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Table 1 Average Enterococcus spp. and E. coli counts (MPN/100 mL) per month and site of collection

From: Quantitative microbial risk assessment for waterborne pathogens in a wastewater treatment plant and its receiving surface water body

MONTH Mean MPN/100 ml
INFLUENT EFFLUENT UPSTREAM DOWNSTREAM
Enterococcus (n = 15) (n = 15) (n = 15) (n = 15)
May (n = 8) 2.90E+ 05 4.30E+ 03 4.08E+ 03 2.33E+ 03
June (n = 8) 3.89E+ 05 4.70E+ 02 1.73E+ 04 2.10E+ 03
July (n = 12) 9.67E+ 05 1.03E+ 03 2.85E+ 04 6.16E+ 03
August (n = 8) 1.75E+ 06 3.33E+ 03 1.99E+ 04 1.59E+ 03
September (n = 8) 3.19E+ 06 2.62E+ 03 2.04E+ 04 3.87E+ 03
October (n = 8) 2.53E+ 06 2.60E+ 02 4.73E+ 04 2.95E+ 03
November (n = 8) 2.60E+ 06 5.45E+ 03 6.39E+ 04 1.91E+ 04
Arithmetic mean (Overall) 1.63E+ 06 2.39E+ 03 2.87E+ 04 5.50E+ 03
Geometric mean (Overall) 1.12E+ 06 1.36E+ 03 1.66E+ 04 3.42E+ 03
E. coli
 May (n = 8) 2.19E+ 06 1.15E+ 03 2.04E+ 04 4.81E+ 03
 June(n = 8) 1.80E+ 06 2.60E+ 02 2.73E+ 04 3.72E+ 03
 July (n = 12) 4.38E+ 06 4.43E+ 02 4.56E+ 04 7.52E+ 03
 August (n = 8) 3.62E+ 06 1.34E+ 03 4.26E+ 04 5.33E+ 03
 September (n = 8) 4.84E+ 06 5.09E+ 03 1.05E+ 05 2.22E+ 04
 October (n = 8) 4.84E+ 06 2.80E+ 03 1.34E+ 05 7.22E+ 03
 November (n = 8) 4.84E+ 06 5.29E+ 03 2.46E+ 06 4.20E+ 04
aArithmetic mean (Overall) 3.83E+ 06 2.21E+ 03 3.81E+ 05 1.29E+ 04
 Geometric mean (Overall) 3.39E+ 06 1.15E+ 03 5.75E+ 04 7.46E+ 03
  1. a This mean was used to compute the risk of infection; n = number of samples collected/month, i.e. a single 500 ml sample was collected every 2 weeks from 4 sample sites to yield 8 samples per month except in July where samples were taken thrice to yield 12 samples. NB: the same samples were used to isolate E.coli/Enterococcus, total number of samples used was 60