Publication Date

Spring 2014

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Katherine K. Cushing


BOD, Dissolved Oxygen, Lower South Bay, Nutrients, TSS, Wastewater

Subject Areas

Environmental science; Environmental management


The San José-Santa Clara Regional Wastewater Facility (Facility), located in the Lower South Bay (LSB), is the largest advanced wastewater treatment plant in San Francisco Bay. From 1957 to 2013, the Facility added a series of expansions and upgrades that increased treatment capacity and improved the quality of treated effluent.

This study addressed the questions: (1) To what extent have expansions and upgrades in the treatment plant during the past six decades resulted in improvements to Facility effluent quality? (2) How and to what extent have the changes in the Facility effluent translated into changes in the water quality of the LSB? Five hypotheses were formulated to evaluate long-term trends and correlations regarding wastewater loads (BOD, TSS, NH4+, NO3-, and PO4) in the LSB. R software was used to analyze the data.

All five hypotheses were confirmed by the data, with a number of qualifications that can be readily explained. The first major finding is that, in spite of substantial increases in population, both influent and effluent flow to the Bay decreased in the past decade. A second major finding is that the data show major load reduction in BOD, TSS, and nutrients corresponding to Facility improvements. Third, anoxia and hypoxia were virtually eliminated following the Facility's upgrade to nitrification, significantly improving DO concentrations in the LSB. Fourth, LSB nutrient concentrations showed significant decreases corresponding with capital improvements to the Facility.