Stormwater Management

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Infusion device reduces hydrogen sulfide

Problem

Hydrogen sulfide concentrations at a municipal outfall in southern Arizona averaged 340 ppm with peaks of 3,400 ppm.

Solution

Workers tapped into the 2-mile force main at the wet well and downstream from the check valve to install the FORSe 5 odor and corrosion control system from Anue Water Technologies. They diverted a fractional flow to the infuser, which treated it with oxygen and ozone, then returned it to the force main.

Result

Liquid grab samples measuring total sulfides showed untreated levels at 17 mg/L, but treated samples at less than 0.2 mg/L, a 99 percent reduction. Vapor measurements showed hydrogen sulfide levels at less than 10 ppm. 760/476-9090; www.anuewater.com

Mixers restore cypress swamp

Problem

Greenfield Lake, a cypress swamp and popular recreation area in Wilmington, N.C., turned the color of pea soup when blue-green algae over-multiplied. The shallow, 100-acre reservoir is primarily fed by stormwater via several drainage pipes.

Solution

City officials installed four SB10000v12 solar-powered mixers from SolarBee, which created enough horizontal and vertical water
movement to disrupt the blue-green algae. The gentle mixing action suspended beneficial green algae near the surface where cells received sunlight and thrived, keeping levels of algae, zooplankton, fish, dissolved oxygen and pH in balance.

Result

Within two months of installing the mixers, officials reported the lake looking better than it had in recent history. Fishermen returned and canoe rentals doubled. Greenfield Lake is now a healthy reservoir. 866/437-8076; www.solarbee.com

Cast mortar liner rehabilitates pipe

Problem

Workers from Republic Services in San Diego, Calif., noticed severe erosion around the inlet of a 48-inch corrugated metal pipe running 8 to 20 feet below grade at the Otay Landfill. An inspection revealed 200 feet of failing pipe.

Solution

The owners hired AP/M PERMAFORM to rehabilitate the line with Centri-Pipe, a system that uses a spincaster to centrifugally cast a 1.25-inch-thick fiber-reinforced concrete liner. Workers applied PL-8000 mortar in three passes. During each application, the operator in the pipe visually confirmed adherence and layer thickness, adjusting the withdrawal speed as needed.

Result

The rehabilitation, completed in eight days, does not impede hydraulic capacity. "Centri-Pipe was a huge savings over other lining systems and the quality of the structural lining exceeded our expectations," says a Republic Services spokesperson. "We'll be using the product on additional pipe as soon as our budget allows." 800/662-6465; www.permaform.net

Trapping device skims debris from waterways

Problem

Stormwater from a combined sewer system serving 12,955 acres of Washington, D.C., conveyed more than 20,000 tons of litter to the Anacostia River annually. To manage the trash, the D.C. Water and Sewer Authority ran skimmer boats on the river, but the efforts were insufficient to comply with state clean water regulations going into effect in January 2010.

Solution

In 2009, the authority installed a 5- by 22-foot-long Bandalong Litter Trap in the lower tidal reach of Watts Branch in the deepest and widest part (40 feet) of the tributary. The floating device uses river currents to guide and capture litter.

Result

In the first 12 months, the trap collected 6,000 pounds of trash with a monthly average of 500 pounds. In 2011, it collected more than 9,000 pounds of debris. In 2012, the authority purchased two more litter traps. 888/730-5819; www.stormwatersystems.com



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