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This article in JEQ

  1. Vol. 26 No. 3, p. 782-788
    Received: June 13, 1996

    * Corresponding author(s): bkr2@cornell.edu


Effect of Processing Mode on Trace Elements in Dewatered Sludge Products

  1. Brian K. Richards *,
  2. John H. Peverly,
  3. Tammo S. Steenhuis and
  4. Barry N. Liebowitz
  1. Dep. of Agric. & Biological Eng., Riley-Robb Hall, Cornell Univ., Ithaca, NY 14853;
    Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907;
    New York State Energy Res. & Dev. Authority, Corporate Plaza West, 286 Washington Ave. Ext., Albany, NY 12203.



Minimization of the concentration and mobility of trace metals is a primary concern when considering the land application of wastewater sludges. The effects of pelletization/drying, composting, incineration, and N-Viro chemical stabilization on composition and mobility of trace metals and P were compared. One day's production of dewatered digested sludge (Syracuse, NY) was used as the sole feedstock so that observed differences would solely be a result of the process used. Mobility was determined using the toxic characteristic leaching procedure (TCLP). Analyte concentrations were essentially constant during dewatered sludge production with mean values (mg kg−1 TS) of 5.6 Cd, 10.7 Co, 130 Cr, 587 Cu, 49.7 Mo, 35.8 Ni, 26 880 P, 132 Pb, and 545 Zn. Concentrations in pellets were similar to dewatered sludge, but were reduced in composted sludge and N-Viro product by the addition of amendments. Incineration concentrated all analytes except Cd and Pb, which experienced volatilization losses. The mode of processing had widely ranging effects on mobilities. The TCLP-mobile fraction (percent of total) of analytes in dewatered sludge was <3% except Ni (7.1%), P (6.0%), and Zn (11.2%). Composting slightly increased Cd mobility, but reduced that of Ni and P. Pelletization increased the mobility of Cd (7.9%), Cu (3.8%), Ni (15.4%), and Zn (15%). The N-Viro process substantially increased mobilities of Cu (43%), Mo (50%), and Ni (24%) at elevated pH. Incineration increased mobilities of Cd and Mo, but reduced Ni, P, and Zn mobility. These results, with those of longer term in situ studies, can be used to guide the selection of sludge processes that minimize potential metal and P mobility.

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