AWWA MTC57537

The purpose of this study at the Olivenhain Water Treatment Plant was to determine the t10, at the nominal operating capacity of 25 million gallons per day (MGD), of a chemical injected at the raw water sodium hypochlorite injection point to the permeate (filtered water) pumps. A tracer study was performed to verify the detention time through the membrane basins. The testing method used here was based on the SPANDS method as suggested in the HACH DR/2010 Spectrophotometer Handbook. A HACH spectrophotometer (HACH DR/2010) was used to analyze water samples that were collected in vacuum-sealed Fluoride Reagent Accu Vac ampuls. The ampuls were read by the spectrophotometer at a wavelength of 580 nanometers. Theoretical data suggest that the system be dosed for a period of time equal to three times the theoretical residence time, t10, value. In order to mimic the theoretical concentration curve, a sampling regime similar to the shape of the curve and based on the "3 times the t10" value was devised. Includes figures.