SAGINAW TWP. - Increased sewer capacity is in the pipeline at the township's Southwest Wastewater Treatment Plant, where the building trades are at work.

Projected to increase capacity from 4.8 million gallons per day to 6.5 million, the upgrade is necessary for the expansion of the Dow Corning Corp.'s Hemlock Semiconductor Plant (HSC) in nearby Thomas Twp. That plant is being built to manufacture monosilane gas, a specialty gas used in the manufacturing of liquid crystal displays and thin-film solar cells.

The $10.3 million sewer work is "a vital part of securing HSC's $1 billion investment," said township Supervisor Timothy Braun.

The year-long project is expected to wrap up in September.

Saginaw Twp. provided a good explanation of the treatment process. Wastewater arrives at the plant site in gravity sewers and then receives primary treatment. Chlorine is also added for odor control. Primary treatment is provided by two mechanically cleaned bar screens and two aerated grit tanks. Screenings and grit materials are disposed of into a dumpster and hauled to a landfill.

Primary effluent treatment is accomplished in two circular primary settling tanks. Sedimentation is pumped from the settling tanks into two high rate anaerobic digesters. Secondary treatment consists of extended aeration with activated sludge in two oxidation ditches. Ferric Chloride is then added to the waste stream for the removal of phosphorous, followed by the addition of polymers to aid in settling.

Secondary clarification occurs in two circular final settling tanks. Sedimentation from these two tanks is returned to the oxidation ditches and transferred as needed to another process for additional settling and disposal. The clear effluent that is discharged from the final settling tanks then enters the last purification stage of the treatment process. Chlorination/disinfection is applied using chlorine gas and jet mixing. The treated effluent is then dechlorinated and further polished in a 6.1 million gallon polishing pond. Sodium Thiosulfate is also added to aid in the dechlorination process prior the discharge to the Tittabawassee River.

"We're doing great out here," said Miller Sage plumbing foreman Jeremy Wilson. "This is a nice little job." He said the plant has a variety of fixtures and pipe, ranging from 36 inches to four inches. "It's clean work, a lot cleaner than you'd expect," he said. "You get some smell in the morning which can be a little rough, but that's about it."

IN THE SAGINAW Township Southwest Wastewater Treatment Plant's de-chlorination building, Plumbers and Steamfitters Local 85 members Harold Dust, left, and Jeremy Wilson go about the task of installing a new 36-inch by 20-inch eccentric reducer into the treatment system. They're working for Miller-Sage.

INSTALLING REINFORCING IRON for a trough around a clarifying pool at the Saginaw Township Southwest Wastewater Treatment Plant are brothers Mario and Dave Hernandez of Iron Workers Local 25, working for C & A Re-Steel.