Effect of calcium oxide dose on thermal reactions, lime speciation, and physical properties of alkaline stabilized biosolids
Authors: Smith, Karen A.; Goins, Lori E.; Logan, Terry J.
Source: Water Environment Research, Volume 70, Number 2, March/April 1998 , pp. 224-230(7)
Publisher: Water Environment Federation
Abstract:Quicklime (CaO) was added to a single sample of dewatered biosolids at rates of 5, 15, 20, 25, 30, 40, and 50% by weight (based on wet weight of the dewatered biosolids) in the laboratory. Temperature rise and water loss were monitored to determine caloric energy expended in heating and evaporation, and these values were compared to heat generation. The limed biosolids were analyzed by x-ray diffraction and thermal gravimetric analysis to determine the lime species present, and the pH rise when added to selected soils. Effects of lime dose on biosolids physical properties were examined by measuring selected physical characteristics of the limed products. Addition of CaO to dewatered biosolids produces heat through the exothermic conversion of CaO to hydrated lime [Ca(OH)2] with only small amounts of heat produced from the exothermic reaction of carbon dioxide (CO2) with Ca(OH)2 to form calcium carbonate (CaCO3). All heat produced was dissipated during heating of the biosolids and evaporation of water. Because of the predominance of Ca(OH)2 in the limed biosolids, care should be taken in using these materials as liming agents and soil amendments because of the very high initial soil pHs (greater than pH 12) that can persist for weeks or more. Increasing lime dose improved the density and water-holding capacity of biosolids and improved their physical consistency.
Document Type: Research article
Publication date: 1998-03-01
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