Features

May 2007, Vol. 19, No.5

Going It Alone 
    

In battling SSOs, in-house design and construction proves to be a successful, cost-effective choice for an Oklahoma city
 

goingitalone.jpg Jerry Ihler and Rusty Whisenhunt

Faced with a consent order to eliminate sanitary sewer overflows (SSOs), the City of Lawton, Okla., needed to act quickly. After a thorough inspection of its collection system, the city knew what work had to be done, but it needed to decide how to do it: Take the traditional route of contracting
the work, or perform the work itself. Lawton opted for the latter choice, forming its own sewer construction division and beginning repair work on an aggressive timetable. After completing Phase 1 of construction on time and under budget — and decreasing SSOs by 95% — Lawton now looks forward to continued success as it completes work on the final two phases of the project.

The future did not always look so bright for Lawton, which in the late 1990s was averaging more than 200 SSOs per year. The collection system of this southwest Oklahoma city comprises more than 6000 manholes and approximately 640 km (400 mi) of sewer lines, much of which dates back to the 1940s and 1950s. About 70% of Lawton’s collection system is made up of locally manufactured concrete pipe, which had deteriorated from long-term exposure to hydrogen sulfide gas.  Read full article (login required)  

 

Sewer Improvements? Sold!
 

A North Dakota city secures a sales tax increase to help fund major collection system improvements
     

Sewer Improvements.jpg Eric C. Dodds, Bruce Grubb, Jim Hausauer, and Steve L. Burian

In 2004, the City of Fargo, N.D., was facing a problem familiar to wastewater utilities: It needed more capital improvements than it could afford.

The city wanted to expand its interceptor sewer system,
provide capacity to manage wet weather flows, establish a sewer rehabilitation and replacement program to manage aging infrastructure, and expand its wastewater treatment facility (WWTF). The price tag: more than $240 million for the next 25 years.

After thoroughly evaluating the planned expenditures, available revenue, and potential funding sources, the city decided to pursue revenue from a dedicated infrastructure sales tax, coupled with reasonable rate increases to fund the improvements. This approach proved to be successful, and the city now is proceeding with its planned improvements to manage the growth and maintain the reliability of its wastewater collection system.  Read full article (login required)  

 

Minimal Disruption 

Historic New England town finds hybrid sewer system a perfect fit

minimaldisruption.jpg David Guertin

A careful review of history reveals that Provincetown, Mass., not Plymouth Rock, was the initial stopping place for the Pilgrims in November 1620. This small town at the tip of Cape Cod was home to America’s first European settlers for approximately 5 weeks before they sailed across Cape Cod Bay to the mainland and stepped ashore.

Located on the narrowest sliver of land on Cape Cod, Provincetown is today a popular resort area. Its population of 3200 can swell to 50,000 in summer as visitors arrive to enjoy the beaches and mild weather.

The explosion of people each summer creates significant infrastructure issues. One of the most pressing is sewer capacity. Since it was first a fishing village in the late 1600s, the town had relied on point source wastewater treatment, primarily cesspools. That changed in 2003, when Provincetown completed work on Phase 1 of a hybrid wastewater collection network that includes a backbone vacuum system complemented by sections of low-pressure and gravity systems. The new system provides service to more than 500 homes and businesses.

The experience has been exceptional. There have been zero complaints, and the town gets frequent requests from homeowners to join the collection network as residents hear from their neighbors about the benefits of the centralized system. Getting the city’s first municipal sewer system took about 300 years, but by all accounts, it was worth the wait. Read full article (login required)   

 

Investigating Ozone

A pilot-scale ozone treatment system shows promise in removing trace levels of pharmaceuticals, steroids, and personal care products from secondary effluent

investigatingozone.jpg Douglas D. Drury, Shane A. Snyder, and Eric C. Wert

The Las Vegas Valley has experienced phenomenal growth in recent years, resulting in increased demand for wastewater treatment. To keep pace with this growth, the Clark County Water Reclamation District (CCWRD; Las Vegas) is planning
to expand the capacity of its Central Wastewater Treatment Plant from 416,350 to 529,900 m3/d (110 to 140 mgd) by 2010. As part of this expansion, CCWRD is increasing the capacity of the plant’s advanced wastewater treatment processes by 113,550 m3/d (30 mgd). CCWRD discharges its treated wastewater into the Las Vegas Wash, which, in turn, flows into the Las Vegas Bay of Lake Mead. The largest reservoir in the United States and the source of drinking water for the Las Vegas Valley, Lake Mead is formed by Hoover Dam, which is located on the Colorado River approximately 48 km (30 mi) southeast of Las Vegas.

In the face of a severe drought and increasing demand for water throughout the Colorado River’s seven-state basin, the surface of Lake Mead has dropped about 24 m (80 ft) during the last 5 years. The U.S. Bureau of Reclamation, which operates Hoover Dam, has forecasted that water levels in Lake Mead will continue to drop before recovering. The Nevada Department of Environmental Protection has indicated that it will evaluate the need for changing the water quality objectives pertaining to flows entering the lake and its tributaries as the lake’s surface lowers.  Read full article (login required)  

 

Operations Forum Features

Scum Busters

The Hanover Sewerage Authority's digester scum removal project

scumbusters.jpg Peter W. Resotka

To gain greater quality control over the periodically scum removal from its secondary anaerobic digester, the Hanover Sewerage Authority (Whippany, N.J.) developed procedures to perform the job in-house.

Scum consists of grease, hair, rags, and other debris that pass through preliminary treatment and into the digesters via raw solids pumps. Usually, scum removal entails draining the entire contents of the digester, removing the floating cover, and lifting out the scum with a clamshell-style loader. However, because Hanover’s secondary digester is used primarily as a settling mechanism with no mixing action, it was feasible to drain the gas from the cover and remove the scum while the tank was on-line. Read full article (login required)

 

A Natural Fit 

Pairing subsurface flow wetlands with a nature center
 

anaturalfit.jpg David A. Flowers

Building subsurface flow wetlands to treat the wastewater from a Wisconsin nature center seemed like a natural fit. What the project’s planners hadn’t counted on was the idea of treatment wetlands catching on. Twelve years later, several more subsurface flow wetlands are successfully treating
domestic wastewater in Wisconsin for single residences, multiple (clustered) residences, and for commercial and institutional concerns. Read full article (login required)  

 

A Matter of Integrity 

Periodic tank inspections help prevent environmentally hazardous spills

amatterofintegrity.jpg Frank Maitland

As part of the U.S. Environmental Protection Agency-mandated spill prevention, control, and countermeasures plan, facilities must regularly inspect the oil-storage tanks for signs of potential leaks. Such inspections, called tank integrity inspections, must be conducted in accordance with a
nationally recognized standard (when applicable) or good engineering judgment.

Under the EPA program, all facilities that are not transportation-related, have a total aboveground oil-storage capacity of more than 1320 gal (5 m3) or underground capacity of more than 42,000 gal (159 m3), and could reasonably spill this oil into navigable U.S. waters or onto their shorelines must prepare a plan.  Read full article (login required)