Animal Waste, Water Quality and Human Health

Transport of livestock-derived pathogens within catchments 239discharged to watercourses (see: design manual for CFWs in Scotland andNorthern Ireland (Carty, 2008)). They are typically used for more lightlycontaminated runoff, such as drainage from roofs and yards that are usedinfrequently by cattle, rather than heavily contaminated, slurry-rich, daily yardand milking parlour washings associated with dairy activity. Since CFWsrepresent a form of wetland habitat creation or restoration, they enhance thelandscape and biodiversity. Indeed, the integrated constructed wetlands (ICWs)concept, which was first pioneered in Ireland, specifically promotes asustainable approach to natural resource management (Harrington, 2005,Harrington, 2007, Harrington, 2009). In Waterford, Ireland, 12 ICWs wereestablished in 1999/2000, ranging from 0.3–2.2 ha in extent (approximately1.4 × the size of the associated steading). These have led to reductions in meanEC concentrations in yard runoff from 8.3 × 10 5 to 5.0 × 10 2 cfu 100 ml −1 (i.e.3.22 log 10 reduction) (Carty 2008), with a log 10 reduction as high as 4.51 (from9.6 × 10 5 to 3.0 × 10 1 cfu 100 ml −1 ) in one 4-cell ICW (Mustafa 2009). Otherreported rates of EC or FC attenuation in CFWs range from 1.61–3.56 log 10(excluding the site in SE Scotland where Gouriveau (2008) reports an increasein FC due to faecal inputs from wild birds), and Knox, Tate et al. (2007) reportlower rates of EC attenuation at higher flow rates in irrigated beef cattle pasturein California. For municipal/domestic wastewater treatment the reported rangeis from 1.29–3.00 log 10 for raw wastewater to 0.19–3.30 log 10 for secondary ortertiary treatment. Although few data are available on pathogen attenuation inrunoff from livestock units, Duggan, Bates et al. (2001) report log 10 attenuationrates for Campylobacter spp. from poultry waste of 3.13 and 2.96, respectively,for sequential and continuous loading to a SSF reedbed. Drewe, Mwangi et al.(2009) report complete removal of Mycobacterium avium (causal agent of aviantuberculosis) within a reedbed treatment system for captive wildfowl waste.Wider ranges of attenuation have been reported for the treatment ofmunicipal/domestic wastewaters: coliphages (0.67–2.64 log 10 ), enterovirus(0.33–1.82 log 10 ), Clostridium (0.28 log 10 –complete), Giardia (0.43 log 10 –complete), Cryptosporidium (0.28 log 10 –complete) and helminths (complete).Overall, the median microbial attenuation for CWs is 1.27 log 10 (Figure 2).6.5.3 Control of livestock on farmlandStreambank fencing and bridging. Where livestock have access to watercourses,faecal contamination can occur as a result of direct voiding and contaminantsbeing washed from their hooves and lower legs. The flux of FIOs and pathogenswill also be enhanced by disturbance of bed sediments, which are oftencontaminated with faecal material (Muirhead, Davies-Colley et al. 2004).