the simple schematic, activated sludge (termed “activated” because bacteria levels have been artificially enhanced) is then either reintroduced into another part of the secondary process or collected for disposal with sludge and solids from the primary treatment stage (sludge is generally spread on fields or sold as fertilizer).

Secondary treatment removes roughly 85 percent of contaminants from wastewater and satisfies EPA standards and the Clean Water Act for discharge into the ocean. The International Wastewater Treatment Plant at San Ysidro was planned to clean water to secondary standards before discharging it 3.5 miles offshore in 93 feet of water (through the South Bay Ocean Outfall). A consortium of environmentalists—spearheaded by the Sierra Club, activist-turned-California Assemblywoman Lori Saldaña and the Surfrider Foundation—sued the International Boundary and Water Commission to force the commission to alter its secondary plans. The environmentalists wanted aerated ponds used instead of activated sludge, a process that produces a less noxious byproduct. Before the lawsuit went through, the IBWC had already run out of money (it had paid $90 million to build the 11-foot-wide South Bay Ocean Outfall and another $8 million to the U.S. Army Corps of Engineers), and Congress was loath to open up the $234 million cap it had put on the project.

Out of money, and sued for its designs for secondary treatment, the IWTP couldn’t move forward with the second phase of construction. But all concerned—the state of California, the environmentalists and the IBWC—realized the futility of preventing the plant from its primary treatment operations, and so the California Water Quality Control Board granted the IBWC a temporary permit for ocean discharge of water that was treated only to advanced primary standards—which violated the Clean Water Act. The IWTP has been discharging water that doesn’t meet American water-quality standards from the day it began operations in April 1997, and construction on the aerated ponds (the IBWC had paid for designs on both types of secondary systems, activated sludge and aerated ponds) has yet to begin.