In Situ Remediation Technologies - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 965

21.2.2.3 Receptor Oriented In Situ Technologies

The “receptor In Situ Technologies” aim at the direct protection of the receptor, like
a well for human drinking water supply or a groundwater well for cattle, or a surface
water body. Combinations of biological and, physical techniques are often applied
at this receptor level, and often concern highly mobile contaminants that are not, or
only slowly, biodegraded in natural systems.

Drinking Water

A typical example is methyl tertiary butyl ether (MTBE), an oxygenation additive in
gasoline. Although the International Agency for Research on Cancer does not clas-
sify this compound as a human carcinogen, the required concentration in water for
MTBE is below 5-15 g/L if it is used for drinking water preparation, as it can be

tasted at these low levels in water (Fischer et al. 2005 ) Although some biodegrada-
tion is reported (Haggblom et al. 2007 ), many groundwater extractions for drinking
water are affected by MTBE. Generally, the extracted water is treated using various
treatment methods. Shih et al. (2003) studied sorption by different granular activated
carbons (GAC) and demonstrated that competitive adsorption of co-contaminants
(like BTX) and natural organic matter in surface or groundwater can greatly reduce
MTBE removal efficiencies. Adsorption with zeolites and treatment with advanced
oxidation techniques using ozone and peroxide is another promising technology,
currently in development ( http://www.sense.nl/research/1869 ).
Chemical oxidation using Fentons Reagent was studied in batch reactors with
anoxic groundwater by Burbano et al. ( 2005 ) who showed highest MTBE removal
at acidic pH, which strongly reduced efficiencies at neutral conditions. Although
MTBE concentrations decreased with 90-99%, mineralisation occurred only for
30-40% leaving tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone and
methyl acetate as the major intermediate contaminants. Thus a second chemical or
biological “polishing step” would be needed to complete the mineralisation.

μ

Surface Water

Another set of technologies are oriented at contaminated sediments with the surface
water system as the receptor. As sediments release their contaminants to surface
water, dependent on river flow characteristics (Smit 2009 ), they will affect the qual-
ity of the surface water as regulated for example in the EU in the Water Framework
Directive ( http://ec.europa.eu/environment/water/water-framework/index_en.html ).
Koelmans et al. ( 2006 ) showed that soot and other black carbon particles
present in sediments strongly bind and accumulate diffuse hydrophobic contami-
nants. These and other researchers are currently transferring this phenomenon into
treatment technologies. Hereto, activated carbon and other sorptive materials are
added to the upper layer of the contaminated sediment to reduce emissions of
strongly sorbing contaminants, such as Polycyclic Aromatic hydrocarbons (PAH's)
and Polychlorinated Biphenyls (PCBs). Cho et al. ( 2009 ) demonstrated short and
long term reductions of up to 90% in bioaccumulation of PCBs in marine clams by