Greenfield invests in cost-saving sludge dewatering system

Greenfield is investing $3.59 million to purchase and install sludge dewatering equipment at its wastewater treatment plant, an investment that officials say will save the city about $350,000 per year moving forward.

The appropriation, approved by the City Council in October, will pay for the purchase and installation of the equipment, as well as electrical upgrades and demolition of old equipment to make space.

The city hauls about 2.1 million pounds of sludge every year for disposal, according to the Department of Public Works, and every load of about 9,000 pounds is roughly 95% water. The cost for hauling and disposing of sludge is significant; it’s expected to top $700,000 in the current fiscal year, according to the Public Works Director Marlo Warner.

With the new equipment, the slurry that originates in the wastewater treatment process will go through a pressing process to remove water in order to significantly reduce the weight and volume of the product. This reduction is expected to yield substantial savings in hauling and disposal costs.

Water Facilities Superintendent Mark Holley said the water removed in the pressing process will be returned to the beginning of the plant, where it will be sent through the process again before being discharged.

The process creates a new solid product, known as “cake,” and the city will have a few different disposal options to consider: haul away one dumpster of the byproduct per week, compost the material, or add additional equipment to turn the cake into fertilizer.

“We will need to do a lot of testing before a disposal method and site can be determined,” Holley said. “We are going to consider all of our options from landfilling to composting.”

The funding for the project became available after estimates for an anaerobic digester project increased significantly and the city decided to place the project on hold and reallocate those funds, according to a statement from Mayor Roxann Wedegartner.

Work will begin in the spring, and the system is expected to be operational by next September.