CLIENT NAME - Sarasota.WaterAtlas.org

2.3.3.1.2 DegasificationRaw water enters the degasification and stripper system, in which countercurrent forced aircombined with hollow plastic media strip hydrogen sulfide from the flow stream. The systemwas installed in 1998 and consists of a stripper tower, two blowers, and a mulch biofilter toscrub the tower offgas. The stripper tower was retrofitted in 2000 with new media, as theoriginal media clogged shortly after installation. After flowing through the tower media,water enters an underground storage vault. Transfer pumps transport the water from thevault to the ground storage tank. Prior to installing this degasification system, the WTFutilized a tray aeration system that was located over the ground storage tank.The system is taken offline for cleaning approximately once every three months. The towermust be cleaned manually, which takes approximately 2 days. When cleaning the tower,operators isolate the degasification system from the wells and the ground storage tank. Theground storage tank is emptied and is not used during this time. The degasification tower isisolated from the underground vault by inserting an inflatable plug into the connectionbetween the tower and the vault. A cleaning solution comprised of sodium hypochlorite andsodium hydroxide is added to the tower. The solution is recirculated through the media forapproximately 2 days to remove biogrowth from the media. The solution is then disposed ofon top of the biofilter. Following the chemical clean, the tower is flushed with water from oneof the wells. After flushing, the wellfield and degasification system are brought back online.Operators also clean the underground vault approximately twice per year by pressurewashing the walls of the vault to remove biogrowth. The floor of the vault was notconstructed with a slope, sludge removal mechanism, or sump pump, so the wasteresulting from the pressure wash is removed with a vacuum truck.Operators also stated that the degasification fans and motors sit in a low spot on the deckof the vault. During heavy rains or when the tower is drained, the bottom of the motors andfans are immersed in water. This has caused some deterioration of the concrete pads andis hard on the equipment according to operators.2.3.3.1.3 Chemical Feed SystemsFigure 2.11 illustrated the chemical feed points at the University WTF. Chemicals shown inbold are those used regularly. The following describes the chemical feed strategiescurrently employed at the University WTF.• Chlorine - The University WTF was upgraded from gaseous chlorine cylinders toliquid sodium hypochlorite in 2002. Free chlorine and detention time in the groundstorage tank are used to meet primary disinfection requirements. Sodium hypochlorite(~12.5% solution) is stored in a 4000-gallon tank and fed to the ground storage tankFINAL - August 31, 2005 38H:\Client\SAR Co_SAR\6873C00 WATER SUPPLY MASTER PLAN UPDATE\Deliverables\TM 2 - Water System Assets\Final\TM2 Final.doc