Animal Waste, Water Quality and Human Health

Transport of microbial pollution in catchment systems 173Primary settled sewage 61 2.4 × 10 6 2.1 × 10 6 2.7 × 10 6 8 1.9 × 10 6 – –Stored settled sewage 26 6.2 × 10 5 3.2 × 10 5 1.1 × 10 6 1 2.9 × 10 5 – –Settled septic tank 41 9.3 × 10 5 5.3 × 10 5 1.6 × 10 6 5 4.3 × 10 5 – –Secondary 871 2.8 × 10 4 *(–) 2.5 × 10 4 3.2 × 10 4 182 4.7 × 10 4 *(+) 3.6 × 10 4 6.1 × 10 4Trickling filter 483 4.1 × 10 4 3.5 × 10 4 4.7 × 10 4 76 5.7 × 10 4 4.2 × 10 4 8.3 × 10 4Activated sludge 262 2.1 × 10 4 *(–) 1.8 × 10 4 2.7 × 10 4 91 4.1 × 10 4 *(+) 2.7 × 10 4 6.0 × 10 4Oxidation ditch 35 2.0 × 10 4 1.0 × 10 4 4.0 × 10 4 5 1.2 × 10 5 – –Trickling/sand filter 11 2.1 × 10 4 1.0 × 10 4 5.3 × 10 4 8 1.1 × 10 4 – –Rotating biological 80 9.6 × 10 3 6.7 × 10 3 1.4 × 10 4 2 3.7 × 10 5 – –contactorTertiary 177 3.0 × 10 2 1.8 × 10 2 5.0 × 10 2 8 2.1 × 10 2 – –Reedbed/grass plot e 73 1.9 × 10 3 7.1 × 10 2 4.3 × 10 3 2 2.3 × 10 3 – –Ultraviolet disinfection e 104 8.3 × 10 1 4.6 × 10 1 1.1 × 10 2 6 9.7 × 10 1 – –a CIs only reported where n ≥ 10b t-tests comparing low- and high-flow GM concentrations only undertaken where n ≥ 10 for both sets of samples; only statisticallysignificant (p < 0.05) differences between base- and high-flow GM concentrations are reported: indicated by *, with the higher GMbeing identified as *(+) and the lower value by *(–)c n indicates number of valid enumerations, which in some cases may be less than the actual number of samples.d t-tests comparing the GM concentrations between the two untreated discharge types show high-flow GM concentrations to besignificantly higher in crude sewage discharges than storm sewage overflows for TC (p < 0.05) and EN (p < 0.001).e t-tests comparing the GM concentrations between the two tertiary-treatment effluent types show GM TC, FC and EN concentrations tobe significantly higher (p < 0.001) in reedbed/grass plot effluents than effluents from UV disinfection for base-flow conditions (thereare too few high-flow samples for these tertiary effluents for meaningful comparisons to be made for high-flow GM concentrations).