Recharge systems for protecting and enhancing groundwate

V
Water quality improvements during
aquifer storage and recovery at ten sites
Peter Dillon, Simon Toze, Paul Pavelic, Joanne Vanderzalm,
Karen Barry, Guang-Guo Ying, Rai Kookana, Jan Skjemstad,
Brenton Nicholson, Rosalind Miller, Ray Correll,
Henning Prommer, Janek Greskowiak and Pieter Stuyfzand
Abstract
Literature reviews and field evaluations at up to ten aquifer storage and recovery sites in USA, Australia and The
Netherlands were undertaken to determine the fate of natural organics, disinfection by-products, selected
endocrine disruptors and pathogens during subsurface storage. This paper summarises American Water Works
Association Research Foundation (AWWARF) project 2618 which evaluated attenuation of these species and incorporated
this knowledge in several types of models.
The paper briefly characterises the field sites and explains the formation and role of geochemical conditions in
the aquifer that influence attenuation rates of these species. Organic matter degradation occurred most rapidly
for larger molecular weight materials, including polysaccharides, and organics containing functional groups susceptible
to microbial degradation. Low molecular weight acidic material was found to persist and had a signature
indistinguishable from native groundwater. Trihalomethanes were degraded under anaerobic conditions with
degradation of chloroform requiring reducing conditions and occurring fastest under sulphate reducing and
methanogenic conditions. Haloacetic acids were degraded under aerobic and anaerobic conditions. Of five
endocrine disrupting chemicals tested, two were degraded under aerobic conditions and none under anaerobic
conditions in the absence of a co-metabolite. A selection of pathogenic viruses, bacteria and protozoa were found
to inactivate during residence within the aquifer with fastest inactivation under aerobic conditions. It is evident
that passage of water through aerobic and anaerobic conditions maximises the opportunity for contaminant
attenuation.
At two sites three models of varying complexity were used to describe changes in water quality on a range of time
scales. While two of the models are not validated they do reflect the observations for a large number of water
quality parameters, suggesting that the process descriptions incorporated may be reasonable, and that an understanding
of the biogeochemical interactions during ASR is emerging.
INTRODUCTION
In many countries high quality drinking water supplies are drawn from aquifers that are recharged naturally by
continuously polluted surface waters. With increasing knowledge of groundwater contamination from point
sources, there is also an increasing reliance on passive remediation for some classes of contaminants. From these
two observations the hypothesis has emerged that while pollution should be avoided, there are sustainable treatment
processes at work in aquifers, and so long as assimilative capacity of an aquifer ecosystem is not overloaded,
an aquifer potentially can provide sustainable water quality improvement during Management of Aquifer Recharge
(MAR). An international project supported by the American Water Works Association Research Foundation was
conducted (Dillon et al., 2005a) to establish rates of attenuation of a limited suite of some of the most ubiquitous
pathogens and organic substances. These rates were measured at ten field sites and, for a few emerging contaminants
of concern, in laboratory studies.
10 – 16 June 2005, Berlin ■ 5th International Symposium ■ AQUIFER RECHARGE ■ ISMAR 2005