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lecture18 - Lecture 18 Leachate and gas production in...

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Unformatted text preview: Lecture 18 Leachate and gas production in landfills Mass balance for MSW landfill Waste in Leachate + gas + transformed mass + waste remaining Precipitation and ground-water inflow leachate + moisture in waste Collection systems Leachate collection Gas collection Compacted soil liner Secondary FML Drainage/protection layer with secondary leachate collection system Solid waste Drainage/protection layer with primary leachate collection system Primary FML Geotextile Gas Vent Layer Geotextile Barrier Protection Top Soil Cover Vegetative Cover Drainage Layer FML Factors that influence leachate generation Precipitation Ground-water intrusion Moisture content of waste Particularly if sludge or liquids are disposed Daily cover during filling period Final cover design Leachate generation at MSW landfill Adapted from: Qian, X., R. M. Koerner, and D. H. Gray. Geotechnical Aspects of Landfill Design and Construction . Upper Saddle River, New Jersey: Prentice Hall, 2002. Jul-88 Jan-89 Jan-90 Jul-89 500 1000 1500 2000 2500 3000 3500 4000 Jul-90 Jan-91 Jul-91 Jul-92 Jan-92 Jan-93 Jan-94 Jul-93 Date LCRS Flow Rate (1phd) Active Filling Cover Installed Cell Closed LCRS = Leachate Collection and Removal System lphd = Liters per hectare per day 1 lphd = 3.65 mm/yr. 1000 mm/yr = 27,400 lphd Average annual precipitation: 1000 mm/yr (39.4 in/year). Closure included placement of a geomembrane cover. Estimating leachate generation in active landfill L A = P + S E WA L A = leachate from active area P = precipitation S = pore squeeze liquid from waste E = evaporation WA = waste moisture adsorption (all in units of L 3 /T) Precipitation See image at the Web site of the National Atmospheric Deposition Program, http://nadp.sws.uiuc.edu/isopleths/maps2002/ppt.gif Accessed May 13, 2004. Pore squeeze liquid Negligible for most wastes Can be significant for wastewater sludges measured in laboratory tests Evaporation Source: Hanson, R.L., 1991, Evapotranspiration and Droughts, in Paulson, R.W., Chase, E.B., Roberts, R.S., and Moody, D.W., Compilers, National Water Summary 1988-89--Hydrologic Events and Floods and Droughts: U.S. Geological Survey Water-Supply Paper 2375, p. 99-104. http://geochange.er.usgs.gov/sw/changes/natural/et/ Moisture adsorption by waste Typical initial moisture content of waste 1.5 in/ft 12 cm/m Field capacity of waste 4 in/ft 33 cm/m Available moisture adsorption capacity of waste 2.5 in/ft 21 cm/m Source: Bagchi, A., 1994. Design, Construction, and Monitoring of Sanitary Landfill , Second Edition. John Wiley & Sons, New York. Leachate generation at active MSW landfill F e b- 9 7 M a r- 9 7 A p r- 9 7 M a y- 9 7 J u n- 9 7 J u l- 9 7 A u g- 9 7 S e p- 9 7 O c t- 9 7 N o v- 9 7 D e c- 9 7 J a n- 9 8 F e b- 9 8 M a r- 9 8 A p r- 9 8 M a y- 9 8 J u n- 9 8 J u l- 9 8 A u g- 9 8 S e p- 9 8 O c t- 9 8 N o v- 9 8 D e c- 9 8 J a n- 9 9 F e b- 9 9 M a r- 9 9 A p r- 9 9 M a y- 9 9 J u n- 9 9 J u l- 9 9 A u g- 9 9 20 40 60 80 100 120 140 160 180...
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This note was uploaded on 12/06/2011 for the course ESD 1.34 taught by Professor Petershanahan during the Spring '04 term at MIT.

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lecture18 - Lecture 18 Leachate and gas production in...

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