The waters around Key West, Fla., are the cleanest in the state and home to the only living coral reefs in the continental United States. The city, wanting to reduce trash, oils, bacteria, and nutrients entering the water, received a grant from the National Fish and Wildlife Foundation to test stormwater filters on Duval Street, located in a major tourist area.
Annalise Mannix, P.E., environmental programs manager for the city, selected Smart Sponge Plus from AbTech Industries in Scottsdale, Ariz., for 11 catch basins where water flows toward the beach. The filters have an antimicrobial agent that targets Enterococcus bacteria, fecal coliforms, and E. coli.
“The filters have trapped hundreds and hundreds of pounds of litter since their installation last September, and reduced the amount of nitrates and phosphorus entering the sensitive environment,” says Mannix. “We’re very happy with them.”
Garbage hogs
Smart Sponge technology has a molecular structure based on polymer technologies that are chemically selective to hydrocarbons. Smart Sponge Plus has an antimicrobial agent chemically and permanently bound to the polymer surface. The filters, custom designed to hydraulic flows, are housed in baskets that mount to the corners of inlets on stainless-steel brackets. The medium encapsulates recovered oil, transforming it into a stable solid for recycling.
Normally, Operations Manage-ment International (OMI) in Key West uses a high-pressure water hose to clean the filters, and a Vacutech machine to vacuum the grease and dirt into the truck. During heavy rainstorms, overflow pours down the 6-inch space between the baskets. However, once they fill with trash, it also can enter the storm drain.
“We’re diligent with our maintenance because Duval Street attracts 10,000 to 20,000 tourists a day to its bars, restaurants, and shops,” says Mannix. “Special events happen there every week, so we spend a lot of time removing litter from those filters.”
Take-out
The filters also helped the city deal effectively with a pollutant spill. In March 2007, employees of a restaurant were carrying a 50-gallon barrel of used cooking oil outside for pick up when they dropped it. Grease splattered across the sidewalk and into the street. A public works crew arrived promptly to pressure-wash the area, but what they couldn’t clean up went down the storm drain. The filters collected four gallons of oil.
“This time, we’re removing and replacing the filters because that much grease probably clogged them,” says Mannix. The restaurant was cited and fined.
Nutrient-separating baffle boxes from Suntree Technologies Inc. in Cocoa, Fla., were installed in 22 locations on the other end of Duval Street. The baffles collect large volumes of material, too. However, when they are full, trapped litter overflows into the street and is collected by the street sweeper.
“I thank the National Fish and Wildlife Foundation for granting us the money to install these filters,” says Mannix. “They are helping us protect the environment.”
