Features

July 2013, Vol. 25, No.7

Dynamic modeling of cyclic aeration process for biological nutrient removal 

An innovative activated sludge process, coupled with an advanced control system, helped the Hampden Township (Pa.) Roth Lane facility meet strict nitrogen and phosphorus effluent limits 

Hampden Township art Ayman R. Shawwa and Dale C. Shope
The Hampden Township Roth Lane Wastewater Treatment Plant in Mechanicsburg, Pa., developed and calibrated a dynamic model to predict the performance of a cyclic or intermittent aeration process for its extended aeration activated sludge process. The water resource recovery facility automatically cycled aeration on and off to create oxic, anoxic, and anaerobic conditions within the reactor’s biomass. Sequencing these conditions in the same order enabled nitrification, denitrification, and biological phosphorus removal in a single reactor. Read full article (login required)  

 

Combining two pump stations into one  

An Ontario pump station design overcomes several challenges, including two extreme hydraulic duty points 

pump station art Rafiq Qutub

Typically, a pump is selected for a single duty point when designing and building a pump station. However, the City of Vaughan in York Region, Ontario, had to satisfy several objectives with one duty pump in building the Molise Kleinburg pump station. 

The pump station was designed and constructed as part of a new residential subdivision in the village of Kleinburg. To improve operational functions, reduce operating and repair costs, and eliminate future capital costs, the Molise Kleinburg pump station was designed to achieve two extreme duty points: one set of interim conditions and another set of final conditions in the future. In effect, the station combines two stations into one. Read full article (login required) 

 

Operations Forum Features

A state of urgency 

Expanding pipe ratings for sewer pipe triage 

pipe triage art Robert F. Buss, Gina Ishida, Mark Holstad, and Nancy Musinski

“Out of sight, out of mind” has been the normal approach in thinking (or not thinking) about buried underground sewer infrastructure, at least until there is a collapse in the street, the public is affected, and the unseen is revealed. The Albuquerque Bernalillo County (N.M.) Water Utility Authority experienced this phenomenon in the early 1990s with the sudden and seemingly random collapse of large-diameter sewer pipelines in various areas of its collection system. Collapses of the authority’s large interceptor pipes in major roadways occurred again in March and April 2011, and again in May and June 2012. 

A careful evaluation of these collapses pointed to aging pipes whose useful lives had been reached or exceeded. Staff predicted that these collapses were only the beginning; more pipes would fail unless steps were taken to rehabilitate or replace them. 

The water authority’s solution was to select a methodology that takes a thorough inventory of the condition of interceptors using risk-based, asset-management principles. Read full article (login required) 

 

A bracing new solution for an old sewer 

The City of Boston turns to a spiral-wound technology to rehab a 140-year-old brick-lined sewer 

spiral wound art Charles Wilson, Frank Ayotte, Edward Duggan, and Irene McSweeney

The Dorchester Brook Sewer (DBS) is one of the several combined sewer systems owned and operated by the Boston Water and Sewer Commission. The 100-year old DBS serves a tributary area in North Dorchester and Lower Roxbury of almost 405 ha (1000 ac) and is a 2743- × 3962-mm (108- × 156-in.) arch-shaped brick structure supported on wooden piles that are driven through thick layers of organic soils. 

In 2007, the commission conducted a study to evaluate combined sewer overflow (CSO) control measures and to develop a recommended plan to meet the court-ordered CSO volume and activation limits. One project under the overall recommended plan involves rehabilitation of a 260-m (840-ft) segment of the DBS between Massachusetts and Norfolk avenues (damage to this section includes longitudinal cracking in the crown of the pipe, with as many as two to three courses of missing and/or delaminated brick layers). 

To address this task and maintain the highest flow capacity while also providing structural integrity to the DBS, the commission decided to use a relatively new rehab method, spiral-wound technology. Read full article (login required)