Biology Reference
In-Depth Information
7.1 Introduction
Groundwater is an immensely important resource, as it provides more than one-third of the
world's drinking water (Morris et al., 2003). An important characteristic that has often been
associated with groundwater is the assumption that, generally, the resource is free of
pathogenic microorganisms (Bhattacharjee et al., 2002). In spite of the cleanliness of
groundwater, many water borne disease outbreaks are caused by the consumption of
groundwater contaminated by pathogenic bacteria and protozoa (Close et al., 2006, Powell et
al., 2003, Macler and Merkle, 2000). According to the WHO, an estimated one billion people
lack access to an improved water supply and two million deaths are attributable to unsafe
drinking water, sanitation and hygiene, with many countries still reporting cholera to the
WHO (WHO, 2004). The use of shallow groundwater for drinking and domestic purposes is a
common feature in many developing countries (Kulabako et al., 2007). In Kampala, the
capital of Uganda, protected springs within the shallow aquifer are a major source of water
supply (Kulabako et al., 2007). The springs are susceptible to pollution related to
anthropogenic activities, even when protected (Kulabako et al., 2008). Previous studies
undertaken on the protected springs in the area have indicated widespread faecal
contamination (Kulabako et al, 2007; Howard et al., 2003; Byamukama et al., 2000).
Due to the importance of
E. coli
as a fecal indicator organism, considerable attention has
been given to understanding their transport and fate in saturated porous media (e.g. Foppen et
al., 2006, Schinner et al., 2010, Bolster et al., 2010). In most of these studies, bacteria strains
isolated from different sources, for example from zoo animals (Foppen et al., 2010), a swine
lagoon (Bolster et al., 2010), a dairy cow manure and sewerage (Haznedaroglu et al., 2008),
or a soil of a pasture used for cattle grazing (Foppen et al., 2010; Lutterodt et al., 2009a,
2009b; Yang et al., 2008) were used. To our knowledge, there is no study reported in the
literature that focuses on the transport of
E. coli
strains isolated
after
they have undergone
transport in an aquifer. These strains may start transport among a wide variety of
microorganisms that have infiltrated from the surface into the groundwater system, and, after
considerable transport has taken place, they may end up as one of the few microorganisms
remaining in the system.
Our objectives were two-fold: 1. To present an assessment of the chemical, physical and
bacteriological status of the springs in the Kampala area of Uganda, and 2. to characterize the
transport of
Escherichia coli
strains isolated from these springs, when considerable transport
through the aquifer has already taken place. The underlying hypothesis was that transport by
such a group of
E. coli
strains could possibly be characterized by a rather homogeneous set of
surface characteristics and transport parameters. To determine transport parameters, we
employed saturated laboratory column experiments with saturated pure quartz sand.
7.2 Materials and methods
7.2.1 Study area
meta-sedimentary rocks and weathering has produced a pronounced topography. The area is
low lying with a high water table (<1.5 m) in the weathered regolith (Kulabako et al.,2007)
and site investigations showed the presence of preferential flow paths, although it is not
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