The Fine Art of Screening
John Keller, Cindy Wallis-Lage, and Isaac Crabtree
Use of a fine screen conjures up a unique set of design considerations and challenges
Historically, coarse screens have been used to protect downstream pumps and unit processes from being damaged by large debris within wastewater collection systems. Because the space between bars ranges from 12 to 50 mm (0.5 to 2 in.), some debris is able to pass through the openings and collect in the downstream processes or piping systems.
This debris accumulates in corners or dead spots of unit processes and becomes malodorous. Furthermore, the debris causes premature wear and tear on pumping equipment and valves if it enters pumping systems. Debris also clogs pipelines, requiring additional maintenance and further reducing pumping capacity, which increases energy costs. Operation and maintenance (O&M) costs to clean up the debris that passes through screens can be substantial.
Chuck Boehm, Donald F. Roecker, and Ralph B. (“Rusty”) Schroedel Jr.
Increase project affordability with local, state, and federal funding
Citing tight spending limits throughout the government, the U.S. Senate Interior Appropriations Subcommittee recently approved a bill that would dramatically cut the fiscal year (FY) 2007 budget for the Clean Water Act State Revolving Fund. Since its creation in 1987, the fund has been a primary source of low-interest federal loans for wastewater construction projects nationwide. But in the last few years, its budget has been reduced by almost 50%, from $1.35 billion in FY 2004 to about $887 million in FY 2006. The most recent proposed budget would further reduce funding by $200 million, to about $688 million.
Given this recent trend, wastewater utility managers should consider, if they have not already, other methods to fund projects and maintain costs. The following funding alternatives may be able to bring critical dollars that can make a project affordable. Read full article .
After the Storm
The executive director of the New Orleans water utility shares what the city faces in dealing with FEMA, U.S. EPA, and contractors
Hurricane Katrina socked the U.S. Gulf Coast with a storm surge that reached at least 8 m (25 ft) above high tide in some areas. The storm surge, commonly defined as a “dome of water” that builds up in association with a hurricane, stretched across an estimated 400 km (250 mi) of coastline. Housing, utilities, businesses, and industry were devastated in three states, but damage was most extensive in New Orleans, the most heavily populated area hit by the hurricane.
On the morning of Aug. 29, 2005, New Orleans’ aging infrastructure was immersed in brackish water and saltwater. The flooding lasted for 3 weeks, severely damaging much of the existing infrastructure and dramatically reducing its useful life. But the true impact of Hurricane Katrina is only now coming to light. One year after the storm, Marcia St. Martin, executive director of the Sewerage and Water Board, shared the many challenges facing a utility after one of the worst natural disasters in U.S. history. Read full article .
Operations Forum Features
Operations Challenge 2006
Texas Teams Two-Step to Victory
Texans ruled the competition at the 19th Annual Operations Challenge at WEFTEC®.06 in Dallas. The TRA CReWSers from the Trinity River Authority in Arlington, Texas — last year’s Division I champions — successfully defended their home turf for another first place finish. In Division II, the top two spots went to Texas teams; the San Antonio Power SAWS and the Dallas Aqua Techs, earning first and second place, respectively. Read full article .
Joan Oppenheimer and Roger Stephenson
Longer sludge retention times can remove some PPCPs
As the advancement of analytical techniques has enabled identification and quantification of chemicals at lower concentrations, the widespread presence of pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting chemicals (EDCs) in wastewater treatment plant effluent has been demonstrated.
Although the activated sludge process was never specifically intended to remove such trace organics as EDCs and PPCPs, studies performed at bench scale and in small facilities have demonstrated that a critical minimum solids retention time (SRT) can achieve good reduction of many EDCs and pharmaceuticals. Read full article .
WEFTEC Equipment Finds
Each year the exhibition at WEFTEC includes thousands of products by hundreds of vendors. To find out what products and displays you found at that impressed you, we asked exhibition goers to tell us what caught their eye and why. Read full article .