Features

January 2011, Vol. 23, No.1

Designing communication, one link at a time

Training and digital logbooks help close the communications gaps at DC Water 

kharkar Salil Kharkar, Aklile Tesfaye, Walter Bailey, Nicholas Passarelli, Joseph Bastian, William Albrittain, and B.J. Lingren

“I don’t know; I just came on duty after a long weekend.”
“I didn’t know the shutdown was completed.”
“I didn’t know the pump was partially clogged.”

These are all examples of routine responses to a problem heard from operations staff at the Blue Plains Advanced Wastewater Treatment Plant operated by the District of Columbia Water and Sewer Authority (DC Water). These accountability deflecting comments point to a weak link characteristic of facilities that operate with multiple shifts, separate process treatment sections, or ongoing construction and upgrades. This weak link is communication.

While communication challenges are universal, medium-size to large plants with multiple shifts and multiple crews on each shift are particularly susceptible. Operations structured as silos are even more prone to this problem. Ultimately, the operations department of DC Water was able to overcome these organizational challenges, identify key impediments to communication, and implement solutions to overcome them. Read full article (login required) 
 

 

Energy-efficient MBRs 

Utilities can significantly reduce operating costs by taking a holistic look at design, operations, and equipment 

wallis Cindy Wallis–Lage and Scott D. Levesque

Membrane bioreactor (MBR) technology has rapidly gained acceptance as an attractive, flexible solution for plant expansion and enhancement, as well as for Greenfield facilities. Increased competition and escalating commodity prices that favor a small-footprint design have made the capital costs of an MBR plant competitive with those of conventional activated sludge plants. However, a key area in which MBRs still need optimization is energy. Read full article (login required) 

 

Getting to know your grit

Sampling study of U.S. grit examines geographical profiles, helps define design needs for removal systems 

higgins Regina Rigsby Higgins, Rodney S. Mrkvicka, and Dana Rippon

Wastewater treatment plant (WWTP) personnel and consulting engineers have a common desire to remove as much grit as possible from their operations.

A properly designed and operating grit-removal system is critical in protecting a plant’s infrastructure. Grit buildup can result in loss of active reactor volume, scouring or plugging of pipelines, accelerated equipment wear, and fouling of diffusers and membranes — while decreasing the intended service life of downstream equipment. Therefore, the most effective headworks design will take into account both the sizes of grit particles in the system and the minimum required velocities to transfer grit. Read full article (login required) 
 

 

Converting Lake Havasu City 

Arizona city nears completion of major sewer expansion project 

kasner Carmen C. Kasner and J. Greg Froslie

The residents of Lake Havasu City, Ariz., know the value of good water quality. The town of roughly 53,000 residents is situated on the eastern shore of Lake Havasu, a reservoir on the Colorado River straddling the border between California and Arizona. With an economy heavily dependent on tourism and recreational fishing and boating, Lake Havasu City has gone to great lengths to address water quality concerns regarding the waterbody for which it was named. A decade ago, city residents relied mainly on septic systems for treating and disposing of wastewater. When this approach was found to be inadequate, Lake Havasu City sought and received voter approval in 2001 to pursue an ambitious public works project — converting more than 20,000 residences from septic systems to centralized wastewater collection and treatment. Read full article (login required) 
 

 

Operations Forum Features

Don’t let your model sit on a shelf 

Getting the most out of your model

Onderak_Pic Eric D. Onderak, Brandon C. Vatter, and Geoffrey M. Grant

Sanitation District No. 1 of Northern Kentucky (SD1; Fort Wright) recently updated and recalibrated its hydraulic model as part of the development of watershed plans required by a consent decree. The updated model is intended to support the watershed plans and future capital improvements.

But the utility wanted to get more bang for its buck. Having invested a significant amount of time and money to produce a detailed hydraulic model, SD1 worked to ensure that this tool moves beyond capital planning to support day-to-day operations and decision-making. SD1 developed a plan to keep the model updated and identified several tasks that could be used to support day-to-day uses. Read full article (login required) 
 

 

Forgotten fouling

Understanding and reversing localized dewatering 

Stone_Pic Mark Stone and Dennis Livingston

All membranes foul. And unlike conventional tertiary filtration, where membrane performance is somewhat decoupled from the biological process, in submerged membrane bioreactor systems (MBRs), “all parameters involved in the design and operation of [MBR] processes have an influence on membrane fouling,” according to a 2006 article in the Journal of Membrane Science.

In other words, membrane fouling is affected by plant hydraulics, operations, and several other factors. Submerged membranes are subjected to unique fouling mechanisms that occur at the microscopic level and at generally controllable rates.

However, a much less studied phenomenon occurs at the macroscopic level, whereby solids accumulate at the membrane surface to form a dense and visible cake. Called “localized dewatering,” this form of fouling can result in reduced performance, flux decline, and high energy consumption. Read full article (login required)

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