scholarly journals Quantitative microbial risk assessment used to evaluate seasonal wastewater treatment limits: case study in Vacaville, CA

2017 ◽  
Vol 18 (3) ◽  
pp. 910-925 ◽  
Author(s):  
Edmund Seto ◽  
Adam W. Olivieri ◽  
Richard E. Danielson
Keyword(s):  
Risk Assessment ◽  
Wastewater Treatment ◽  
Treatment Plant ◽  
Enteric Viruses ◽  
Secondary Effluent ◽  
Quantitative Microbial Risk Assessment ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Annual Risk ◽  
Receiving Water

Abstract A quantitative microbial risk assessment (QMRA) was conducted to support renewal of the City of Vacaville wastewater discharge permit and seasonal (summer) filtration requirements. Influent and final disinfected effluent from the city's wastewater treatment plant, as well as 11 receiving water stations, were monitored for indicator organisms (i.e. total and fecal coliforms, Escherichia coli, Enterococcus, male-specific bacteriophage (MS2), and the Bacteroidales) and several pathogens (i.e. Giardia cysts, Cryptosporidium oocysts, infectious Cryptosporidium, and Norovirus GI and GII). QMRA annualized risks of infection for selected pathogens enteric viruses, Giardia and Cryptosporidium. Estimated median annualized risk for recreational exposure in either disinfected secondary and/or filtered disinfected secondary effluent is on the order of 1.1 × 10−3 per person per year (pppy) for enteric viruses and would be roughly one order of magnitude lower if local receiving water dilution of the treatment plant effluent was taken into account. Estimated median annual risk for recreation exposure in disinfected secondary effluent is 1.8 × 10−3 pppy for Cryptosporidium and 1 log10 less with filtration during the summer months. The estimated median annual risk for landscape exposure (e.g. golfing) to secondary disinfected effluent is 7.6 × 10−7 pppy for enteric viruses. Estimated median annualized risk is 1.7 × 10−7 pppy for enteric viruses and 3.0 × 10−5 to 3.6 × 10−6 pppy for parasites for use of secondary disinfected effluent with irrigated agriculture. Estimated annualized risks for recreational exposure to the local receiving waters were approximately 10 to 1,000 times greater than direct recreational exposure to the final filtered and disinfected effluent. All risk estimates associated with exposure to final treated plant effluent (i.e. secondary filtered and disinfected) were close to or lower than the California level of acceptable annual risk of infection of 10−4 pppy for recreational exposure. Risk estimates provide further evidence to support the use of seasonal treatment limits requiring summer filtration for public health protection.

scholarly journals Microbial risk assessment of local handling and use of human faeces

2006 ◽  
Vol 5 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Caroline Schönning ◽  
Therese Westrell ◽  
Thor Axel Stenström ◽  
Karsten Arnbjerg-Nielsen ◽  
Arne Bernt Hasling ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Incidence Rates ◽  
Quantitative Microbial Risk Assessment ◽  
Risk Of Infection ◽  
Accidental Ingestion ◽  
Storage Container ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Local Use ◽  
Annual Risk

Dry urine-diverting toilets may be used in order to collect excreta for the utilisation of nutrients. A quantitative microbial risk assessment was conducted in order to evaluate the risks of transmission of infectious disease related to the local use of faeces as a fertiliser. The human exposures evaluated included accidental ingestion of small amounts of faeces, or a mixture of faeces and soil, while emptying the storage container and applying the material in the garden, during recreational stays to the garden, and during gardening. A range of pathogens representing various groups of microorganisms was considered. Results showed that 12-months' storage before use was sufficient for the inactivation of most pathogens to acceptable levels. When working or spending time in the garden the annual risk of infection by Ascaris was still slightly above 10-4 in these scenarios, although the incidence rate for Ascaris is very low in the population in question. Measures to further reduce the hygienic risks include longer storage, or treatment, of the faeces. The results can easily be extended to other regions with different incidence rates.

scholarly journals Quantitative Microbial Risk Assessment for Workers Exposed to Bioaerosol in Wastewater Treatment Plants Aimed at the Choice and Setup of Safety Measures

2018 ◽  
Vol 15 (7) ◽  
pp. 1490 ◽  
Author(s):  
Annalaura Carducci ◽  
Gabriele Donzelli ◽  
Lorenzo Cioni ◽  
Ileana Federigi ◽  
Roberto Lombardi ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Sensitivity Analysis ◽  
Wastewater Treatment ◽  
Health Risk ◽  
Average Risk ◽  
Quantitative Microbial Risk Assessment ◽  
Exposure Limits ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
The Impact

Biological risk assessment in occupational settings currently is based on either qualitative or semiquantitative analysis. In this study, a quantitative microbial risk assessment (QMRA) has been applied to estimate the human adenovirus (HAdV) health risk due to bioaerosol exposure in a wastewater treatment plant (WWTP). A stochastic QMRA model was developed considering HAdV as the index pathogen, using its concentrations in different areas and published dose–response relationship for inhalation. A sensitivity analysis was employed to examine the impact of input parameters on health risk. The QMRA estimated a higher average risk in sewage influent and biological oxidation tanks (15.64% and 12.73% for an exposure of 3 min). Sensitivity analysis indicated HAdV concentration as a predominant factor in the estimated risk. QMRA results were used to calculate the exposure limits considering four different risk levels (one illness case per 100, 1.000, 10.000, and 100.000 workers): for 3 min exposures, we obtained 565, 170, 54, and 6 GC/m3 of HAdV. We also calculated the maximum time of exposure for each level for different areas. Our findings can be useful to better define the effectiveness of control measures, which would thus reduce the virus concentration or the exposure time.

scholarly journals Quantitative microbial risk assessment of SARS-CoV-2 for workers in wastewater treatment plants

2021 ◽  
Vol 754 ◽  
pp. 142163 ◽  
Author(s):  
Rafael Newton Zaneti ◽  
Viviane Girardi ◽  
Fernando Rosado Spilki ◽  
Kristina Mena ◽  
Ana Paula Campos Westphalen ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Quantitative Microbial Risk Assessment ◽  
Microbial Risk Assessment ◽  
Microbial Risk

scholarly journals Sapovirus in Wastewater Treatment Plants in Tunisia: Prevalence, Removal, and Genetic Characterization

2018 ◽  
Vol 84 (6) ◽  
pp. e02093-17 ◽  
Author(s):  
Miguel F. Varela ◽  
Imen Ouardani ◽  
Tsuyoshi Kato ◽  
Syunsuke Kadoya ◽  
Mahjoub Aouni ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Wastewater Treatment ◽  
Bayesian Estimation ◽  
Quantitative Pcr ◽  
Censored Data ◽  
Wastewater Treatment Plants ◽  
Quantitative Microbial Risk Assessment ◽  
Content Type ◽  
Microbial Risk Assessment ◽  
Microbial Risk

ABSTRACTSapovirus(SaV), from theCaliciviridaefamily, is a genus of enteric viruses that cause acute gastroenteritis. SaV is shed at high concentrations with feces into wastewater, which is usually discharged into aquatic environments or reused for irrigation without efficient treatments. This study analyzed the incidence of human SaV in four wastewater treatment plants from Tunisia during a period of 13 months (December 2009 to December 2010). Detection and quantification were carried out using reverse transcription-quantitative PCR (RT-qPCR) methods, obtaining a prevalence of 39.9% (87/218). Sixty-one positive samples were detected in untreated water and 26 positive samples in processed water. The Dekhila plant presented the highest contamination levels, with a 63.0% prevalence. A dominance of genotype I.2 was observed on 15 of the 24 positive samples that were genetically characterized. By a Bayesian estimation algorithm, the SaV density in wastewater was estimated using left-censored data sets. The mean value of log SaV concentration in untreated wastewater ranged between 2.7 and 4.5 logs. A virus removal efficiency of 0.2 log was calculated for the Dekhila plant as the log ratio posterior distributions between untreated and treated wastewater. Multiple quantitative values obtained in this study must be available in quantitative microbial risk assessment in Tunisia as parameter values reflecting local conditions.IMPORTANCEHuman sapovirus (SaV) is becoming more prevalent worldwide and organisms in this genus are recognized as emerging pathogens associated with human gastroenteritis. The present study describes novel findings on the prevalence, seasonality, and genotype distribution of SaV in Tunisia and Northern Africa. In addition, a statistical approximation using Bayesian estimation of the posterior predictive distribution (“left-censored” data) was employed to solve methodological problems related with the limit of quantification of the quantitative PCR (qPCR). This approach would be helpful for the future development of quantitative microbial risk assessment procedures for wastewater.

scholarly journals Quantitative Microbial Risk Assessment Models for Consumption of Raw Vegetables Irrigated with Reclaimed Water

2006 ◽  
Vol 72 (5) ◽  
pp. 3284-3290 ◽  
Author(s):  
Andrew J. Hamilton ◽  
Frank Stagnitti ◽  
Robert Premier ◽  
Anne-Maree Boland ◽  
Glenn Hale
Keyword(s):  
Risk Assessment ◽  
Reclaimed Water ◽  
Quantitative Microbial Risk Assessment ◽  
Risk Of Infection ◽  
Worst Case ◽  
Microbial Risk Assessment ◽  
Microbial Risk ◽  
Risk Assessment Models ◽  
Crop Type ◽  
Annual Risk

ABSTRACT Quantitative microbial risk assessment models for estimating the annual risk of enteric virus infection associated with consuming raw vegetables that have been overhead irrigated with nondisinfected secondary treated reclaimed water were constructed. We ran models for several different scenarios of crop type, viral concentration in effluent, and time since last irrigation event. The mean annual risk of infection was always less for cucumber than for broccoli, cabbage, or lettuce. Across the various crops, effluent qualities, and viral decay rates considered, the annual risk of infection ranged from 10−3 to 10−1 when reclaimed-water irrigation ceased 1 day before harvest and from 10−9 to 10−3 when it ceased 2 weeks before harvest. Two previously published decay coefficients were used to describe the die-off of viruses in the environment. For all combinations of crop type and effluent quality, application of the more aggressive decay coefficient led to annual risks of infection that satisfied the commonly propounded benchmark of ≤10−4, i.e., one infection or less per 10,000 people per year, providing that 14 days had elapsed since irrigation with reclaimed water. Conversely, this benchmark was not attained for any combination of crop and water quality when this withholding period was 1 day. The lower decay rate conferred markedly less protection, with broccoli and cucumber being the only crops satisfying the 10−4 standard for all water qualities after a 14-day withholding period. Sensitivity analyses on the models revealed that in nearly all cases, variation in the amount of produce consumed had the most significant effect on the total uncertainty surrounding the estimate of annual infection risk. The models presented cover what would generally be considered to be worst-case scenarios: overhead irrigation and consumption of vegetables raw. Practices such as subsurface, furrow, or drip irrigation and postharvest washing/disinfection and food preparation could substantially lower risks and need to be considered in future models, particularly for developed nations where these extra risk reduction measures are more common.

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