Aerobic Digesters Provide Versatility

Oct. 1, 2010
Systems are easily installed at existing plants

Schreiber’s GRO and GR systems are very versatile, and that versatility provides often-overlooked benefits for existing plants. The GRO can function as an aeration basin or an aerobic digester. The GR is even more flexible, as it can be set up for aeration/clarification or for combinations of digester/thickener/clarifier. For example, with a dual GR system, one GR can be used as an aeration/clarification unit, while the other can be used as a digester/thickener unit; the thickener can be easily converted to function as a clarifier at any time.

Expanding non-Schreiber plants can easily replace older anaerobic digesters with Schreiber units. Converting existing basins, such as older clarifiers or anaerobic digester basins, into aerobic digesters or adding new aerobic digesters to enhance solids removal capability and efficiency can accomplish this.

A few advantages of aerobic digesters over anaerobic digesters include simplicity of operation and maintenance, lower capital costs, lower levels of BOD and phosphorus, fewer effects from upsets such as the presence of toxic interferences or changes in loading and pH, less odor, lack of danger of explosion, shorter retention periods and small size.

Schreiber has designed and installed several dual GR plants in which one unit serves as an aeration/clarification unit and other serves as a digester/thickener/clarification unit. At the Mirasol, Mo., plant, the GR digester was sized to allow digestion/clarification in the initial phase, thus satisfying the clarifier duality that is required in many states; it will be converted to a digester/thickener in a future plant expansion. The plant can be easily expanded to double the ADF by adding only one GR unit for aeration/clarification. In Cass County, Mich., a dual train GR system is currently operated with one unit as an aeration/clarification unit while the other basin serves as a digester/thickener. The thickener can be easily and quickly converted to a clarifier if needed. The Schreiber process equipment, along with two tertiary Fuzzy Filters, allows the plant to achieve a total phosphorus concentration of less than 0.2 mg/L.

Even non-Schreiber process plants that are undergoing expansion can benefit from aerobic digesters. Schreiber is producing equipment for a new standalone digester (GRO) and a thickener that will be installed in an existing anaerobic digester during a plant expansion in Stanford, Ky. In Du Quoin, Ill., two old clarifiers were converted into aerobic digesters during a plant expansion.

In Belleville, Ill., Schreiber installed dual aeration units and dual clarifiers for a 4-mgd plant expansion. The facility is also demolishing an old anaerobic digester and adding a new digestion system during the plant expansion. Schreiber’s ability to use one of the aeration units as a digester during the digester system’s demolition and installation scored big points with the engineer and owner during the process selection phase, especially from a capital standpoint.  Schreiber’s aerobic digesters offer the additional benefits of demonstrating the efficiency and reliability of the Schreiber process, as well as the support and customer service that are hallmarks of Schreiber’s operating philosophy.

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