October 2012, Vol. 24, No.10

The Clean Water Act at 40 


Special section

CWA art 1 -
This special section reflects on the regulatory, technological, and financial advances spurred by the Clean Water Act as well as looks forward to what’s next for water quality and the sector. Read full article (open-acess) 


Hybrid aeration systems

The key to energy efficiency for medium-size wastewater treatment plants.

hybrid art 2 George W. Smith

In most wastewater treatment plants, aerating activated sludge systems consumes the majority of the plant’s power. Thus, the efficiency of the aeration system used with the activated sludge process becomes a major factor in designing an economically operated plant. Too frequently, however, only the efficiency of the aerator device is taken into consideration, while design parameters affecting the overall process aeration efficiency (PAE) are neglected. 

To reduce power use, attention has to be given to blending process modes, such as reactors in series operating with up-front oxygen deficit conditions, and blending aerator devices, such as mechanical aerators up-front and fine-bubble aeration in the back part of the process. This type of blending of process and equipment is called “hybrid aeration,” and it can result in aeration energy savings of up to 50%. Read full article (login required)


Tightening security measures

An Arizona county implements a security report card program for its wastewater reclamation facilities, seeing good results.

Security art 5 Bryon Elwell and Jackson Jenkins
In hard economic times, it is worthwhile to remember that some security improvements can be inexpensive and still highly effective. With that in mind, the Pima County (Ariz.) Regional Wastewater Reclamation Department (RWRD) sought to have its 550 staff members work together to sequentially strengthen security at its wastewater facilities and offices. Read full article (login required)


Operations Forum Features

Estimating nitrification capacity simply

A straightforward method for estimating maximum specific nitrifier growth rates can enable operators to optimize plant performance

Peng art 3 Weihua Peng

To properly design, upgrade, or operate an activated sludge wastewater treatment plant (WWTP), designers or operators must understand its nitrification capacity. 

For operators in particular, such an understanding is critical for optimizing a plant’s processes and achieving its maximum potential capacity. 

Although maximum specific nitrifier growth rates are the key parameter for estimating WWTP nitrification capacity, various studies have reported a wide range of growth rates. Because each WWTP has its own specific wastewater characteristics, selecting a particular growth rate to fit a facility’s unique situation can prove difficult. 

However, a simplified method involving a series of straightforward tests using common laboratory equipment is available for estimating a WWTP’s maximum specific nitrifier growth rate by measuring overall nitrification rates. Read full article (login required)


Engaging maintenance managers to reduce FOG

WSSC and food service establishments are protecting the Potomac River from fats, oil, and grease in National Harbor, Md.

FOG art 4 Wayne H. Ludwig Jr.
By any account, the Washington Suburban Sanitary Commission (WSSC; Laurel, Md.) operates on a grand scale, serving more than 1.8 million customers in Prince George’s and Montgomery counties in Maryland. A consent agreement with the U.S. Environmental Protection Agency and others recently expanded the commission’s responsibilities to include monitoring and enforcing a formal fats, oil, and grease (FOG) program. With the creation of the FOG Unit in 2006, the department’s six inspectors focused much of their time on reviewing 9105 food service establishments (FSEs). Read full article (login required)