Wastewater treatment facility uses plants to remove phosphorus

The Fleming Island Wastewater Treatment Facility is using plants as part of a demonstration project to remove phosphorus from wastewater that eventually heads toward the Clay County lake.

For the past 36 years, give or take a few, algae has been heavily prevalent at the lake, covering the water in blooms which sometimes release toxins and pose health hazards, reported Jacksonville News. Last month, when the delayed demonstration project was finally completed, levels of phosphorus being released through the wastewater fell by 96%.

According to Mark Merkelbach, a wetland scientist who is a partner in Sustainable Water Investment Group (SWIG), a company the St. Johns River Water Management District contracted to put the filtering idea, they are actually exceeding a phosphorus removal goal. The key ingredient is a material that is trucked in as chemical leftovers from treatment plants that make drinking water. 

The phosphorus in the sewage wastewater bonds with the aluminium and stays in the layer of the field above the rocks, while the water filters into the drain pipe and flows back to the treatment plant, according to SWIG. Then it is sprayed with chlorine and put in pipelines that carry reused water, which is used to water the lawns all around Fleming Island and Doctors Lake.

The company wants to eventually get other utilities and government agencies to look at using its system to clean water all around Florida.

“It’s much more efficient than other systems that are out there,” said Jim McCarthy, president of the North Florida Land Trust, a Jacksonville nonprofit that partnered with SWIG to get the company’s system into use in Florida. “It’s a really highly successful project. We’re ready to take it to other places.”

According to state employees who checked Doctors Lake for algae last week, no blooms were found.  Water from the sewage treatment plant makes up about 15% of the water flowing into Doctors Lake’s watershed, said Dean Dobberfuhl, water resources bureau chief for the water management district.

There are other sources of phosphorus nearby as well. To mitigate the issue, the management district signed a $1.5 million deal with the Clay County Utility Authority in January to subsidise work near the lake connecting septic systems to sewer lines.

Early this year, a new step was added to the plant’s treatment process, which involved setting up a pipeline to carry already-cleaned water from the treatment plant to a field right beside it covering a little more than an acre, reported Jacksonville News. Crews installed a layer of rocks and a drain pipe with holes in the top where water could flow in, then covered them with a layer of material that is designed to absorb phosphorus.

SWIG’s field filters about two million gallons of wastewater a day. The system is designed to absorb 35,000 pounds of phosphorus over six years, reported Jacksonville News. After six years, the field will probably capture about 88% of the phosphorus in wastewater.