Sewage plant awarded

PALMER -- The city of Palmer has an award-winning sewer system. The city was one of five recipients of the commissioner's awards presented by the State of Alaska Department of Environmental Conservation (DEC) for preventing pollution. Three private sector companies and one nonprofit corporation also received awards. Palmer was the only local government to be recognized by the program, which is in its first year.

DEC public service manager Tom Turner presented the award on behalf of commissioner Michele Brown at city hall earlier this month. Turner said Palmer's award recognized the accomplishments of employees rather than managers or contracted consultants.

"Sometimes you can just ask the people that work there and come up with an idea that works," Turner said.

In this case, the idea came from public works employees Doug Walker and Paul Gibbs, who designed a plan that turns Palmer's sewer sludge into topsoil for landscaping instead of trucking it to a landfill.

The new plan also includes new aeration equipment and a remote-controlled dredge that cleans the sewage settling ponds without draining them. The plan could save money on settling pond maintenance and extend the life of the ponds.

"The old way of cleaning [the ponds] was to put on hip boots and get down in there," Gibbs said.

The sewer plant has three ponds. There are two primary ponds and one secondary treatment pond. Previously, workers had to drain the ponds periodically for cleaning. Every time a pond is taken off-line, Palmer loses about half of its sewage processing capacity -- a situation that would become more difficult as the city grows. There's also automatic red tape with state and federal regulators for taking a pond off-line.

The old way of doing things was also labor intensive. Gibbs and Walker knew the ponds would have to be drained and cleaned more frequently in the future. In short, they saw city expenses snow-balling along with the amount of time they spent at one of the most unpleasant tasks at public works.

"Every time you drained one of them, you had to worry about the other two -- it was difficult and expensive, and we couldn't do it often enough," Gibbs said.

The microbes that eat sludge in the ponds are only active at or above 10 degrees Celsius, according to Walker. Staying ahead of sludge build-up is a challenge for any sewer plant that gets below freezing during winter.

"The problem is carried over from year to year because you only have about five months of treatment time," Walker said.

Sewage sludge is acidic, nutrient-rich and heavy. Rather than truck the sludge to a landfill or bury it on site, Walker and Gibbs came up with a plan to turn it into topsoil by mixing it with lime that is created as a by-product from a nearby acetylene manufacturing plant owned by Air Liquide. The lime balances the acidity of the sludge, and public works uses the topsoil for landscaping around the sewer plant.

Acetylene is made by mixing calcium carbide with water. When you mix the two, acetylene fumes off and a mixture of calcium hydroxide -- or lime -- and water is left over. The lime pit behind Air Liquide's plant looks like a giant bowl of gelatinous, chalk-colored pudding. It's not very marketable compared to dry powder lime.

Occasionally, agricultural and forestry researchers, area farmers and road builders have taken advantage of the free lime and saved Air Liquide the hassle of trucking the lime pudding to a landfill. Right now, the lime pit is nearly empty and there is a drying bed near the sewer plant where lime and sewage sludge are spread and plowed together.

"Sometimes the best ideas come from the people who work where the rubber hits that road," Turner said when he presented the award.