Leaching behaviour of hazardous demolition waste

Our plain-English summary of Leaching behaviour of hazardous demolition waste, by N. Roussat, J. Méhu, M. Abdelghafour, et al (Waste Management, 2008).

The study

• Authors: N. Roussat, J. Méhu, M. Abdelghafour, P. Brula
• Journal: Waste Management
• Published: 2008;28(11):2032-40
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Demolition wastes are generally disposed of in unlined landfills for inert waste. However, demolition wastes are not just inert wastes. Indeed, a small fraction of demolition waste contains components that are hazardous to human health and the environment, e.g., lead-based paint, mercury-contained in fluorescent lamps, treated wood, and asbestos. The objective of this study is to evaluate the release potential of pollutants contained in these hazardous components when they are mixed with inert wastes in unlined landfills. After identification of the different building products which can contain hazardous elements and which can be potentially pollutant in landfill scenario, we performed leaching tests using three different lysimeters: one lysimeter containing only inert wastes and two lysimeters containing inert wastes mixed with hazardous demolition wastes. The leachates from these lysimeters were analysed (heavy metals, chlorides, sulphates fluoride, DOC (Dissolved Organic Carbon), phenol index, and PAH). Finally, we compared concentrations and cumulative releases of elements in leachates with the limits values of European regulation for the acceptance of inert wastes at landfill. Results indicate that limit values are exceeded for some elements. We also performed a percolation column test with only demolition hazardous wastes to evaluate the specific contribution of these wastes in the observed releases.

In plain English

This French laboratory study measured what leaches from demolition rubble mixed with small amounts of hazardous waste, in test columns (lysimeters) simulating an unlined inert-waste landfill. Asbestos was not tested. The authors explained that asbestos is very chemically stable in water and that its health risk comes from inhaling fibres. Three columns were filled with demolition rubble. One held inert waste only. One held a small share of hazardous waste (fluorescent lamps, lead-based paint, treated wood, bituminous surfacing). The third held more of these, plus chimney material and gypsum plaster. Testing ran 190 days, with watering stopped every other week in the last two months; leachate was compared with European limits for inert-waste landfills. Six substances exceeded limits in at least one column containing hazardous waste: arsenic, cadmium, chromium, fluoride, sulphates and dissolved organic carbon. Chromium was above the limit in all three columns. A separate test of the hazardous wastes alone also exceeded several limits. The authors concluded that hazardous wastes significantly increased pollutants in leachate, that sulphates came from gypsum, and that selective deconstruction before demolition is necessary.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory leaching experiment: three lysimeters (test columns) simulating an inert waste landfill scenario, tested over 190 days with watering stopped 1 week out of 2 in the last 2 months, plus a standard TS14405 percolation column test of the hazardous wastes alone
• Who was studied: Reconstituted samples of real demolition waste (concrete, foundation, bricks, soils, tiles; 570 to 575.6 kg per lysimeter). The three samples were a 'reference' sample with inert waste only, a 'little polluted' sample and an 'over polluted' sample. The study was carried out at INSA-Lyon, France.
• Exposure: Leaching of pollutants from hazardous building wastes mixed with inert waste. The wastes tested were fluorescent lamps, lead-based paint, chimney duct with soot, treated wood (a copper, boron and propiconazol product, not CCA), bituminous surfacing, and gypsum plaster. Asbestos was deliberately not included in the tests.
• Main results:
  • In at least one sample containing hazardous waste, six elements exceeded European limit values (concentration or cumulative release): arsenic, cadmium, chromium, fluoride, sulphates and DOC (dissolved organic carbon).
  • For DOC, only the 'over polluted' sample exceeded the limit, in its first eluate: 263 mg/l against a limit of 160 mg/l.
  • Cadmium in the 'over polluted' sample exceeded the limit once, in the fourth-week eluate, and only slightly: 0.021 mg/l against a limit of 0.020 mg/l.
  • Chromium concentrations were above the 0.1 mg/l limit in all three lysimeters, including the reference sample.
  • Cumulative sulphate releases were above the L/S = 2 limit of 560 mg/kg for all three samples.
  • Fluoride and arsenic concentrations were much higher than the limit values (2.5 mg/l for fluoride, 0.06 mg/l for arsenic).
  • Mercury was the only analysed element not detected in the lysimeter leachates.
  • PAH concentrations in leachate from the 'over polluted' sample were much higher than in the other two samples.
  • In the percolation column test of hazardous wastes alone, DOC was about ten times the limit value. Arsenic, copper, zinc, fluoride and sulphates also exceeded limits, copper by a wide margin.
• The authors' conclusion: The authors concluded that hazardous wastes cause a significant increase of pollutants in leachate, in particular arsenic, fluoride, chromium, DOC and PAH. They found that sulphate releases come from gypsum rather than from the hazardous wastes. In their view, selective deconstruction before demolition is necessary.
• Limitations the authors state:
  • The lysimeter results alone did not show that the released pollutants came specifically from the hazardous wastes, which is why the column test was added.
  • Some PAH may have been adsorbed by clean materials in the column and so not detected in the leachate.
  • The authors could not determine the source of cadmium in the 'over polluted' sample.
  • The total liquid/solid ratio of the lysimeters (1.3) was below 2, but the results were still compared with the L/S = 2 limit values.

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