Decay rate of virus and faecal indicator bacteria (FIB) in seawater and the concentration of FIBs in different wastewater systems

• Published in: Microbial risk analysis 2018-04, Vol.8, p.14-21
• Main Authors: Eregno, Fasil Ejigu, Tryland, Ingun, Myrmel, Mette, Wennberg, Aina, Oliinyk, Anastasiia, Khatri, Mamata, Heistad, Arve
• Format: Article
• Language: English
• Subjects: Adenovirus; Decay rate; Faecal indicator bacteria; MS2; Seawater; Wastewater
• ISSN: 2352-3522; 2352-3530
• DOI: 10.1016/j.mran.2018.01.001

•An experiment was conducted on the virus and FIB decay rate in seawater from different depths.•An experimental study was conducted on the growth potential of FIB in greywater and E. coli showed a tendency of growth whereas IE did not.•Monitoring of FIB in different wastewater systems conducted to evaluate the impact of source separation system on FIB reduction. Information about the concentration, growth and decay rates of enteric microorganisms in different wastewater systems and water bodies is crucial for quantitative microbial risk assessment (QMRA). In general, there is little information about this and in particular about the decay rates of faecal bacteria and viruses at different depths of the marine environment where many wastewater treatment plants discharge their effluent. This study was designed to investigate the concentration of faecal indicator bacteria (FIB) in different types of wastewater, the potential for growth of FIB in greywater, and the decay rates of FIB and pathogenic viruses in seawater samples from different depths. The intent of this work was to mimic summer water quality. Average concentrations of total coliforms (TC), Escherichia coli (E. coli) and intestinal enterococci (IE) (log10 per 100 ml) were 7.2, 6.7 and 6.1 in blackwater; 6.7, 6.1 and 3.8 in greywater; and 6.8, 6.6 and 5.2 in municipal wastewater, respectively. The numbers of TC and E. coli increased when greywater was stored for 24 h at 20 °C but decreased after 96 h. No growth of IE was observed in the greywater. The decay rate experiment showed that viruses and FIB were inactivated relatively rapidly at 20 °C in seawater collected from 1 m depth, while a slow inactivation was observed at 4 °C in seawater collected from 60 m depth, with a significant difference in decay rates (p