What a waste? Sludge nearly ready for sale

Published 12:01 am Tuesday, December 20, 2011

Ben Hillyer/The Natchez Democrat — Natchez waste water treatment plant lab technician Terrance Logan takes biosolids samples from the sludge drying greenhouse.

NATCHEZ — The City of Natchez is stockpiling a load of sewer sludge in hopes of turning it into a load of cash.

Natchez City Engineer David Gardner said the city is currently collecting a large pile of the biosolid made from decontaminated and dried out sewage sludge at the Natchez Wastewater Treatment plant’s solar-powered greenhouse.

Once a large amount has been accumulated, it will be sent to the state Department of Environmental Quality for quality testing.

Gardner said a smaller sample of the biosolid made at the plant has already been tested by DEQ, and the plant received a Class-A certification, which means the biosolid can be used as organic fertilizer. He said the stockpile’s quality will be tested again to make sure it is up to standards.

Gardner said the city will then apply for a license from the Department of Agriculture to sell the fertilizer. He said the city could use the fertilizer itself or give it away without a license, but selling it requires the license.

The sludge from the plant’s sewage lagoon is dredged and then pumped to a belt press that presses out some moisture before being dried in the greenhouse. The robot aerates the sludge to help evenly dry out the material.

The biosolid stockpile, Gardner said, should be large enough by sometime this spring to be tested and then possibly sold as fertilizer.

The city could not only profit from the sale of the fertilizer, Gardner said, but it is also saving money by not spending an average of $200,000 each year to remove the sludge from the plant.

Instead, Gardner said, Natchez Water Works took out a $200,000 20-year loan from the state’s revolving loan program to fund the remaining costs of upgrades to the plant for the fertilizer program. The loan covered costs not funded by the $4.3 million in American Recovery and Reinvestment Act funds for the project.

Gardner said the city will pay $31,000 a year on the loan until its paid off in 2031.

“We’re only paying $31,000 versus paying the $200,000 we have been paying,” he said. “It’s a huge savings.”

The upgrades to the plant for the sludge-recycling program started in early 2010 and were completed earlier this year. The upgrades included the construction of the greenhouse and the installation of a mechanical filter system the sludge passes through.

The greenhouse also has a computer system that can manipulate weather conditions to speed up the biosolid’s drying process.

Water Works also bought a $15,000 used 18-wheeler truck approximately a month ago for the project. He said the truck transports the biosolid on a trailer approximately 100 yards from the filter press conveyor belt to be dried and stored in one of the two greenhouses.

Gardner said the city was renting a truck to use at the plant, and its purchase is saving money in the long run.

Water Works also received an award from the Mississippi Development Authority’s Energy Division in October for the fertilizer project. Gardner said the award was in recognition of energy reduction and technology used for the program.

“We’re just really excited about this project,” he said. “We’re saving a lot of money and turning a liability — the toxic sludge — into a beneficial use.”