Low Chlorine Concentrations Research Articles

Electrochemical degradation of bisphenol A in chloride electrolyte—Factor analysis and mechanisms study

Electrochemical oxidation technology is a powerful method in the degradation of recalcitrant organics, due to the high oxidizing ability of active chlorine and reactive oxygen species generated in the cell. However, influencing factor analysis and intermediates detection during the electrochemical removal of organics has not been extensively studied in the chloride electrolyte. In this study, an orthogonal test array design of L16(4)3 was carried on with Pt anode in NaCl electrolyte, using the typical endocrine disruptor bisphenol A (BPA) as the model pollutant. The influencing order of the three main factors for BPA degradation rate was current density>initial organic concentration>chloride concentration, based on the analysis of variance in this experiment. This emphasized the very significance of the active chlorine and hydroxyl radicals which were closely related with the potential of the system and the applied current density. Then both organic and inorganic Cl-byproducts were determined. The concentration of chloride decreased to 9.88mM with an initial of 10mM in the 480-min electrolysis and extremely low concentration of active chlorine was produced in this system (maximized at 0.037mM) for the first set. Neither chlorate nor perchlorate was detected with the Pt anode. The factor of current density influenced greatest on the formation of chloroform due to the amount of active chlorine affected by the current density. Finally, intermediates generated in the electrolysis cell were concretely investigated. Compared with traditional chlorination, the amount of chlorinated-BPA (2, 2′-D2CBPA and T4CBPA) generated was relatively less (2.46 and 10.00μM equiv BPA), which might be due to their fast simultaneously transformation in the electrochemical system. With the isopropylidene bridge cleavage of chlorinated-BPA, one-ring aromatic compounds (2,6-dichlorophenol, 2,6-dichloro-2,5-cyclohexadiene, 2,4,6-trichlorophenol) occurred at the same time. Finally, chlorinated-BPA was totally transformed and low molecular chlorinated compounds were detected to the end of the experiment. This is one of the very few studies dealing with chlorinated organic intermediates formed in chloride electrolyte, and thus these findings may have significant technical implications for electrochemical treatment of wastewater containing BPA.

Recent advances to control spoilage microorganisms in washing water of fruits and vegetables: the use of electrolyzed water

Washing water used for processing fruits and vegetables can convey spoilage fungi and bacteria. The common procedure to reduce microbial contamination involves the use of chlorine based compounds. Recently, electrolyzed water (EW) has been evaluated as an alternative measure in controlling microbial spoilage contamination occurring during washing steps. This work reviews results related to the application of EW for controlling microbial viability responsible for decay development during storage period. EW produced with sodium bicarbonate as electrolyte reduced Penicillium spp. population in water and, consequently, green mould decay in citrus fruits; the use of sodium chloride in EW production inactivated spores of Fusarium sp. in water and reduced pineapple decay during storage at 12°C for 20 days as well as controlled yeast and mould population in date fruit up to six months of cold storage. EW was also found effective in controlling spoilage bacteria on ready-to-eat produce. Pseudomonas fluorescens, Pantoea agglomerans, and Rhanella aquatilis were undetectable in electrolyzed process water amended with sodium chloride although similar treatment slightly reduced Erwinia carotovora load inoculated onto lettuce. EW at low free chlorine concentration reduced viability of Pseudomonas spp. and psychrotrophic bacteria in both simulated and industrial washing water. EW treatment of fresh cut lettuce dipped in microbial contaminated water reduced Pseudomonas spp. of about 1 log cfu g-1 delaying spoilage symptoms that occurred early in untreated vegetables. These results demonstrate that the use of EW can control spoilage microorganisms in washing water, reduce cross-contamination phenomena and delay fruit and vegetable decay.

Tribological and Corrosion Properties of Nickel/TiC Bilayered Coatings Produced by Electroless Deposition and PACVD

Ni/TiC bilayered coatings are deposited on hot-working steel (H11) by plasma-assisted chemical vapor deposition and electroless technique. The TiC layer is deposited at 490 °C using a gas mixture of TiCl4, CH4, H2, and Ar, and a dense nanostructured TiC coating with minimum excessive carbon phases and low chlorine concentration is produced. The effects of the Ni intermediate layer on the microstructure, tribology, and corrosion behavior of the nanostructured TiC coating are investigated. The friction coefficient of the Ni/TiC bilayered coating (Ni thickness = 4 µm) at 500 cycles is much smaller than that of the coating without the Ni intermediate layer. The smallest friction coefficient is about 0.2, and the hardness values of the Ni/TiC bilayered samples with three different Ni layer thicknesses of 2, 4, and 6 µm are 2534, 3070, and 2008 Hv, respectively. The wear mechanism of the Ni/TiC bilayered coatings is abrasive induced by plastic deformation and fatigue during the sliding process. The smaller groove width on the 4-µm electroless nickel-Ni3P/TiC bilayered coating correlates with the larger H/E ratio and the 4-µm nickel/TiC bilayered sample shows the better wear resistance. The polarization resistance of the 6-µm electroless nickel-Ni3P/TiC coating in 0.05 M NaCl and 0.5 M H2SO4 increases by about 8 and 15 times, respectively. The Ni intermediate layer increases the toughness of the coating and adhesion between the hard coating and steel substrate thereby enhancing the tribological properties and corrosion resistance.

Bacteria in drinking water sources of a First Nation reserve in Canada

Approximately 20% of the 600 First Nations reserves across Canada are under a drinking water advisory, often due to unacceptable levels of bacteria. In this study, we detected fecal bacteria at an alarmingly high frequency in drinking water sources in a fly-in First Nations community, most notably in buckets/drums of homes without running water where Escherichia coli levels ranged from 20 to 62,000CFU/100mL. The water leaving the water treatment plant was free of E. coli and its free residual chlorine concentration (0.67mg/L) was within the range typically observed for treated water in Canada. Water samples from taps in homes served by cisterns, and those sampled from the water truck and community standpipe, always showed unacceptable levels of E. coli (1 to 2100CFU/100mL) and free residual chlorine concentrations below the 0.2mg/L required to prevent bacterial regrowth. Samples from taps in homes served by piped water had lower levels of E. coli (0 to 2CFU/100mL). DNA- and RNA-based 16S rRNA Illumina sequencing demonstrated that piped and cisterns water distribution systems showed an abundance of viable cells of Alphaproteobacteria indicative of biofilm formation in pipes and cisterns. The alpha diversity, based on observed OTUs and three other indices, was lowest in water truck samples that supplied water to the cistern and the low free residual chlorine concentration (0.07mg/L) and predominance of Betaproteobacteria (63% of viable cells) that were immediately detected after the truck had filled up at the water treatment plant was indicative of contamination by particulate matter. Given these findings, First Nation residents living without running water and relying on inadequate water distribution systems are at higher risk of contracting water-born illnesses. We urge all governments in Canada to expand their investments in supporting and sustaining water as a human right in Canada's First Nations communities.

Adsorption of Coliform Bacteria from water by Activated Carbon

Usually chlorine added ratio during the treatment process is directly proportional to the microorganisms in water, so the use of any technique that will lead to reducing the amount of microorganisms in the water will lead to use of low concentrations of chlorine. Therefore, this study aimed to using commercial activated carbon to adsorb the rate of microorganisms such as coliform bacteria. The use of continuous adsorption system (fluidize bed) under different operating conditions and in field conditions. The results showed that the best percentage removal of coliform bacteria was 91.3% within 24 hours under the operational condition bed depth 15 cm, filtration rate 15.3 m³/m²/h and particle size 1 mm, removal rates gradually decreased with time until it reached 15% after 168 hours and went to zero after 192 hours. The results that obtained in this study proved the feasibility of the use of commercial activated carbon to remove coliform bacteria from water.

Partial Characterization of Tamarind (Tamarindus indica L.) Kernel Starch Oxidized at Different Levels of Sodium Hypochlorite

The effects of different levels of sodium hypochlorite (1–4 g/100 g dry solids active chlorine) on the physicochemical, pasting, and structural properties of tamarind kernel starches were investigated. The isolated starch had low traces of non-starch components, such as protein, fat, and ash, indicating its purity. Both the carboxyl and carbonyl contents in the oxidized starches increased significantly with the increase in chlorine concentration. The introduction of carboxyl and carbonyl groups resulted in significantly lower amylose content. The swelling power of oxidized starches was significantly lower than native starch and the solubility values increased when the chlorine concentration increased at all the measured temperatures. The percentage of light transmittance increased progressively after oxidation. Pasting properties showed that in treatments at high active chlorine concentrations, the peak viscosity decreased more drastically than in treatments at low chlorine concentration, indicating a greater degradation of starch. The morphology of the starches was not altered after oxidation. After oxidative treatment no change in the X-ray diffraction pattern was observed but intensity of the peaks increased. Therefore, tamarind kernel being underutilized raw material, has a great potential as a non-conventional source of starch and desirable properties of this starch can be enhanced by oxidation for applications in food industry.

Thermodynamic stability and structure of cuprous chloride surfaces: a DFT investigation.

Density functional theory together with ab initio atomistic thermodynamics has been utilized to study the structures and stabilities of the low index CuCl surfaces. It is shown that the Cl-terminated structures are more stable than the Cu-terminated configurations, and that the defective CuCl(110)-Cu structure is more stable than the stoichiometric CuCl(110) surface. The equilibrium shape of a cuprous chloride nanostructure terminated by low-index CuCl surfaces has also been predicted using a Wulff construction. It was found that the (110) facets dominate at low chlorine concentration. As the chlorine concentration is increased, however, the contributions of the (100) and (111) facets to the Wulff construction also increase giving the crystal a semi-prism shape. At high chlorine concentration, and close to the rich limit, the (111) facets were found to be the only contributors to the Wulff construction, resulting in prismatic nanocrystals.

Relative insignificance of virus inactivation during aluminum electrocoagulation of saline waters.

Combined removal and inactivation of the MS2 bacteriophage from model saline (0-100 mM NaCl) waters by electrochemical treatment using a sacrificial aluminum anode was evaluated. Both chemical and electrodissolution contributed to coagulant dosing since measured aluminum concentrations were statistically higher than purely electrochemical predictions using Faraday's law. Electrocoagulation generated only small amounts of free chlorine in situ but effectively destabilized viruses and incorporated them into Al(OH)3(s) flocs during electrolysis. Low chlorine concentrations combined with virus shielding and aggregation within flocs resulted in very slow disinfection rates necessitating extended flocculation/contact times to achieve significant log-inactivation. Therefore, the dominant virus control mechanism during aluminum electrocoagulation of saline waters is "physical" removal by uptake onto flocs rather than "chemical" inactivation by chlorine. Attenuated total reflectance-Fourier transform infrared spectroscopy provided evidence for oxidative transformations of capsid proteins including formation of oxyacids, aldehydes, and ketones. Electrocoagulation significantly altered protein secondary structures decreasing peak areas associated with turns, bends, α-helices, β-structures, and random coils for inactivated viruses compared with the MS2 stock. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) measurements showed rapid initial RNA damage following a similar trend as plaque assay measurements of infectious viruses. However, ssRNA cleavage measured by qRT-PCR underestimated inactivation over longer durations. Although aluminum electrocoagulation of saline waters disorders virus capsids and damages RNA, inactivation occurs at a sufficiently low rate so as to only play a secondary role to floc-encapsulation during residence times typical of electrochemical treatment.

Effect of chlorine and temperature on free-living protozoa in operational man-made water systems (cooling towers and hot sanitary water systems) in Catalonia.

In recent decades, free-living protozoa (FLP) have gained prominence as the focus of research studies due to their pathogenicity to humans and their close relationship with the survival and growth of pathogenic amoeba-resisting bacteria. In the present work, we studied the presence of FLP in operational man-made water systems, i.e. cooling towers (CT) and hot sanitary water systems (HSWS), related to a high risk of Legionella spp. outbreaks, as well as the effect of the biocides used, i.e. chlorine in CT and high temperature in HSWS, on FLP. In CT samples, high-chlorine concentrations (7.5 ± 1.5 mg chlorine L(-1)) reduced the presence of FLP by 63.8 % compared to samples with low-chlorine concentrations (0.04 ± 0.08 mg chlorine L(-1)). Flagellates and amoebae were observed in samples collected with a level of 8 mg chlorine L(-1), which would indicate that some FLP, including the free-living amoeba (FLA) Acanthamoeba spp., are resistant to the discontinuous chlorine disinfection method used in the CT studied. Regarding HSWS samples, the amount of FLP detected in high-temperatures samples (53.1 ± 5.7 °C) was 38 % lower than in low-temperature samples (27.8 ± 5.8 °C). The effect of high temperature on FLP was chiefly observed in the results obtained by the culture method, in which there was a clear reduction in the presence of FLP at temperatures higher than 50 °C, but not in those obtained by PCR. The findings presented here show that the presence of FLP in operational man-made water systems should be taken into account in future regulations.

The chlorination and chlorine resistance modification of composite polyamide membrane

ABSTRACTMembrane‐based separation technology is one of the most active separation technologies being employed in water treatment. Polyamides (PA) are widely used membrane materials because they exhibit excellent performance, such as high flux with high salt rejection, and enhanced stability against wide range of pH and temperature. Unfortunately, PA membranes exhibit extremely poor resistance to chlorine leading to increased operation costs and decreased membrane lifetime. In this study, we find new ways for prolonging membrane lifetime and reducing the operating costs by investigating the chlorination and modification of PA membranes. Varying concentrations of hypochlorite were used to chlorinate a commercial reverse osmosis membrane (BW‐30, DOW). The results showed that short‐time exposure to high concentrations of hypochlorite could cause more serious problems to membranes than long‐time exposure to low concentrations under the similar total exposure. The performance of the chlorinated membranes was recovered to some extent after treatment with NaOH solution (pH 10), indicating that the alkali treatment could initiate the reversible regeneration of chlorinated membranes. Furthermore, an industrial grade epoxy resin was used to modify the membranes to enhance the chlorine resistance via the reaction between the amide nitrogen and epoxy bond. The successful modifications were confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Moreover, the chlorination tests showed that the modifications performed in these experiments enhanced the chlorine resistance of the membranes, especially for the membranes exposed to low concentration of chlorine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41584.

Effect of electrolysed water on Campylobacter numbers on poultry carcasses under practical operating conditions at processing plants

This study investigated the effectiveness of spraying electrolysed water for reducing the numbers of Campylobacter on chicken carcasses. Previous studies have used solutions with free chlorine concentrations above 25 ppm and low pH to treat inoculated carcasses. The four trials described here were carried out at process plants treating naturally contaminated, hot, birds with electrolysed sodium chloride or sodium carbonate solutions, plain water, or no water. The birds were chilled after treatment. Free chlorine concentrations were all below 20 ppm, pH was 7 units or more, and redox potentials were below 830 mV. None of the treatments produced more than a 0.3-log reduction in Campylobacter numbers compared to counts on untreated carcasses. This study concludes that, at the low chlorine concentrations allowed in the EU, spraying with electrolysed water is not an effective method of reducing the number or prevalence of Campylobacter on chicken carcasses.

A compact point-of-use water purification cartridge for household use in developing countries.

Simple, low-cost household interventions are known to be effective in lowering the incidence of waterborne diseases in developing countries. However, high costs along with operational and maintenance issues have prevented the successful adoption of these interventions among the affected communities. To address these limitations, a cost-effective, gravity-driven water purification cartridge has been developed by employing the synergistic disinfection action of low concentrations of silver and chlorine on bacteria and viruses. The silver and chlorine treatment components within the cartridge have been developed using inexpensive materials and integrated with a life indicator and auto-shut-off-mechanism within a compact form factor. The antibacterial as well as antiviral performance of the cartridge was tested by using ground water spiked with Escherichia coli and MS2 bacteriophage. The results show that, although individually, the silver and chlorine treatment systems were unable to inactivate the test strains, the integrated cartridge inactivates both bacteria as well as viruses up to the log reduction requirement of the USEPA guide standard for microbiological water purifiers over its designated life of 2,000 liters.

A Review on Formation and Decay Kinetics of Trihalomethanes in Water of Different Qualities

Despite the many disadvantages associated with the use of chlorine for disinfecting drinking water, chlorination is still the main method used for this purpose worldwide. Low chlorine concentrations in water distribution systems increase health risks whereas high chlorine concentrations are associated with the formation of disinfection by‐products such as trihalomethanes which are suspected carcinogens. Due to their negative health impacts, trihalomethanes occurrence in finished drinking water has received great attention from researchers and scientists worldwide. This manuscript critically reviews and discusses up to date knowledge on the occurrence of trihalomethanes in chlorinated drinking water and their associated health risks and identifies research gaps. The models for trihalomethane formation and decay have been compiled with special emphasis on the impact of the bromide ion on the total trihalomethane levels and speciation. Furthermore, the fate and transport of trihalomethanes in drinking water supplies and in groundwater have been investigated. Finally, management options for the reduction of trihalomethanes in chlorinated drinking water such as the removal of precursors from raw water, the use of alternative disinfectants and the removal of trihalomethanes from finished drinking water have been critically investigated and discussed.

Occupational exposures of airborne trichloramine at indoor swimming pools in Taipei

Ten indoor swimming pools in Taipei, Taiwan were included in the study to assess the exposure of people to airborne trichloramine (NCl3) and also to discover the factors that might affect the associated concentrations. An active air sampling method was performed to determine the levels of NCl3, while questionnaires were administered to swimming pool workers, including lifeguards, swimming instructors, and management employees. The results show that the concentrations of trichloramine ranged from 0.017 to 0.15mgm−3, which were generally lower than what have been reported from other studies. Symptoms of sore throat and phlegm were more frequent among lifeguards and swimming instructors (exposure group) than management employees (reference group) (odds ratios were 11.28 and 4.22 for sore throat and phlegm, respectively). It seems that the current exposure limit for airborne NCl3, which was recommended by WHO, was not lower enough to protect the health of pool attendants. Regulated level of free available chlorine in Taipei (i.e., 0.3–0.7ppm) is lower than what is required in other countries (e.g., 1–3ppm in the UK). This might be the main reason why the concentrations of NCl3 reported elsewhere were higher than what were found in this research. Further international comparisons will help to elucidate if low free chlorine concentration should be adopted as an operating standard. For the indoor swimming pools in Taipei, the air quality is suggested to be improved, since even with the low concentrations of NCl3, higher respiratory ailments among pool workers were observed.

低濃度残留塩素時の海生生物付着事例について

Cooling efficiency at coastal industrial plants with seawater-based cooling systems is often reduced due to water flow blockage caused by marine biofouling. Maintenance of a residual chlorine concentration of 0.1–0.3 mg/L for 18 h/day is known to be an effective countermeasure, but it is often impossible to maintain so high a concentration because of chlorine-induced corrosion and/or environmental considerations. There have been only a few reports examining the effects of low concentrations of residual chlorine, so we carried out a study to evaluate the marine biofouling potential at residual chlorine concentrations of 0.05 mg/L or less, and to identity any related problems. The study was conducted at a factory on the shore of Ise Bay, Japan, at which no residual chlorine was detected in the discharge water. For 63 days (27 Apr. to 29 Jun. 2010) we regularly observed the extent of marine biofouling on a coarse-mesh vinylon net placed parallel to the water flow inside a cooling-water pipe through which seawater with a total residual chlorine concentration averaging 0.055 mg/L (range: 0.02–0.12 mg/L) was run continuously. We also checked the condition of the net on 6 Dec. 2010 after 30 days of uninterrupted exposure to the water flow. In both cases, much biofouling was observed on the test net. Thus, low levels of residual chlorine, even when applied continuously, appear insufficient to prevent biofouling and an attendant reduction in cooling efficiency.

Halogen-induced organic aerosol (XOA): a study on ultra-fine particle formation and time-resolved chemical characterization

The concurrent presence of high values of organic SOA precursors and reactive halogen species (RHS) at very low ozone concentrations allows the formation of halogen-induced organic aerosol, so-called XOA, in maritime areas where high concentrations of RHS are present, especially at sunrise. The present study combines aerosol smog-chamber and aerosol flow-reactor experiments for the characterization of XOA. XOA formation yields from alpha-pinene at low and high concentrations of chlorine as reactive halogen species (RHS) were determined using a 700 L aerosol smog-chamber with a solar simulator. The chemical transformation of the organic precursor during the aerosol formation process and chemical aging was studied using an aerosol flow-reactor coupled to an FTIR spectrometer. The FTIR dataset was analysed using 2D correlation spectroscopy. Chlorine induced homogeneous XOA formation takes place at even 2.5 ppb of molecular chlorine, which was photolysed by the solar simulator. The chemical pathway of XOA formation is characterized by the addition of chlorine and abstraction of hydrogen atoms, causing simultaneous carbon-chlorine bond formation. During further steps of the formation process, carboxylic acids are formed, which cause a SOA-like appearance of XOA. During the ozone-free formation of secondary organic aerosol with RHS a special kind of particulate matter (XOA) is formed, which is afterwards transformed to SOA by atmospheric aging or degradation pathways.

Partitioning of halogens between mantle minerals and aqueous fluids: implications for the fluid flow regime in subduction zones

We have performed phase equilibrium experiments in the system forsterite–enstatite–pyrope-H2O with MgCl2 or MgF2 at 1,100 °C and 2.6 GPa to constrain the solubility of halogens in the peridotite mineral assemblage and the fluid–mineral partition coefficients. The chlorine solubility in forsterite, enstatite and in pyrope is very low, 2.1–3.9 and 4.0–11.4 ppm, respectively, and it is independent of the fluid salinity (0.3–30 wt% Cl), suggesting that some intrinsic saturation limit in the crystal is reached already at very low chlorine concentrations. Chlorine is therefore exceedingly incompatible in upper-mantle minerals. The fluorine solubility is 170–336 ppm in enstatite and 510–1,110 ppm in pyrope, again independent of fluid salinity. Forsterite dissolves 1,750–1,900 ppm up to a fluid salinity of 1.6 wt% F. At higher fluorine contents in the system, forsterite is replaced by the minerals of the humite group. The lower solubility of chlorine by three orders of magnitude when compared to fluorine is consistent with increasing lattice strain. Fluid–mineral partition coefficients are 100–102 for fluorine and 103–105 for chlorine. Since the latter values are orders of magnitude higher than those for hydroxyl partitioning, fluid flow from the subducting slab through the mantle wedge will lead to an efficient sequestration of H2O into the nominally anhydrous minerals in the wedge, whereas chlorine becomes enriched in the residual fluid. Simple mass balance calculations reveal that rock–fluid ratios of up to >3,000 are required to produce the elevated Cl/H2O ratios observed in some primitive arc magmas. Accordingly, fluid flow from the subducted slab into the zone of melting in the mantle wedge does not only occur rapidly in narrow channels, but at least in some subduction zones, fluid pervasively infiltrates the mantle peridotite and interacts with a large volume of the mantle wedge. Together with the Cl/H2O ratios of primitive arc magmas, our data therefore constrain the fluid flow regime below volcanic arcs.

Inactivation and Photorepair of Enteric Pathogenic Microorganisms with Ultraviolet Irradiation

Abstract Ultraviolet inactivation of enteric pathogenic microorganisms, including Shigella dysenteriae, Salmonella typhimurium, and human rotavirus (HRV-Wa) and somatic coliphages (MS2 and T4), was investigated in different water samples. Significant differences in the sensitivity of the bacteria and viruses to ultraviolet radiation were observed. Viruses were more resistant to ultraviolet disinfection than all the enteric bacteria tested in this study. With the exception of S. typhimurium, which showed flattening and tailing, strong first-order relationships between the logarithm of survival and the ultraviolet dose were observed. While S. dysenteriae and S. typhimurium were found to undergo photoreactivation after ultraviolet exposure, the photoreactivation decreased significantly with higher ultraviolet doses. Moreover, the inactivated bacteria exhibited different photoreactivation rates with different water samples. Combination of a low ultraviolet dose and a low concentration of chlorine not only inh...

THERMAL IMPACTS OF A COAL POWER PLANT ON THE PLANKTON IN AN OPEN COASTAL WATER ENVIRONMENT

Over a five-year period, this study examined the overall impact of coal power plant cooling processes on entrained copepods and the local plankton community on the west coast of Korea. Mortality differences between the intake and discharge water of the single most dominant copepod, Acartia hongi, were positively correlated with temperature differences between the two locations. Laboratory tests showed copepod sensitivity to temperature increase, and with very low chlorine concentration applied, thermal stress was the major source of copepod mortality. Chlorophyll a concentration, ciliate abundance, and total copepod abundance at the intake showed no discernable differences from the values at the discharge. Most likely, this was due to rapid mixing of the population in the discharge water with adjacent populations in the macrotidal open coastal water environment.

Stability of and attachment to lettuce by a culturable porcine sapovirus surrogate for human caliciviruses.

Human noroviruses (HuNoVs) are the leading cause of food-borne illness, accounting for 58% of U.S. cases. Because HuNoVs are unculturable, surrogates are needed to investigate transmission routes and evaluate disinfection methods. However, the current surrogates, feline calicivirus (FCV) and murine NoV (MNV), are less tolerant than HuNoVs to acid and chlorine, respectively. Porcine sapovirus (SaV) is the only culturable enteropathogenic calicivirus. In this study, the resistance of SaV to physicochemical treatments was compared to that of HuNoVs (by reverse transcription-PCR), FCV, and MNV (by infectivity assays). Sapovirus and HuNoV (viral RNA) showed similar resistances to heat (56°C) and to different concentrations of chlorine. However, SaV was more resistant than HuNoVs to ethanol treatment (60% and 70%). Like HuNoVs, SaV was stable at pH 3.0 to 8.0, with a <1.0 log(10) 50% tissue culture infective dose (TCID(50)) reduction at pH 3.0 compared to the value for pH 4.0 to 8.0. SaV and MNV showed similar resistances, and both were more resistant than FCV to heat inactivation (56°C). FCV was more resistant than MNV and SaV to ethanol, and all three viruses showed similar resistances to treatment with low concentrations of chlorine for 1 min. Those results indicate that SaV is a promising surrogate for HuNoVs. Next, we used SaV as a surrogate to examine virus attachment to lettuce at different pHs. Sapovirus attached to lettuce leaves significantly at its capsid isoelectric point (pH 5.0), and the attached viral particles remained infectious on lettuce after 1 week of storage at 4°C. The culturable SaV is a good surrogate for studying HuNoV contamination and transmission in leafy greens and potential disinfectants.