Case study – GEM vs DAF, efficiencies of GEM system over dissolved air floatation (DAF)

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Courtesy of Clean Water Technology, Inc.

Introduction
Clean Water Technology, Inc., the creator of the Gas Energy System (GEM), provides the most advanced primary treatment system on the market. The GEM System provides superior reduction of total suspended solids (TSS), biological and chemical oxygen demand (BOD/COD), fats, oils and grease (FOG) and turbidity.

Challenge
A Frozen Food Manufacturer was searching for a sustainable wastewater treatment solution to the issues they were experiencing with their existing DAF (dissolved air flotation) System. Using their DAF to discharge 375,000 gallons per day with a variable flow range of 130-500 gallons per minute (246 avg.), the Client was faced with high chemical costs, environmental surcharges and sludge removal costs.

Solution
CWT was contracted to demonstrate the GEM System’s capabilities in reducing TSS, FOG and BOD/COD,, as well as to compare performance against the existing DAF system. A one-week demonstration period was conducted to evaluate the GEM System’s performance on the client’s waste stream and discharge.

The GEM System achieved a greater overall reduction in TSS, COD and turbidity than the currently installed DAF System. Even those trials using NO chemical resulted in good contaminant removal rates. Furthermore, as chemicals were reduced to achieve 100 NTU, the GEM System consumed less chemicals and produced less sludge volume.

The existing DAF System must operate continuously, requiring wastewater to be constantly fed into the process in order for it to remain functional. Current chemical dosing practices requires that pH maintain a level of 5.5 to achieve best results. Since wastewater is constantly fed into the DAF System, large quantities of acid and caustic in addition to polymers must be injected into the process.

The GEM System can operate in a start/stop fashion. Various streams can accumulate over a 24-hour period in the EQ tank where water and pH is automatically homogenized requiring substantially less volume of acid and caustic. With all chemical regimes, the GEM System achieved significantly greater contaminant removal rates throughout the demonstration than the DAF unit, allowing the Client large potential savings on chemicals, surcharges and fines.

Sludge Data
Although the GEM System and DAF system sludge results were closely related when taken directly from the beach, the GEM System sludge obtained better flotation and water decanting than the DAF system sludge, as indicated in the photos below. After 2.5 hours of decanting, the GEM System solids consumed 5% of the container, leaving the remaining volume for easily decanted clean water. Furthermore, with the GEM System, there was no sludge carry over back to the treatment process as is more common with traditional DAF systems.

Conclusion

  • When the GEM System is installed in late 2008, this Client will realize the following benefits:
  • Significantly smaller footprint than conventional DAF’s
  • Reduced TSS, FOG and BOD/COD.
  • 25-50% savings in sludge storage, hauling and disposal.
  • Easy Operation with start/stop auto controls or continuous run capabilities
  • No capital expenditures required for growth in flow due to expandability of GEM System

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