Features

July 2009, Vol. 21, No.7

Lucky No. 9

Plant upgrades and a new CSO-abatement facility reduce untreated discharges to the Connecticut River by 92%

luckyno9.jpg William D. Fuqua and Ralph J. Jagelavicius

Until recently, the Connecticut River received more than 1.9 million m³/yr (0.5 billion gal/yr) of untreated wastewater via combined-sewer overflows (CSOs), and a significant portion of that came from CSO outfall No. 9 in Holyoke, Mass. To improve river water quality, the U.S. Environmental Protection Agency issued Holyoke an administrative consent order to abate both dry and wet weather overflows by September 2004. After that, CSO outfall No. 9 would not be permitted more than four untreated overflows per year.

On Dec. 17, 2003, Holyoke issued a request for proposals (RFP) to design and build a new CSO-abatement facility that could handle at least 889,500 m³/yr (235 million gal/yr), upgrade its wastewater treatment facilities, and operate and maintain both systems for the next 2 decades. All construction had to be completed and accepted within 3 years.

Not only did the team selected by Holyoke meet the RFP challenge, it completed the facility 1 year ahead of schedule. The project yielded $10 million in savings, improved water quality, and brought Holyoke into compliance.  Read full article (login required) 

 

In Search of Mercury Solutions

Milwaukee works to solve the many mysteries of mercury reduction

insearchof.jpg Tom Nowicki

Across the United States, water reclamation agencies are trying to solve the mystery of how to achieve stringent mercury limits. Like many agencies, the Milwaukee Metropolitan Sewerage District (MMSD) has testedmultiple mercury-reduction approaches, with varied results.  Read full article (login required) 

 

Risk, Regulations, and Responsibility

What have we learned about microconstituents?

riskregulations.jpg Don Thompson and Katherine Bell

Microconstituent identification and quantification techniques are advancing quickly, while health and environmental impact assessments are slower to progress, given the complex and time-consuming nature of these studies. Research has identified treatment technologies for the destruction or removal of microconstituents, but application has been minimal. In addition, relatively fewinvestigations have been completed that use natural waters and focus on the very low observed microconstituent concentrations in these waters.

Regulatory agencies, environmental watch groups, and potable-water suppliers and their consumers are at the forefront of expressing concerns about these contaminants. The next evolution of this issue will be the anticipated need for state and federal regulatory action. Several topics of debate will be involved with regulatory developments, including enforcement levels and prescribed treatment methods. Regulators also will have to designate responsibility for treating microconstituents and paying for associated capital and operational costs.  Read full article (login required) 

 

Operations Forum Features

Big Prevention in a Small Footprint

Wisconsin utility uses innovative design methods to overcome site limitations and fix a sanitary-sewer overflow problem

bigprevention.jpg Christopher J. Tippery, Craig Schuenemann, Pei–Chih Chiang, and Thomas J. Nejedlo

The Racine (Wis.) Wastewater Utility has “safety sites,” or predetermined locations, for sanitary-sewer overflows (SSOs) to prevent backups into residential and commercial basements. One safety site historically has experienced several significant SSO events, including a recent 500,000-gal (2000-m³) overflow. The utility wanted to eliminate the risk of overflows at this location. AECOM (Los Angeles) completed smoke-testing, as well as flow and rainfall monitoring, and developed a hydraulic model to evaluate two options to prevent SSOs: Increase the downstream capacity of the sanitary-sewer interceptor system, or store the SSO volume for the duration of the design storm event. The latter solution was selected, and the limited available sites were evaluated and prioritized, based on design and construction issues.

The site would have to hold 500,000 gal (or 2000 m³, for a 25-year storm event) until it could be pumped back into the interceptor sewer. The difficulty was finding an accommodating site. This article focuses on the design and construction methods needed to determine the storage-volume basin site and the configuration and operational requirements for providing the required storage while resolving site limitations and construction issues.  Read full article (login required) 

 

A European Approach to Grit Removal

A Chicago utility surveys plants at home and aboard to design the best headworks facility for wet weather and normal flows

aeuropeanapproach.jpg Raymond Iehl, Edward Podczerwinski, Eric Comption, and Kendra Sveum

The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) has utilized aerated grit chambers with chain-and-flight collectors for more than 50 years. While these chambers have proven effective, MWRDGC has found the chain-and-flight system to be expensive to operate and maintenance-intensive. MWRDGC sought an approach that would enable the continued use of aerated grit chambers but effectively remove grit in a different, less costly way.

After completing a series of facility surveys worldwide, MWRDGC and the design team developed a unique approach for its Calumet Water Reclamation Plant (CWRP): a traveling bridge with a scraper modified to include an airlift and fixed submersible pump at the head end of the grit chamber. This combination is well suited to handle grit loading under both dry and wet weather conditions while reducing maintenance requirements and associated costs.  Read full article (login required)