AWWA ACE68913

AWWA ACE68913 Addressing TSS Generation in the World's Longest Municipal Brine Line
Conference Proceeding by American Water Works Association, 11/01/2008

Wetterau, Greg; Burbano, Marie Sedran; Haller, Richard; Dezham, Parivash

More info

Full Description

The Santa Ana Watershed Project Authority (SAWPA) owns and operates a 72 mile brine lineserving groundwater desalination facilities and other industrial and domestic users in SanBernardino and Riverside Counties in California. Problems have been experienced recentlywith the generation of large concentrations of suspended solids within the brine line,resulting in added maintenance to remove settled solids as well as significant billing issuesfor the authority. Dischargers to the brine line are charged based on a combination of flow,suspended solids, and biochemical oxygen demand (BOD) at their point of discharge.SAWPA is in turn charged for these same parameters by a downstream sanitation district atthe transition from the SAWPA pipeline to the sanitation district's. Suspended solidsmeasured at the downstream monitoring point have been roughly double what they aregoing into the pipeline, creating concerns about an equitable manner to allocate costs forroughly 4,000 tons per year of solids that cannot be measured at the discharge points.It has been considered that these solids may come from some combination of chemical andbiological interactions between the brine flows and domestic wastewater, which currentlymakes up 40 percent of the brine line water. SAWPA authorized an extensive water qualitystudy to determine and characterize the source or sources of this solids generation. It wasdetermined during the first stage of testing that both chemical precipitation from hardnessand silica and biomass formation were significant contributors to the suspended solidsgeneration. Based on these preliminary results, SAWPA instituted a hardness fee to alldischargers in order to help cover the revenue imbalance created by the suspended solids.The final stages of the water quality study are expected to be complete in October 2008 andwill include chemical precipitation and biogrowth models to project and verify contributionsof suspended solids from each of these sources. Results of this study will be used as the basisfor permanent changes to the rate structure for brine line dischargers and will be used todevelop a recommended maintenance program to address the solids generation. Includes tables, figures.