Microturbines process methane into energy

Problem
The Sheboygan (Wis.) Regional Wastewater Treatment Plant, which treats up to 15 mgd, had a surplus of biogas. More than 25 percent of the gas was being flared at the plant site. At the same time, the municipality wanted to reduce electricity costs.

Solution
Ten clean-burning biogas-fueled C30 Microturbines from Capstone Turbine Corporation generate up to 300 kW of electrical power (2,300 MWh per year). Heat recovery modules on each turbine capture exhaust heat, which is used to maintain the digesters 95-degree F temperature and heat buildings. A gas-cleaning system removes moisture and siloxanes from the raw gas.

Result
The ultra-low emission microturbines cut the plant’s electric and natural gas bills by 40 percent, and earn renewable energy and emissions credits. The microturbines can recover 1 million Btu per hour, or about 73,000 therms per year — enough to heat 60 homes for a year. Despite a significant rise in rates, the plant’s electric bill has seen little change. In addition, the plant has sold over 2,000 renewable energy credits. 818/734-5300; www.capstoneturbine.com.

  Covered sludge beds eliminate odor issues

Problem
The Northern Moraine Wastewater Reclamation District in Illinois serves three communities in the Island Lake area with a total population of 12,000. The district treats 1.1 mgd, discharging into a nearby river. The facility had stored treated and dried biosolids outside. “The material got wet every time it rained or snowed, causing odor concerns and raising handling costs,” says operations supervisor Todd Sheridan. The facility needed covered storage space for the drying beds.

Solution
Sheridan discovered Hercules Truss Arch Buildings from ClearSpan Fabric Structures in a product catalog. He ordered two 65-by 70-foot buildings to cover the drying beds.

Result
Sheridan is pleased with the buildings. “They were assembled in less than a week,” he says. “The light that comes through the covers is great.” Both structures now store biosolids, but Sheridan says, “I’m sure we will find even more uses for the buildings down the road.” 866/643-1010; www.clearspan.com.

  Flat aluminum tank covers solve odor challenges

Problem
The City of Wyoming, Mich., processes wastewater for 140,000 residents. The city needed a biosolids storage solution to control odor and allow expansion to serve a growing population.

Solution
The city installed a 120-feet-diameter concrete biosolids storage tank with a truss-supported, extruded flat aluminum cover for odor containment, provided by CST Covers. The aluminum weight-bearing design proved durable and corrosion-resistant. Facility operators also have walkable, slip-resistant access without a bridge. “The flat cover design significantly reduced foul air volume and allowed cost savings on the foul-air handling and odor-control system,” says Jack Staat of CST Covers. The city also replaced two dome covers on biosolids tanks with flat aluminum covers and added truss-supported extruded flat aluminum covers for four 103-feet-diameter primary settling tanks and their open-top flow-splitting chambers. Those covers include nonstandard railings and manlift sockets at access hatches.

Result
“Once we understood the cover was weight bearing, our choice and installation became cleaner and simpler,” says Tom Wilson, plant maintenance supervisor. “The flat cover provides better aesthetics and overall appearance.” The entire project was allotted 12 months for completion but was finished in nine months. 913/621-3700; www.cstindustries.com.

  Tanks treat wastewater from air-quality system

Problem
Constellation Energy’s Brandon Shores Power Plant in Baltimore, Md., was in need of new tanks that would adhere to strict air-quality guidelines, and provide appropriate processing, storage and treatment resources for handling wastewater from the plant’s air-quality control system.

Solution
Fisher Tank Company worked with Bowen Engineering to design, fabricate and construct 14 field-erected welded steel tanks specially designed to support the emission control system. The tanks included clarifiers, reactor vessels, equalization tanks and holding tanks. Each was designed and fabricated in-house according to precise specifications. The company designed, fabricated and installed clarifier troughs, internal baffles and mixer platforms, as well as agitator bridges and rake supports. Crews also completed the project by field painting the tanks, and erecting two 85-feet tall, 48,000-pound shop-fabricated lime silos.

Result
In-house blasting and shop priming ensured that plate material arrived on site ready for construction and final coatings, contributing to the efficiency of the construction schedule and to the overall quality of the system. The upgrade to the plant reduces sulfur dioxide emissions by an estimated 95 percent and mercury emissions by 90 percent. 610/494-7200; www.fishertank.com.

  Tank-cleaning machine reduces grease buildup in stations

Problem
Virginia Public Works Equipment in Virginia Beach was struggling with grease buildup in its lift stations. The utility needed an effective way to resolve the cleaning issues without demanding more manpower and budget. ­­

Solution
The utility purchased an EZ-8 rotary impingement tank-cleaning machine from Gamajet. The machine eliminates confined-space entry and delivers powerful impact cleaning. Powered by the department’s jetter and combination cleaning trucks, the unit was configured for 80 gpm/300 psi. The machine thoroughly cleans the wet well in 12 minutes. Another half cycle is run periodically to further decimate the grease pad, which is then suctioned into the cleaning truck or washed downstream.

Result
With the addition of the Gamajet machine, the utility can prevent buildup in their lift stations and provide better service to constituents with increased safety and less demand on resources. 877/426-2538; www.gamajet.com.

  Modular railing solves employee safety issues

Problem
Located on an offshore island in Athens Bay in Greece, the Psyttalia Wastewater Treatment Plant protects the Saronic Gulf and the general environment of the region. The plant is the largest in Europe and one of the largest in the world. It needed over 50,000 feet of safety railing to ensure a safe working environment. The railing needed to be versatile to accommodate the many angles and elevation changes around the perimeter.

Solution
The facility chose a KeeKlamp modular railing system provided by Kee Safety.

Result
The system eliminated onsite welding and hot work permits and allowed for easy field modification to meet all job site requirements. It also eliminated the movement and installation of large offsite welded structures, saving time and expense. 800/851-5181; www.keesafety.com/us.

  Composite building panels provide solution for contact basins

Problem
A group of tertiary treatment plants with open reclaimed water contact basins near the City of Oceanside in Southern California needed to minimize chlorine loss while preventing algal blooming from prolonged exposure to sunlight.

Solution
Strongwell provided a design that used its COMPOSOLITE structural building panels, with an internal core structure that can handle more weight and cover the reservoirs without extra structural support. The panels are affordable, do not corrode, and are safe to touch and walk on. The panels are 24 inches wide by 3 inches thick and are available in many lengths.

Result
The lightweight, high-strength panels were delivered on one truck with minimal effort to off-load and store. Construction crews installed the panels on site with minimal field trimming and reduced labor costs. Project managers were pleased with the quality and ease of installation and said they would bid the product in future projects. 276/645-8000; www.strongwell.com.

  Crystalline chemical system waterproofs below-grade treatment system

Problem
The Miami-Dade Water and Sewer Department recently upgraded the South District Wastewater Treatment Plant to a high-level disinfection facility with a peak flow capacity of 285 mgd, an increase of 27 percent. The plant is the largest domestic wastewater injection site, and one of the largest deep bed sand filter plants in the country. The contractor sought to waterproof the below-grade systems to ensure long-term durability.

Solution
Over 52,000 square feet of surface area was treated with a two-coat crystalline chemical system manufactured by Xypex Chemical Corporation to waterproof and protect the transfer pump station, flocculation tanks and filters. The second phase incorporated crystalline technology as an admixture for waterproofing and protection of an oxygenation train, four new clarifiers, associated splitter boxes and a pump station. An estimated 400,000 pounds of the product was used for a substantial portion of 70,000 cubic yards of poured-in-place concrete.

Result
Crystalline waterproofing enhanced the structural durability of the concrete and lowered the life cycle maintenance costs of the entire system including clarifiers, pump stations and flocculation tanks. 800/961-4477; www.xypex.com.