October 2009, Vol. 21, No.10

What’s Old Is New Again

Ozone is gaining greater prominence as interest grows in microconstituent removal, water reuse

feature1 art Jeff Neemann, Nick Burns, Bob Hulsey, and Gary Hunter

Although ozone has been used to treat water for more than 100 years, it did not receive widespread use in the United States until the late 1970s and early 1980s, when both drinking water and wastewater treatment facilities began to use it as a disinfectant. However, as the use of ozone increased, utilities were drawn to its oxidant and microflocculation properties. Due to recent research showing that ozone can be effective in removing some microconstituents, there has been a resurgence of interest in using ozone for drinking water and wastewater treatment, as well as water reuse. Read full article (login required)


Good Grease

Adding FOG to its anaerobic digester helps a California city increase biogas output, reduce sewer overflows

feature2 art Richard V. York and Joseph A. Magner

The Millbrae, Calif., publicly owned treatment works was faced with an aging combined heat and power (CHP) system that was difficult to maintain. By feeding inedible kitchen grease (IKG) into its anaerobic digesters, Millbrae was able to fund a project that replaced the cogeneration system and other aging plant infrastructure. Plant performance has been far greater than anticipated since the project was initiated. After 30 months of operation, Millbrae is reaping the benefits of increased biogas, decreased solids volume and weight, and improved digester stability. Read full article (login required) 


Affordable Modifications

As a low-cost alternative to tank replacement, CFD analysis can be used to evaluate and optimize flow through aerated grit chambers for improved grit removal

feature3 art Marie Burbano, William McConnell, Carrie Knatz, Daniel Bisson, and Brian Tarbuck

As part of a long-term combined-sewer overflow (CSO) control program, the Greater Augusta (Maine) Utility District has identified that its plant’s aerated grit chambers need improvement.

Because of the chambers’ poor performance, the plant becomes inundated with grit, leading to significant operational and maintenance problems in downstream processes. The plant has been experiencing clogged primary sludge piping, excessive wear on the primary sludge pumps, and grit deposition in downstream process tanks.

It is financially infeasible to either replace the existing grit tanks with a new process or rehabilitate the tanks with significant modifications to the existing concrete. Therefore, the district analyzed the feasibility of more-affordable in-tank modifications through the use of computational fluid dynamics (CFD) modeling. Read full article (login required) 


Operations Forum Features


A planning tool for selecting wastewater treatment technologies 

Feature 4 art Brad A. Finney, Robert A. Gearheart, Andrew Salverson, George Zhou, Mary Burke, and Jong Chan Ly

Most large communities have sufficient economic and technical resources to ensure that the new facility planning process adequately matches their needs with the wide range of available treatment technologies. Smaller communities however, frequently lack either the economic resources or technical expertise to support a facility planning process that examines the broadest range of appropriate treatment technologies. Frequently, the consultants, public works staff, and community decision-makers have training or experience with only a limited range of “conventional” treatment technologies, and the facility planning process fails to consider a wide range of potentially applicable alternative technologies.

However, a free, easily accessible, and evolving computer-based tool exists to help ensure that all possible treatment options are considered. The Water and Wastewater Treatment Technologies Appropriate for Reuse (WAWTT AR) model is a prefeasibility planning tool intended to assist planners in selecting suitable water and wastewater treatment options appropriate to the material and manpower resources available to particular communities throughout the world. Read full article (login required) 


How To Troubleshoot and Underperforming Pump Station 

(Part 1 of 2)

Feature 5 art Derek L. Morin, Tim Kelleher, Paul Tomaskovic, Dave Lookenbill,

Most, but not all, pump station startups go smoothly. During startup, an observant owner or a pump station maintenance worker may comment that the wet-well drawdown appears slow. Checking the flow rate using a calibrated flowmeter or conducting a wet-well drawdown test can quickly dismiss these concerns. But what if the flow rate indicates that the observer is correct, and the pump station not only is pumping slow but is pumping at 50% design capacity? What if there is no visible explanation for degraded performance? What tests should be performed, and how should the investigation proceed? How much time and money will the investigation take? These are difficult questions to answer immediately.

The possible causes for poor pump station performance are numerous, and finding the correct cause quickly can be daunting. In such circumstances, it is important to use a methodical process to gain and maintain the owner’s confidence and to ensure that all of the issues are found and resolved efficiently. Read full article (login required)