June 2012, Vol. 24, No.6

At a crossroads

The evolution of U.S. stormwater regulations

Brown art Seth Brown
Upcoming changes to the U.S. Environmental Protection Agency (EPA) stormwater program will be “the greatest in a generation,” according to one EPA official. Considering this statement, it’s worth examining the history of the regulations in relation to their current directions. Read full article (login required) 


The Philadelphia story

A triple-bottom-line assessment of traditional and green infrastructure options for controlling CSO events in Philadelphia’s watersheds

Clements_Art Janet Clements, Robert Shafer Raucher, Howard Neukrug, Dave Mills, John Cromwell, Eric Horsch, and Leland Deck

The Philadelphia Water Department is committed to developing an integrated watershed management approach for combined sewer overflow control. This approach includes traditional “gray” infrastructure measures, as well as a range of low-impact development (LID) and “green” infrastructure techniques. Central to this strategy are commitments to greening, sustainability, open space, waterfront revitalization, outdoor recreation, and quality of life.

To better understand the total benefits and to evaluate the use of green infrastructure citywide, the department sought a triple-bottom-line analysis. This analysis examined the financial, environmental, and social implications associated with various combined sewer overflow control options, including both green- and gray-infrastructure-based solutions. Read full article (login required) 


Viruses to the rescue?

Researchers evaluate the feasibility of using a virus-based biocontrol to remove biofilm from membrane bioreactors

Choi art Jeongdong Choi, Shireen Meher Kotay, and Ramesh Goel
Seeking an improved method for addressing the problem of biofouling, researchers at the University of Utah (Salt Lake City) conducted a feasibility study to assess the possibility of using lytic bacteriophages — viruses that infect bacteria and cause lysis, meaning that the bacteria break open — to control growth of the microorganisms responsible for biofouling within membrane bioreactors. The study found that using bacteriophages, or “phages” as they are commonly known, holds promise for reducing biofilm formation in membrane bioreactors. Read full article (login required) 


Why many control systems fail

Few utilities consider how the ‘human factor’ influences treatment performance

Reiger_Art Leiv Rieger and Gustaf Olsson
When implementing real-time process control systems at wastewater treatment plants (WWTPs), several technical problems may have to be addressed. Sensors have to be reliable. Controllers should be properly designed and tuned. Fault detection should be implemented and safety nets designed. Actuators must have adequate control authority to deal with changing influent quality and quantity. But in their 1998 Water Science Technology (Vol. 37, No. 12, pp. 397–401) article “Reviewing, assessing, and speculating,” G. Olsson and B. Newell argue that it is the “human factor” that is often neglected even though it creates more problems than the technology. Read full article (login required) 


Operations Forum Features

Unstratified filtration medium

Sioux Falls, S.D., facility analyzes depth filtration with an anthracite coal unstratified filter medium and finds positive results

Schmidt art Christopher G. Schmit, Sean R. Sieler, Delvin E. DeBoer, Lyle Johnson, and Dawn Horner
According to research conducted for the city of Sioux Falls, S.D., the Sioux Falls Water Reclamation Plant could replace dual-media filters in its final clarifiers with depth filtration using anthracite coal unstratified media filters and still maintain acceptable effluent quality. By using unstratified filters with a large effective size, as well as air and water backwash, the plant could maximize filter run lengths and still meet effluent requirements. Read full article (login required) 


Optimizing low-level nitrogen removal

The Bethune Point Wastewater Treatment Facility in Florida uses a glycerin-based nonflammable, nonhazardous supplemental carbon source and online nitrate analyzers for process control

Johnson art Gary R. Johnson, James C. Thurrott, and Manjiang Chen

Problematic nitrogen removal at the Bethune Point Wastewater Treatment Facility in Daytona Beach, Fla., eventually led to pilot-testing of three nonflammable supplemental carbon sources. On-line nitrate analyzers, coupled with a programmable logic controller (PLC), provided a robust process control system. The selected supplemental external carbon source best suited to the five-stage Bardenpho process, combined with the analyzers and PLC, has provided the facility with a more reliable alternative for meeting nitrogen permit limits. Read full article (login required) 


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