Efficacy of virus detection and elimination in natural waters and sediments - laboratory and technical scale investigations
Final Report Abstract
Microbiological raw water quality assessments are mostly based on bacterial indicators, but there is an increasing demand for additional indicators for fecal contaminations which reflect the behavior of other pathogens, such as viruses and parasites. Using an outdoor artificial stream system with a channel volume of 30,000 liters, seasonal influences on the elimination of bacteria and viruses from wastewater-contaminated water were followed in a series of experiments in three consecutive years. Elimination of microorganisms and viruses in surface waters was significantly influenced by environmental factors, like temperature and solar radiation. During all seasons, indicator bacteria (E. coli and intestinal enteroccci) were more rapidly eliminated than bacterial viruses (bacteriophages) and human viruses (human adenoviruses and human noroviruses), demonstrating that bacterial indicators are insufficient indicators with regard to long-term virus contaminations of fecal origin. Human adenoviruses displayed similar elimination kinetics as somatic bacteriophages (coliphages), suggesting that the use of coliphages as indicator viruses may be useful for monitoring of virus persistence and long term fecal contaminations. Detection methods for human viruses were optimized. It became very clear that molecular methods for detection of human viruses in environmental samples should be accompanied by quality controls for inhibitory factors for reliable results. Monolithic columns were found to have a high potential as a future reliable concentration method. Adenovirus type 41 was detected in all adenovirus-positive water samples. With regard to direct testing of human pathogenic viruses with putative indicator functions for monitoring of contaminated waters, adenoviruses turned out to be more reliable indicators than noroviruses. Noroviruses were not consistently detected in fecally polluted waters and the detection method was especially vulnerable towards inhibitory factors co-concentrated with virus concentration from water samples. Melting curve analyses of PCR amplification products of environmental samples proved useful as a first screening step for samples intended for further epidemiologic serotype analyses. To gain information on the fate of colloid-associated viruses in the subsurface, virus distribution in a sediment system between the immobile solid phase and mobile colloidal carriers consisting of Fe- and Al-oxides was studied as a function of pH. This was done i) in a batch system containing pea gravel coated with gibbsite and goethite and ii) in two natural sediments from a floodplain containing low and high amounts of Fe- and Al-oxides, using bacteriophages MS2 and PhiX174 as virus surrogates. Special attention was paid to the impact of oxic and anoxic conditions. Difficulties were encountered with lowering the redox potential i) in the gravel system without disturbing the matrix too much through the additon of reducing agents and ii) in some samples of the natural sediments. Besides, achieving stable pH values in the natural sediments prooved very challenging. Results showed that regardless of the redox conditions, bacteriophages did not adsorb to mobilized mineral colloids even though charge conditions were conducive to sorption. The following explanations are discussed: i) sorption sites on solid phase are more abundant than on the mineral phase. ii) mineral colloids contain organic matter which would block sorption sites. The effect of anoxic conditions on bacteriophage sorption in natural sediments did not confirm published results (i.e. lower bacteriophage elimination under anoxic conditions). Rather, our findings suggest that the geochemical process induced by the change in redox potential (i.e. incomplete metabolism of organic matter) may control bacteriophage distribution in a water-sediment-system. The pure presence of Fe- and Al-oxides, known to provide high affinity sorption sites to bacteriophages, does not guarantee bacteriophage retention. Our results suggest that organic matter needs to be considered when assessing the retention potential of Fe- and Al-oxides for viruses in the context of virus breakthrough in anoxic systems.
Publications
- (2012). Combination of crossflow ultrafiltration, monolithic affinity filtration, and quantitative reverse transcriptase PCR for rapid concentration and quantification of model viruses in water. Environm. Sci. Technol. 46, 10073-10080
Pei, L., Rieger, M., Lengger, S., Ott, S., Zawadsky, C., Hartmann, N.M., Selinka, H.-C., Tiehm, A., Niessner, R., Seidel, M.
(See online at https://doi.org/10.1021/es302304t) - (2013). Monitoring of adenovirus serotypes in environmental samples by combined PCR and melting point analyses. Virology J. 10:190 (2013)
Hartmann, N.M., Dartscht, M., Szewzyk, R., Selinka, H.-C.
(See online at https://doi.org/10.1186/1743-422X-10-190) - (2013). Möglichkeiten und Grenzen beim Einsatz von Indikatorviren zur Überwachung virusbelasteter Oberflächengewässer. PhD Thesis. Technical University Berlin
Hartmann, N.M.
- (2014). A mass balance approach to the fate of viruses in a municipal wastewater treatment plant during summer and winter seasons. Water Sci. Technol. 69.2, 364-370
Ulbricht, K., Selinka, H.-C., Wolter, S., Rosenwinkel, K.-H., Nogueira, R.
(See online at https://doi.org/10.2166/wst.2013.722)
