Date of Award


Document Type


Degree Name

Master of Science in Earth and Environmental Sciences


Chemistry and Biochemistry

First Reader/Committee Chair

Fryxell, Joan


This study examined the effects of drought on the City of San Bernardino Municipal Water Department’s (SBMWD’s) wastewater treatment plant (WWTP) wastewater flow rates and constituent concentrations. The study utilized data obtained from the SBMWD’s monthly discharge monitoring reports (DMRs), dating from 2007 to 2015. For each report the SBMWD Water Reclamation Plant (WRP) and Rapid Infiltration and Extraction (RIX) facility influent and effluent flow rates, along with concentrations of ammonia, biochemical oxygen demand (BOD), total suspended solids (TSS), total inorganic nitrogen (TIN), and total dissolved solids (TDS) were examined. Even though influent and effluent flow rates were examined for both WRP and RIX facilities, a majority of the flow-rate research concentrated on WRP influent flow rates because changes of influent flow rates cascade down the treatment process from WRP influent flow rates to RIX effluent flow rates.

Impacts of the drought were analyzed by comparing drought statistics, for the Riverside-San Bernardino area, to influent flow rate trends and relevant constituent concentrations. Relevant constituent data were determined based on if they were discharged near their National Pollutant Discharge Elimination System (NPDES) permit limits. Pearson Correlation Analyses were used to assess any relationships between influent flow rates and relevant constituents.

WRP influent flow rates and TIN concentrations were the only two parameters explored by this project that exhibited measurable changes related to the drought. WRP influent flow rates observed an inverse relationship with drought because persisting drought conditions led to decreased wastewater flow rates. TIN concentrations had a positive relationship with drought conditions based on the inverse correlation between influent flow rates, and the graphical relationship between drought conditions and TIN concentrations. The Pearson correlation coefficient for TIN concentrations and influent flow rates was -0.630 with a p-value less than 0.05, which is a strong negative relationship. Inconsistencies were observed during 2010 and 2011, which were non-drought periods. During non-drought periods it was expected that flow rates would be highest and constituent concentrations would be lowest. This was not the case because during 2010 and 2011 flow rates were lowest and TIN concentrations were highest, contradicting all other data. The drought-related justification for these abnormalities was that the implementation of the 20x2020 Water Conservation Plan, a California water management plan enacted in 2009, increased water conservation and reduced wastewater flow rates. However, there are many other factors that were not explored by this project that could have led to decreased wastewater flow rates, such as housing foreclosure rates peaking during 2010. Further studies are recommended.