The Cedar Key Water and Sewer District (District) has been identified by the Florida
Department of Environmental Protection (FDEP) as a major offender of the Stage 1
Disinfectants/Disinfection Byproducts Rule (D/DBPR) since 2003. The water supply
at 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 at
Cedar Key ranges from approximately 5 to 13 mg/L, depending on which of the water
supply wells is in service. The treatment process utilized by the District at the time of
pilot 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) levels
in 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 the
regulatory 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 evaluating
technologies to meet the Rule. The District evaluated multiple processes including
chlorine dioxide, forced draft aeration, enhanced coagulation followed by
ultrafiltration (UF), and the MIEX® magnetized anion exchange process utilizing both
a conventional contactor/settler (Dual Stage) configuration and a newly developed
High Rate (HR) fluidized bed configuration. Both MIEX® System configurations
were investigated (2/2/2006 through 2/22/2006) as pre- and post-treatment to lime
softening to determine the most effective treatment train for DOC removal and
disinfection byproduct (DBP) reduction. After trialing these technologies the District
selected the MIEX® magnetized anion exchange process utilizing the HR fluidized
bed configuration as pre-treatment to lime softening. A full-scale 250 gallons per
minute (gpm) system was commissioned in November 2006 and was the first HR
MIEX® System to start-up in the United States.
This paper summarizes the results of the trials of both the Dual Stage and High
Rate MIEX® configurations where the optimum treatment train achieved 76% DOC
reduction and resulted in a Simulated Distribution System (SDS) TTHM level of 49.7
µg/L and SDS HAA5 level of 14.8 µg/L. The performance of the full-scale HR
MIEX® System since start-up in November 2006 is also discussed as well as
integration of the system into the existing treatment works. Includes reference, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 250 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 11/01/2007 |
