San Francisco Bay board adopted 40% nitrogen‑load reduction permit after decade of science and regional planning

The San Francisco Bay Regional Water Board adopted a nutrient permit in July 2024 that sets aggregate nitrogen reduction goals intended to reduce the potential for harmful algal blooms and low dissolved oxygen events, a board staff presenter said at a State Water Board meeting.

Board staff explained that municipal wastewater treatment plants (about 40 POTWs in the region) historically contributed the majority of nitrogen loads to the bay and that a severe heterosigma bloom in August 2022 — followed by a similar event in 2023 — produced widespread fish kills and public concern. Staff concluded there was “reasonable potential” for effluent nitrogen to cause or contribute to basin‑plan violations of the narrative biostimulatory substances objective; federal permitting rules require effluent limits when reasonable potential exists.

Using modeling…