Brennan Highlights Remote Dredge In Wastewater Cleanup
J.F. Brennan Company used a remotely controlled dredge to complete the cleanup of two wastewater pools recently for a large producer of transportation fuels.
The company removed wastewater sludge from impoundments on a refinery site, dewatering the material with six 2-meter belt filter presses. The remotely controlled dredge added a layer of safety to the project, the company said, preventing any health risks that a leverman might face if exposed to hydrogen sulfide gas released during dredging.
In a company newsletter, Brennan described how it treated the sludge by conditioning it with a combination of ferric chloride and polymer to promote dewatering. Ferric chloride also controls hydrogen sulfide, a hazardous, flammable and toxic compound fluid found in the sludge that could have been released as a gas during dewatering.
Brennan designed a solution to chemically bind hydrogen sulfide by adding ferric chloride to the sludge while it was contained in the dredge pipe, thus inactivating the gas and reducing the hazard, with the added benefit of improving solids-water separation, the company said.
“By addressing the hazard before personnel exposure, the process ensured both safety and efficiency,” the company said.
Brennan used a belt filter press to dewater the dredged sludge mechanically. The equipment introduced conditioning chemicals to the slurry, allowing for mixing. The slurry flowed over a fabric belt that looped through the machine. As the belt looped, water drained through, retaining solids on top. Rakes furrowed the solids to further remove moisture.
“At this site, solids dropped off the press onto a stacking conveyor, which deposited them into dump trucks,” according to the newsletter. “Rinse water was captured and returned to the pond being dredged, while the dewatered material was hauled to a landfill for disposal by the owner.”
The company said one benefit of mechanical dewatering processes like belt filter presses is increased efficiency. Unlike passive methods, such as geotextile tube dewatering, which can take weeks or months to dewater material sufficiently, belt filter presses produce truckable material immediately upon processing.
