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Point Loma Wastewater Treatment Plant (FAQ 1)

Historical Background

Aerial Photo of Point Loma Wastewater Treatment  Plant

The Point Loma Wastewater Treatment Plant (PLWTP) treats approximately 175 million gallons of wastewater each day for the City of San Diego and 15 other cities and districts in the region. The plant uses an Advanced Primary Treatment process to remove suspended solids and biological oxygen demand from the wastewater before its discharge into the ocean through a 4.5 mile-long outfall pipe into 320 feet of water. The plant’s discharge of treated wastewater (effluent) is monitored by an extensive ocean monitoring program.


  • Preliminary Treatment: screening process during which larger pieces of inorganic material (wood, plastics, cloth, along with sand, gravel and grit) are removed from the wastewater.
  • Primary Treatment: Process in which suspended organic solids in the wastewater settle out in sedimentation basins as sludge.
  • Advanced Primary Treatment: Addition of chemicals (such as ferric chloride and/or anionic polymers) to sedimentation basins to promote settling of small organic particles.
  • Secondary Treatment: Use of bacteria to break down organic solids in the wastewater (such as "activated sludge" process).
  • Tertiary Treatment: removal of additional suspended solids after primary and secondary treatment, usually accomplished by filtration through a medium such as sand or anthracite coal.

There is guiding legislation from the Federal Clean Water Act, the Federal Ocean Pollution Reduction Act (OPRA), the California Ocean Plan and the California Coastal Zone Management Act. The Environmental Protection Agency (EPA) and the Regional Water Quality Control Board (RWQCB) regulate the discharge and treatment of wastewater under the Clean Water Act.


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