Nitrogen loading to San Francisco Bay from wastewater plants and refineries

In the last decade scientists have become increasingly concerned over nutrient levels in the Bay-Delta, including ammonia, a form of nitrogen, which at elevated concentrations has toxic effects in aquatic ecosystems. The interactive table below is based on nutrient data collected over the course of a year, starting in the the summer of 2012, by refineries and wastewater treatment plants. These dischargers were required by the Regional Water Quality Control Board to monitor and report data regarding nitrogen and phosphorus discharges at a level never before required, based on concerns that the Bay is becoming susceptible to the effects of nutrient enrichment, or eutrophication.

Data here is limited to average daily flow, total nitrogen (TN) and ammonia (NH3), which are common parameters used to judge treatment effectiveness. Note that given the drastic differences in daily loads and pollutant concentrations, data is presented on a logarithmic scale. Explore the data by clicking on the headers and scroll down to learn more about this data. This graphic will not work in older browsers, including Internet Explorer.

Click on a column header to sort.
Wastewater Agency or Refinery
Avg Daily Flow
(MGD)
Total Nitrogen (TN)
average daily
load (kg/day)
average daily
conc. (mg/L)
Total Ammonia (NH3)
average daily
load (kg/day)
average daily
conc. (mg/L)

About This Data

The data presented here was made available by the San Francisco Regional Water Quality Control Board, who in November 2012 started released data received from wastewater agencies. This data was submitted to the Regional Board in response to a request for information so that regulators could better understand the magnitude and scope of nutrient inputs to the Bay from the various wastewater dischargers around the Bay.

By sorting the columns based on TN and NH3 loads you can get an idea which treatment plants conduct nutrient conversion, including the treatment plants in San Jose and Palo Alto. At these plants, total nitrogen is quite high, though ammonia concentrations are very low, given conversion to NO3 through nitrification. Plants in the Lower South Bay were required decades ago to implement advanced treatment measures and many others are considering such upgrades. Plants with the largest ammonia loads are located in the Central Bay, including SF's Bayside Plant, EBMUD, and East Bay Dischargers Authority (EBDA).

Effluent discharged from POTWs to the Bay have wide variations in nitrogen concentrations. Some facilities, such as the three facilities in the Lower South Bay and those which discharge to shallow waters, are required to remove a vast majority of ammonia from wastewater prior to discharge. This is due to lower circulation and mixing in this area, compared with the Central Bay. There are no plants discharging to the Bay which conduct nutrient removal, though several conduct nitrification, which is the conversion of ammonia to nitrite (NO2) and then to nitrate (NO3) and some acheive partial denitrification, such as the San Jose/Santa Clara plant.

This graphic was adopted from an interactive table developed by the New York Times. For questions or comments about this map please contact Ian Wren (ian@baykeeper.org)