Genotoxic response of Austrian groundwater samples treated under standardized UV (254 nm)--disinfection conditions in a combination of three different bioassays

The UV Dose Used for Disinfection of Drinking Water in Sweden Inadequately Inactivates Enteric Virus with Double-Stranded Genomes

Irradiation with ultraviolet light (UV) at 254 nm is effective in inactivating a wide range of human pathogens. In Sweden, a UV dose of 400 J/m² is often used for the treatment of drinking water. To investigate its effect on virus inactivation, enteric viruses with different genomic organizations were irradiated with three UV doses (400, 600, and 1000 J/m²), after which their viability on cell cultures was examined. Adenovirus type 2 (double-stranded DNA), simian rotavirus 11 (double-stranded RNA), and echovirus 30 (single-stranded RNA) were suspended in tap water and pumped into a laboratory-scale Aquada 1 UV reactor. Echovirus 30 was reduced by 3.6-log₁₀ by a UV dose of 400 J/m². Simian rotavirus 11 and adenovirus type 2 were more UV resistant with only 1-log₁₀ reduction at 400 J/m² and needed 600 J/m² for 2.9-log₁₀ and 3.1-log₁₀ reductions, respectively. There was no significant increase in the reduction of viral viability at higher UV doses, which may indicate the presence of UV-resistant viruses. These results show that higher UV doses than those usually used in Swedish drinking water treatment plants should be considered in combination with other barriers to disinfect the water when there is a risk of fecal contamination of the water.

Performance and microbial protein expression during anaerobic treatment of alkali-decrement wastewater using a strengthened circulation anaerobic reactor

Herein, a strengthened circulation anaerobic (SCA) reactor was employed for the treatment of actual alkali-decrement wastewater. The degradation mechanism of polyester oligomers and the relationship between the treatment performance and microbial community structure were systematically investigated using various advanced techniques. Results suggest that the accumulation of volatile fatty acids has an inhibitory effect on methanogenic activity. Molecular weight distributions suggest that only incomplete degradation of oligomers was achieved, due to acetogenic inhibition in the lower part of the SCA reactor. Meta-proteomic approach analysis revealed that the methanogens containing heterodisulfide reductase were the primary species involved in methane metabolism. Based on these findings, a possible degradation mechanism for alkali-decrement wastewater in the SCA reactor is proposed. This high-performance anaerobic reactor could be further scaled-up and optimized to serve as a promising and effective unit for the treatment of other refractory industrial wastewaters.

Clastogenecity evaluation of water of Lake Sevan (Armenia) using Tradescantia micronucleus assay

The clastogenic effects of water samples in seven locations of Lake Sevan (Armenia) with the application of Trad-MCN (micronuclei) bioassay using Tradescantia (clone 02) were investigated. A significant increase in the frequency of micronuclei in tetrads of pollen microspores and tetrads with micronuclei exposed to the test samples compared to the control has been revealed. A multivariate analysis indicated linkage between the frequencies of occurrence of micronuclei in the cells and Ni and Co ions. The results were compared with the endpoints of another Tradescantia-based test system (stamen hair mutation test) performed on the same water samples and generation of the plant: occurrences of micronuclei in sporogenic cells coincided with that of non-surviving stamen hair.

Potential risks from UV/H2O2 oxidation and UV photocatalysis: A review of toxic, assimilable, and sensory-unpleasant transformation products

UV based advanced oxidation processes (UV-AOPs) that efficiently eliminate organic pollutants during water treatment have been the subject of numerous investigations. Most organic pollutants are not completely mineralized during UV-AOPs but are partially oxidized into transformation products (TPs), thereby adding complexity to the treated water and posing risks to humans, ecological systems, and the environment. While the degradation kinetics and mechanisms of pollutants have been widely documented, there is little information about the risks associated with TPs. In this review, we have collated recent knowledge about the harmful TPs that are generated in UV/H₂O₂ and UV photocatalysis, two UV-AOPs that have been studied extensively. Toxic and assimilable TPs were ubiquitously observed in more than 80% of UV-AOPs of organic pollutants, of which the toxicity and assimilability levels changed with variations in the reaction conditions, such as the UV fluence and oxidant dosage. Previous studies and modeling assessments showed that toxic and assimilable TPs may be generated during hydroxylation, dealkylation, decarboxylation, and deamination. Among various reactions, TPs generated from dealkylation and decarboxylation were generally less and more toxic than the parent pollutants, respectively; TPs generated from decarboxylation and deamination were generally less and more assimilable than the parent pollutants, respectively. There is also potential concern about the sensory-unpleasant TPs generated by oxidations and subsequent metabolism of microorganisms. In this overview, we stress the need to include both the concentrations of organic pollutants and the evaluations of the risks from TPs for the quality assessments of the water treated by UV-AOPs.

UV Induced Mutagenicity in Water: Causes, Detection, Identification and Prevention

At first it seemed that UV processes for disinfection and advanced oxidation were "harmless", as they didn't involve the addition of "dangerous" chemicals nor seemed to result in the formation of toxic byproducts. However, recently it has become clear that also during UV processes mutagentic/genotoxic byproducts may be formed. It was found that these are nitrogen containing aromatic compounds, which are formed by the reaction of photolysis products of nitrate with (photolysis products of) natural organic matter. Now more has become clear on the formation process of these compounds, it is possible to limit or even prevent their formation during e.g. UV/H₂O₂ processes. Besides, it appears to be possible to remove such byproducts by means of filtration processes. Thus, UV based processes can safely be applied in water treatment.

Assessment of mutagenicity of water from Lake Sevan, Armenia with application of Tradescantia (clone 02)

For many decades water resources in Armenia have been affected by anthropogenic activity, therefore, a regular bioindication of genotoxic effects of the water bodies is desirable. The genotoxicity of water samples collected from different parts of Lake Sevan were assessed by means of Trad-SHM (stamen hair mutation) assay using Tradescantia (clone 02). Here we report a significant increase in the frequency of somatic mutations and morphological changes in the Tradescantia inflorescences exposed to the water samples compared to the control. The somatic mutations (recessive mutation and white mutation events) were mostly linked to the concentration of Al, Ni, As, Co and Pb in Artanish, Tsapatakh and Karchaghbyur, Noradus, Martuni and Litchk, while morphological changes (non-surviving hairs) were related to Co level in Tsapatakh and Karchaghbyur. The results obtained show that Lake Sevan contains substances which may cause genotoxicity and teratogenicity in Tradescantia and probably also in aquatic animals. The results also show that Trad-SHM assay can be used for monitoring natural resources.

Influence of process conditions and water quality on the formation of mutagenic byproducts in UV/H2O2 processes

UV/H2O2 processes in drinking water treatment may generate byproducts which cause an increased response in Ames fluctuation assays. As this probably involves a mixture of substances in very low concentrations, it is challenging to identify the individual byproducts. Therefore it was studied under which conditions mutagenic byproducts are formed and how this can be prevented. It was found that positive Ames fluctuation test responses only are obtained when Medium Pressure UV lamps are used, and not with Low Pressure lamps. This probably is explained by the photolysis of nitrate, which plays an important role in the formation of mutagenic byproducts. The most important parameters involved in the formation of such byproducts were demonstrated to be the nitrate concentration, the natural organic matter, the UV spectrum of the lamps, and the UV dose applied. These factors explain up to 74-87% of the Ames fluctuation test responses after UV/H2O2 drinking water treatment. By taking this into account, drinking water utilities can estimate whether UV processes applied in their case may cause the formation of mutagenic byproducts, and how to take measures to prevent it.

Oxidative stress-mediated genotoxicity of wastewaters collected from two different stations in northern India

Oxidative stress-mediated genotoxicity of wastewaters taken from two different cities, Saharanpur (SWW) and Aligarh (AWW), were compared with a battery of short-term assays namely the Allium cepa genotoxicity test, the plasmid-nicking assay, and the Ames fluctuation test. Both test-water samples - when used undiluted - increased the frequency of chromosomal abnormalities and/or micronuclei and alterations in the mitotic index of root cells of Allium cepa. Bridges and fragmentation of the chromosome were the predominant effects of the Saharanpur water sample while the Aligarh sample induced mainly chromosome fragmentation. Single- and double-strand breaks were also observed in plasmid DNA treated with these test wastewaters. The plasmid-nicking assay performed on SWW resulted in linearization of plasmid DNA when 18μl was tested (in a total reaction volume of 20μl). However, with the same amount of AWW, all three forms of plasmid, viz. supercoiled, open circular and linear were observed. Supplementation with specific scavengers of reactive oxygen species (ROS) caused a significant decline in mutagenicity of test-water samples in all the tests, pointing at oxidative stress as the mediator of the observed genotoxicity. The role of heavy metals in the AWW-induced oxidative stress and that of phenolics in SWW cannot be ruled out.

Micronucleus assays with Tradescantia pollen tetrads: an update

Micronucleus (MN) assays with early pollen tetrad cells of Tradescantia (Trad-MN assays) are at present the most widely used bioassays with plants for the detection of genotoxins in the environment. So far, ∼ 160 chemicals have been tested and ∼ 100 articles that concern complex environmental mixtures were published. This article summarises the results of Trad-MN studies, which have been carried out during the last 15 years with individual compounds and investigations concerning the pollution of environmental compartments (soil, water and air). The evaluation shows that the effects of certain genotoxins such as heavy metals, radionuclides, pesticides and air pollutants can be easily detected with this test. Comparisons with results obtained in MN studies with mitotic (root tip) cells indicate that meiotic tetrad cells are in general more sensitive. Important issues for future research concern the evaluation of the suitability of wildlife Tradescantia species that are sometimes used instead of specific clones (such as #4430 for which standardised protocols have been developed) as well as the assessment of the predictive value of Trad-MN results in regard to the prediction of cancer hazards in humans and adverse effects at the ecosystem level. The fact that the genotoxic effects of certain compound such as metals, which can be detected with plant bioassays, in particular with the Trad-MN assay but not in other commonly used bioassays (e.g. in bacterial tests) makes them an essential element in the batteries for environmental monitoring.

Formation and removal of genotoxic activity during UV/H(2)O(2)-GAC treatment of drinking water

The objective of this study was to determine the genotoxic activity of water after UV/H(2)O(2) oxidation and GAC filtration. Pre-treated surface water from three locations was treated with UV/H(2)O(2) with medium pressure (MP) lamps and passed through granulated activated carbon (GAC). Samples taken before and after each treatment step were extracted and concentrated by solid phase extraction (SPE) and analyzed for genotoxicity using the Comet assay with HepG2 cells and the Ames II assay. The Comet assay showed no genotoxic response in any of the samples. In the Ames II, no genotoxic response was obtained with the TAMix (a mix of six strains), but the TA98 strain showed an increase in genotoxic activity after MP-UV/H(2)O(2) for all three locations. GAC post treatment effectively reduced the activities to control levels at two of the three locations and to below the level of the pre-treated water at one site. The results indicate that UV/H(2)O(2) treatment may lead to the formation of genotoxic by-products, which can be removed by subsequent GAC filtration.

[The Vienna School of Water Hygiene from the End of World War II until now]

After the economic stagnation of the 1930s and World War II the water-hygiene had to revive. Besides basic research for large projects as the 3rd Viennese water-conduct, the Danube hydroelectric power station in Hainburg and the Marchfeldkanal new fields were opened. The evidence of fecal spring-water contamination by determination of the spectral-absorption-coefficients avoids the delay by bacterial cultivation and enables immediate satellite-transmission to central stations for turning-off the afflux. Determination of the origin (human and ruminant) of isolated E. coli by Real-time-PCR indicates necessities for sanitation. Investigation on UV-water-disinfection, considering also the formation of carcinogenic and genotoxic compounds, resulted in the only European national UV-norm and the establishment of one of the wordwide four testing institutions of UV-water-disinfection. The department for water-hygiene of the Medical University of Vienna carries out specific duties in various national committees of public health importance as well as in collaboration with EU, WHO, ISO and other international commissions.

Biofouling control in water by various UVC wavelengths and doses

UV light irradiation is being increasingly applied as a primary process for water disinfection, effectively used for inactivation of suspended (planktonic) cells. In this study, the use of UV irradiation was evaluated as a pretreatment strategy to control biofouling. The objective of this research was to elucidate the relative effectiveness of various targeted UV wavelengths and a polychromatic spectrum on bacterial inactivation and biofilm control. In a model system using Pseudomonas aeruginosa, the inactivation spectra corresponded to the DNA absorption spectra for all wavelengths between 220 and 280 nm, while wavelengths between 254 nm and 270 nm were the most effective for bacterial inactivation. Similar wavelengths of 254-260-270 nm were also more effective for biofilm control in most cases than targeted 239 and 280 nm. In addition, the prevention of biofilm formation by P. aeruginosa with a full polychromatic lamp was UV dose-dependent. It appears that biofilm control is improved when larger UV doses are given, while higher levels of inactivation are obtained when using a full polychromatic MP lamp. However, no significant differences were found between biofilms produced by bacteria that survived UV irradiation and biofilms produced by control bacteria at the same microbial counts. Moreover, the experiments showed that biofilm prevention depends on the post-treatment incubation time and nutrient availability, in addition to targeted wavelengths, UV spectrum and UV dose.

Removal effect on Mesocyclops leukarti and mutagenicity with chlorine dioxide

Mesocyclops leukurti of zooplankton propagates excessively in eutrophic water body and it cannot be effectively inactivated by the conventional drinking water treatment process. In order to tackle this problem, a study of removal effect on Mesocyclops leukarti with chlorine dioxide in a waterworks was performed. The results showed that Mesocyclops leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide preoxidation combined with the conventional drinking water treatment process. Higher oxidizability and molecular state of chlorine dioxide in water is the key to the inactivation of Mesocyclops leukarti. The chlorite, disinfection by-products (DBPs) of chlorine dioxide, was stable at 0.45 mg/L, which is lower than that critical value of the USEPA. GC-MS examination showed that the quantity of organic substance in the water treated by chlorine dioxide obviously decreased. Ames test further revealed that the mutagenicity was reduced by chlorine dioxide with respect to prechlorine. The propagation of Mesocyclops leukarti can be inactivated effectively and safely by chlorine dioxide pre-oxidation.

UV inactivation of adenovirus type 41 measured by cell culture mRNA RT-PCR

Adenoviruses are among the most resistant waterborne pathogens to UV disinfection, yet of the 51 serologically distinct human adenoviruses, only a few have been evaluated for their sensitivities to UV irradiation. Human enteric adenoviruses (Ad40 and Ad41) are difficult to cultivate and reliably assay for infectivity, requiring weeks to obtain cytopathogenic effects (CPE). Inoculated cell cultures often deteriorate before the appearance of distinctive CPE making it difficult to obtain reliable and reproducible data regarding UV inactivation. Adenovirus is a double-stranded DNA virus and produces messenger RNA (mRNA) during replication in host cells. The presence of viral mRNA in host cells is definitive evidence of infection. We recently developed a rapid and reliable cell culture-mRNA RT-PCR assay to detect and quantify adenovirus infectivity. Viral mRNA recovered from cell cultures 5-7 days after infection was purified on oligo-dT latex, treated with DNase, and amplified by RT-PCR using the primers specific for a conserved region of the hexon late mRNA transcript. Treatment of approximately 10(4) Ad41 with different doses of 254 nm germicidal UV radiation resulted in a dose-dependent loss of infectivity. As UV doses were increased from 75 to 200 mJ/cm2, virus survival decreased and no virus infectivity (measured by detectable mRNA) was found at a dose of 225 mJ/cm2 or higher. Our results using the cell culture mRNA RT-PCR assay indicate that Ad41 is more resistant to UV radiation than in a previous study using a conventional cell culture infectivity assay. Results were more similar to those found for Ad 40 using CPE as a measure of infectivity in another previous study.

Evaluation of industrial, hospital and domestic wastewater genotoxicity with the Salmonella fluctuation test and the SOS chromotest

An evaluation of the genotoxic potential of different wastewaters collected in the Rouen area was performed with the SOS chromotest (on Escherichia coli PQ37) and the Salmonella fluctuation test on Salmonella typhimurium strains TA98, TA100 and TA102 with or without metabolic activation. The samples were taken during two 1-week periods, one in January and one in April 2003. Six sites were selected for wastewater sampling in order to allow a comparative study between an area of mixed discharge (industrial, hospital and domestic) and an area of primarily domestic discharge. Out of a total of 71 daytime samples tested, 46 (65%) were positive in at least one assay: 22 samples out of 33 in January (67%), and 24 samples out of 38 in April (63%). The two genotoxicity tests have different sensitivities. Indeed, the Salmonella fluctuation test allowed the detection of 56% of the samples as genotoxic in January (18 out of 33), and 63% in April (24 out of 38) while the SOS chromotest allowed the detection of 18% of the samples as genotoxic, whatever the sampling period. The samples collected in domestic wastewater are at least as genotoxic as the samples collected in mixed wastewater. The possible source of the detected genotoxicity (industrial, hospital or domestic) is discussed. The results of this study show that the different types of wastewaters present a genotoxic risk. Additional studies should be undertaken in the analytical field in order to try to identify and quantify the compounds responsible for the genotoxicity. This difficult task will be necessary in order to identify the sources of toxicants and thus to take preventive and/or curative measures to limit the toxicity of the wastewater.

The Salmonella mutagenicity of industrial, surface and ground water samples of Aligarh region of India

The genotoxicity of three water bodies, viz. industrial waste water of Aligarh city, ground water pumped out from the industrial area of Aligarh, and river water of Yamuna, downstream of Agra, was carried out by means of Ames plate incorporation test and the Ames fluctuation test. All the test samples were significantly mutagenic in both the testing systems. The ground water and river water samples were subjected to XAD concentration prior to the mutagenicity/genotoxicity testing, while the industrial waste water was used directly. Whereas TA98, TA102 and TA104 strains have been found to be maximally sensitive in the Ames plate incorporation assay conducted for various water samples, TA98 and TA100 strains were the most responsive strains in the Ames fluctuation test. The apparent disparity in the sensitivity patterns of various Ames strains by plate incorporation and fluctuation assays could be attributed to a large extent to the different conventional ways of interpretation of the data in these systems.

Comparison of UV inactivation of spores of three encephalitozoon species with that of spores of two DNA repair-deficient Bacillus subtilis biodosimetry strains

When exposed to 254-nm UV, spores of Encephalitozoon intestinalis, Encephalitozoon cuniculi, and Encephalitozoon hellem exhibited 3.2-log reductions in viability at UV fluences of 60, 140, and 190 J/m(2), respectively, and demonstrated UV inactivation kinetics similar to those observed for endospores of DNA repair-defective mutant Bacillus subtilis strains used as biodosimetry surrogates. The results indicate that spores of Encephalitozoon spp. are readily inactivated at low UV fluences and that spores of UV-sensitive B. subtilis strains can be useful surrogates in evaluating UV reactor performance.