After recent increases in landfill tipping fees for wastewater plants, the city of Cumming’s plant is considering new technology to reduce costs.
Last week, city officials, Civil Engineering Consultants and Templeton and Associates hosted a demonstration of Bio-Scru, a technology developed by BRC Inc., that dries biosolids, turning them from a “sludge” form to a powdered form that can be used as a fertilizer and is much lighter and easier to deal with, at the Cumming Utilities’ Advanced Water Reclamation facility, located at 4605 Environmental Campus Drive.
“The purpose of this dryer that is here today is to demonstrate the technology and how it reduces the volume,” said Sean Mac, director of solution sales for BRC. “For example, if you have five 5-gallon buckets of sludge, if you put it through our dryer, you’ll probably end up with one-and-half buckets of sludge, so instead of taking five truckloads to the landfill, you’ll most likely take one-and-a-half or you can beneficially reuse the material as a Class A soil amendment that you can sell to local agriculture or use on your own fields.”
Mac said though the technology has existed for some time, it has caught on in Georgia recently due to the increased tipping fees.
City officials have not yet decided to implement the technology, which would be much larger than the system on display and would require a new building to house it all at the facility, Plant Supervisor Jimmy Andrews said.
“We’re investigating the units right now,” Andrews said. “It’s really up to the officials to make that final determination, and they will look at cost savings for the city and for the public, because all of our money comes from the public, and we have to be good stewards of it.”
Andy Lovejoy, with Civil Engineering Consultants, a firm that provides engineering services for the city, said this wasn’t the first time the city looked at the technology, but it is likely more feasible than just a few years ago.
“We looked at this technology five or six years ago when costs were increasing a little bit and the economics to put this facility into place, five or six years ago, the payback would have been maybe 15 to 20 years, and the economics weren’t worth it there,” Lovejoy said. “With the increased landfill tipping fees, the economics have gotten to where we think that the payback may be kind of on the conservative side 10 to 12 years. It’s starting to make sense.”
As wastewater flows through the facility for treatment, a part of the process involves treating water through a biological process using microorganisms to absorb phosphates. As the population grows, some of the organisms must be removed.
“The biosolids are actually the dewatered microorganisms,” Andrews said. “We have to maintain a certain population of microorganisms in the activated sludge process, and to do that every day we have to get rid of about two tons of completely dry biosolids, every single day. The way we do that is we dewater them, then we send them to a landfill.”
When removed from the water, the sludge is processed to remove water, though the reduction is much higher using the proposed technology.
“The city dewaters their sludge using a centrifuge, and the water content of that dewatered sludge is 87% water,” Lovejoy said. “The material after the drying process is probably 2 to 5 percent depending on how dry it is.”
Under the Bio-Scru system, the sludge is pumped through driers and other processes to transform the sludge to a powdered material.
While the city currently hauls the sludge away, some municipalities are able to spray theirs on open land, but Andrews said the city didn’t have the hundreds or possibly thousands of acres that would be required.
If the city decides to use the new drying process, the dry waste could be used as a fertilizer for city parks and rec, sold or given away to the public or hauled away at a cheaper price than the current system.
“There’s a lot of golf courses that will take this product, mix it with sand and then they apply it to the greens because it’s a real mild fertilizer,” Andrews said. “It’s not like a commercial fertilizer where you have to worry about burning the grass with over-application.”