AWWA ACE68676

This powerpoint presentation begins by providing a brief overview of a water system and then provides aquifer storage and retrieval (ASR) operations, including: ASR as a supplement to treatment plant production during high-use periods and in winter during high turbidity events; injection typically from Nov-March at two of four wells approximately 3.5 mgd; storage goal of 500 mg, recovery from 3 of 4 wells approximately 6.7 mgd, 100% recovery with use of groundwater rights. Initial investigations included the following: monitor THM concentrations over a 30-day storage period, with weekly measurements of THM at each of four wells; collect samples from each well and finished water from TP; and, time series analysis after 30-d storage (every 10- min for 1 h). The analytical methodology included: U.S. Environmental Protection Agency Method 524.2; purgeable organic compounds by capillary column GC/MS; alternate methods 551.1 and 552.2 (liquid extraction with ECD); all provide full speciation; Hach Procedure 10132; colorimetric read on spectrophotometer; all results reported as chloroform (CHCl3); and, estimated detection limit of 6 ug L-1. Study findings include the following: THM concentration appears to be related to storage volume; formation occurs rapidly during storage period; rate of dissipation indicates that THMs are not evenly distributed in stored water; lack of observation in ASR 1 and 2 suggests a localized phenomenom; dissipation of THMs does not appear to be a function of mixing/dilution (based on geochem data); TOC probably the limiting factor in formation; and, (triangle) SUVA indicates potential source of additional TOC/DOC. Includes tables, figures.