Municipal Wastewater Treatment - Prichard, Alabama

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Courtesy of TenCate Geosynthetics Netherlands bv

TenCate  develops and produces materials that function to increase performance, reduce costs, and deliver measurable results by working with our customers to provide advanced solutions.

THE CHALLENGE

Prichard AL is a town of about 30.000 people north of Mobile. AL Paul David, the Sewer Board Superintendent, oversees the contract management of two (21 wastewater treatment plants. Actual plant management is provided by Severn Trent Services. The Carlos Morris WWTP is a permitted 4.0 MGD plant and the Brooks WWTP is a permitted 1.5 MGD plant

The original design of both plants utilized sand drying beds. However, because the Mobile area is one of the wettest areas of the country, the drying beds were very inefficient and not able to effectively handle the daily production of digester biosolid sludge. Additionally, the removal of the dried sludge from the beds was extremely labor intensive and time consuming.

Small communities often struggle to maintain utilities and this plant was having problems staying in compliance with their discharge permits due to the lack of upgrades needed in the plant. A court-mandated consent decree .requiring improved performance, had Mr. David looking for cost effective solutions to handle the sludge.

As his primary digester was impacted with sludge, he had no place to waste from the clarifiers. As the blanket of sludge built up in the clarifiers, he risked being out of compliance with his discharge permit To supplement the drying beds. Mr. David periodically had mobile belt presses brought in to dewater the sludge.

THE SOLUTION

Having successfully used TenCate Geotube containment and dewatering technology on other Industrial and municipal sludge dewatering projects. Smith Industrial Services (SIS) was awarded the contract to dewater the sludge at the PrichardWWTP using Geotube technology. SIS placed 30' circumference x 50' long Geotube® units in the existing sand drying beds.

Geotube dewatering technology would provide a cost-effective way to help the WWTP stay in compliance with their discharge permits and continue to operate without interruption.

Dewatering with Geotube'r; technology is a three-step process. In the confinement stage, the Geotube container is filled with waste materials. The Geotube container's unique fabric confines the fine grains of the material.

In the dewatering phase, excess water simply drains from the Geotube container. The decanted water is often of a quality that can be reused or returned for processing or to native waterways without additional treatment

In the final phase, consolidation, the solids continue to density due to desiccation as residual water vapor escapes through the fabric. Volume reduction can be as high as 90 percent

Proper chemical conditioning is critical to successfully dewatering sludge in Geotube units. WaterSolve LLC, a full service provider of water treatment products, conducted bench scale tests to identify the optimum polymer and dosage. Dewatering polymers were evaluated based on water release rate, water clarity as well as size
and stability of the floe. Solve9244, a cationic emulsion was chosen as the best flocculant for this project

THE PERFORMANCE

Between March and July of 2007. SIS pumped over 4 million gallons of sludge at 3% - 5% solids into 28 Geotube units. The first dewatered solids were hauled off in roughly 60 days from the start Solids were 18%-20%, easily meeting the paint filter test going into the landfill. Given the lack of detention time available in the digester until upgrades could be completed, Geotube' dewatering technology proved to be the ideal solution.

The TSS permit parameters for the Prichard vWVTP are now in compliance, biosolids management is under control, ammonia levels have been reduced, the solids blanket levels are down in the clarifiets and are easily adjusted by pumping into the Geotube' units anytime.  The cost of Geotube technology is less than S200 pet ton over the scales vs. historical bids ranging S300 -S400perton.

'The bags have proved themselves to be cost competitive as well as operationally and environmentally agreeable. I was quite amazed ai the volume ot solids accumulated with such a passive operation.' said Mr. David.

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