Geochemical modeling of leaching from MSWI air-pollution control residues
Astrup, T. ; Dijkstra, J.J. ; Comans, R.N.J. ; Sloot, H.A. van der; Christensen, T.H. - \ 2006
Environmental Science and Technology 40 (2006)11. - ISSN 0013-936X - p. 3551 - 3557.
incinerator bottom ash - solid-waste combustion - fly-ash - part ii - solubility - speciation - landfill - leachate - field - identification
This paper provides an improved understanding of the leaching behavior of waste incineration air-pollution-control (APC) residues in a long-term perspective. Leaching was investigated by a series of batch experiments reflecting leaching conditions after initial washout of highly soluble salts from residues. Leaching experiments were performed at a range of pH-values using carbonated and noncarbonated versions of two APC residues. The leaching data were evaluated by geochemical speciation modeling and discussed with respect to possible solubility control. The leaching of major elements as well as trace elements was generally found to be strongly dependent on pH. As leaching characterization was performed in the absence of high salt levels, the presented results represent long-term leaching after initial washout from a disposal site, that is, liquid-to-solid ratios above 1-2 L/kg. The leaching of Al, Ba, Ca, Cr, Pb, S, Si, V, and Zn was found influenced by solubility control from Al2O3, Al(OH)3, Ba(S,Cr)O4 solid solutions, BaSO4, Ca6Al2(SO4)3(OH)12·26H2O, CaAl2Si4O12·2H2O, Ca(OH)2, CaSiO3, CaSO4·2H2O, CaZn2(OH)6·2H2O, KAlSi2O6, PbCO3, PbCrO4, Pb2O3, Pb2V2O7, Pb3(VO4)2, ZnO, Zn2SiO4, and ZnSiO3. The presented dataset and modeling results form a thorough contribution to the assessment of long-term leaching behavior of APC residues under a wide range of conditions.
Effect of inoculum addition modes and leachate recirculation on anaerobic digestion of solid cattle manure in an accumulation system
El-Mashad, H.M. ; Loon, W.K.P. van; Zeeman, G. ; Bot, G.P.A. ; Lettinga, G. - \ 2006
Biosystems Engineering 95 (2006)2. - ISSN 1537-5110 - p. 245 - 254.
waste - landfill - fermentation - temperature - degradation - biowaste - batch
The effect of both leachate recirculation (at 40 and 50 °C) and the mode of inoculum addition (at 50 °C) on the performance of a non-mixed accumulation (i.e. fed batch) system treating solid cattle wastes was investigated, using laboratory scale reactors at a filling time of 60 days. A relatively high methane production rate (MPR) and low stratification of intermediates occur with leachate recirculation. The leachate recirculation volume flow and methane production rate are smaller at 40 °C than at 50 °C: 0·31 and 0·7 l [CH4] l¿1 [reactor] day¿1, respectively. The increased MPR at higher temperature is at one hand caused by the increase of microbial activity, at the other hand by the lower viscosity causing the increased leachate recirculation volume. Dividing the inoculum in equal doses and distributing them with the feed positively affects the system behaviour as compared to adding the same inoculum amount at the reactor bottom at the start only. Without addition of inoculum a very poor system performance was observed. The average MPR was 0·2, 0·4 and 0·5 l [CH4] l¿1 [reactor] day¿1 for the reactor without inoculum, inoculum addition at the reactor bottom and inoculum addition in different equal doses, respectively.