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This article in JEQ

  1. Vol. 10 No. 1, p. 54-59
    Received: July 12, 1980

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Modeling Sewage Sludge Decomposition in Soil: I. Organic Carbon Transformation1

  1. Y. P. Hsieh,
  2. Lowell A. Douglas and
  3. Harry L. Motto2



Mineralization of an activated and a digested sewage sludge in soil was studied in laboratory incubations. The activated sludge had a much higher mineralization rate than the digested sludge, mainly due to a larger portion of active organic carbon and less stability of the organic matter. After around 2 months of incubation, the mineralization rates of both sludges approached a square foot function of time. The amount of active organic carbon is a characteristic of sewage sludge and is important in determining the aerobic-anaerobic status of the system. The mineralization of sewage sludges was proportional to the rate of sludge application at least up to 8% in the digested sludge and up to 4% in the activated sludge systems at 22°C. Between 8 and 22°C, the mineralization rate of sludges in soil increased about 1.9 times for every 10°C increase in temperature. Moisture levels between 0.06 and 0.33 bars had no significant effect on mineralization of the sludges. A regression model was developed in the form of an exponential function among the cumulative organic carbon mineralized and factors of time, sludge rate, and temperature. The model requires a minimal number of parameters to define the system and was least biased in regression analysis over a wide range of conditions.

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