Indigenous Enteric Viruses Research Articles

Coliphages and enteric viruses in the particulate phase of river water.

The present study was undertaken to determine if indigenous enteric viruses and coliphages are free or associated with suspended particulate matter in natural waters. River water was filtered on filters of decreasing porosities (100-0.25 micron) that were pretreated with detergent to eliminate viral adsorption while retaining particulates. This filtered water was refiltered in virus-adsorbing conditions to retain free viruses. The virus-adsorbing filter retained most of the enteric viruses (77.4%) and coliphages (65.8%), which indicated that these viruses were probably free or associated with particles with a diameter of less than 0.25 micron. These observations are important because in water treatment plants small particulates are often the most difficult to eliminate.

Use of a vacuum filtration technique to study leaching of indigenous viruses from raw wastewater sludge

The relative efficiences of a buffered beef extract solution, sewage secondary effluent, and distilled water, were compared in a study designed to simulate leaching of indigenous enteric viruses from raw primary sewage sludge. The initial sludge liquid fractions, termed sludge liquor, and leachates from five successive washings with one of the three test fluids were removed from the sludge samples by vacuum filtration through stainless steel mesh screens. The highest calculated efficiency for virus leaching was 2.8 ±1.4% obtained with the beef extract solution. This indicated leaching to be a very inefficient process and may suggest that viruses present in sewage sludges will remain highly solids-associated following land disposal. The ratio of indigenous viruses in the leachates vs sludge liquor, for any particular sample, was found to be statistically dependent upon the square of the sludge samples original percentage solids content. Together, the developed leaching technique and statistical equation provide a simple way to compare the relative amounts of leachable viruses present in samples of raw wastewater sludge.

Fate of Human Enteric Viruses (Rotaviruses and Entero Viruses) in Sewage after Primary Sedimentation

A wastewater treatment plant, which treats sewage by either mechanical primary sedimentation or lime coagulation, was used for modelling the fate of human enteric viruses after these treatments. The occurrence of human rotaviruses and enteroviruses was monitored in sewage influent, effluent and sludge samples. The level of indigenous enteric viruses in raw sewage was very high (up to 10 000 I.U./l); the values for rotavxrus and enterovxrus were of the same magnitude, although no correlation was found between the levels of both kinds of human enteric viruses. Both rotaviruses and enteroviruses were removed from sewage and transferred to sludge at similar rates after mechanical sedimentation, although rotaviruses were more efficiently recovered from sludge samples than enteroviruses. After chemical coagulation by lime treatment, most human enteric viruses in sludge were inactivated. Lime coagulation should be regarded as a most effective single-step treatment for the removal of viral pathogens such as rotaviruses and enteroviruses from sewage.

Improved method for recovery of enteric viruses from wastewater sludges

Various parameters involved in recovering indigenous enteric viruses from wastewater sludges aided by buffered beef extract elution and subsequent organic flocculation concentration were examined. A statistically significant ( P=0.03) reciprocal correlation was found to exist between the ratio of eluant to sludge solids content used during the elution step, and the efficiency of subsequently concentrating viruses from the produced sludge eluates by means of organic flocculation. A hypothesis is proposed by which to explain the concentration of viruses during beef extract-induced organic flocculation.

Stability of viruses in waste water sludge eluates.

The survival of indigenous enteric viruses in samples of unconcentrated and concentrated waste water sludge eluates, which had been prepared using a combination beef extract elution - organic flocculation concentration procedure, was studied at 2, 23, and -70 degrees C. Changes of virus titer occurring in the samples were followed during an 84-day observation period, with rates of change then calculated by least-squares regression. Virus survival in both types of eluates was statistically dependent (p less than or equal to 0.05) upon storage temperature. Based upon the observed rates of inactivation the average times which would be required for a 90% decrease (one log10 unit) in virus titer for unconcentrated eluates are 27 days at 23 degrees C, 198 days at 2 degrees C, and 375 days at -70 degrees C. The calculated average times required for a 90% decrease in virus titer for concentrated eluates are 22 days at 23 degrees C, 132 days at 2 degrees C, and 246 days at -70 degrees C. In both types of eluates the rates of virus inactivation at 2 degrees C were statistically different from those observed at 23 degrees C, but not different from those observed at -70 degrees C. The three study temperatures were selected to approximate holding of samples in an air-conditioned room, fluid on wet ice (H2O), and frozen on dry ice (CO2).

Survival of indigenous enteric viruses during storage of waste water sludge samples.

The stability of indigenous enteric viruses in samples of settled primary and mixed-liquor activated sludges was studied at 2, 23, and -70 degrees C. Changes of virus titer which occurred in these samples were followed during an 84-day observation period, with rates of change then calculated by least-squares regression. Virus survival was found to be statistically dependent (p less than or equal to 0.05) upon storage temperature but not sludge solids content. Based upon the observed rates of inactivation, the average times which would be required for a 90% decrease in virus titer are 26 days at 23 degrees C, 180 days at 2 degrees C, and 163 days at -70 degrees C. As a group, the rates of virus inactivation observed at 2 degrees C were statistically different (p less than or equal to 0.05) from those observed at 23 degrees C, but not different from those observed at -70 degrees C. The three study temperatures were selected to approximate holding of samples in an air-conditioned room, on wet ice (H2O), and on dry ice (CO2).

Detection of Indigenous Enteric Viruses in Raw Sewage Effluents of the City of Athens, Greece, During a Two Year Survey

In a two year survey of enteric viruses in urban sewage effluents of Athens, Greece, during 1982–1983, indigenous Enteroviruses and Adenoviruses have been detected. Enteroviruses, (Polio, Coxsackie B and Echo) were recovered on Vero or BGM cells by inoculation of samples, after a pre-concentration step utilizing glass powder. Adenoviruses were recovered on Hep2 cells after being Precipitated with protamine sulfate. The viral content was in the order of 102 -103 cytopathogenic units (CPU) per litre of sample. Seasonal fluctuations of the various serotypes recovered were observed. The peak of Adenoviruses was found in early spring whereas Enteroviruses peaked in late summer-early fall. The most frequently recovered serotypes within each group were : Polio III (47%), Coxsackie B5 (56%), Echo 7 (61%) and Adeno 7 (43%). Similar isolation frequencies, except for Polio, were found in humans as well. As regards Polioviruses, all strains recovered from sewage were found to be vaccine-related by the intratypic serodifferentiation test.

Evaluation of the Load of Enteroviruses in a Biological Wastewater Treatment Plant

The numbers of enteroviruses, classical bacterial indicators and physico-chemical parameters were recorded for raw and treated wastewaters from the NANCY (FRANCE) activated sludge treatment plant, over 24 and 72 hours periods. Sampling was performed manually by collection of 2 and 3 hour interval dip samples and by sequential automatic samplers. The results obtained with both methods are in good agreement; 24 hours composite samples with automatic sampling are representative of enteroviruses flux and thus allow studies of the efficiency of removal treatments. According to both sampling methods, the efficiency of the NANCY wastewater treatment plant is about 84 % for the removal of indigenous enteric viruses.

Virological Study of Drinking and Wastewater Disinfection by Ozonation

During laboratory assays of microbiological inactivation in a pilot water treatment plant (36 1/h) with drinking water artificially contaminated with poliovirus 1 and fecal indicator bacteria, ozonation shows a very strong disinfection power. There is no significant difference in the sensibility of these microorganisms to ozone. In the same laboratory plant during raw wastewater disinfection assays, the indigenous enteric viruses present a greater resistance to ozone than the indigenous fecal indicators. These results point out the important difference between the use of laboratory strains and indigenous microorganisms and confirm the interest in ozone disinfection for virucidal purposes.

Procedure for the recovery of airborne human enteric viruses during spray irrigation of treated wastewater

Because of the relatively low number of indigenous enteric viruses recovered from secondary wastewater effluents, their presence in air (aerosols) as a result of wastewater spray irrigation requires extensive sampling. Methodology to allow the recovery of indigenous enteroviruses from aerosols generated at an operational wastewater irrigation site was tested under both laboratory and field conditions.

Talc-celite layers in virus recovery from potable waters experimentally contaminated with field isolates and sewage

The efficiency of the talc-Celite technique was tested by using potable water samples experimentally-contaminated with (a) strains of enteric viruses recovered from field samples of wastewaters (b) indigenous enteric viruses contaminated, in raw sewage. An average of 88.0% of in-put virus could be recovered when potable water samples contaminated, in separate experiments, with five different isolates of enteric viruses (a vaccine strain of polio 1, non-vaccine strain of polio 1, echo I, coxsackie B3, and reovirus) were concentrated by this technique. When potable water samples containing either 0.05% or 0.1% of raw sewage were processed by this method, about 86.0% of the indigenous enteric virus plaque forming units could be recovered.