AWWA WQTC65833

The Cedar Key Water and Sewer District (District) has been identified by the FloridaDepartment of Environmental Protection (FDEP) as a major offender of the Stage 1Disinfectants/Disinfection Byproducts Rule (D/DBPR) since 2003. The water supplyat Cedar Key is a groundwater that is under the influence of surface water.The typical background level of Dissolved Organic Carbon (DOC) in the raw water atCedar Key ranges from approximately 5 to 13 mg/L, depending on which of the watersupply wells is in service. The treatment process utilized by the District at the time ofpilot testing during early 2006 consisted of the addition of a coagulant (DelPac 2020)prior to conventional lime softening which removed only around 13% of the DOC.After disinfection with free chlorine, the typical total trihalomethane (TTHM) levelsin the distribution system ranged from 300 to 450 µg/l and the haloacetic acid(HAA5) levels ranged from 150 to 300 µg/l, both of which were well above theregulatory constraints of 80 µg/l and 60 µg/l, respectively.Soon after promulgation of the Stage 1 D/DBP Rule by the U.S.Environmental Protection Agency (USEPA), the District began proactively evaluatingtechnologies to meet the Rule. The District evaluated multiple processes includingchlorine dioxide, forced draft aeration, enhanced coagulation followed byultrafiltration (UF), and the MIEX® magnetized anion exchange process utilizing botha conventional contactor/settler (Dual Stage) configuration and a newly developedHigh Rate (HR) fluidized bed configuration. Both MIEX® System configurationswere investigated (2/2/2006 through 2/22/2006) as pre- and post-treatment to limesoftening to determine the most effective treatment train for DOC removal anddisinfection byproduct (DBP) reduction. After trialing these technologies the Districtselected the MIEX® magnetized anion exchange process utilizing the HR fluidizedbed configuration as pre-treatment to lime softening. A full-scale 250 gallons perminute (gpm) system was commissioned in November 2006 and was the first HRMIEX® System to start-up in the United States.This paper summarizes the results of the trials of both the Dual Stage and HighRate MIEX® configurations where the optimum treatment train achieved 76% DOCreduction and resulted in a Simulated Distribution System (SDS) TTHM level of 49.7µg/L and SDS HAA5 level of 14.8 µg/L. The performance of the full-scale HRMIEX® System since start-up in November 2006 is also discussed as well asintegration of the system into the existing treatment works. Includes reference, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

7

File Size:

1 file , 250 KB