June 2006, Vol. 18, No.6

Let It Rain 

 Coarse monomedia filtration reduces TSS, BOD in wet weather flows

WETRainArtJune2jpg Daniel L. Bentivogli and Lisa A. Davey

As wastewater utilities look for cost-effective methods to treat wet weather flows, they might want to consider coarse monomedia filtration. Unlike conventional filtration systems, this process has proven to be a cost-effective option for treating combined sewer overflow (CSO) and sanitary sewer overflow (SSO) streams at remote locations. The City of Geneva, N.Y.; CRA Infrastructure & Engineering Inc. (Buffalo, N.Y.); and the New York State Energy Research and Development Authority recently undertook a pilot study to determine whether coarse monomedia filtration can treat total suspended solids (TSS) and biochemical oxygen demand (BOD) in preliminarily treated wastewater during wet weather events. Results were promising.  Read Full Article.


Keeping the Lid on Odors 

King County, Wash., plans to avoid odor and corrosion problems in its new collection system 

WETOdorsJune06jpg Bruce Ball, Grizelda Sarria, and Dirk Apgar

Odors aren’t part of the plan for a new collection system in King County, Wash. The utility intends to build new wastewater treatment facilities for a rapidly growing part of its service area. It has committed to keeping Brightwater Project odors to less than 3 dilutions to threshold (D/T) at its fence lines, as well as achieving a 99.9% hydrogen sulfide removal efficiency. To ensure that the new collection system would meet these goals, the project team had to determine where and how much foul air could be released in the proposed collection system, then choose appropriate odor control systems.  Read Full Article.


Elemental Odor Control

New trends in activated carbons 

WETelementalOdorArtJune06jpg James R. Graham

For decades, wastewater treatment plants have used activated carbon systems for odor control. The advantages of these systems are clear: They have few moving parts, require minimal operator intervention, and are simple to operate and maintain. Over time, these odor-control media have become more effective, safe, and environmentally friendly. Today, plants can choose from a variety of activated carbons, including some newer media that are becoming more popular.  Read Full Article


Operations Forum Features

Just Right

OFJustRightJune06jpg David L. Phillips and Michael M. Fan

Once upon a time, the University of California—Davis wastewater treatment plant had a manually controlled aeration system for its oxidation ditch. But its influent varied greatly, and the plant staff was afraid of providing too little dissolved oxygen (DO) to meet treatment needs, so they often provided too much and overaerated the ditch. This control strategy wasted energy and promoted unstable biological conditions.

Frustrated with this state of affairs, treatment plant staff began looking for an option that would handle constant variation while providing just enough oxygen to meet treatment needs. After evaluating options, the project team decided that an automated control system with continuous dissolved oxygen monitors and variable speed drives would best meet the plant’s needs.  Read Full Article.


Nitrification Myths 

Operators should recognize several common misperceptions about nitrification 

OFMythJune06jpg James P. Scisson Jr.

For approximately 30 years, wastewater treatment plants have been designed, constructed, or modified to achieve nitrification. During this time, nitrification’s basic principles have become better known, and the practice has been refined. In many cases, however, these principles have been ignored or misconstrued. Over time, the resulting distortions have been transformed into myths that are presented as truths, and have infiltrated engineering lingo and even some regional design standards.

Such myths lead to unwieldy designs for treatment plants that impede performance. The myths also hamper operators by discouraging or inhibiting them from experimenting to determine a plant’s true capacity or to find the range of nitrification performance that provides cost-effective and stable operation under many conditions.


This article debunks eight common myths surrounding nitrification and explains in simple terms what conditions are needed for nitrification.  Read Full Article . 


Water Watchdogs

Developing a Water Monitoring Program for Security Purposes In Washington, D.C.

OFWatchdogJune06jpg William Keefer and Maureen Donnelly

Homeland security is an important issue throughout the United States, and especially in Washington, D.C. Recognizing that the nation’s drinking water supplies and facilities could be vulnerable to intentional chemical and biological contamination, the District of Columbia Water and Sewer Authority (WASA) developed a water security program to prevent, detect, and respond to intentional contamination.

WASA collaborated with several local utilities and government agencies to develop the key components of a water security program composed of various operational and response protocols, including, in particular, a water quality monitoring program. The objectives of the water quality monitoring program are to develop and implement alarm levels based on multiple water quality parameters and response protocols. This program allows WASA to evaluate various types of equipment, as well as site location characteristics that optimize monitoring with respect to water security needs.  Read Full Article .