Quantitative assessment of the removal of indicator bacteria in full-scale treatment plants

2004 ◽  
Vol 4 (2) ◽  
pp. 47-54 ◽  
Author(s):  
W.A.M. Hijnen ◽  
G.J. Medema ◽  
D. van der Kooij
Keyword(s):  
Quantitative Information ◽  
Average Concentration ◽  
Full Scale ◽  
Indicator Bacteria ◽  
Quantitative Microbial Risk Assessment ◽  
Water Recovery ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Drinking Water Standard ◽  
Micro Organisms

The elimination of thermotolerant coliforms (Coli44) and spores of sulphite-reducing clostridia (SSRC) in full-scale water treatment was determined by large volume sampling. The objective was to determine the elimination capacity of full-scale treatment processes for micro-organisms, both vegetative bacteria and bacterial spores. In two short-periods in winter and summer, information was collected about the elimination of Coli44 and SSRC by the overall treatment, the contribution of the unit processes and the variability in elimination. Coli44 concentrations in the source waters were reduced by 3.2 to 6.3 log to an average concentration sufficiently low to achieve more than 99% compliance with the drinking water standard. The elimination of SSRC was lower (1.4 to 4.2) and SSRC were observed occasionally (>1%) in finished water by the routine weekly sampling of 100 ml samples. The study also yielded much information about the elimination efficacy of unit processes at the different locations, which enables process optimization and improved process control. Moreover, it is demonstrated that this quantitative information on removal of indicator bacteria by full-scale treatment systems can be used as input for quantitative microbial risk assessment. Further research will be focussed on comparative studies on the removal of faecal indicators and pathogens by unit processes and the improvement of the enumeration methods of pathogens in the source water (recovery efficiencies, specificity).

scholarly journals Determination of Removal Efficiencies for Escherichia coli, Clostridial Spores, and F-Specific Coliphages in Unit Processes of Surface Waterworks for QMRA Applications

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1525 ◽  
Author(s):  
Anna-Maria Hokajärvi ◽  
Tarja Pitkänen ◽  
Päivi Meriläinen ◽  
Ari Kauppinen ◽  
Ville Matikka ◽  
...  
Keyword(s):  
Pilot Scale ◽  
Full Scale ◽  
Source Water ◽  
Quantitative Microbial Risk Assessment ◽  
Sand Filtration ◽  
Ph Change ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Water Ph ◽  
Removal Efficiencies

The removal efficiencies of bacteria, bacterial spores, and viruses after a change in source water and water pH in coagulation were studied at pilot scale in coagulation with flotation, rapid sand filtration, and disinfection with UV and chlorine. The results were compared to the treatment efficiencies of full-scale waterworks and data from literature. A quantitative microbial risk assessment (QMRA)-method was applied to estimate the numbers of illness cases caused by Campylobacter and norovirus after simulation of six operational malfunction scenarios. Coagulation with flotation and disinfection were more efficient in removing Clostridium spp. spores and MS2 coliphages than sand filtration in the pilot scale experiments (p < 0.001–0.008). The removal of E. coli was more efficient in sand filtration and in disinfection compared to coagulation with flotation (p = 0.006 and 0.01). Source water or pH change in coagulation had not significant effects on the removal efficiency of microbes. In QMRA, when disinfection was not in use, an increase in the number of illness cases compared to the normal situation was noticed. The variability in the number of illness cases demonstrated the importance of site-specific data in QMRA. This study provides new information on applying QMRA in both pilot and full-scale waterworks.

scholarly journals Systematic review of the relative concentrations of noroviruses and fecal indicator bacteria in wastewater: considerations for use in quantitative microbial risk assessment

2021 ◽  
Author(s):  
Zelfa Hamadieh ◽  
Kerry A. Hamilton ◽  
Andrea I. Silverman
Keyword(s):  
Risk Assessment ◽  
Wastewater Treatment ◽  
Health Risks ◽  
Conversion Factor ◽  
Conversion Ratio ◽  
Indicator Bacteria ◽  
Quantitative Microbial Risk Assessment ◽  
Fecal Indicator ◽  
Microbial Risk Assessment ◽  
Microbial Risk

Abstract Human noroviruses are a leading cause of food- and water-borne disease, which has led to an interest in quantifying norovirus health risks using quantitative microbial risk assessment (QMRA). Given the limited availability of quantitative norovirus data to input to QMRA models, some studies have applied a conversion factor to estimate norovirus exposure based on measured fecal indicator bacteria (FIB) concentrations. We conducted a review of peer-reviewed publications to identify the concentrations of noroviruses and FIB in raw, secondary-treated, and disinfected wastewater. A meta-analysis was performed to determine the ratios of norovirus-FIB pairs in each wastewater matrix and the variables that significantly impact these ratios. Norovirus-to-FIB ratios were found to be significantly impacted by the norovirus genotype, month of sample collection, geographic location, and the extent of wastewater treatment. Additionally, we evaluated the impact of using a FIB-to-virus conversion factor in QMRA and found that the choice of conversion ratio has a great impact on estimated health risks. For example, the use of a conversion ratio previously used in the World Health Organization Guidelines for the Safe Use of Wastewater, Excreta and Greywater predicted health risks that were significantly lower than those estimated with measured norovirus concentrations used as inputs. This work emphasizes the gold standard of using measured pathogen concentrations directly as inputs to exposure assessment in QMRA. While not encouraged, if one must use a FIB-to-virus conversion ratio to estimate norovirus dose, the ratio should be chosen carefully based on the target microorganisms (i.e., strain, genotype, or class), prevalence of disease, and extent of wastewater treatment.

Enteric virus presence in green vegetables and associated irrigation waters in a rural area from Argentina. A quantitative microbial risk assessment

LWT ◽  
2021 ◽  
Vol 144 ◽  
pp. 111201 ◽  
Author(s):  
Prez Verónica Emilse ◽  
Victoria Matías ◽  
Martínez Laura Cecilia ◽  
Giordano Miguel Oscar ◽  
Masachessi Gisela ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Rural Area ◽  
Enteric Virus ◽  
Quantitative Microbial Risk Assessment ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Irrigation Waters
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