Animal Waste, Water Quality and Human Health

Transport of livestock-derived pathogens within catchments 24110 6 cfu m −2 h −1 during high-flow conditions following rainfall. Detailedmonitoring of drain flow from the base of six corrals on a farm in SW Scotlandshowed a log 10 attenuation in EC concentration of 0.53–1.63 through thewoodchip fill (Vinten, Donnelly et al. 2006). Where the drain slots werebackfilled with subsoil or topsoil, a very marked increase in log 10 attenuationwas recorded (range, 2.99–4.53), which presumably reflects the filtering anddie-off of microbes within the soil fill. The study also indicated that EN tend tosurvive longer than EC within the woodchip matrix, and may possibly showsigns of growth.6.5.4 Control of manure application to landLocation and timing of application/Incorporation of manures in soil. CoGAPsgenerally include recommendations on the location and timing (e.g. avoidanceof steep slopes, wet conditions and frozen ground) of manure applications, andon the incorporation of manure. While these undoubtedly contribute to theattenuation of microbial transport within catchments, there are few empiricaldata on attenuation rates.6.5.5 Vegetated buffer strips (see: Table 6.2, Section E)Vegetated buffer strips (VBSs), or “vegetative filter strips” (VFSs), are strips ofland located either along river banks (“riparian buffer strips” (RBSs) or onslopes, designed to attenuate surface fluxes of sediments and other pollutants.While most attenuation occurs within the VBS, (Hussein, Ghadiri et al. 2008)report some retention of sediment-adsorbed C. parvum in the backwater zonecreated upslope of the buffer. Where land is grazed, RBSs need to be fencedto prevent direct faecal contamination, thereby also precluding livestock accessto watercourses. CoGAPs usually include restrictions on the application ofmanure within a certain distance of watercourses, thus effectively creating orre-enforcing existing RBSs. As with CFWs, VBSs enhance landscape/habitatdiversity and provide nesting/breeding sites and migration corridors for wildlife(Bradbury & Kirby 2006).Reported microbial attenuation rates range from zero to complete removal, withlower quartile, median and upper quartile values of 0.48, 1.00 and 1.68 log 10 ,respectively (Figure 2). It should be noted that these data will often overestimatethe impact of RBSs, since significant numbers of FIOs and pathogens may enterwatercourses via subsurface flow generated within the RBS. This is especiallylikely where there is rapid bypass flow through a soil, notably in naturallywell-structured soils with continuous macropores or artificially drained soils(Collins 2004). Also, some microbes that become trapped at the surface may