Case Studies

Water Supply

The Issue: Fouling-Related Maintenance Downtime

The Solution: Sabre's Chlorine Dioxide ClO2 Generator

Background

The 23-year old plant sends all of its 15 million gallons per day (mgd) output to the City of Huntsville, its only customer. About 8 mgd is distributed for drinking water, including a seven mile pipeline for two prison farms, and the balance sent through a 30 mile pipeline to a power plant for cooling water.

Chlorine dioxide treatment was originally installed, upstream of clarification and filtration, to combat a serious algae problem on the clarifier basin, which derived from elimination of free chlorine that was needed to comply with trihalomethane (THM) limits per EPA's Safe Drinking Water Act.

Original does of 5 parts per million (ppm) "helped a lot" with the taste and odor problems related to the algal growth. When new rules mandated less than 1 ppm chlorite, chlorine dioxide feed was reduced to 2 ppm, and was still very effective. Current usage is sad to still be driven by those "aesthetic" problems.

Chlorine Dioxide Application Considerations

The Sabre Chlorine Dioxide Generator includes seperate rotometers for the pre-cursor chemicals, which are educated under vacuum through a mix chamber, where chlorine dioxide is formed.

This design has eliminated fouling in the throat and nozzle of the vessel where the chemicals are mixed. With previous generators used at the plant, this fouling was happening every three to five days, causing downtime fo half hour to an hour for cleaning that sometimes required disassembling.

Chlorine Dioxide Treatment Approach

"Biogrowth maintenance is needed to prevent the clarifier basins from being overrun, which would decrease filtration efficiency, and increase the need for back-washing."

Results

Sabre generators are deployed at the raw water intake at the river, and also 300 yards from the plant, which is 4.5 miles from the river. Each is capable of delivering 300 lb/day of chlorine dioxide, at a maximum rate of 2.5 ppm, and averaging 1.5 ppm annually. Only the generator near the plant is needed for most of the year. Daily production per generator ranges from 75-300 lbs, and averages 125 lbs.

The Science of Success

Sabre's patented Tuned Reaction Column™ is said to eliminate clogging and insure a steady stream of precursor chemicals - allowing the unit to operate efficiently at lower water flows without variation in meter reading and with a greater turndown ratio, and without need for frequent flushing, disassembly, or cleaning.

Follow Up

Chlorine dioxide is generated at a minimum of 95% efficiency, with no more that 5% excess chlorine. Typical systems produce 10 to 1000 lbs/day. systems with capacities up to 100,000 lbs/day are avaialble.