July 2011, Vol. 23, No.7

Projects

The District of Columbia Water and Sewer Authority (DC Water; Washington, D.C.) held a ceremonial groundbreaking for two new projects May 17 at its Blue Plains Advanced Wastewater Treatment Plant. The projects, a thermal hydrolysis and anaerobic digester system and an enhanced nutrient removal facility, together will cost $1.4 billion.

The thermal hydrolysis system and anaerobic digesters, which will cost $400 million, will “pressure-cook” and digest the plant’s solids to produce combined heat and power, generating 13 MW of electricity. The enhanced nutrient removal facility, which will cost $1 billion, will reduce the amount of nitrogen in the plant’s effluent to meet the new U.S. Environmental Protection Agency and Chesapeake Bay Program goals of 2.1 million kg/yr (4.7 million lb/yr) or less in 2014. This nitrogen limit is one of the most stringent in the world.

Both projects are expected to be completed in 2014. DC Water General Manager George S. Hawkins said that the new digesters should cut the amount of electricity Blue Plains pulls from the local grid by a third. “That’s enough to power 8000 homes,” Hawkins said. “We’re also saving $10 million in trucking costs and reducing our carbon emissions by cutting the amounts of solids at the end of the process in half.”

Blue Plains will be the first plant in North America to use thermal hydrolysis for wastewater treatment. It also will be the largest thermal hydrolysis plant in the world, according to Hawkins.

 

The City of   San Francisco and the U.S. Environmental Protection Agency in May broke ground on the Newcomb Avenue Streetscape Model Block Improvement Project, a first-of-its-kind project on the 1700 block of Newcomb Avenue to transform the block into one of the most sustainable streets in San Francisco. The streetscape improvement project will replace significant areas of concrete with new landscaping and street trees, introduce stormwater planters and permeable pavers to allow rainwater to permeate into the ground, repave the street, and promote pedestrian safety and traffic calming.

Low-impact development tools mimic natural hydrologic conditions and include increasing permeable, vegetated areas to assist the infiltration and evapotranspiration of stormwater, in turn minimizing the volume of stormwater discharges. By using low-impact development tools, pollutant flows are reduced and the need for more expensive traditional treatment is minimized.

The $1.6 million project is funded through grants from the U.S. Environmental Protection Agency’s San Francisco Bay Water Quality Improvement Fund, the San Francisco Public Utilities Commission, and Community Challenge grants, in addition to an appropriation from the San Francisco Redevelopment Agency.

Construction on the project is expected to take 4 months. Once complete, residents have committed to providing ongoing maintenance by organizing community cleanup days to keep the street clean and green. The city will monitor the stormwater performance of the new streetscape improvements.

 

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) in May announced that it has chosen Comverge Inc. (Norcross, Ga.) to significantly expand its existing energy demand response program. The company will help MWRD devise a program to decrease its energy use during peak demand by more than 300% compared to previous years’ use. MWRD will be able to quickly and efficiently reduce its energy usage if the region’s electricity grid is on the verge of a brownout or blackout.

 

Thames Water (Swindon, England), the United Kingdom’s largest water and wastewater services company, is beginning a project to enhance and expand solids treatment operations at its Basingstoke (Hampshire) and Bracknell (Berkshire) Sewage Treatment Works. Thames Water appointed Black & Veatch (Overland Park, Kan.) to manage the engineering, procurement, and construction of the upgraded works.

The upgrades at each site include belt presses; cake conveyors; a polymer dosing system; a 2000-m2 solids storage building; a solids storage tank, pumps and pipework; and a return liquor tank, pumps and pipework.

The major upgrades will convert liquid-treated waste into a solids cake that offers a reduced risk of nitrate pollution runoff when introduced as a soil improver. Additionally, transporting solids cake rather than liquid requires fewer truckloads. With the upgrades, truck movements at Basingstoke will be reduced by 50% and at Bracknell by 80%.

The upgrades also will increase the capacity of each treatment works to accommodate future population growth.

 

In April, City of Dallas Water Utilities (DWU) announced the completion of its 4.3-MW biogas capture and refining facility. Ameresco Inc. (Framingham, Mass.) designed, built, and will operate the plant, which is designed with a capacity to reduce the greenhouse-gas-emission equivalent of carbon dioxide emissions from more than 3500 passenger vehicles per year, or the electricity use equivalent of more than 2500 homes for 1 year.

The new wastewater biogas plant, which will generate electricity and thermal load to power DWU’s facilities, is expected to save the city at least $1.5 million annually and offset approximately 60% of the electricity that DWU pulls from the grid.

In May, DWU announced that it awarded a contract to Envirogen Technologies Inc. (Kingwood, Texas) to build two biological odor control systems. The new odor control systems will remove 99% of hydrogen sulfide from air at the wastewater operation’s aerated grit chamber and Pump Station C.

The systems will handle hydrogen sulfide concentrations of 40–81 ppm (by volume) at an airflow rate of 305 m3/min (10,770 ft3/min) for the aerated grit system, and 8–15 ppm at 2634 m3/min (93,000 ft3/min) for Pump Station C. Equipment will be delivered and installed during the second half of 2011.

 

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