Environmental Engineering Reference
In-Depth Information
the fluvial network. Rural pollution from agricul-
tural upstream areas encompasses diffuse
overland flow (Doran and Linn 1979; Kay
et al. 2008b) and subsurface flow (Rahe
et al. 1978; Unc and Goss 2003) to watercourses as
well as direct deposition to surface waters where
livestock have access to them (Collins 2004; Kay
et al. 2007a, 2007b). Diffuse microbial sources
associated with runoff frompasture land are likely
tobesupplemented inthe lowlandsbyapplications
of slurry, farmyard manure and sewage sludge to
arable land, as well as contamination from point
sources such as runoff from farmyards and animal
waste storage facilities on livestock farms
(Geldreich 1996; Jones and Obiri-Danso 1999;
Obiri-Danso and Jones 1999; Crowther
et al. 2002; Collins 2004; Edwards and Kay 2008;
Stapleton et al. 2008).
Fig. 21.1
Source, pathway, receptor model.
waters, or where heavy rainfall results in over-
loading of the treatment works (Kay et al. 2008a,
2008b).
Rivers
Rivers receive microbial pollution from a number
of sources, including most of the key flooding
components identified in Figure 21.2. The
relative contributions that are received from
each component vary according to antecedent
rainfall patterns, season and individual catchment
characteristics.
Urban 'non-foul' (including roof discharge)
Urban non-point-source pollution has been
increasingly recognized for its impact on the
microbial quality of receiving water, especially
under high or storm flows. Urban diffuse sources
of microbial pollution to the surface drainage
system include surface runoff from impervious
surfaces (including roofs), misconnections of foul
sewers into surface water drains and additionally,
in the UK, dual manholes allowing foul sewer
blockages to cause overspills into the surface wa-
ter drainage system (O'Keefe et al. 2005; Fewtrell
and Kay 2007; Stapleton et al. 2008).
Rural diffuse
Inurbanareas, ruraldiffusepollutionwillbelargely
represented as an upriver boundary condition.
Microbial pollution from rural catchment sources
is likely to predominate in upstream areas and be
transported downstream to larger urban areas by
Microbial 'quality'
Areviewofmicrobial concentrations infloodcom-
ponents was conducted by searching a number of
web-based databases including PubMed and ISI
Web of Knowledge, search engines including
Google and Google Scholar, and individual rele-
vant websites, including the UK's Department
for Environment, Food and Rural Affairs (Defra),
the Environment Agency and the World Health
Organization. The main focus of the review was
pathogen concentrations, but faecal indicator con-
centrationswere alsoexamined (Smithet al. 2007).
Fig. 21.2
Component flood flows.
