November 2008, Vol. 20, No.11

Hidden Potential

Recycled water and the water–energy–carbon nexus

Hidden Potential Dawn Taffler, Dawn Lesley, and Alan Zelenka



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There is an undeniable nexus among water, energy, and greenhouse gas (GHG) emissions, or carbon. A substantial amount of energy is used to divert, convey, treat, deliver, and dispose of water in California. The water sector uses 19% of California’s electricity and 32% of its natural gas. When wereduce energy use, we also reduce GHG emissions. Recent concerns about such emissions and their contribution to climate change have created new opportunities to promote water recycling as a means to conserve energy. Read full article (login required)


Fad or Future?

An expert evaluates whether digester-gas-fed fuel cells and microturbines are cost-effective sources of power

Fad or Future Nicholas A. Mignone



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In 1915, the superintendent of Atlanta’s Peachtree Creek Wastewater Treatment Plant covered the vents on Imhoff tanks and used the gas for heating and cooking. In 1926, anaerobic digester gas was used to operate an engine. These are the earliest documented attempts to collect and use municipal “sludge gas” in the United States. Since then, anaerobic digester gas has been used in several applications, two of which — stationary fuel cells and microturbines — are much discussed today as alternative sources of electricity and hot water. But how cost-effective are they? Read full article (login required)


Vulnerable No More

The City of Henderson, Nev., evaluated its sewers and reclaimed-water lines to assess their risk for damage from erosion

Vulnerable No More Matthew K. Wilkinson

Sewers and reclaimed-water lines can be vulnerable to erosion, especially in arid regions prone to infrequent but substantial storms. This is the case in Henderson, Nev., where sewers in normally dry channels known as “washes” have been damaged by highly erosive flows following severe storms. To prevent a recurrence of such problems, Henderson’s Department of Utility Services conducted a unique, proactive process for determining the extent to which the city’s sewers and reclaimed-water lines are at risk of erosion from stormwater flows in channels and washes.Read full article (login required)


Operations Forum Features

Fully Operational MBRs

Operator input can lead to stronger membrane bioreactor design

Fully Operational MBRs Viraj deSilva

The use of membrane bioreactor (MBR) plants has grown rapidly worldwide, but the operational issues associated with MBRs still are not fully understood by operators or design engineers. Most MBR facilities have begun operation in just the past 5 years. To determine the challenges faced during day-to-day operations, the author conducted an informal survey of MBR plants. Several MBR facilities — using both hollow fiber and flat-plate MBRs — were examined to determine how the facility could have been designed to be more operator-friendly and if their treatment process had been optimized since startup.Read full article (login required)


The Tools and the Talent

Given sufficient authority and a better human–machine interface, operators can minimize dewatering costs

The Tools and the Talent David Quast, Peter LaMontagne, and Roger Knuteson

Soaring prices have prompted many wastewater treatment plants to reduce dewatering polymer use. There are many ways to do this. Some options, such as installing newer equipment, are capital-intensive. Others, such as putting operators in charge of dewatering performance, cost very little but provide excellent results.

“Putting operators in charge” does not mean giving operators specific directives, such as, “Try not to use more than 15 gal/min [57 L/min] of polymer, and keep the cake at least 27% solids.” Such instructions are fine but usually are not issued frequently enough to reflect actual changes in dewatering processes. Instead, a Minnesota treatment plant uses a different approach: Its operators have the authority, continually and independently, to change the process — hour by hour — to keep dewatering costs minimized. Read full article (login required)


U.S. EPA Clean Water Act Recognition Awards

Congratulations to the winners for outstanding water quality achievements

US EPA Clean Water Act Recognition Awards n/a


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The winners of the 23rd annual U.S. Environmental Protection Agency (EPA) Clean Water Act Recognition Awards have demonstrated outstanding achievements in the water quality field. Nominated by regulators and evaluated by speciallyappointed selection panels, these U.S. wastewater treatment facilities, programs, and projects met EPA’s rigorous criteria. These winners were honored at an awards ceremony held during WEFTEC®.08 in Chicago. Read full listing of award winners.