Abstract
Municipal solid waste (MSW) and sewage sludge (SS) were combined and anaerobically converted into carboxylate salts by using a mixed culture of acid-forming microorganisms. MSW is an energy source and SS is a source of nutrients. In this study, MSW and SS were combined, so they complemented each other. Four fermentors were arranged in series for a countercurrent fermentation process. In this process, the solids and liquid were transferred in opposite directions, with the addition of fresh biomass to fermentor 1 and fresh liquid media to fermentor 4. An intermediate lime treatment of solids exiting fermentor 3 before entering fermentor 4 was applied to improve the product acid concentration from the untreated MSW/SS fermentations. All fermentations were performed under anaerobic conditions at 40°C. Calcium carbonate was added to neutralize the carboxylic acids and to control the pH. Iodoform was used as a methanogen inhibitor. Carboxylic acid concentration and gas composition were determined by gas chromatography. Substrate conversion was measured by volatile solids loss, and carboxylic acid productivity was calculated as the function of the total carboxylic acids produced, the amount of liquid in all fermentors, and time. The addition of intermediate lime treatment increased product concentration and conversion by approx 30 and 15%, respectively. The highest carboxylic acid concentrations for untreated MSW/SS fermentations with and without intermediate lime treatment were 22.2 and 17.7 g of carboxylic acid/L of liquid, respectively. These results confirm that adding a treatment step between fermentor 3 and fermentor 4 will increase the digestibility and acid productivity of the fermentation.
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Holtzapple, M. T., Ross, M. K., Chang, N. S., Chang, V. S., Aldelson, S. K., and Brazel, C. (1997), In ACS Symposium Series 666, Saha, B. C. and Woodward, J., eds., American Chemical Society, Washington, DC, pp. 130–142.
Hileman, B. (1999), Chem. Eng. News 77, 16–23.
EPA. (1998), Municipal Solid Waste Generation, Recycling and Disposal in the United States: Facts and Figures for 2003, Environmental Protection Agency, Washington, DC, www.epa.gov/garbage/pubs/msw05rpt.pdf.
EPA. (1999), Biosolids Generation, Use and Disposal in the United States, 1977. US EPA 530-R-99-009, Environmental Protection Agency, Washington, DC, www.epa.gov/oigearth/ereading_room/BIOSOLIDS_FINAL_REPORT.pdf.
Sterzinger, G. (1995), Technol. Rev. 98, 34–40.
DeBaere, L., Verdonck, O., and Verstraete, W. (1985), Biotechnol. Bioeng. Symp. 15, 321–330.
Ghosh, S., Conrad, J. R., and Klass, D. L. (1975), J. Water Pollut. Control Fed. 47, 30–45.
Holtzapple, M. T., Davison, R. R., Ross, K., et al. (1999), Appl. Biochem. Biotechnol. 77/79, 609–631.
Aiello-Mazzarri, C. (2002), PhD dissertation, Texas A&M University, College Station.
Rapier, C. R. (1995), MS thesis, Texas A&M University, College Station.
Ross, M. K. (1998), PhD dissertation, Texas A&M University, College Station.
Groleau, D., and Frosberg, C. W. (1981), Can. J. Microbiol. 27, 517–530.
Holtzapple, M. T., Lundeen, J. E., Sturgiss, R., Lewis, J. E., and Dale, B. E. (1992), Appl. Biochem. Biotechnol. 34, 5–21.
Caldwell, D. R., and Bryant, M. P. (1966), Appl. Microbiol. 14, 794–801.
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Aiello-Mazzarri, C., Coward-Kelly, G., Agbogbo, F.K. et al. Conversion of municipal solid waste into carboxylic acids by anaerobic countercurrent fermentation. Appl Biochem Biotechnol 127, 79–93 (2005). https://doi.org/10.1385/ABAB:127:2:079
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DOI: https://doi.org/10.1385/ABAB:127:2:079