Activated Carbon Permeable Reactive Barrier for Groundwater Remediation
The proper management of contaminated groundwater has been a widespread and
costly issue. Effective and sustainable control of petroleum contamination is crucial for
reducing the potential risk to human health and the environment, eliminating the potential of
long-term liability, and allowing flexible future land development. To this end, emerging insitu remediation treatments have received considerable attention over the last decade.
Activated carbon, which possesses high porosity and surface area and is traditionally
used for air and water treatment, has proved effective in immobilization of petroleum
hydrocarbons such as polyaromatic hydrocarbons (PAHs) and total petroleum hydrocarbon
(TPH) in our previous studies. Thus, we propose its potential application for groundwater
remediation. Activated carbon can be installed as a permeable reactive barrier that intercepts
the contaminated plume, in which the organic compounds can be adsorbed and held in place
so that only clean groundwater passes through.
In this project we aim to investigate the effectiveness of activated carbon permeable
reactive barrier. In natural environment, there have been concerns about the effects of
dissolved organic matter and inorganic colloids (iron oxide) on contaminant adsorption.
These organic/inorganic colloids in groundwater possibly inhibit adsorption of trace organic
contaminants on activated carbon through competitive adsorption and steric blocking, or by
contrast, provide additional partitioning domain that enhances organics solubilisation and
results in colloid-facilitated contaminant transport. On the other hand, under engineered
settings, non-ionic and anionic surfactants (e.g., Triton X-100 and SDS) have been frequently
used to enhance organics extraction in remediation processes. However, surfactants that are
left behind in the environment will cause environmental concerns and its subsequent
treatment increase operational cost significantly. Based on our previous results, activated
carbon permeable reactive barrier is potentially capable of removing both surfactants and
organic contaminants simultaneously.
With these concerns in mind we will conduct a range of bench-scale laboratory
experiments to investigate the adsorption of petroleum hydrocarbons, colloids, and
surfactants on activated carbon. This study follows on from projects undertaken by NRE
students in 2009.
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Humic and Fulvic acids for Treatment of Acid Mine Drainage Affected Waters
Solid Energy New Zealand Limited is interested in supporting a research project into the
use of humic and fulvic acids, manufactured from Solid Energy’s southland lignite resource,
for water treatment purposes. This includes the use of humic and fulvic acids to adsorb
metals and remove fine colloidal and flocculated sediment and sludge from water bodies.
Particular focus will be on the treatment of waters affected by acid mine drainage (AMD) that
are low in pH and elevated in metals such as iron and aluminium with varying proportions of
trace metals. The research will include the following elements:
Objectives:
- Characterization of Humic and Fulvic acids and Determination of its optimal application
for Treatment of Acid Mine Drainage Affected Waters
- Field-scale Demonstration of the Effectiveness of Humic and Fulvic acids for Treatment
of Acid Mine Drainage Affected Waters
Methodology:
- Design of dosing systems at Stockton coal mine site subject to successful laboratory
outcomes.
- Set-up of equipment for humic/fulvic acid application and performance monitoring using
the existing wastewater treatment system.
- Undertaking pilot-scale field trials under a range of environmental conditions according
to possible variations in site operations and wastewater water quality.
Third professional year students undertaking this study are expected to take on a part of the
project and work with a Masters student.
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Applications of Lignite-derived Humic and Fulvic Acids for Soil Remediation
Solid Energy New Zealand is exploring potential applications of lignite-derived
humic/fulvic acids for soil remediation. Natural organic matter (e.g., fulvic acid and humic
acid) has been well recognized to strongly bind with a number of heavy metals such as
copper, lead, mercury, aluminium, and iron. The binding constants of natural organic matter
were found to be about 1010 - 1012, which are nearly comparable with those of anthropogenic
chelating agents (for example, stability constant of Pb-EDDS complex is about 1013) that are
widely used for enhancing heavy metal extraction from contaminated soils. This signifies that
addition of natural organic matter may be an effective way to accomplish soil remediation.
In this study we will investigate the potential use of humic acid and fulvic acid
manufactured from Solid Energy’s southland lignite resource for decontamination of soils.
Particular focus will be on two remediation alternatives: (1) stabilization of heavy metals in
place; or (2) extraction of heavy metals from contaminated soils. The first goal is achieved by
enhancing sorption to an immobile phase of humic/fulvic acids on soil minerals that
significantly reduce metal mobility and bioavailability in contaminated soils. The second is
through metal complexation to a mobile (dissolved) phase of humic/fulvic acids that promote
metal extraction from contaminated soils. The adequacy and effectiveness of the two methods
highly depend on site conditions and operational control. For instance, the first approach is
likely to be favourable when the site environment has low pH, high ionic strength, or high
contents of clay minerals and Fe/Al oxides, because humic/fulvic acids tend to be precipitated
and/or associated with soil minerals which in turn result in immobilization of heavy metals.
On the other hand, the reverse of the above geochemical conditions will promote the use of
the second approach because dissolved humic/fulvic acids serve as strong complexing agents
for metal extraction.
Therefore, we will manipulate a range of geochemical conditions to assess the
interactions between humic/fulvic acids, heavy metals, and soils such that we can determine
the appropriate approach of utilizing lignite-derived humic/fulvic acids for soil remediation.
For the first approach (immobilization), we will evaluate the leachability (TCLP and SPLP
tests) and bioavailability (Ruby’s physiologically based extraction test) of the heavy metals
that are supposed to be immobilized in place by soil-bound humic/fulvic acids. For the
second approach (extraction), we will assess the extraction kinetics and speciation of metals
(using Visual MINTEQ) as well as model the transport of heavy metals and dissolved
humic/fulvic acids (by modifying a transport model previously developed (Tsang et al.,
2007)). Third professional year students undertaking this study are expected to take on a part
of the project.
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