SLUDGE VICTIMS

motorcycles have been among the bulkier waste screened out of the water and trapped in catch basins, said Margie Nellor, the districts' director of technical services.

More mundane household garbage - coffee grounds or eggshells, for example - are captured in special chambers and hauled away to landfills.
SELF-PROPELLED PLANT Then the separation begins. Along one path, water passes through increasing levels of purification until it emerges clear. It is used to water grass and shrubs in places such as city parks.

Along a second path flows the sludge. Through giant settling tanks and digesters, sewage sludge slowly sheds its pathogens, the disease-causing microbes found in human and animal waste.

It also releases a smelly gas, methane, that is used to power both plants. Except in emergencies, there is enough gas to keep lights, computers, automated machinery and everything else running 24 hours a day.

Water is then removed from the sludge until it is moist, but solid.

Charles Egigian Nichols, the Orange County Sanitation Districts' good-humored and precise recycling manager, won't even call it sludge once the process is finished. He prefers the term "biosolids" - a word that makes a distinction between the foul material that enters his plant and the commodity that emerges, which he believes is clean and useful.

"Biosolids are essentially pathogen-free," Nichols said as he described the process to visitors on a recent tour. "You and I could eat it."

But he acknowledges that doing so would be illegal. It can't even be used as fertilizer on edible crops in the raw form that comes out of the sewage-treatment plant. That requires further processing.

And that's where the workers at Pima Oro step in. "Cake sludge" is their descriptive term for the truckloads of material they are paid to haul out of Orange County sewage plants daily, most of it headed for Thermal. Once there, the sludge is formed into windrows, long piles about 7 feet high. The few remaining pathogens are baked out of the sludge under the harsh desert sun.

Microbes in the sludge generate heat, which kills pathogenic bacteria. After about 15 days, the pathogens have dropped to "background" levels that match those of everyday dirt, McManigal said.

Orange County fertilizer is not only better than more common organic fertilizers, such as cow or chicken manure, but cheaper, its promoters say.

"Farmers pay $500 a truckload for chicken manure," McManigal said. "Ours is $75."