October 2007, Vol. 19, No.10

Advancing With ATAD

After comparing different digesters, a Spanish utility opted to deploy autothermal thermophilic aerobic digesters as part of a centralized approach to treating solids

AdvancingwithATADFP.jpg Juan García, Jairo Gómez, Ana M. Lasheras, Estibaliz Huete, Natalia Echeverría, and Jaime L. García–Heras
In the Province of Navarra in northern Spain, more than 80 treatment plants collect wastewater from a population of approximately 430,000 equivalent inhabitants. Seeking a cost-effective approach for collecting and treating the solids generated at the province’s many facilities, the Navarra de Infraestructuras Locales S.A. (NILSA; Pamplona, Spain) — the water authority for the province — conducted a study to assess the feasibility of constructing a centralized process for treating solids. After comparing various treatment configurations, NILSA concluded that the most advantageous method would entail deploying autothermal thermophilic aerobic digester (ATAD) technology at a handful of plants to treat solids from smaller facilities nearby. Read full article (login required)  


To Trench or Not To Trench?

Florida city weighs the pros and cons of pipe bursting and open-cut pipe replacement    

totrenchornottotrench.jpg Charles S. Parker
In the last 15 years, advances in trenchless technologies have emerged across Europe and are finding their way into the United States. One of the fastest-growing methods is pipe bursting, in which the existing pipe is shattered into small pieces and pushed into the surrounding soil, and a new pipe of like or larger size is towed into the borehole. Pipe bursting can be used for water transmission mains, wastewater force mains, and gravity sewer lines. According to a July 2004 article in Civil Infrastructure by April Goodwin and B.C. Macauley, pipe bursting is “ideal for urban applications where an existing pipeline has exceeded its useful life.”

However, there are some instances in which conventional open-cut replacement of the existing pipe is necessary. Before any design is proposed using trenchless pipe-bursting technology or conventional open-cut replacement, municipalities should perform a site-specific engineering analysis of design requirements, pros and cons, permit requirements, and costs of each method.  Read full article (login required)  


Screen Selection Simplified

Understanding your choices

Screeningselection.jpg Gerhard Forstner
Whether building a new wastewater treatment plant or performing an upgrade, equipment selection is one of the most important steps in plant design. For better or worse, the equipment will be there for many years to come.

Any plant operator can tell you horror stories about situations when equipment failed. In many cases, the problem is not the equipment itself but rather the fact that it is unsuitable for the application. This problem is magnified in a plant’s headworks, which act as a wastewater treatment plant’s first line of defense. If the headworks equipment does not operate properly, it will affect every subsequent process downstream.  Read full article (login required)   


Operations Forum Features

Let the Light Shine In          

Proper maintenance helps keep UV disinfection operations smooth

LettheLightShineIn.jpg Gary Hunter
Many wastewater treatment facilities now use ultraviolet (UV) light to disinfect their treated wastewater before discharging it to a receiving waterbody. Although the UV process is fairly simple, it requires regular maintenance to keep it operating at peak performance levels
UV disinfection processes have three basic components: the process itself and its electrical and mechanical systems. The process depends on influent quality and the disinfection goals. The electrical system consists of the lamps, wiring, and control system. The mechanical system includes the quartz sleeves, frames, cleaning mechanism, and reactor configuration. All need proper attention, operation, and maintenance to function effectively.  Read full article (login required)   


The Possessed Toilet Syndrome 

Preventing toilet eruptions during sewer main jetting     

possessedtoiletsyndrome.jpg Ravi Srivastava, Randy Siddens, Brent Harris, Nate Ader, Jerry Barcelona, and
As any employee involved in the management of a wastewater collection system would acknowledge, operating and maintaining such a system has its tales of joy and discovery and its legends of nightmares and disasters.

For example, using jetting equipment to clean or deroot gravity sanitary sewer lines sometimes causes customers to complain of their toilets burping, gargling, or erupting
like a volcano. Occasionally, customers have called in to voice their concern and fears of strange noises and air and water emanating from toilets— typically called possessed toilet syndrome.  Read full article (login required)  


The Nitty Gritty 

Grit washing system design

nittygritty.jpg George Wilson, George Tchobanoglous, and Jimmie Griffiths
With grit removed from influent, the only steps left are to remove organics from the slurry created by the separation (washing) and remove the water from the slurry to produce a product acceptable for landfill disposal (dewatering). But as with most things, that task is not as simple as it first appears. Read full article (login required)