Animal Waste, Water Quality and Human Health

174Animal Waste, Water Quality and Human HealthTable 5.7 Reduction in faecal indicator organism (FIO) concentrations in specificprimary, secondary and tertiary treatment effluents compared with the geometric meanconcentrations for the level of treatment which provides the input to these treatment plants(i.e. untreated sewage and primary- and secondary-treated effluent, respectively), based onthe geometric mean concentrations reported in Table 5.6 a .Treatment type FIO b Reduction(cfu 100 mL −1 ):Reduction (%):Base flow High flow Base flow High flowPrimary effluents compared with untreated sewage cPrimary settled TC 8.5 × 10 5 2.21sewage FC 0 0EN 0 0Stored settled TC 1.5 × 10 7 38.56sewage FC 1.1 × 10 7 66.13EN 1.3 × 10 6 67.66Settled septic TC 1.4 × 10 7 35.55tank FC 9.4 × 10 6 56.68EN 9.9 × 10 5 51.69Secondary effluents compared with primary-treated effluentTrickling filter TC 2.9 × 10 7 1.1 × 10 7 95.22 88.47FC 1.0 × 10 7 4.1 × 10 6 95.88 88.08EN 1.3 × 10 6 9.3 × 10 5 96.98 94.17Activated sludge TC 2.9 × 10 7 1.1 × 10 7 97.39 88.69FC 1.0 × 10 7 4.1 × 10 6 97.34 88.95EN 1.3 × 10 6 9.4 × 10 5 98.43 95.88Oxidation ditch TC 2.9 × 10 7 – 97.30 –FC 1.0 × 10 7 – 98.03 –EN 1.3 × 10 6 – 98.51 –Trickling/sand TC 2.9 × 10 7 – 97.88 –filter FC 1.0 × 10 7 – 97.97 –EN 1.3 × 10 6 – 98.41 –Rotating TC 2.9 × 10 7 – 97.73 –biological FC 1.0 × 10 7 – 98.46 –contactor EN 1.3 × 10 6 – 99.29 –Tertiary effluents compared with secondary-treated effluentReedbed/ TC 1.0 × 10 6 – 96.59 –grass plot FC 3.2 × 10 5 – 95.94 –EN 2.6 × 10 4 – 93.24 –UV disinfection TC 1.1 × 10 6 – 99.86 –FC 3.3 × 10 5 – 99.92 –EN 2.8 × 10 4 – 99.71 –a Reductions only calculated where n ≥ 10 (– indicates n < 10).b FIOs: TC = total coliforms, FC = faecal coliforms, EN = enterococci.c No meaningful figures can be calculated for high-flow conditions (see text).