March 2009, Vol. 21, No.3

Better Treatment Focusing on SRT, Not Solids Inventory

Rethinking the goal helps two municipal agencies improve activated sludge performance

bettertreatment.jpg Eric J. Wahlberg, Barbara Browne, Noble Fulcher, Biju George, Donald Linn, Larry Scanlan, Dan Siler, Wendy Anderson, Mike Daniels, Steve Rogowski, and Steve Walker

The activated sludge process is widely used because of its performance, versatility, and controllability. Unfortunately, its controllability also may be the source of operating problems, including poor solids settleability and noncompliant effluent quality. Even when properly designed, operated, and maintained, an activated sludge process is expensive and will only become more so as power costs increase.  

Given this expense and biosolids disposal challenges, treatment plant owners and operators must shift their focus. Rather than simply “making permit” (meeting the National Pollutant Discharge Elimination System [NPDES] permit requirements that regulate effluent quality), owners and operators should strive to “make permit and produce biosolids as cost-effectively as possible.” This goal better accounts for the environmental, economic, and energy pressures today’s owners and operators face.   Read full article (login required)  


Good Things From Small Packages

 Decentralized reclamation systems can help conserve potable water supplies

goodthings.jpg Ron Crites and Rob Beggs

Water reuse does not have to be an all-or-nothing proposition. Even small-scale projects can have notable effects on potable water supplies.

 In the following two case studies, decentralized reclamation systems extended or conserved the community’s potable water supplies.   Read full article (login required)  


Don’t Hide

 Communication is the key to gaining public support for capital improvement programs

donthide.jpg Tyrone Jue

The San Francisco Public Utilities Commission (PUC) is the water, wastewater, and municipal power agency for the city and county of San Francisco. In 2006, the commission launched a multifaceted public involvement effort as part of   its long-term capital plan to rebuild aging wastewater infrastructure. To date, this strategy has led to a close working relationship with its most vocal opponents, as well as better public and media awareness of sewerage system needs.

When the estimated cost of the plan was unveiled at more than $4 billion in April 2008, there was little public outcry. In fact, most stakeholders and the media urged PUC to not delay the project.   Read full article (login required)  


Operations Forum Features

Under Pressure To Perform

Developing an operation and maintenance program for wastewater air-release valves

underpressure.jpg Lloyd Lewis

Air-release valves (ARVs) in a wastewater collection system automatically release trapped air in pressure sewers, force mains, and on some sanitary wastewater pumps. Air-release and vacuum valves (ARVVs) relieve trapped air from pressure sewers and force mains and provide vacuum-relief functions, as well as air release. Failure of these types of valves can create problems, such as sanitary-sewer overflows, air binding of force mains and pressure sewers, reduced pumping efficiency, and force main and pressure  sewer collapse due to inadequate vacuum relief.

The pump maintenance unit of the Oakland County (Mich.) Water Resource Commissioner (WRC) is responsible for operating and maintaining ARVs and ARVVs in nine Oakland County communities. In total, PMU is responsible for the operation and maintenance of 342 ARVs and ARVVs. Based upon lessons learned during the last 12 years, WRC has developed several strategies for ARV and ARVV operations and maintenance activities. Proper operation and maintenance activities ensure that ARVs and ARVVs function properly, which, in turn will ensure that force mains and pressure sewers convey sanitary flow reliably and efficiently.   Read full article (login required)  


Alarming Trends

Remote monitors at multiple locations help avert SSOs

alarmingtrends.jpg Gregory M. Quist, David Drake, Chad Davisson, and Don Wasko

Sanitary-sewer overflows (SSOs) are a common and serious problem for wastewater collection operators. The U.S. Environmental Protection Agency estimates that at   least 40,000 SSOs occur annually in the United States, releasing between 3 billion and 10 billion gal (11 and 38 million m3) of untreated wastewater into the environment.

Supervisory control and data acquisition systems have been used to help monitor flows in sanitary collection systems since the 1960s, but only since the beginning of the 21st century has the technology advanced to the point of enabling monitoring systems to be deployed in large numbers in collection systems. Previously, monitors were so expensive that only a few could be deployed.

Continuous real-time monitoring of a large number of manholes and lift stations in a collection system enables operators to avoid spills by alerting them to unusual water-level conditions long before a spill occurs and provides time to take corrective action. The Olivenhain Municipal Water District (OMWD; San Diego) and the City of Carlsbad, Calif., are two municipalities that have implemented such a sewer monitoring network that has successfully prevented sewer overflows under a variety of conditions.   Read full article (login required)  


Small, Green, and Useful

 Encouraging Green Development With Decentralized Wastewater Approaches

smallgreenuseful.jpg Robert J. Freeman and Joyce Hudson

The southeastern United States — along with the rest of the country — will see dramatic population increases during the next 20 years. A projected increase of 16 million people in Florida, North Carolina, and Georgia would equate to more than a 1.5-billion-gal/d (65.8-m3/s) demand for water and the resulting wastewater production.

Decentralized wastewater treatment systems have the potential to provide a critical infrastructure element of wastewater treatment in a cost-effective and beneficial 
 manner, as well as enable green development and more efficient land use, helping meet this population demand.

Experience with decentralized systems in several southeastern states has demonstrated their benefits and provided models of sound management to ensure successful operation at an affordable cost.   Read full article (login required)   

©2009 Water Environment Federation. All rights reserved.