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Modern landfill leachates – quality and treatment

Modin, Hanna LU (2012) Report 1054.
Abstract (Swedish)
Popular Abstract in Swedish

Deponier (soptippar) har förändrats kraftigt de senaste decennierna. Detta beror främst på ändrad lagstiftning vilken i sin tur till stor del bygger på en önskan att skydda miljön. Dock har lag¬stiftningen implementerats utan riktig kännedom om dess konsekvenser för utsläppen från deponier på lång sikt. För att öka förståelsen för konsekvenserna genomfördes det forsknings¬projekt som beskrivs här. Resultaten visar att även om utsläppen av organiskt material och näringsämnen är mycket mindre ur moderna deponier så är skillnaderna mellan äldre och nyare deponiers inre inte så stora som kunde förväntas, i alla fall inte på kort sikt. Detta gör att utsläppen av tungmetaller blir i ungefär samma... (More)
Popular Abstract in Swedish

Deponier (soptippar) har förändrats kraftigt de senaste decennierna. Detta beror främst på ändrad lagstiftning vilken i sin tur till stor del bygger på en önskan att skydda miljön. Dock har lag¬stiftningen implementerats utan riktig kännedom om dess konsekvenser för utsläppen från deponier på lång sikt. För att öka förståelsen för konsekvenserna genomfördes det forsknings¬projekt som beskrivs här. Resultaten visar att även om utsläppen av organiskt material och näringsämnen är mycket mindre ur moderna deponier så är skillnaderna mellan äldre och nyare deponiers inre inte så stora som kunde förväntas, i alla fall inte på kort sikt. Detta gör att utsläppen av tungmetaller blir i ungefär samma storleksordning.

Deponier orsakar utsläpp till luft och vatten. Fram till för inte så länge sedan slängdes vad som helst på en deponi, till exempel stora mängder hushållsavfall. Som de flesta vet så innehöll en vanlig soppåse en stor andel nedbrytbart material, bland annat matrester. När detta bryts ned i deponin förbrukas syre och därför är de flesta deponier syrefria. När organiskt material bryts ned i den syrefria miljön bildas så kallad deponigas som är en växthusgas. Vatten som kommer i kontakt med avfallet i deponin kallas för lakvatten och innehåller en mängd olika för¬o¬ren¬ingar. De största miljöproblemen med lakvatten har hittills varit orsakade av organiskt material och salter, inklusive näringsämnen. För att komma tillrätta med miljö¬problemen har lag¬stiftarna förbjudit deponering av organiskt avfall. Eftersom det är biologiska ned¬brytnings¬processer som styr lakvattnets sammansättning i gamla deponier så kan moderna deponier med små mängder organiskt material förväntas vara väldigt annorlunda. På vad sätt de är annorlunda var huvudfrågan för det aktuella forskningsprojektet.

Resultaten visar att det trots allt går att uppmäta en liten nedbrytningspotential i sådant avfall som hamnar på moderna deponier. Därför kan syrefria förhållanden uppstå även där. Utsläppen av deponi¬gas kommer troligen inte att bli särskilt stora, men syrebristen verkar leda till att lakvattnets kemi inte blir så annorlunda som förväntat. Läckaget av tungmetaller påverkas kraftigt av syre¬tillgången, och det har funnits farhågor om att utsläppen av metaller skulle vara mycket större i moderna deponier. Så verkar dock inte vara fallet; de verkar bli ungefär lika stora eller något större. Forskningen visar att vissa metaller kan komma att ha förhöjda halter i lakvattnet även efter lång tids urlakning, så i likhet med äldre deponier kan de moderna förväntas vara en belastning under lång tid vilket i deponisammanhang kan betyda decennier, århundraden eller ännu längre.

Den största skillnaden mellan lakvatten från moderna och gamla deponier är de låga halterna av organiskt kol och ammonium i de moderna. Ammonium betraktas som den allvarligaste föroreningen från gamla deponier på lång sikt, men i vissa moderna deponier är dess halter extremt låga. Det betyder att i framtiden behöver reningen av lakvatten inte längre fokusera på organiskt material och närings-ämnen vilket varit vanligast hittills. I stället kan den fokusera på att ta hand om till exempel tungmetaller. En del av studien handlade om att rena lakvatten från tungmetaller med olika filter. Aktivt kol, benmjöl och järnfilspån visade sig kunna avskilja många metaller, men inget material kunde ensamt ta bort alla. En kombination av filtermaterial skulle kunna vara ett relativt billigt sätt att rena framtidens lakvatten, men det är viktigt att tänka på att det material som fungerar för ett vatten kanske inte fungerar för ett annat. (Less)
Abstract
Waste management in Europe has changed, mainly as a result of stricter regulations, most notably the European Landfill Directive 1999/31/EC. In Sweden, landfill tax and a ban on the landfilling of waste with total organic carbon content over 10 % have diverted large amounts of waste from landfills. The biogeochemistry of landfills has changed due to their reduced organic content. The research presented in this thesis aimed at improving understanding of leachate quality in modern landfills. Biodegradation and leaching tests were employed on wastes typical of a waste manage¬ment system shifting away from landfilling. Multivariate data analysis using principal component analysis and canonical correlation analysis was employed to identify... (More)
Waste management in Europe has changed, mainly as a result of stricter regulations, most notably the European Landfill Directive 1999/31/EC. In Sweden, landfill tax and a ban on the landfilling of waste with total organic carbon content over 10 % have diverted large amounts of waste from landfills. The biogeochemistry of landfills has changed due to their reduced organic content. The research presented in this thesis aimed at improving understanding of leachate quality in modern landfills. Biodegradation and leaching tests were employed on wastes typical of a waste manage¬ment system shifting away from landfilling. Multivariate data analysis using principal component analysis and canonical correlation analysis was employed to identify processes governing leachate quality and relations between leachate parameters. As heavy metals are expected to be relatively more pronounced in modern landfills, sorption to granular activated carbon, bone meal and iron fines was evaluated as a means of removing heavy metals from leachate.

The main difference in two leachates from landfills with less than 10 % organic carbon in the waste in relation to leachates from older landfills containing municipal solid waste was the extremely low ammonium content. Very low dissolved organic carbon content was also observed. Leaching of heavy metals in the same order of magnitude as in MSW landfills was observed in modern landfills. The results further indicate that a certain degradation potential must be expected, even in the carbon poor wastes deposited in modern landfills. Therefore reducing conditions will be likely to occur in the landfills. Although landfill gas formation will be low, degradation is likely to significantly affect the biogeochemical conditions, thus affecting metal leaching and rendering it relatively similar to that in municipal solid waste landfills. However, since the amounts of biodegradable organic matter are smaller they will be depleted sooner than in municipal solid waste landfills. As a result, the long term differences may be greater.

The multivariate data analysis identified variation in the concentration of salts as the most important process governing leachate quality. This variation had various causes, including dilution, depletion and varying input materials. Redox potential was also identified as an important process. In the cases where samples were taken before and after treatment, the effect of the treatment strongly influenced the results. All the sorption materials studied had the potential to remove heavy metals, but none was effective against all the metals in the leachate. They also all had the drawback of releasing unwanted substances into the leachate. This illustrates the importance of site-specifically evaluating all treatments and analysing a large number of substances in the leachates, not just those targeted by the treatment.

The main pollutants to be expected in modern landfills with only small amounts of organic matter will probably be inorganic, e.g. heavy metals. While the organic matter emitted by older landfills can be changed into more or less inert forms, metals can never be destroyed, just concentrated, diluted or moved to another medium. Enhancing biodegradation and flushing pollutants by allowing water to infiltrate into landfills is advocated as a sustainable management option for municipal solid waste landfills. However, in the case of mainly inorganic landfills, containment aimed at keeping the metals in the landfills for as long as possible rather than dispersing them into the environment might be a better option. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Docent Kjeldsen, Peter, Residual Resources Engineering, Department of Environmental Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Heavy metals, European Landfill Directive, Biodegradation, Landfill leachate, Leaching tests, Multivariate data analysis, Organic matter, Sorption filters
volume
Report 1054
pages
184 pages
publisher
Water Resources Engineering, Lund University
defense location
Lecture hall V:B, Department of Building and Environmental Technology, John Ericssons väg 1, Lund University Faculty of Engineering
defense date
2012-04-20 10:15
external identifiers
  • other:CODEN: LUTVDG/(TVVR-1054)(2012)
ISSN
1101-9824
ISBN
978-91-7473-286-3
language
English
LU publication?
yes
id
d42d4993-7a95-4cc5-a8e8-6c3ef2507e2f (old id 2374071)
date added to LUP
2012-03-27 13:14:57
date last changed
2016-09-19 08:44:48
@phdthesis{d42d4993-7a95-4cc5-a8e8-6c3ef2507e2f,
  abstract     = {Waste management in Europe has changed, mainly as a result of stricter regulations, most notably the European Landfill Directive 1999/31/EC. In Sweden, landfill tax and a ban on the landfilling of waste with total organic carbon content over 10 % have diverted large amounts of waste from landfills. The biogeochemistry of landfills has changed due to their reduced organic content. The research presented in this thesis aimed at improving understanding of leachate quality in modern landfills. Biodegradation and leaching tests were employed on wastes typical of a waste manage¬ment system shifting away from landfilling. Multivariate data analysis using principal component analysis and canonical correlation analysis was employed to identify processes governing leachate quality and relations between leachate parameters. As heavy metals are expected to be relatively more pronounced in modern landfills, sorption to granular activated carbon, bone meal and iron fines was evaluated as a means of removing heavy metals from leachate.<br/><br>
The main difference in two leachates from landfills with less than 10 % organic carbon in the waste in relation to leachates from older landfills containing municipal solid waste was the extremely low ammonium content. Very low dissolved organic carbon content was also observed. Leaching of heavy metals in the same order of magnitude as in MSW landfills was observed in modern landfills. The results further indicate that a certain degradation potential must be expected, even in the carbon poor wastes deposited in modern landfills. Therefore reducing conditions will be likely to occur in the landfills. Although landfill gas formation will be low, degradation is likely to significantly affect the biogeochemical conditions, thus affecting metal leaching and rendering it relatively similar to that in municipal solid waste landfills. However, since the amounts of biodegradable organic matter are smaller they will be depleted sooner than in municipal solid waste landfills. As a result, the long term differences may be greater.<br/><br>
The multivariate data analysis identified variation in the concentration of salts as the most important process governing leachate quality. This variation had various causes, including dilution, depletion and varying input materials. Redox potential was also identified as an important process. In the cases where samples were taken before and after treatment, the effect of the treatment strongly influenced the results. All the sorption materials studied had the potential to remove heavy metals, but none was effective against all the metals in the leachate. They also all had the drawback of releasing unwanted substances into the leachate. This illustrates the importance of site-specifically evaluating all treatments and analysing a large number of substances in the leachates, not just those targeted by the treatment.<br/><br>
The main pollutants to be expected in modern landfills with only small amounts of organic matter will probably be inorganic, e.g. heavy metals. While the organic matter emitted by older landfills can be changed into more or less inert forms, metals can never be destroyed, just concentrated, diluted or moved to another medium. Enhancing biodegradation and flushing pollutants by allowing water to infiltrate into landfills is advocated as a sustainable management option for municipal solid waste landfills. However, in the case of mainly inorganic landfills, containment aimed at keeping the metals in the landfills for as long as possible rather than dispersing them into the environment might be a better option.},
  author       = {Modin, Hanna},
  isbn         = {978-91-7473-286-3},
  issn         = {1101-9824},
  keyword      = {Heavy metals,European Landfill Directive,Biodegradation,Landfill leachate,Leaching tests,Multivariate data analysis,Organic matter,Sorption filters},
  language     = {eng},
  pages        = {184},
  publisher    = {Water Resources Engineering, Lund University},
  school       = {Lund University},
  title        = {Modern landfill leachates – quality and treatment},
  volume       = {Report 1054},
  year         = {2012},
}