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Comparative analysis of pathogen occurrence in wastewater: management strategies for barrier function and microbial control
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This project was initiated to fill knowledge gaps on the occurrence of pathogens in different streams of wastewater, e.g. greywater and domestic wastewater. The aims were also to measure the removal of pathogens in different treatment processes, conventional and innovative, and correlate the removal to that of common microbial process indicators, such as faecal coliforms, enterococci, Cl. perfringens spores and bacteriophages. One study also assessed the correlation between the removal of microorganisms and some commonly measured physico-chemical process indicators. The results can be applied in microbial risk assessments (MRAs) of urban wastewater systems.

Indicators and parasitic (oo)cysts were enumerated with standard methods and viruses with rtPCR. High levels of Giardia cysts and enteroviruses were found in untreated wastewater (103.2 and 104.2 L-1 respectively) indicating high incidences in the society. Noroviruses were also often found in high numbers (103.3 L-1) during winter, but less frequent and in lower numbers (102.3 L-1) during the rest of the year. This temporal variation correlated to the clinical laboratory reporting of noroviruses. A temporal variation was also shown for Giardia with significantly lower cyst counts in untreated wastewater during spring. Cryptosporidium oocysts were not as numerous in untreated wastewater (5 L-1) reflecting a lower incidence in the society than for the other pathogens during the time of the study. Since temporal variation had a larger impact than spatial, site-specific measurements may not be necessary to perform screening level MRAs of wastewater discharge and reuse. Good data can be found in the literature and corrected for by recovery of the detection method, flow and incidence in the society. Removal of microorganisms in wastewater treatments varied from 0 to >5.8 log due to process combination and organism in question. Treatment in integrated hydroponics removed microorganism more efficiently than did secondary conventional treatment, though having longer hydraulic retention time. Tertiary treatment and treatment in a membrane bioreactor (MBR) showed better removal potential than treatment in upflow anaerobic sludge blankets (UASB) in a pilot plant. Human virus genomes were less removed and Giardia cysts more removed than all of the studied indicators. Enumeration with PCR, however, may underestimate infectious virion removal. Spores of sulphite-reducing anaerobes and somatic coliphages were significantly less removed than E. coli and enterococci in all the studied processes. Bacterial indicator and spore removals correlated to enterovirus genome removal (p<0.05), but the predictive values were low (R<0.4). Removals between microbial indicators and NH4-N, Kjeldal-N, COD and TOC correlated stronger (10-18<p<0.02; 0.43<R<0.90).

To manage the risk with reuse and discharge of wastewater, treatment performance targets have been calculated as a step in a hazard analysis and critical control point (HACCP) approach. These targets varied from 0 to 10.4 log removal due to water (grey or wastewater), organism (rotavirus, Campylobacter or parasitic (oo)cysts) and exposure (drinking water, surface water, aerosols, irrigation of crops or public parks). Faecal contamination in greywater was measured by coprostanol and was shown to be 980 times lower than in wastewater, corresponding to 2.9 log removal in treatment. Somatic coliphages were suggested to function as an index of virus removal in wastewater treatment processes as well as to be included in the monitoring of bathing water. The guideline level was suggested to be 300 PFU 100 mL-1 based on MRA of enteroviruses. This level in a water sample would equal a probability of infection of 0.3% (95th percentile 4%). The risk is overestimated if animal sources dominate the faecal pollution. Development in methods to track sources of faecal pollution showed that if somatic coliphages are enumerated together with phages infecting Bacteroides strain GA17, discriminating human from animal faecal pollution is possible based on the ratio between the phages

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , ix, 67 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1021
Keyword [en]
bacteria, parasites, treatment
National Category
Water Engineering
Identifiers
URN: urn:nbn:se:kth:diva-233ISBN: 91-7178-059-9 (print)OAI: oai:DiVA.org:kth-233DiVA: diva2:7996
Public defence
2005-06-02, Sal V2, Teknikringen 72, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101013Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2010-10-13Bibliographically approved
List of papers
1. Faecal contamination of greywater and associated microbial risks
Open this publication in new window or tab >>Faecal contamination of greywater and associated microbial risks
2003 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 37, no 3, 645-655 p.Article in journal (Refereed) Published
Abstract [en]

The faecal contamination of greywater in a local treatment system at Vibyasen, north of Stockholm, Sweden was quantified using faecal indicator bacteria and chemical biomarkers. Bacterial indicator densities overestimated the faecal load by 100-1000-fold when compared to chemical biomarkers. Based on measured levels of coprostanol, the faecal load was estimated to be 0.04 g person(-1) day(-1). Prevalence of pathogens in the population and the faccal load were used to form the basis of a screening-level quantitative microbial risk assessment (QMRA) that was undertaken for rotavirus, Salmonella typhimurium, Campylobacter jejuni, Giardia lamblia and Cryptosporidium parvum. The different exposure scenarios simulated-direct contact, irrigation of sport fields and groundwater recharge-gave unacceptably high rotavirus risks (0.04<P-inf<0.60) despite a low faecal load. The poor reduction of somatic coliphages, which were used as a virus model, in the treatment was one main reason and additional treatment of the greywater is suggested. Somatic coliphages can under extreme circumstances replicate in the wastewater treatment system and thereby underestimate the virus reduction. An alternative QMRA method based on faecal enterococci densities estimated similar risks as for rotavirus. Growth conditions for Salmonella in greywater sediments were also investigated and risk modelling based on replication in the system increased the probability of infection from Salmonella 1000-fold, but it was still lower than the risk of a rotavirus infection.

Keyword
greywater, risk assessment, bacterial indicators, coprostanol, cholesterol, enteric pathogens
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5180 (URN)10.1016/S0043-1354(02)00352-4 (DOI)000180422800019 ()
Note
QC 20101013Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved
2. Removal of noro- and enteroviruses, Giardia cysts, Cryptosporidium oocysts and faecalindicators at four secondary wastewater treatment plants in Sweden
Open this publication in new window or tab >>Removal of noro- and enteroviruses, Giardia cysts, Cryptosporidium oocysts and faecalindicators at four secondary wastewater treatment plants in Sweden
Show others...
(English)In: Water environment research, ISSN 1061-4303, E-ISSN 1554-7531Article in journal (Refereed) Submitted
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-10699 (URN)
Note
QC 20101013Available from: 2009-07-08 Created: 2009-07-08 Last updated: 2017-12-13Bibliographically approved
3. Removal of viruses, parasitic protozoa microbial indicators and correlation with process indicators in conventional and membrane processes in a wastewater pilot plant
Open this publication in new window or tab >>Removal of viruses, parasitic protozoa microbial indicators and correlation with process indicators in conventional and membrane processes in a wastewater pilot plant
Show others...
2006 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 7, 1449-1457 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate variations in the occurrence and removal of enterovirus and norovirus genomes, Giardia cysts, Cryptosporidium oocysts and the most commonly used faecal indicators in a Swedish wastewater pilot plant. Paired samples were taken from the inlet and outlet of each treatment line: tertiary filtration, membrane bioreactor (MBR) and upflow anaerobic sludge blankets (UASB). (Oo)cysts and indicators were enumerated using standard methods and viruses using RT-PCR. Giardia cysts and enteroviruses were constantly detected, mean numbers 10(3.11) cysts and 10(4.0) PCR units L-1, respectively. Oocysts were found in 5/19 samples, mean number 5 L-1. Noroviruses were found in 6/7 influent samples, with an average titre of 10(3 28) L-1, during winter, but only in 2/15 in the rest of the year (mean 200 L-1). MBR treatment removed indicators more efficiently than did the other two lines, with 5 log removal of E. coli. Human virus genome removal did not differ between the MBR and tertiary treatment line. Microorganism removal in UASB was significantly lower for all the organisms studied. E. coli, enterococci and Cl. perfringens removal was correlated (p < 0.05) with enterovirus genome removal, with R-values around 0.4. However, values for removal of indicators were more strongly correlated to each other. Removal of viruses based on enumeration using RT-PCR probably underestimates infectious virion removal.

Keyword
wastewater treatment, MBR, UASB, enterovirus, norovirus, PCR, Giardia cysts, Cryptosporidium oocyst, faecal indicators, removal, phages
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5182 (URN)10.1016/j.watres.2006.01.039 (DOI)000236840800014 ()2-s2.0-33645112004 (Scopus ID)
Note
QC 20101013. Updated from manuscript to article in journal.Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved
4. Removal of micro-organisms in a small-scale hydroponics wastewater treatment system
Open this publication in new window or tab >>Removal of micro-organisms in a small-scale hydroponics wastewater treatment system
2005 (English)In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 40, no 6, 443-447 p.Article in journal (Refereed) Published
Abstract [en]

Aims: To measure the microbial removal capacity of a small-scale hydroponics wastewater treatment plant. Methods and Results: Paired samples were taken from untreated, partly-treated and treated wastewater and analysed for faecal microbial indicators, i.e. coliforms, Escherichia, coli, enterococci, Clostridium perfringens spores and somatic coliphages, by culture based methods. Escherichia coli was never detected in effluent water after >5.8-log removal. Enterococci, coliforms, spores and coliphages were removed by 4.5, 4.1, 2.3 and 2.5 log respectively. Most of the removal (60-87%) took place in the latter part of the system because of settling, normal inactivation (retention time 12.7 d) and sand filtration. Time-dependent log-linear removal was shown for spores (k = -0.17 log d-1, r2 = 0.99). Conclusions: Hydroponics wastewater treatment removed micro-organisms satisfactorily. Significance and Impact of the Study: Investigations on the microbial removal capacity of hydroponics have only been performed for bacterial indicators. In this study it has been shown that virus and (oo)cyst process indicators were removed and that hydroponics can be an alternative to conventional wastewater treatment.

Keyword
Coliforms, Coliphages, Enterococci, Hydroponics, Removal, Spores, Wastewater treatment
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5183 (URN)10.1111/j.1472-765X.2005.01689.x (DOI)000202967500009 ()2-s2.0-20044378137 (Scopus ID)
Note
QC 20100928Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved
5. Proposed guidelines for bathing water based on the occurrence of somatic coliphages
Open this publication in new window or tab >>Proposed guidelines for bathing water based on the occurrence of somatic coliphages
(English)In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765XArticle in journal (Other academic) Submitted
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5184 (URN)
Note
QC 20101013Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved
6. Tracking the origin of faecal pollution in surface water. An ongoing project within the European Union research programme
Open this publication in new window or tab >>Tracking the origin of faecal pollution in surface water. An ongoing project within the European Union research programme
2004 (English)In: Journal of Water and Health, ISSN 1477-8920, E-ISSN 1996-7829, Vol. 2, no 4, 249-260 p.Article in journal (Refereed) Published
Abstract [en]

The objectives of this study are to generate knowledge about methods to track the sources of faecal pollution in surface waters, with the aim of having one or a few easy procedures applicable to different geographic areas in Europe. For this, a first field study using already proposed methods (genotypes of F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, phenotypes of faecal coliforms and enterococci, and sterols) has been done in five areas representing a wide array of conditions in Europe. The present faecal indicators (faecal coliforms, enterococci, sulfite reducing clostridia and somatic coliphages) have also been included in this first field study. At the same time some emerging methods have been settled or adapted to water samples and assayed in a limited number of samples. The results of this first field study indicate that no single parameter alone is able to discriminate the sources, human or non-human, of faecal pollution, but that a 'basket' of 4 or 5 parameters, which includes one of the present faecal indicators, will do so. In addition, numerical analysis of the data shows that this 'basket' will allow the successful building of predictive models. Both the statistical analyses and the studied predictive models indicate that genotype II of F-specific RNA bacteriophages, the coprostanol and the ratio coprostanol: coprostanol+epicoprostanol are, out of the studied parameters, those with a greater discriminating power. Either because unsuccessful adaptation of the methods to water samples or because the preliminary assays in water samples indicated low discriminating capability, only three (sorbitol-fermenting bifidobacteria, some species of bifidobacteria detected by PCR with specific primers and phages infecting Bacteroides tethaiotaomicron) of the newly assayed methods have been considered for a second field study, which is currently underway. Expectations are that these new tools will minimize the number of parameters in the 'basket', or at least minimize the difficulty in assaying them

National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-5185 (URN)
Note
QC 20101013Available from: 2005-05-03 Created: 2005-05-03 Last updated: 2017-12-04Bibliographically approved

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