Frank Rogalla, Steve Tarallo, Patricia Scanlan, and Cindy Wallis–Lage
Much can be learned from recent work in Europe as well as the United States
Since passage of the Clean Water Act in 1972, great progress has been made in the United States toward achieving higher levels of wastewater treatment, and all stakeholders should be proud of the accomplishments to improve and protect the nation’s waterways.
With the recent emergence of sustainability as a guiding principle, however, wastewater management is now taking a new direction. Sustainability is driving the industry to take on the new challenge of transforming wastewater treatment from an energy-consuming and waste-producing activity to one with positive net energy production and minimal residuals. Read full article (login required)
Lori Kennedy, Lydia Holmes, Steve McDonald, Rosey Jencks, and Greg Braswell
San Francisco’s green approach to stormwater management promises to reduce energy use, increase natural habitat, and enhance the quality of urban life
San Francisco is one of only two cities in California with a combined sewer system. The system is the oldest on the West Coast, with most sewers more than 70 years old. While it meets current regulatory requirements, the aging infrastructure is occasionally overwhelmed by wet weather flows, resulting in street flooding and combined sewer overflows (CSOs). The San Francisco Public Utilities Commission (PUC) is developing a Sewer System Master
Plan, a 30-year roadmap for sewer system improvements. The master plan aims to address many challenges, such as aging infrastructure, odors, and CSOs, while improving the sewer system and quality of life for city residents.
As part of the master plan, PUC requested an analysis of low-impact development (LID) to reduce wet weather flows into the combined sewer system. LID is an innovative approach to stormwater management that relies on decentralized, small-scale stormwater facilities and site-design techniques to reduce stormwater volume and peak flow rates, as well as to remove stormwater pollutants. Unlike traditional stormwater management, LID relies on natural hydrologic systems to slow down, capture, infiltrate, and treat rainwater where it falls. Typical LID practices for urban areas include ecoroofs, vegetated swales, rain gardens, permeable pavement, urban forestry, roof-drain disconnection, rainwater harvesting, and stream daylighting. Read full article (login required)
Paul J. Headland and Mohamed A. Younis
The soils spring some surprises during trenchless construction
Construction projects can be unpredictable. Preparation is helpful, but communication is key to completing the work successfully.
As part of its expansion of Arlington National Cemetery, the Baltimore District of the U.S. Army Corps of Engineers
constructed a stormwater collection system to convey surface runoff through a 1.22-m-diameter (48-in.-diameter) pipeline from a point south of the Jefferson Davis Highway (in the cemetery) to a new outfall on the Boundary Channel’s south bank, next to the southern bank of the Potomac River.
The Army Corps hired a contractor to install the pipeline, giving the project team hydraulics criteria, including runoff area and design flow, a suggested pipeline alignment, and a fixed location for its southern terminus. The contract documents included performance requirements for the overall design and for construction of temporary excavation support for the open-cut elements of the work, but they left the detailed design to the contractor. This minimized construction costs by allowing the contractor to select his own means and methods. Read full article (login required)
Operations Forum Features
Nitrifying in the Cold
Douglas J. Nelson and Thomas R. Renner
A Wisconsin facility experiments with IFAS to ensure nitrification in winter
In 2004, the State of Wisconsin Department of Natural Resources decided that the 1.5-mgd (5700-m3/d) Village of Mukwonago Wastewater Treatment Facility (WTF) must remove ammonia year-round. If WTF continued to rely on its conventional activated sludge facility, maintaining nitrification
during winter in southeastern Wisconsin would require several additional aeration tanks to provide the higher solids retention time to ensure nitrification.
But instead of beginning construction planning immediately, the community wanted to test other options that could avert the construction and get the needed performance out of the existing tanks.
The facility began an evaluation of integrated fixed-film activated sludge (IFAS) technology using a full-scale demonstration test program to meet the community’s request. WTF ran two sets of experiments using parallel IFAS and non-IFAS process trains from January through March 2006 and January through March 2007 to evaluate the ability of IFAS technology to meet the facility’s new ammonia removal requirements without requiring construction of additional aeration tanks. Read full article (login required)
Test-Driving Stormwater BMPs
The Delaware Department of Transportation uses an interstate highway service area to monitor performance of stormwater management technologies
When looking for a spot to test the effectiveness of stormwater runoff best management practices (BMPs), the Delaware Department of Transportation (DelDOT) decided to take a middle-of-the-road approach — literally.
DelDOT owns and operates a 33-ac (13-ha) service area that lies in the median of Interstate 95. The service area includes two fueling stations, a large food court and rest area, pet exercise areas, and parking for trucks, cars, and buses. The site also includes a stream, Leatherman’s Run, which is piped beneath the plaza through two large box culverts.
The stream directly receives all stormwater discharges from the site, making it an ideal setting for DelDOT’s multiyear project. In the past 4 years, DelDOT has installed and tested several types of stormwater quality retrofit BMPs, such as catch-basin inserts, filtration and hydrodynamic devices, and bioretention cells, during many storm events. Preliminary data indicate that these retrofits are having some benefit in reducing pollutant discharge to the stream. Read full article (login required)
Ray Hyland and Lauren Zuravnsky
Green infrastructure approaches for CSO control in urban areas
Although green infrastructure is not currently used as a major combined sewer overflow (CSO) control method in most urban areas, it is being used to complement engineered solutions and has the potential to gradually improve storage
capacity and system performance with increased implementation. Green infrastructure approaches are urban strategies for source control of stormwater and CSO pollution that include green roofs, tree planting, rain gardens, vegetated swales, pocket wetlands, infiltration planters, vegetated median strips, and similar techniques.
Several U.S. cities are using green infrastructure as progressive elements for urban improvement and realizing the public relations benefit of “being green.” This article examines the green infrastructure options implemented by Chicago; Milwaukee; New York City; Portland, Ore.; and Seattle. These cities were chosen based on the scale and duration of their green infrastructure programs. Read full article (login required)