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Case Study — Calera Creek Water Recycling Plant Improvement for a Class A, Odor-free Biosolid

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The term Autothermal Thermophilic Aerobic Digestion, or ATAD, was first used in 1978. The process has gained popularity as it often achieves cost and space savings when compared to anaerobic and conventional aerobic digestion. In addition, the process results in a Class “A” biosolid.

In September, 2000, the Calera Creek Water Recycling Plant, in Pacifica, California, installed a “First generation” ATAD. Although an effective digester, this system provided oxygen levels below those required by the microorganisms. As a result, mercaptans and odorous compounds were produced; a situation unacceptable to the residents of Pacifica.

The “Second Generation” ATAD systems incorporate process modifications over the “First Generation” ATAD systems including improved process control and mixing that have resulted in virtually no odor generation, greater volatile solids reduction and lower end-product volume.

Keywords: Autothermal Thermophilic Aerobic Digestion; Oxidation Reduction Potential (ORP); biofilter; storage nitrification/denitrification reactor

Document Type: Research Article


Publication date: 2011-01-01

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