Processes that occur during storageand final disposal ofsolid waste were studied, with emphasis on physical andchemical aspects and their effects on the water environment,within the New European Union perspective for landfilling(Council Directive 1999/31/EC, 1999).
In the new scenario, landfilling is largely restricted;waste treatments such as incineration, composting, recycling,storage and transportation of materials are intensified.Landfill sites are seen as industrial facilities rather thanmerely final disposal sites. Four main issues were investigatedwithin this new scenario, infield- and full-scale, mostly atSpillepeng waste management park, southern Sweden.
Adequacy of storage piles. Regarding the increasing demandfor waste storage as fuel, the adequacy of storage in piles wasinvestigated by monitoring industrial waste (IND) fuel pile andrefuse derived fuel (RDF) storage. Intense biodegradationactivity, which raised the temperature into the optimum rangefor chemical oxidation reactions, was noticed during the firstweeks. After about six months of storage, self-ignitionoccurred in one IND fuel pile and in the RDF storage. Heat, O2and CO2distribution at different depths of the monitoredINDpile suggested that natural convection plays an importantrole in the degradation process by supplying oxygen andreleasing heat. The results suggested that storage techniquesthat achieve a higher degree of compaction, such as baling, arepreferable to storage in piles.
Discharge from landfill for special/hazardous waste.Regarding changes in the composition of the waste sent tolandfills and the consequences for its hydrological performancein active and capped landfills, discharge from a full-scalelandfill for special/hazardous waste (predominantly fly ashfrom municipal solid waste (MSW) incineration) was modelledusing the U.S. EPAHELP model. Hydraulic properties of thespecial waste were compared with those from MSW. Lowerpractical field capacity and higher hydraulic conductivity atspecial waste cells led to faster production of greater amountsof discharge (already during operation) in response toinfiltration, than that observed in MSW landfill cells. Thisfeature must be considered when designing on-site leachatetreatment systems for special waste landfills.
Stormwater runoff and pollutant transport. Theintensification of waste handling practices exposed to rainfallat waste management parks in the new scenario led to aninvestigation of about 22 constituents of stormwater runoff andpollutant transport from different areas/activities and roadswithin the Spillepeng site. The concentration values for someparameters in some areas and roads exceeded the concentrationsfound in leachate from covered landfill. Concerning chemicaloxygen demand and nutrients, the stormwater from Spillepengshowed a higher range of median concentration values in thestormwater than is typical of ranges for roadways, andresidential and industrial areas in Sweden. The reverseoccurred for heavy metals, excluding copper.
Groundwater monitoring programmes. In particular, theadequacy of groundwater monitoring programmes at landfillsites, was investigated. Significant differences between up-and down-gradient wells as well as trends not visualized bydirect inspection of time series data were detected withstatistical analyses. The non-parametric rank-sum test was morepowerful and robust than the t-test in detecting differencesbetween up- and down-gradient paired monitoring wells. Theseasonal Kendall test was more powerful than the Mann-Kendalltest to detect trends for individual constituents.Non-parametric slope estimators and the Winter's Method wereused to estimate the time needed to reach the EU mandatorylimits of nitrate and ammonia in potable water. However,indications of aquifer heterogeneity suggest that these trendsmay reflect local effects, rather than a real improvement in,or degradation of, the groundwater quality. Nevertheless, theinclusion of statistical procedures in landfill monitoringprogrammes is suggested, as an additional useful tool.
Keywords: convective flow, groundwater pollution, leachatemodelling, non-parametric statistics, self-ignition, solidwaste, storage of fuel material, stormwater runoff, timeseries.
Stockholm: Kemiteknik , 2000. , xvi, 82 p.