Secondary Treatment

Secondary treatment removes practically all organic and inorganic solids that remain in primary effluent. Purification processes found in nature are duplicated, including biological treatment and clarification.

BIOLOGICAL TREATMENT - Primary effluent is distributed to aeration basins. Living micro-organisms, called "activated sludge," feed on organic material remaining in primary effluent and multiply. Oxygen, blown in through thousands of diffusers, accelerates the biological process.

CLARIFICATION - After the micro-organisms deplete their food supply, treated wastewater flows into secondary clarifying tanks where settling of the biomass occurs. The majority of the settled solids (activated sludge) is returned to aeration basins to continue purifying incoming primary effluent. Excess waste activated sludge is collected, thickened and pumped to digesters.

Secondary effluent, the cleaned wastewater, is virtually free of pollutants and is compatible with the marine environment. The effluent is discharged through the five-mile ocean pipeline; a portion is recycled for process and irrigation uses within the treatment plant.