Emerging contaminants in groundwater - NERC Open Research ...

OR/11/013
A feature of some emerging contaminants is their recalcitrance to sewage treatment or
drinking water treatment which allows them to pass through into the treated water. Filtration
using granulated activated carbon (GAC) has been used widely to remove organic
micropollutants from drinking water. However, small and/or very polar molecules can be
difficult to remove by this method. Stackelberg et al. (2007) showed that there was
substantial but not complete degradation or removal of 113 organic micropollutants by
conventional DWT. Gibs et al. (2007) showed that 50 out of 98 such contaminants did not
substantially degrade in the presence of chlorine during typical residence times in drinking
water distribution systems.
The octanol/water partition coefficient (Kow) has been used to provide an analogue of removal
recalcitrance, with polar compounds having a low or negative log (Kow). Figure 2.1 shows the
time taken for breakthrough of selected pesticides using GAC annotated with the Kow value. A
number of widely used compounds are poorly removed. Johnson et al. (2007b) demonstrate
that removal of some oestrogens can be as low as 30%.
Other treatment options can be:
use of powdered active carbon (PAC) which has a higher surface area
ozonation
nano-filtration. Verliefde et al. (2007) assess nano-filtration as a solution using a
priority list of micropollutants
However it has been questioned whether advanced treatment to remove endocrine disrupting
compounds and pharmaceuticals from wastewater is cost-effective due to the increased energy
consumption and associated economic costs and CO2 emissions (Jones et al., 2007; 2005).
Pesticide concentration (µg/L)
Figure 2.1 Concentration versus GAC performance annotated with log Kow for selected pesticides
(after Hall, 2010)
2.3 ‘RECEPTOR’ CONCEPTS: HAZARDS
Receptors can be humans drinking tap water, other living creatures such as invertebrates and
fish, or the environment more widely. Risks to the receptor depend upon the hazards related
to the contaminant in question and the frequency and concentration of exposure to that
substance. Here we give an overview of two hazards, toxicity and endocrine disruption,
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