Impact of operational conditions on drinking water biofilm dynamics and coliform invasion potential.

Biofilms within drinking water distribution systems serve as a habitat for drinking water microorganisms. However, biofilms can negatively impact drinking water quality by causing water discoloration and deterioration and can be a reservoir for unwanted microorganisms. In this study, we investigated whether indicator organisms for drinking water quality, such as coliforms, can settle in mature drinking water biofilms. Therefore, a biofilm monitor consisting of glass rings was used to grow and sample drinking water biofilms. Two mature drinking water biofilms were characterized by flow cytometry, ATP measurements, confocal laser scanning microscopy, and 16S rRNA sequencing. Biofilms developed under treated chlorinated surface water supply exhibited lower cell densities in comparison with biofilms resulting from treated groundwater. Overall, the phenotypic as well as the genotypic characteristics were significantly different between both biofilms. In addition, the response of the biofilm microbiome and possible biofilm detachment after minor water quality changes were investigated. Limited changes in pH and free chlorine addition, to simulate operational changes that are relevant for practice, were evaluated. It was shown that both biofilms remained resilient. Finally, mature biofilms were prone to invasion of the coliform, Serratia fonticola. After spiking low concentrations (i.e., ±100 cells/100 mL) of the coliform to the corresponding bulk water samples, the coliforms were able to attach and get established within the mature biofilms. These outcomes emphasize the need for continued research on biofilm detachment and its implications for water contamination in distribution networks. IMPORTANCE: The revelation that even low concentrations of coliforms can infiltrate into mature drinking water biofilms highlights a potential public health concern. Nowadays, the measurement of coliform bacteria is used as an indicator for fecal contamination and to control the effectiveness of disinfection processes and the cleanliness and integrity of distribution systems. In Flanders (Belgium), 533 out of 18,840 measurements exceeded the established norm for the coliform indicator parameter in 2021; however, the source of microbial contamination is mostly unknown. Here, we showed that mature biofilms, are susceptible to invasion of Serratia fonticola. These findings emphasize the importance of understanding and managing biofilms in drinking water distribution systems, not only for their potential to influence water quality, but also for their role in harboring and potentially disseminating pathogens. Further research into biofilm detachment, long-term responses to operational changes, and pathogen persistence within biofilms is crucial to inform strategies for safeguarding drinking water quality.

Electrochemically assisted production of biogenic palladium nanoparticles for the catalytic removal of micropollutants in wastewater treatment plants effluent.

Biogenic palladium nanoparticles (bio-Pd NPs) are used for the reductive transformation and/or dehalogenation of persistent micropollutants. In this work, H2 (electron donor) was produced in situ by an electrochemical cell, permitting steered production of differently sized bio-Pd NPs. The catalytic activity was first assessed by the degradation of methyl orange. The NPs showing the highest catalytic activity were selected for the removal of micropollutants from secondary treated municipal wastewater. The synthesis at different H2 flow rates (0.310 L/hr or 0.646 L/hr) influenced the bio-Pd NPs size. The NPs produced over 6 hr at a low H2 flow rate had a larger size (D50 = 39.0 nm) than those produced in 3 hr at a high H2 flow rate (D50 = 23.2 nm). Removal of 92.1% and 44.3% of methyl orange was obtained after 30 min for the NPs with sizes of 39.0 nm and 23.2 nm, respectively. Bio-Pd NPs of 39.0 nm were used to treat micropollutants present in secondary treated municipal wastewater at concentrations ranging from µg/L to ng/L. Effective removal of 8 compounds was observed: ibuprofen (69.5%) < sulfamethoxazole (80.6%) < naproxen (81.4%) < furosemide (89.7%) < citalopram (91.7%) < diclofenac (91.9%) < atorvastatin (> 94.3%) < lorazepam (97.2%). Removal of fluorinated antibiotics occurred at > 90% efficiency. Overall, these data indicate that the size, and thus the catalytic activity of the NPs can be steered and that the removal of challenging micropollutants at environmentally relevant concentrations can be achieved through the use of bio-Pd NPs.

The influence of H2 partial pressure on biogenic palladium nanoparticle production assessed by single-cell ICP-mass spectrometry.

The production of biogenic palladium nanoparticles (bio-Pd NPs) is widely studied due to their high catalytic activity, which depends on the size of nanoparticles (NPs). Smaller NPs (here defined as <100 nm) are more efficient due to their higher surface/volume ratio. In this work, inductively coupled plasma-mass spectrometry (ICP-MS), flow cytometry (FCM) and transmission electron microscopy (TEM) were combined to obtain insight into the formation of these bio-Pd NPs. The precipitation of bio-Pd NPs was evaluated on a cell-per-cell basis using single-cell ICP-MS (SC-ICP-MS) combined with TEM images to assess how homogenously the particles were distributed over the cells. The results provided by SC-ICP-MS were consistent with those provided by "bulk" ICP-MS analysis and FCM. It was observed that heterogeneity in the distribution of palladium over an entire cell population is strongly dependent on the Pd2+ concentration, biomass and partial H2 pressure. The latter three parameters affected the particle size, ranging from 15.6 to 560 nm, and exerted a significant impact on the production of the bio-Pd NPs. The TEM combined with SC-ICP-MS revealed that the mass distribution for bacteria with high Pd content (144 fg Pd cell-1 ) indicated the presence of a large number of very small NPs (D50 = 15.6 nm). These results were obtained at high cell density (1 × 105 ± 3 × 104 cells µl-1 ) and H2 partial pressure (180 ml H2 ). In contrast, very large particles (D50 = 560 nm) were observed at low cell density (3 × 104 ± 10 × 102 cells µl-1 ) and H2 partial pressure (10-100 ml H2 ). The influence of the H2 partial pressure on the nanoparticle size and the possibility of size-tuned nanoparticles are presented.

Online microbial monitoring of drinking water: How do different techniques respond to contaminations in practice?

Safeguarding the microbial water quality remains a challenge for drinking water utilities, and because of population growth and climate change, new issues arise regularly. To overcome these problems, biostable drinking water production and water reuse will become increasingly important. In this respect, high-resolution online microbial monitoring during treatment and distribution could prove essential. Here, we present the first scientific and practical comparison of multiple online microbial monitoring techniques in which six commercially available devices were set up in a full-scale drinking water production plant. Both the devices' response towards operational changes and contaminations, as well as their detection limit for different contaminations were evaluated and compared. During normal operation, all devices were able to detect abrupt operational changes such as backwashing of activated carbon filters and interruption of the production process in a fast and sensitive way. To benchmark their response to contaminations, the calculation of a dynamic baseline for sensitive separation between noise and events is proposed. In order of sensitivity, enzymatic analysis, ATP measurement, and flow cytometric fingerprinting were the most performant for detection of rain- and groundwater contaminations (0.01 - 0.1 v%). On the other hand, optical classification and flow cytometric cell counts showed to be more robust techniques, requiring less maintenance and providing direct information about the cell concentration, even though they were still more sensitive than plate counting. The choice for a certain technology will thus depend on the type of application and is a balance between sensitivity, price and maintenance. All things considered, a combination of several devices and use of advanced data analysis such as fingerprinting may be of added value. In general, the strategic implementation of online microbial monitoring as early-warning system will allow for intensive quality control by high-frequency sampling as well as a short event response timeframe.

Online microbial fingerprinting for quality management of drinking water: Full-scale event detection.

Microbial regrowth during drinking water distribution can result in a variety of problems such as a deviating taste and odor, and may even pose a risk to public health. Frequent monitoring is essential to anticipate events of biological instability, and relevant microbial parameters for operational control of biostability of drinking water should be developed. Here, online flow cytometry and derived biological metrics were used to assess the biological stability of a full-scale drinking water tower during normal and disturbed flow regime. Pronounced operational events, such as switching from drinking water source, and seasonal changes, were detected in the total cell counts, and regrowth was observed despite the short hydraulic residence time of 6-8 h. Based on the flow cytometric fingerprints, the Bray-Curtis dissimilarity was calculated and was developed as unambiguous parameter to indicate or warn for changing microbial drinking water quality during operational events. In the studied water tower, drastic microbial water quality changes were reflected in the Bray-Curtis dissimilarity, which demonstrates its use as an indicator to follow-up and detect microbial quality changes in practice. Hence, the Bray-Curtis dissimilarity can be used in an online setup as a straightforward parameter during full-scale operation of drinking water distribution, and combined with the cell concentration, it serves as an early-warning system for biological instability.

High-rate activated sludge systems combined with dissolved air flotation enable effective organics removal and recovery.

High-rate activated sludge (HRAS) systems typically generate diluted sludge which requires further thickening prior to anaerobic digestion (AD), besides the need to add considerable coagulant and flocculant for the solids separation. As an alternative to conventional gravitational settling, a dissolved air flotation (DAF) unit was coupled to a HRAS system or a high-rate contact stabilization (HiCS) system. The HRAS-DAF system allowed up to 78% removal of the influent solids, and the HiCS-DAF 67%. Both were within the range of values typically obtained for HRAS-settler systems, albeit at a lower chemical requirement. The separated sludge had a high concentration of up to 47 g COD L-1, suppressing the need of further thickening before AD. Methanation tests showed a biogas yield of up to 68% on a COD basis. The use of a DAF separation system can thus enable direct organics removal at high sludge concentration and with low chemical needs.

Flow cytometry for immediate follow-up of drinking water networks after maintenance.

Drinking water networks need maintenance every once in a while, either planned interventions or emergency repairs. When this involves opening of the water pipes, precautionary measures need to be taken to avoid contamination of the drinking water at all time. Drinking water suppliers routinely apply plating for faecal indicator organisms as quality control in such a situation. However, this takes at least 21 h of waiting time, which can be crucial when dealing with major supply pipes. A combination of flow cytometric (FCM) bacterial cell counts with FCM fingerprinting techniques is proposed in this study as a fast and sensitive additional technique. In three full scale situations, major supply pipes with 400-1050 mm diameter were emptied for maintenance, shock-chlorinated and flushed with large amounts of clean drinking water before taking back in operation. FCM measurements of the discharged flushing water revealed fast lowering and stabilizing bacterial concentrations once flushing is initiated. Immediate comparison with clean reference drinking water used for flushing was done, and the moment when both waters had similar bacterial concentrations was considered as the endpoint of the necessary flushing works. This was usually after 2-4 h of flushing. FCM fingerprinting, based on both bacteria and FCM background, was used as additional method to verify how similar flushing and reference samples were and yielded similar results. The FCM approved samples were several hours later approved as well by the drinking water supplier after plating and incubation for total Coliforms and Enterococci. These were used as decisive control to set the pipes back in operation. FCM proved to be a more conservative test than plating, yet it yielded immediate results. Application of these FCM methods can therefore avoid long unnecessary waiting times and large drinking water losses.

The antibacterial and anti-biofouling performance of biogenic silver nanoparticles by Lactobacillus fermentum.

Biofouling is a major challenge in the water industry and public health. Silver nanoparticles (AgNPs) have excellent antimicrobial properties and are considered to be a promising anti-biofouling agent. A modified method was used to produce small sized and well-dispersed biogenic silver nanoparticles with a mean size of ~6 nm (Bio-Ag0-6) using Lactobacillus fermentum. The morphology, size distribution, zeta potential and oxidation state of the silver were systematically characterized. Determination of minimal inhibitory and bactericidal concentration results revealed that biogenic silver Bio-Ag(0-6) can effectively suppress the growth of the test bacteria. Additionally, the inhibition effects of Bio-Ag(0-6) on biofilm formation and on established biofilms were evaluated using P. aeruginosa (ATCC 27853) as the model bacterium. The results from microtiter plates and confocal laser scanning microscopy demonstrated that Bio-Ag(0-6) not only exhibited excellent antibacterial performance but also could control biofilm formation and induce detachment of the bulk of P. aeruginosa biofilms leaving a small residual matrix.

Doping of biogenic Pd catalysts with Au enables dechlorination of diclofenac at environmental conditions.

By using the metal reducing capacities of bacteria, Pd nanoparticles can be produced in a sustainable way ('bio-Pd'). These bio-Pd nanoparticles can be used as a catalyst in, for example, dehalogenation reactions. However, some halogenated compounds are not efficiently degraded using a bio-Pd catalyst. This study shows that the activity of bio-Pd can be improved by doping with Au(0) ('bio-Pd/Au'). In contrast with bio-Pd, bio-Pd/Au could perform the removal of the model pharmaceutical compound diclofenac from an aqueous medium in batch experiments at neutral pH and with H(2) as the hydrogen donor (first order decay constant of 0.078 ± 0.009 h(-1)). Dehalogenation was for both catalysts the only observed reaction. For bio-Pd/Au, a disproportional increase of catalytic activity was observed with increasing Pd-content of the catalyst. In contrast, when varying the Au-content of the catalyst, a Pd/Au mass ratio of 50/1 showed the highest catalytic activity (first order decay value of 0.52 ± 0.02 h(-1)). The removal of 6.40 µg L(-1) diclofenac from a wastewater treatment plant effluent using bio-Pd was not possible even after prolonged reaction time. However, by using the most active bio-Pd/Au catalyst, 43.8 ± 0.5% of the initially present diclofenac could be removed after 24 h. This study shows that doping of bio-Pd nanoparticles with Au(0) can be a promising approach for the reductive treatment of wastewaters containing halogenated contaminants.

Biogenic silver nanoparticles (bio-Ag 0) decrease biofouling of bio-Ag 0/PES nanocomposite membranes.

Biofouling is a major problem for the application of membrane technology in water and wastewater treatment. One of the practical strategies to decrease biofouling is the use of advanced anti-biofouling membrane material. In this study, different amounts of biogenic silver nanoparticles (bio-Ag(0)) were embedded in polyethersulfone (PES) membranes, using the phase-inversion method. The effects of the bio-Ag(0) content on the structure of the membrane and its filtration performance were systematically investigated. The results demonstrated that silver-containing nanostructures were uniformly distributed on membrane surface. Bio-Ag(0) incorporation slightly increased the hydrophilicity of the PES membrane and increased the permeate flux. The anti-bacterial and anti-biofouling properties of the bio-Ag(0)/PES nanocomposites membrane were tested with pure cultures (Escherichia coli and Pseudomonas aeruginosa) and a mixed culture (an activated sludge bioreactor), respectively. The bio-Ag(0)/PES composite membranes, even with the lowest content of biogenic silver (140 mg bio-Ag(0)m(-2)), not only exhibited excellent anti-bacterial activity, but also prevented bacterial attachment to the membrane surface and decreased the biofilm formation during a 9 weeks test.

Catalytic dechlorination of diclofenac by biogenic palladium in a microbial electrolysis cell.

Diclofenac is one of the most commonly detected pharmaceuticals in wastewater treatment plant (WWTP) effluents and the receiving water bodies. In this study, biogenic Pd nanoparticles ('bio-Pd') were successfully applied in a microbial electrolysis cell (MEC) for the catalytic reduction of diclofenac. Hydrogen gas was produced in the cathodic compartment, and consumed as a hydrogen donor by the bio-Pd on the graphite electrodes. In this way, complete dechlorination of 1 mg diclofenac l(-1) was achieved during batch recirculation experiments, whereas no significant removal was observed in the absence of the biocatalyst. The complete dechlorination of diclofenac was demonstrated by the concomitant production of 2-anilinophenylacetate (APA). Through the addition of -0.8 V to the circuit, continuous and complete removal of diclofenac was achieved in synthetic medium at a minimal HRT of 2 h. Continuous treatment of hospital WWTP effluent containing 1.28 µg diclofenac l(-1) resulted in a lower removal efficiency of 57%, which can probably be attributed to the affinity of other environmental constituents for the bio-Pd catalyst. Nevertheless, reductive catalysis coupled to sustainable hydrogen production in a MEC offers potential to lower the release of micropollutants from point-sources such as hospital WWTPs.

Bio-palladium: from metal recovery to catalytic applications.

While precious metals are available to a very limited extent, there is an increasing demand to use them as catalyst. This is also true for palladium (Pd) catalysts and their sustainable recycling and production are required. Since Pd catalysts exist nowadays mostly under the form of nanoparticles, these particles need to be produced in an environment-friendly way. Biological synthesis of Pd nanoparticles ('bio-Pd') is an innovative method for both metal recovery and nanocatalyst synthesis. This review will discuss the different bio-Pd precipitating microorganisms, the applications of the catalyst (both for environmental purposes and in organic chemistry) and the state of the art of the reactors based on the bio-Pd concept. In addition, some main challenges are discussed, which need to be overcome in order to create a sustainable nanocatalyst. Finally, some outlooks for bio-Pd in environmental technology are presented.

Biogenic palladium enhances diatrizoate removal from hospital wastewater in a microbial electrolysis cell.

To decrease the load of pharmaceuticals to the environment, decentralized wastewater treatment has been proposed for important point-sources such as hospitals. In this study, a microbial electrolysis cell (MEC) was used for the dehalogenation of the iodinated X-ray contrast medium diatrizoate. The presence of biogenic palladium nanoparticles (bio-Pd) in the cathode significantly enhanced diatrizoate removal by direct electrochemical reduction and by reductive catalysis using the H(2) gas produced at the cathode of the MEC. Complete deiodination of 3.3 µM (2 mg L(-1)) diatrizoate from a synthetic medium was achieved after 24 h of recirculation at an applied voltage of -0.4 V. An equimolar amount of the deiodinated metabolite 3,5-diacetamidobenzoate (DAB) was detected. Higher cell voltages increased the dehalogenation rates, resulting in a complete removal after 2 h at -0.8 V. At this cell voltage, the MEC was also able to remove 85% of diatrizoate from hospital effluent containing 0.5 µM (292 µg L(-1)), after 24 h of recirculation. Complete removal was obtained when the effluent was continuously fed at a volumetric loading rate of 204 mg diatrizoate m(-3) total cathodic compartment (TCC) day(-1) to the MEC with a hydraulic retention time of 8 h. At -0.8 V, the MEC system could also eliminate 54% of diatrizoate from spiked urine during a 24 h recirculation experiment. The final product DAB was demonstrated to be removable by nitrifying biomass, which suggests that the combination of a MEC and bio-Pd in its cathode offers potential to dehalogenate pharmaceuticals, and to significantly lower the environmental burden of hospital waste streams.

Palladium nanoparticles produced by fermentatively cultivated bacteria as catalyst for diatrizoate removal with biogenic hydrogen.

A new biological inspired method to produce nanopalladium is the precipitation of Pd on a bacterium, i.e., bio-Pd. This bio-Pd can be applied as catalyst in dehalogenation reactions. However, large amounts of hydrogen are required as electron donor in these reactions resulting in considerable costs. This study demonstrates how bacteria, cultivated under fermentative conditions, can be used to reductively precipitate bio-Pd catalysts and generate the electron donor hydrogen. In this way, one could avoid the costs coupled to hydrogen supply. The catalytic activities of Pd(0) nanoparticles produced by different strains of bacteria (bio-Pd) cultivated under fermentative conditions were compared in terms of their ability to dehalogenate the recalcitrant aqueous pollutants diatrizoate and trichloroethylene. While all of the fermentative bio-Pd preparations followed first order kinetics in the dehalogenation of diatrizoate, the catalytic activity differed systematically according to hydrogen production and starting Pd(II) concentration in solution. Batch reactors with nanoparticles formed by Citrobacter braakii showed the highest diatrizoate dehalogenation activity with first order constants of 0.45 ± 0.02 h⁻¹ and 5.58 ± 0.6 h⁻¹ in batches with initial concentrations of 10 and 50 mg L⁻¹ Pd, respectively. Nanoparticles on C. braakii, used in a membrane bioreactor treating influent containing 20 mg L⁻¹ diatrizoate, were capable of dehalogenating 22 mg diatrizoate mg⁻¹ Pd over a period of 19 days before bio-Pd catalytic activity was exhausted. This study demonstrates the possibility to use the combination of Pd(II), a carbon source and bacteria under fermentative conditions for the abatement of environmental halogenated contaminants.

The antibacterial activity of biogenic silver and its mode of action.

In a previous study, biogenic silver nanoparticles were produced by Lactobacillus fermentum which served as a matrix preventing aggregation. In this study the antibacterial activity of this biogenic silver was compared to ionic silver and chemically produced nanosilver. The minimal inhibitory concentration (MIC) was tested on Gram-positive and Gram-negative bacteria and was comparable for biogenic silver and ionic silver ranging from 12.5 to 50 mg/L. In contrast, chemically produced nanosilver had a much higher MIC of at least 500 mg/L, due to aggregation upon application. The minimal bactericidal concentration (MBC) in drinking water varied from 0.1 to 0.5 mg/L for biogenic silver and ionic silver, but for chemically produced nanosilver concentrations, up to 12.5 mg/L was needed. The presence of salts and organic matter decreased the antimicrobial activity of all types of silver resulting in a higher MBC and a slower inactivation of the bacteria. The mode of action of biogenic silver was mainly attributed to the release of silver ions due to the high concentration of free silver ions measured and the resemblance in performance between biogenic silver and ionic silver. Radical formation by biogenic silver and direct contact were found to contribute little to the antibacterial activity. In conclusion, biogenic nanosilver exhibited equal antimicrobial activity compared to ionic silver and can be a valuable alternative for chemically produced nanosilver.

Degradation of acetaminophen by Delftia tsuruhatensis and Pseudomonas aeruginosa in a membrane bioreactor.

The incidence and fate of pharmaceuticals in the water cycle impose a growing concern for the future reuse of treated water. Because of the recurrent global use of drugs such as Acetaminophen (APAP), an analgesic and antipyretic drug, they are often detected in wastewater treatment plant (WWTP) effluents, receiving surface waters and drinking water resources. In this study, the removal of APAP has been demonstrated in a membrane bioreactor (MBR) fed with APAP as the sole carbon source. After 16 days of operation, at a hydraulic retention time (HRT) of 5 days, more than 99.9% removal was obtained when supplying a synthetic WWTP effluent with 100 µg APAP L(-1). Batch experiments indicated no sorption of APAP to the biomass, no influence of the WWTP effluent matrix, and the capability of the microbial consortium to remove APAP at environmentally relevant concentrations (8.3 µg APAP L(-1)). Incubation with allylthiourea, an ammonia monooxygenase inhibitor, demonstrated that the APAP removal was mainly associated with heterotrophic bacteria and not with the ammonia-oxidizing bacteria. Two APAP degrading strains were isolated from the MBR biomass and identified as Delftia tsuruhatensis and Pseudomonas aeruginosa. During incubation of the isolates, hydroquinone - a potentially toxic transformation product - was temporarily formed but further degraded and/or metabolized. These results suggest that the specific enrichment of a microbial consortium in an MBR operated at a high sludge age might be a promising strategy for post-treatment of WWTP effluents containing pharmaceuticals.

Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes.

The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the association of silver nanoparticles with the bacterial cell surface of Lactobacillus fermentum (referred to as biogenic silver or bio-Ag(0)) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag(0) particles, preventing aggregation during encapsulation. In this study, bio-Ag(0) was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag(0) and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag(+) from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag(0)(powder) m(-2) in a submerged plate membrane reactor operated at a flux of 3.1 L m(-2) h(-1). Upon startup, the silver concentration in the effluent initially increased to 271 µg L(-1) but after filtration of 31 L m(-2), the concentration approached the drinking water limit ( = 100 µg L(-1)). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m(-2) h(-1), showing the potential of this membrane technology for water disinfection on small scale.

Virus removal by biogenic cerium.

The rare earth element cerium has been known to exert antifungal and antibacterial properties in the oxidation states +III and +IV. This study reports on an innovative strategy for virus removal in drinking water by the combination of Ce(III) on a bacterial carrier matrix. The biogenic cerium (bio-Ce) was produced by addition of aqueous Ce(III) to actively growing cultures of either freshwater manganese-oxidizing bacteria (MOB) Leptothrix discophora or Pseudomonas putida MnB29. X-ray absorption spectroscopy results indicated that Ce remained in its trivalent state on the bacterial surface. The spectra were consistent with Ce(III) ions associated with the phosphoryl groups of the bacterial cell wall. In disinfection assays using a bacteriophage as model, it was demonstrated that bio-Ce exhibited antiviral properties. A 4.4 log decrease of the phage was observed after 2 h of contact with 50 mg L(-1) bio-Ce. Given the fact that virus removal with 50 mg L(-1) Ce(III) as CeNO(3) was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal.

Inactivation of murine norovirus 1 and Bacteroides fragilis phage B40-8 by mesophilic and thermophilic anaerobic digestion of pig slurry.

Mesophilic (37 degrees C) and thermophilic (52 degrees C) anaerobic digestion of pig slurry induced at least a 4-log decrease in murine norovirus 1, used as a surrogate virus for porcine norovirus, after 13 and 7 days, respectively. Bacteroides fragilis phage B40-8, employed as a universal viral model, was lowered by 2.5 log after 7 days. The viral titer declined due to temperature and matrix effects.

Removal of diatrizoate with catalytically active membranes incorporating microbially produced palladium nanoparticles.

There is an increasing concern about the fate of iodinated contrast media (ICM) in the environment. Limited removal efficiencies of currently applied techniques such as advanced oxidation processes require more performant strategies. The aim of this study was to establish an innovative degradation process for diatrizoate, a highly recalcitrant ICM, by using biogenic Pd nanoparticles as free suspension or immobilized in polyvinylidene fluoride (PVDF) and polysulfone (PSf) membranes. As measured by HPLC-UV, the removal of 20mg L(-1) diatrizoate by a 10mg L(-1) Pd suspension was completed after 4h at a pH of 10. LC-MS analysis provided evidence for the sequential hydrodeiodination of diatrizoate. Pd did not lose its activity after incorporation in the PVDF and PSf matrix and the highest activity (k(cat)=30.0+/-0.4h(-1) L g(-1) Pd) was obtained with a casting solution of 10% PSf and 500mg L(-1) Pd. Subsequently, water containing 20mg L(-1) diatrizoate was treated in a membrane contactor, in which the water was supplied at one side of the membrane while hydrogen was provided at the other side. In a fed batch configuration, a removal efficiency of 77% after a time period of 48h was obtained. This work showed that membrane contactors with encapsulated biogenic nanoparticles can be instrumental for treatment of water contaminated with diatrizoate.