1,721,101 research outputs found
Bioreactor tests preliminary to landfill in situ aeration: A case study
No full textLab scale tests in bioreactor were carried out in the framework of the characterization studies of a landfill
where in situ aeration (possibly followed by landfill mining) had been proposed as part of the novel waste
management strategy in a region in northern Italy.
The tests were run to monitor the effects produced by aerobic conditions at different temperatures on
waste sampled at different depths in the landfill, with focus on the carbon and nitrogen conversion during
aeration. Temperatures ranging from 35 to 45 C were chosen, in order to evaluate possible inhibition
of biodegradation processes (namely nitrification) at 45 C in the landfill.
The results obtained showed positive effects of the aeration on leachate quality and a significant reduction
of waste biodegradability. Although a delay of biodegradation processes was observed in the reactor
run at 45 C, biodegradation rates increased after 2 months of aeration, providing very low values of the
relevant parameters (as in the other aerated reactors) by the end of the study.
Mass balances were carried out for TOC and N-NH4+; the findings obtained were encouraging and provided
evidence of the effectiveness of carbon and nitrogen conversion processes in the aerated landfill
simulation reactors
Leaching of organic compounds from waste and soils
No full textThe desorption characteristics of organic pollutants were determined for different
media. Emphasis was placed on the desorption of policyclic aromatic hydrocarbons (PAHs) and
BTEX (Benzene, Toluene, Ethylbenzene, Xylenes). The first group includes substances that sorb
strongly to the soil, are only partially soluble in water and are non volatile. The separation of the
solid phase from the eluate was found to be especially crucial to the testing. The second group
comprises volatile compounds with a relative high solubility in water. In relation to the testing of
the substance leaching, dispersion of the compounds to the air was the critical issue.
Factors that have been investigated in more detail are the effects of the organic carbon content
of the media, the contact time between the material and the leaching medium, the liquid to solid
ratio (L/S) and the facilitated leaching due to transport with soil-constituent DOC, colloids or
particles. The experiments include both batch and column test
Tests for the evaluation of ammonium attenuation in MSW landfill leachate by adsorption into bentonite in a landfill liner
No full textUncontrolled leachate emissions are one of the key factors in the environmental impact of municipal solid waste (MSW) landfills. The concentration of ammonium, given the anaerobic conditions in traditional landfills, can remain significantly high for a very long period of time, as degradation does not take place and volatilisation is not significant (the pH is not high enough to considerably shift the equilibrium towards un-ionised ammonia).
Recent years have witnessed a continuous enhancement of landfill technology in order to minimize uncontrolled emissions into the environment; bottom lining systems have been improved and more attention has been devoted to the study of the attenuation of the different chemicals in leachate in case of migration through the mineral barrier.
Different natural materials have been considered for use as components of landfill liners in the last years and tested in order to evaluate the performance of the different alternatives. Among those materials, bentonite is often used, coupled with other materials in two different ways: in addition to in situ soil or in geocomposite clay liner (GCL).
A lab-scale test was carried out in order to further investigate the influence of bentonite on the attenuation of ammonium in leachate passing through a landfill liner. Two different tests were conducted: a standardized batch test with pulverized bentonite and a batch test with compacted bentonite. The latter was proposed in order to better simulate the real conditions in a landfill liner.
The two tests produced values for the partition coefficient K-d higher than the average measured for other natural materials usually utilized as components of landfill liners. Moreover, the two tests showed similar results, thus providing a further validation of the suitability of the standard batch test with pulverized bentonite.
A thorough knowledge of attenuation processes of ammonium in landfill liners is the basis for the application of risk analysis models for the evaluation of the failure of bottom liners or their components
Landfill aeration in the framework of a reclamation project in Northern Italy
No full textIn situ aeration by means of the Airflow technology was proposed for landfill conditioning before landfill
mining in the framework of a reclamation project in Northern Italy. A 1-year aeration project was carried
out on part of the landfill with the objective of evaluating the effectiveness of the Airflow technology for
landfill aerobization, the evolution of waste biological stability during aeration and the effects on leachate
and biogas quality and emissions.
The main outcomes of the 1-year aeration project are presented in the paper.
The beneficial effect of the aeration on waste biological stability was clear (63% reduction of the respiration
index); however, the effectiveness of aeration on the lower part of the landfill is questionable, due
to the limited potential for air migration into the leachate saturated layers.
During the 1-year in situ aeration project approx. 275 MgC were discharged from the landfill body with
the extracted gas, corresponding to 4.6 gC/kgDM. However, due to the presence of anaerobic niches in the
aerated landfill, approx. 46% of this amount was extracted as CH4, which is higher than reported in other
aeration projects. The O2 conversion quota was lower than reported in other similar projects, mainly due
to the higher air flow rates applied.
The results obtained enabled valuable recommendations to be made for the subsequent application of
the Airflow technology to the whole landfill
Test methods for assessing the biological stability of biodegradable waste
No full textThis paper presents some results of investigations for the characterization of waste excavated from closed landfills and of waste sampled during mechanical-biological pretreatment before disposal in landfill. The results reported are those obtained with the tests carried out for the assessment of the biological stability of the waste. Some of the considered tests, such as the ones for the determination of the respiration activity and the biogas production, are well known and have been applied for years; other tests, such as the ones for the determination of BOD5 and COD in leaching test eluate and of the black index, are among the tests considered by the international research community for possible utilization for the evaluation of waste biological stability. Good correlations were found for most of the results obtained, proving the reliability of the test methods used. In particular, the effectiveness of biodegradation during waste pretreatment processes can be easily monitored by measuring the respiration index and/or the BOD5 and COD in leaching test eluate; for the characterization of waste from landfills, the use of respiration index can be recommended. In both cases the COD in leaching test eluate may provide additional useful information especially in the case of low values for the respiration index. Moreover, the black index test may be considered with some limits that will be discussed, providing good results in a simple and cost effective way
Use of the Contingent Valuation Method in the assessment of a landfill mining project
No full textA comprehensive approach for the evaluation of the economic feasibility of landfill mining (LFM) should
take into account not only the direct costs and revenues for the private investor, but also the social benefits
or costs (generally called externalities), in such a way that projects generating major social benefits
(and no significant private revenues) are not overlooked.
With a view to contributing to the development of a common framework for the evaluation of LFM projects,
this paper presents the results of a case study where the issue of the assessment of social benefits
from a LFM project is addressed. In particular, the Contingent Valuation Method is applied for the monetary
assessment of the community-perceived benefits from the remediation of an old uncontrolled
waste deposit by means of LFM and the conversion of the area into a park.
Based on the results of a survey carried out on a random sample of people living near the old landfill,
the economic values of the individual willingness to pay (WTP) for LFM and the subsequent creation of a
public park were calculated and the correlations with the relevant variables (distance from the landfill
site, age, income, sex, education level) assessed. The results were then suitably extended and the monetary
value of the welfare increase of the whole population resident in the area and potentially affected
both by LFM and the creation of the park was calculated
LAB SCALE TESTS BEFORE IN SITU AEROBIC STABILIZATION OF AN OLD LANDFILL
No full textLab scale tests in bioreactor were carried out in the framework of the
characterization studies of a landfill where in situ aeration followed by landfill mining has been proposed as part of the novel waste management strategy in a region in northern Italy. The results obtained showed positive effects of the aeration on leachate quality and a significant reduction of waste putrescibility. The experiments were carried out with focus on carbon and
nitrogen balance in the reactors; the data obtained provided information to be considered for full scale application
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