Regrowth of fecal coliforms in class A biosolids. |
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Authors: | Domènec Jolis |
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Affiliation: | Clean Water Enterprise, Public Utilities Commission, San Francisco, CA 94124, USA. djolis@sfwater.org |
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Abstract: | Eight types of Class A biosolids were tested for fecal coliform (FC) reactivation and/or regrowth at 20, 35, and 50 degrees C for 21 days. Growth of FC did not occur at 20 or 50 degrees C, but it was observed in two samples incubated at 35 degrees C after a lag period of 48 hours. In undigested biosolids, final FC concentration exceeded 10(4) MPN/g, whereas in thermophilically digested biosolids, the final FC concentration remained below 10(3) MPN/g, as FC regrowth may have been affected by the presence of the anaerobic bacterial consortium responsible for the digestion process. Fecal-coliform reactivation and regrowth within treatment plant operations seem unlikely but can occur in land application of biosolids. |
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