January 2009, Vol. 21, No.1

Plan Ahead With MBRs

This new Arizona treatment plant helps with both current and future water-management needs

levesque Scott Levesque, Cindy Wallis–Lage, Brad Hemken, Stephen Bontrager, and Shawn Kreuzwiesner

Peoria, Ariz., is a Phoenix suburb and one of the fastest-growing cities in the United States. In 2001, the city began working toward a two-pronged goal: increasing wastewater treatment capacity and producing effluent suitable for aquifer recharge.  The project team determined that a membrane bioreactor (MBR) system not only would meet today’s needs but also could be expanded easily to accommodate future growth without incurring major capital expenses.  Read full article (login required)


A Handy Solution

Dynamic modeling can help utilities minimize both the risks and costs of capital projects

merlo Rion Merlo, Denny Parker, Jose Jimenez, Eric Wahlberg, and John Bratby
Wastewater treatment is an increasingly costly business, so project teams should use the most proven, advanced tools. This includes the modeling tools used at the beginning of a project.

For years, engineers used simple, steady-state models when designing wastewater treatment plants. These tools, which included “safety factors” to account for
unknowns, were developed when construction costs were lower and federal grants often subsidized local utility costs.

The safety factors, which often are justified as “engineering judgment,” simply incorporate historical presumptions about unknowns and design criteria. Some of the unknowns are created by the design tools themselves. They could be removed by using more advanced tools, such as dynamic models.

While both steady-state and dynamic models are based on the fundamental principles of physics, chemistry, and biochemistry, dynamic models account for variations over time. This ability can significantly affect treatment plant designs, capacity ratings, and system optimizations. Dynamic modeling could cut costs and improve performance.  Read full article (login required) 


Regulatory Update Needed

 The Secondary Treatment Regulation is no longer relevant to advanced wastewater treatmentfacilities

Muirhead.jpg Woodie Mark Muirhead, Rob Baur, Mary Darr, Greg Farmer, Jose Jimenez, Wayne Schutz, and Ron Taylor

 The 36-year-old Secondary Treatment Regulation (40 CFR 133.102) has little relevance to wastewater treatment facilities that must meet stringent nitrogen and phosphorus limits. Advanced wastewater treatment facilities consistently reduce effluent 5-day biochemical oxygen demand (BOD) and total suspended solids (TSS) concentrations to less than 30 mg/L. However, permit writers lack the flexibility to exclude requirements for these parameters from National Pollutant Discharge Elimination System (NPDES) permits.  Read full article (login required) 


Preventive Maintenance

Tune up your work force now to avoid costly repairs later

storm.jpg Margie Andersen and Robert Greene

Water and wastewater utilities are facing what could become a perfect storm. At the same time their work force is aging, the labor market has an inadequate supply of skilled workers who can replace those who inevitably will retire. The gap between the available labor supply and
the likely demand could keep utilities from functioning properly.

Facing such a scenario, the Metropolitan Sewer District of Greater Cincinnati (MSD) is using a work-force planning model to project staffing and development needs. Because of upcoming infrastructure updates, the utility will need a significant number of additional engineering staff and other technical personnel during the next 15 years. The model helps MSD assess its current work force and compares it to the work force that will be needed 1, 2, and 5 years from now.  Read full article (login required) 


Operations Forum Features

A Handy Solution

Staff develop odor-control units at a fraction of the cost of paying someone else to design and build them

Turley_Art.jpg Mike Turley

In the center of downtown New Lenox, Ill., a small wastewater treatment plant was built in 1960 to serve the village’s 2000 residents. As the village grew, so did the plant, until it was expanded to serve 25,000 people. The 2004 expansion added odor control for new tanks and the sludge storage tanks. These new carbon odor units
worked well, but there were still odor problems associated with a gravity thickener and six aerobic digesters that had to be addressed.

Odor problems have been a major concern since a 1990 plant expansion. Hydrogen sulfide emissions from a covered tank were measured as high as 10 ppm. Plant staff decided to tackle the odors on their own. After a few in-house projects, hydrogen sulfide odors measure zero ppm. While ammonia and some odors do remain, they are not in high enough concentrations to be noticeable on plant grounds.  Read full article (login required) 


Pattern Recognition

Using diurnal flow to predict and prevent odors

haan_art Bryan Haan

Sporadic odors in a collection system are almost impossible to eliminate completely and usually come from an isolated event. Although odors may seem random at first, monitoring can reveal trends that quite often relate to diurnal flow patterns. Diurnal flows, which are basically the trend between collection system flows and human
activity, can change throughout the day.

Adapting your approach or modeling your dor treatment to account for diurnal flow is not as difficult as it may sound. You may already have access to many of the resources needed to develop a greater understanding of the odor issues and how to proceed with treatment options. These options should be optimized to match the diurnal flow pattern to reduce treatment cost and increase treatment levels. Understanding this influence and correlating it with system retention times also may explain phantom odors.  Read full article (login required)