Most of Central Florida withdraws water from the
Floridian Aquifer by means of deep wells. The water that comes from
both the inland fresh water wells and the coastal saline wells is
typically high in total dissolved solids (TDS) and chlorides. Both the
fresh water and saline water supplies usually contain elevated
hydrogen sulfide concentrations. Indian River County is a coastal
community on the East Coast of Central Florida, with Vero Beach its
largest city and county seat. The county owns and operates two reverse
osmosis (RO) plants and wanted to reduce construction and operating
costs for these facilities while effectively removing hydrogen
sulfide.
The county's two RO water production plants blend finished product
water with raw water between a 3:1 and 4:1 ratio. The plants' combined
finished water is stripped of hydrogen sulfide by forced draft
aerators. The off-gas discharge of hydrogen sulfide has resulted in
numerous odor complaints from area neighbors.
To control odors at regional facilities, Indian River County developed
a program to study the various odor control systems to remove the
hydrogen sulfide odor at the plant aerators. The South County RO Plant
had a maximum finished water flow of 7.06 mgd/day with a 4 mg/L
hydrogen sulfide concentration. The hydrogen sulfide load at the
facility aerator is 236 lbs./day.
At the South County Water Treatment Plant, as well as other treatment
facilities, odor complaints had escalated as development has
encroached on the existing public treatment works. With the
development of South County Park and South County Middle School, the
Indian River County School Board insisted on treatment to remove the
hydrogen sulfide odor in the vicinity of the water treatment
plant. The county Utilities Department recognized the need to also
initiate action to comply with pending US Environmental Protection
Agency Clean Air Act legislation.
In 1995, Indian River County Utilities staff began looking at options
for removing hydrogen sulfide from the product water and concentrate
gas stream at the county water treatment plant aerators. The hydrogen
sulfide removal options, the basis for moving forward with
odor-control testing, were as follows:
- In-line oxidation system
- Two-stage wet scrubber system
- Catalytic/adsorptive carbon system
- Ozone dissolution system
Authors: William F. McCain, P.E., Capital
Projects Engineer, Indian River County; Richard L. Johnson, P.E.,
Principal Engineer, Montgomery Watson America, Inc.; Bradford
H. O'Keefe, Water Superintendent, Indian River County.
If you would like to view the complete text of
this paper, please register with
us.
|