Environmental Engineering Reference
In-Depth Information
TABLE 7.9
Conversion or Transport of Inorganic and Organic Components in a Landill Bioreactor
Component
Transport or Conversion Mechanism
Heavy metals (Cd, Cu, Cr, Fe, Hg, Ni, Pb, Zn)
Reduction of Fe, Cr, Hg
Complexation with organic or inorganic components and
mobilization
Precipitation as hydroxide (Cr) or sulides (Cd, Cu, Fe,
Hg, Ni, Pb, and Zn) after sulfate reduction
Sorption and ion exchange with waste
Precipitation under alkaline conditions
Halogenated aliphatics including PCE, TCE,
dibromomethane
Volatilization and mobilization in leachate due to high
vapor pressure and solubility
Chlorinated benzenes such as hexachlorobenzene,
trichlorobenzene, and dichlorobenzene
Volatilization and sorption on waste due to low solubility
and high k ow
Phenols and nitroaromatics such as
dichlorophenol, nitrophenol, and nitrobenzene
Low volatility, vapor pressure, and k ow , with high
solubility in leachate
PAHs and pesticides (lindane and dieldrin)
Low volatility and mobility due to low vapor pressure
and high k ow
Source:
Adapted from Mulligan C.N., Environmental Biotreatment , Government Institutes, Rockville, MD, 395  pp.,
2002.
uniformly within the waste. The design of leachate collection systems was able at all sites
to maintain leachate levels of under 30 cm of head on the liner. Slope stability was not
problematic and any issues were easily corrected but proper design and operations were
necessary to provide for slope stability. As there was more potential for ires in aerobic
landills than anaerobic, monitoring, and liquid addition without delay are essential. Fires
or “hot spots” appear to have greater potential in aerobic landills but can be managed
with good monitoring of temperature and aeration and subsequent addition of liquids.
Issues for the anaerobic bioreactors were similar to regularly operated landilled.
In summary, the development of landill bioreactors will continue due to its advantages
over conventional landills. Further efforts will be necessary to optimize leachate recircu-
lation, gas generation, and removal of recalcitrant compounds. There are still many chal-
lenges including regulator reluctance, ability to wet the waste uniformly, and availability
of design criteria. Slope stability and settlement will differ from traditional landills due
to the increased moisture content and degradation rates and thus will need to be properly
monitored.
7.5.1.5 Natural Attenuation
Although we discussed natural attenuation and its application for groundwater in Chapter
3, and will be discussed in greater detail in Chapter 9, we want to turn our attention here
to the use of monitored natural attenuation (MNA) of soil to reduce the toxicity and con-
centration of contaminants in a soil-water system. This subject has been treated in detail
by Yong and Mulligan (2004). This concept of passive remediation has gained acceptance
by many jurisdictions and regulatory agencies. To ensure effectiveness, monitoring guide-
lines and criteria have been (or are being) established. The soil and the contaminants must
be compatible to ensure the reactions of effective and optimum partitioning of the con-
taminants with the soil solids and the reactions and interactions to reduce the toxicity of
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