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Low-pressure (LP) UV treatment after chlorine disinfection was associated with enhanced formation of trichloronitromethane (TCNM), a halonitromethane disinfection by-product (DBP), due to the chlorination of tryptophan. Evidence was found that the concentration of TCNM from tryptophan increased quickly to the maximum for the first instance. Moreover, the increase of TCNM under UV exceeded 10 times than under dark. Then, it was found to have an obvious decrease in the formation of TCNM, even finally hardly disappear. In order to elucidate reasons for this phenomenon, the effects of light intensity, initial tryptophan concentration, free chlorine concentration, pH, and tert-butanol (TBA) on the formation of TCNM were investigated under UV/chlorine treatment. Finally, the effects of tryptophan on the formation of TCNM and the direct photodegradation of TCNM under LP UV irradiation were studied for analyzing the possible pathways of TCNM formation from amino acid. Since amino acids are very common in water sources, further research into chemical oxidation of these species by LP UV and chlorine is recommended. It can help us to find the precursors of TCNM formation and reduce the risk of TCNM formation for drinking water and wastewater utilities. [ABSTRACT FROM AUTHOR]

Chlorine, the most commonly used sanitizer for fresh produce washing, has constantly shown inferior sanitizing efficacy in the presence of organic load. Conventionally this is attributed indirectly to the rapid chlorine depletion by organics leading to fluctuating free chlorine (FC) contents. However, little is known on whether organic load affects the sanitization process directly at well-maintained FC levels. Hereby, a sustained chlorine decay approach was employed to study the inactivation of Escherichia coli O157:H7 under stabilized washing conditions. Chlorine solution was first incubated with organic load for up to 4 h, modeling the chlorination in produce washing lines. The FC level was then stabilized at five targeted values for sanitization study. Our study showed decreased sanitizing efficacy as the organic load increased. At 5 s residence time and pH 6.5, a minimum of 0.5 and 7.5 mg/L FC were needed to achieve a 5 log reduction at 0 and 900 mg/L chemical oxygen demand (COD), respectively. The decrease was more pronounced at lower FC, higher COD, higher pH, and shorter residence time values. The organics-associated interference with FC measurement and disruption of chlorine/bacteria interaction, together with the chlorine demand of concentrated inoculum per se, collectively resulted in inadequate sanitization. Finally, our results were compared with existing studies conducted under dynamic conditions in the context of different experimental settings. This study provided a feasible method for studying the bacteria/sanitizer interaction while ruling out the confounding effect from fluctuating FC levels, and it indicated the direct, negative impact of organic load. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants (WWTPs) have been identified as potential sources of antibiotic resistance genes (ARGs) but the effects of tertiary wastewater treatment processes on ARGs have not been well characterized. Therefore, the objective of this study was to determine the fate of ARGs throughout a tertiary-stage WWTP. Two ARGs, sul1 and bla, were quantified via quantitative polymerase chain reaction (qPCR) in solids and dissolved fractions of raw sewage, activated sludge, secondary effluent and tertiary effluent from a full-scale WWTP. Tertiary media filtration and chlorine disinfection were studied further with the use of a pilot-scale media filter. Results showed that both genes were reduced at each successive stage of treatment in the dissolved fraction. The solids-associated ARGs increased during activated sludge stage and were reduced in each subsequent stage. Overall reductions were approximately four log10 with the tertiary media filtration and disinfection providing the largest decrease. The majority of ARGs were solids-associated except for in the tertiary effluent. There was no evidence for positive selection of ARGs during treatment. The removal of ARGs by chlorine was improved by filtration compared to unfiltered, chlorinated secondary effluent. This study demonstrates that tertiary-stage WWTPs with disinfection can provide superior removal of ARGs compared to secondary treatment alone. [ABSTRACT FROM AUTHOR]

The article discusses prevention of contamination and maintenance of efficient operation of a reverse osmosis membrane through chemical and physical disinfection of feedwater. Topics discussed include techniques addressing biofouling such as modification of membrane surfaces and bacteria; use of chlorine as a disinfectant in feedwater and use of ultraviolet radiation for killing protozoa. Other topics include use of chlorine dioxide, chloramine and chemical biocides for the same.

Physical and chemical disinfection methods have been proposed with the aim of controlling Legionella water contamination. To date, the most effective procedures for reducing bacterial contamination have not yet been defined. The aim of this study was to assess the long-term effectiveness of various disinfection procedures in order to reduce both culturable and nonculturable (NC) legionellae in different hospital water networks treated with heat, chlorine dioxide, monochloramine, and hydrogen peroxide. The temperature levels and biocide concentrations that proved to give reliable results were analyzed. In order to study the possible effects on the water pipes, we verified the extent of corrosion on experimental coupons after applying each method for 6 months. The percentage of positive points was at its lowest after treatment with monochloramine, followed by chlorine dioxide, hydrogen peroxide, and hyperthermia. Different selections of Legionella spp. were observed, as networks treated with chlorinebased disinfectants were contaminated mainly by Legionella pneumophila serogroup 1, hyperthermia was associated with serogroups 2 to 14, and hydrogen peroxide treatment was associated mainly with non-pneumophila species. NC cells were detected only in heat-treated waters, and also when the temperature was approximately 60°C. The corrosion rates of the coupons were within a satisfactory limit for water networks, but the morphologies differed. We confirm here that chemical disinfection controls Legionella colonization more effectively than hyperthermia does. Monochloramine was the most effective treatment, while hydrogen peroxide may be a promising alternative to chlorine-based disinfectants due to its ability to select for other, less virulent or nonpathogenic species. [ABSTRACT FROM AUTHOR]

The use of chlorine as a disinfectant in the fresh-cut produce industry has been identified as a concern mainly due to public health issues. In fact, this chemical, commonly used as hypochlorous acid and hypochlorite, has already been prohibited in some European countries, due to the potential production of toxic by-products, such as chloroform and other trihalomethanes, chloramines and haloacetic acids. The search for alternative methods of disinfection is therefore a current and on-going challenge in both Academia and Industry. Some methods are well described in the literature on the disinfection of food-contact surfaces and process water and also on the decontamination of the produce. These methods are commonly classified as biological (bacteriocins, bacteriophages, enzymes and phytochemicals), chemical (chlorine dioxide, electrolyzed oxidizing water, hydrogen peroxide, ozone, organic acids, etc) and physical (irradiation, filtration, ultrasounds, ultraviolet light, etc). This review provides updated information on the state of art of the available disinfection strategies alternative to chlorine that can be used in the fresh-cut industry. The use of combined methods to replace and/or reduce the use of chlorine is also reviewed. [ABSTRACT FROM AUTHOR]

Over one-half of foodbome diseases are believed to be of viral origin. The ability of viruses to persist in the environment and fresh produce, as well as their low infectious dose, allows even a small amount of contamination to cause serious foodbome problems. Moreover, the consumer's demands for fresh, convenient, and safe foods have prompted research into alternative food disinfection technologies. Our study focuses on viral inactivation by both conventional and alternative nonthermal disinfection technologies on different fresh ready-to-eat food products. The use of chlorine, as well as that of nonthermal technologies such as UV light and ultrasound (US), was tested for different treatment times. UV nonthermal technology was found to be more effective for the disinfection of human adenoviruses (hAdVs) compared with US, achieving a log reduction of 2.13, 1.25, and 0.92 for lettuce, strawberries, and cherry tomatoes, respectively, when UV treatment was implemented for 30 min. US treatment for the same period achieved a log reduction of 0.85, 0.53, and 0.36, respectively. The sequential use of US and UV was found to be more effective compared with when the treatments were used separately, for the same treatment time, thus indicating a synergistic effect. In addition, human adenoviruses were inactivated sooner, when chlorine treatment was used. Therefore, the effect of each disinfection method was dependent upon the treatment time and the type of food. [ABSTRACT FROM AUTHOR]

Household-based chlorine disinfection is widely effective against waterborne bacteria and viruses, and may be among the most inexpensive and accessible options for household water treatment. The microbiological effectiveness of chlorine is limited, however, by turbidity. In Tanzania, there are no guidelines on water chlorination at household level, and limited data on whether dosing guidelines for higher turbidity waters are sufficient to produce potable water. This study was designed to assess the effectiveness of chlorination across a range of turbidities found in rural water sources, following local dosing guidelines that recommend a 'double dose' for water that is visibly turbid. We chlorinated water from 43 sources representing a range of turbidities using two locally available chlorine-based disinfectants: WaterGuard and Aquatabs. We determined free available chlorine at 30 min and 24 h contact time. Our data suggest that water chlorination with WaterGuard or Aquatabs can be effective using both single and double doses up to 20 nephelometric turbidity units (NTU), or using a double dose of Aquatabs up to 100 NTU, but neither was effective at turbidities greater than 100 NTU. [ABSTRACT FROM AUTHOR]

In water, chlorine reacts with nitrogen-containing compounds to produce disinfection byproducts such as nitrogen trichloride which induces ocular and respiratory irritations in swimming pool workers. A technical solution has been used to reduce NCI3 exposure to acceptable levels, by adding a stripping step to the water recycling loop. The pollutants extracted are currently rejected into the atmosphere without treatment. However, the physical properties of NCI3 could be harnessed to induce its controlled degradation by direct or indirect light This paper describes the way to transform NCI3 into oxidizing chlorine by photocatalysis under laboratory conditions. Photocatalytic oxidation efficiently degrades gaseous nitrogen trichloride, producing compounds such as HC10. About 60% of NCI3 decomposed was converted into HOO which could be used as a disinfection compound. A kinetic model is proposed for the photocatalytic process based on a convection/diffusion model. The Langmuir-Hinshelwood model was applied to the chemical part of the mechanism. The apparent quantum yield was also estimated to assess the optimal irradiance for NCI3 transformation. The results show that photocatalysis performs much better than photolysis alone for NCI3 removal, i.e. at least 25 times more efficient. [ABSTRACT FROM AUTHOR]

In this study, multiple roles of biofilm EPS were assessed with respect to the resistance of biofilm and detached biofilm clusters to chlorine disinfection. Strains from an opportunistic pathogen, Pseudomonas aeruginosa (wild type, EPS- and EPS+) with altered extracellular polymeric substances (EPS) secretion capabilities were tested. The impact of biofilm EPS quantity on disinfection was evaluated by monitoring biofilm viability, biofilm structure, removal of dissolved organic matter (DOM), and viability of detached biofilm simultaneously during chlorine disinfection. The obtained results suggested that the presence of EPS increased biofilm and detached biofilm resistance to chlorine in both presence and absence of DOM. The quantity of EPS had an effect on biofilm structure and the structural characteristics were closely related to both overall biofilm viability and the spatial distribution of viable cells within the biofilm. Additionally, the increased amount of EPS influenced selective removal of DOM with polar functional groups. However the DOM removal did not have a significant impact on the viability of biofilm cells during chlorine disinfection. Meanwhile, the viability of detached biofilm clusters, particularly the EPS overproducing strain, was significantly increased in the presence of DOM. The combined results suggested that biofilm EPS played multiple roles toward influencing the resistance of both biofilm and detached biofilm to disinfectant. [ABSTRACT FROM AUTHOR]

Abstract: The food industry has recognized electrolyzed oxidizing water (EOW) as a promising alternative decontamination technique. However, there is not a consensus about the sanitizing mechanism of EOW. In this study, we evaluated the disinfection efficacy of different types of EOW on Escherichia coli. Based on the hypothesis of hydroxyl radicals existing in EOW, in the present study, the hydroxyl radicals existed in slightly acidic electrolyzed water (SAEW) and acidic electrolyzed water (AEW) diluted to different levels were detected quantitatively. An ultraviolet (UV) spectrophotometer was used to scan EOW with different pH values. Accounting for the results of UV scanning to EOW with different pH value and the disinfection efficacy of different types of EOW, it can be concluded that considering the lower chlorine concentration of EOW compared with traditional chlorine disinfectants, the existing form of chlorine compounds rather than the hydroxyl radicals played important role in the disinfection efficacy of EOW. [Copyright &y& Elsevier]

The first step in processing raw water from the Pakra lake for use in fertilizer production at Petrokemija is oxidation of total organic carbon matter with gaseous chlorine, Cl2. Thereupon it is clarified and filtered with the help of a clarification reactor and sand filters. Construction of the clarification reactor and process sand filters enables only the removal of the suspended matter from the raw water, without affecting its overall hardness. Process control of the clarification reactor and removal of the suspended matter from the raw water is achieved by adding corresponding mass concentration water solutions of aluminum sulphate, Al2(SO4)3 ⋅ 18 H2O and organic polyelectrolyte. The effectiveness of flocculation is carried out by laboratory determination of the m-alkalinity difference between inlet and outlet of raw water from the clarification reactor. For the most effective clarification of raw water, the optimal empirical value of the m-alkalinity difference is 0.65 mmol L-1 in the pH range of raw water from 7.0 to 8.0. Prior to processing clarified water by ionic decarbonatisation and demineralisation for protection of the ionic exchange resin from excess free Cl2, a corresponding mass concentration of a sodium bisulfite water solution, NaHSO3, is added. An improved system is proposed for continuous measurement of mass concentrations of free Cl2 in raw and clarified water, and pH difference value at the inlet and outlet of the clarification reactor. The proposed system can achieve optimal dosage of gaseous Cl2 in the raw water, improving the clarification process in the reactor as well as optimal dosage of water solution of NaHSO3. It is shown that the average pH difference from 0.65 to 0.75 at the inlet and outlet of the clarification reactor in the pH range of the raw water from 7.0 to 8.0 is an equally effective replacement for the laboratory determination of m-alkalinity. Also shown is the connection between dosage mass of the gaseous Cl2 in the raw water, pH difference value at the inlet and outlet of the clarification reactor and dosage mass of the NaHSO3. The proposed system for the continuous measurement of mass concentration of free Cl2 and pH values in the raw and clarified water achieved a better and safer system of processing raw water with annual savings of gaseous Cl2 of 15 % and NaHSO3 of 50 %. [ABSTRACT FROM AUTHOR]

Abstract: Total coliforms and Escherichia coli (E. coli) were quantified as representatives of fecal pollution in Ampang Jajar landfill site (AJLS) leachate. Leachate samples were monitored for six months and an average of total coliforms and geometric mean of E. coli was determined. The highest concentrations of total coliforms and E. coli were 0.66×104 and 0.15×104 colony forming units (CFU) per 100mL, respectively. The inactivation of these organisms was studied by using sodium hypochlorite with 4% available chlorine. The indicator bacteria showed high susceptibility to chlorine and a 100% inactivation of total coliforms and E. coli was achieved at 1.5 and 0.5mg/L Cl2 dosages when contact times of 50 and 90s were applied, respectively. Optimum conditions of inactivation analysed by using response surface methodology (RSM) were 0.91mg/L Cl2 and 43.5s contact time whereby 99% E. coli and 50% total coliform inactivation was obtained. [Copyright &y& Elsevier]

Chlorination remains a predominant method for disinfecting drinking water. Electrogeneration of chlorine has the potential to become the favoured method of chlorine production if costs can be lowered and chlorine generation efficiencies can be improved. A novel perforated electrode flow through (PEFT) cell design has been developed to address these problems. The electrodes were made from low-cost graphite sheets and stainless steel mesh and separated by a non-conducting fabric membrane. This electrode configuration allows reduction of electrode separation to 0.1 mm or less, minimizing cell resistance and increasing electrical efficiency. The new PEFT configuration generates hypochlorite from a 0.5 mol L brine at a current efficiency of better than 60%. As an inline in situ device, it produces chlorine concentrations known to be sufficient to disinfect water, from chloride concentrations as low as 0.004 mol L (available in most natural waters) by a single pass of the water through the cell operating at 11 V. The possibility of a portable device operated by a 12-V battery is indicated. [ABSTRACT FROM AUTHOR]

Abstract: The risk of undesirable by-products from chlorine disinfection in fresh-cut industries, together with its limited efficacy, has led to a search for alternative agents. The aim of this study was to test several alternative putative antimicrobial substances to reduce Escherichia coli O157:H7, Salmonella spp. and Listeria spp. populations on fresh-cut apple. Carvacrol, vanillin, peroxyacetic acid, hydrogen peroxide, N-acetyl-l-cysteine and Citrox were selected for their results in in vitro assays against E. coli O157:H7 and Listeria spp., to be tested on fresh-cut apple plugs. Apple flesh was inoculated by dipping in a suspension of a mix of the studied pathogens at 106 cfumL−1, and then treated with the antimicrobial substances. All treatments were compared to deionized water and a standard sodium hypochlorite treatment (SH, 100mgL−1, pH 6.5). Pathogen population on apple plugs was monitored for up to 6 days at 10°C. Bacterial reductions obtained by peroxyacetic acid (80 and 120mgL−1), vanillin (12gL−1), hydrogen peroxide (5, 10, 20mLL−1) and N-acetyl-l-cysteine (5 and 10gL−1) were similar or higher than reduction obtained by SH. In addition, bacterial populations were maintained at low levels throughout storage. No cells of any of the pathogens were detected in the peroxyacetic acid, hydrogen peroxide, Citrox and SH washing solutions after apple treatment. Peroxyacetic acid, hydrogen peroxide and N-acetyl-l-cysteine could be potential disinfectants for the fresh-cut industry as an alternative to chlorine disinfection. However, their effect on sensory quality and effectiveness under commercial processing conditions should be evaluated. [ABSTRACT FROM AUTHOR]

Plattnerite (β-PbO2) is a corrosion product that develops on lead pipes that have been in contact with free chlorine present as a residual disinfectant. The reductive dissolution of PbO2 can cause elevated lead concentrations in tap water when the residual disinfectant is switched from free chlorine to monochloramine. The objectives of this study were to quantify plattnerite dissolution rates in the presence of chlorine disinfectants, gain insights into dissolution mechanisms, and measure plattnerite's equilibrium solubility in the presence of free chlorine. The effects of free chlorine and monochloramine on the dissolution rates of plattnerite were quantified in completely mixed continuous-flow reactors at relevant pH and dissolved inorganic carbon conditions. Plattnerite dissolution rates decreased in the following order: no disinfectant > monochloramine > chlorine, which was consistent with the trend in the redox potential. Compared with experiments without disinfectant, monochloramine inhibited plattnerite dissolution in continuous-flow experiments. Although free chlorine maintained steady-state lead concentrations below the action level of 15 μg/L in flow-through experiments, in batch experiments lead concentrations exceeded the action level for longer residence times and approached an equilibrium value that was several orders of magnitude higher than that predicted from available thermodynamic data. [ABSTRACT FROM AUTHOR]

Abstract: Carbon isotope fractionation was observed during dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) by a mixed culture containing Dehalococcoides ethenogenes strain 195. Fractionation was examined when 1,2,3,4-TeCDD was added as the only chlorinated compound and when 1,2,3,4-TeCDD was added with a known growth substrate, tetrachloroethene (PCE). The 1,2,3,4-TeCDD was dechlorinated to 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD) which was enriched in 13C relative to 1,2,3,4-TeCDD with isotope separation factors, ε C, of 1.3±0.2‰ and 1.7±0.4‰ (average±95% confidence interval (CI)) in cultures with and without PCE, respectively. The 1,2,4-TrCDD was further dechlorinated to 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD) which was depleted in 13C relative to 1,2,4-TrCDD with ε C of −2.4±0.4‰ and −2.9±0.8‰ (average±95% CI) in cultures with and without PCE, respectively. This demonstrates carbon isotope fractionation during sequential reductive dechlorination of PCDDs, where isotope fractionation during dechlorination of the intermediate was substantial and a 13C depleted lightly chlorinated PCDD congener was ultimately formed during dechlorination of more highly chlorinated PCDD congeners. Despite reproducible, statistically significant differences between isotope compositions of the parent, 1,2,3,4-TeCDD and daughter, 1,2,4-TrCDD and 1,3-DCDD congeners in triplicate bottles of both treatments, fractionation factors for 1,2,3,4-TeCDD could not be determined for all replicates by regression analysis of the plot of the Rayleigh equation. It is possible that dissolution of 1,2,3,4-TeCDD imposed a kinetic limitation on dechlorination, thus masking isotope fractionation during its dechlorination. [ABSTRACT FROM AUTHOR]

Abstract: Carbon dioxide is seldom used as pH reducer in swimming pools. Nevertheless it offers two interesting advantages. First, its use instead of the usual hydrochloric acid avoids the characteristic and serious accident of mixing the disinfectant with that strong acid, which forms a dangerous chlorine gas cloud and, second, it allows the facility to become slightly a depository of that greenhouse gas. This work introduces the experience of using CO2 as pH reducer in real working swimming pools, showing three more advantages: lower chlorine consumption, lower presence of oxidants in the air above the swimming pool and a diminished formation of trihalomethanes in the swimming pool water. Experiments lasted 4years and they were run in three swimming pools in the Barcelona area, where the conventional system based upon HCl and a system based upon CO2 were consecutively exchanged. [Copyright &y& Elsevier]

Chlorine is one of the most used water disinfectant agent used on the world. The use of chlorine in the treatment of drinking water has virtually eliminated waterborne diseases, because chlorine can kill or inactivate most microorganisms commonly found in water. The majority of drinking water treatment plants in Romania use some form of chlorine to disinfect drinking water: to treat the water directly in the treatment plant and/or to maintain a chlorine residual in the distribution system to prevent bacterial regrowth. Unfortunately it's used results in formation of some disinfection by products (DBPs) that are suspected from harmful effects on humans. Such of disinfection byproducts are trihalomethanes (THMs). Trihalomethanes are a group of volatile organic compounds that can form when the chlorine used to disinfect drinking water reacts with naturally occurring organic matter (e.g., decaying leaves and vegetation). The preliminary results presented in this paper shown that the THMs levels from Gilau Water treatment Plants and Cluj-Napoca distribution system. The results have higher values in the summer period relative to other seasons. [ABSTRACT FROM AUTHOR]

Abstract: An automatic pH–ORP (oxidation–reduction potential) titration device was developed and applied to dynamically control the wastewater chlorination and dechlorination doses in this study. In the pH–ORP titration and back-titration process, the monitoring peaks and valleys on the pH and ORP profiles could indicate the influent concentrations of chlorine-consumed materials (mainly ammonia nitrogen for chlorination) and residual chlorines (for dechlorination). The required chlorination dose can be optimized by multiplying the identified ammonia concentration to the optimal Cl/N ratio (chlorine to ammonia nitrogen weight ratio). The required dechlorination dose was also found to be correlated to the residual chlorine concentration with linear relationship. Therefore, an innovative and dynamic feed-forward dose control strategy was proposed. Finally, a series of continuous wastewater chlorination and dechlorination experiments were conducted to evaluate this proposed control strategy. Two control factors, CFC and CFD , were also used to regulate the doses to meet the water qualities for different wastewater reclamation proposes. The experimental result has shown that both chlorination and dechlorination doses were effectively controlled, and appropriate disinfection efficiencies and remaining chlorine residuals in effluent were achieved. [Copyright &y& Elsevier]

Abstract: Chemical inactivation of microorganisms is a common process widely employed in many fields such as in treatment of water, preservation in food industry and antimicrobial treatments in healthcare. For economy of applications and efficiency of treatment establishment the minimum dosage of breakpoint in the chemical application becomes essential. Even though experimental investigations have been extensive, theoretical understanding of such processes are demanding. Commonly employed theoretical analyses for the inactivation of microorganisms and depletion of chemicals include kinetics expressing the rates of depletion of chemical and microorganisms. The terms chemical demand (x) and specific disinfectant demand (α) are often used in theoretical modeling of inactivation. The value of specific disinfectant demand (α) has always been assumed to be a constant in these models. Intracellular concentration built up within the cells of the microorganisms during inactivation could lead to possible weakening effects of microorganisms thereby requiring lower doses as disinfection proceeds makes the assumption of constant α inaccurate. Model equations are formulated based on these observations co-relating the parameters α and x with a progressive inactivation (N/N 0). The chemical concentration (C) is also presented in terms of the inactivation time (t) and the survival ratio (N/N 0) for given pH and temperature conditions. The model is examined using experimentally verified Ct data of Giardia Cysts/chlorine system. The respective values of x for different survival ratios were evaluated from the data using MatLab software. Proposed model correlating for the disinfectant demand (x) with the survival ratio (N/N 0) fits satisfactorily with those evaluated from data. The rate constants for different pH and temperature conditions are evaluated which showed compatibility with the Arrhenius model. The dependence of frequency factors with pH indicated compatibility with accepted models. The Ct values regenerated with the kinetic data shows a very accurate fit with published data. [Copyright &y& Elsevier]

Abstract: A kinetic model was proposed to describe the generation of active chlorine species (ACS) in circulating 3% NaCl solution subjected to the treatments of low-amperage (0.01A) pulsating direct current (PC) as a first step towards an effective circulation electrochemical brine disinfection process with low ACS level. The model was developed based on the mass balance between the electrochemical production and evaporation loss of ACS during the process, and found to predict reasonably well the sigmoidal ACS concentration profiles. Kinetic analysis revealed that at the same amperage, ACS was generated at a lower level by PC treatment than by normal direct current (DC) treatment through lowering of the frequency of current pulse and the capacity of condenser in the pulse circuit. This implies that PC could be more useful than DC for the delicate control of ACS at an appropriately low level during circulating electrochemical brine disinfection. [Copyright &y& Elsevier]

Abstract  Following leaf application of salicylic acid (SA), calcium chloride, hydrogen peroxide and 6-benzylaminopurine (BA), Manila grass (Zoysia matrella) plants were exposed to day/night temperature of 7/2 °C for 120 h in a growth chamber. The lower content of malondialdehyde (MDA) and H2O2 and higher activities of ascorbate peroxidase (APX), guaiacol peroxidase (POD) and catalase (CAT) during exposure to low temperature in pre-treated plants in comparison with control plants demonstrated that these compounds improved the chilling tolerance of Manila grass. [ABSTRACT FROM AUTHOR]

In previous papers, we showed that (i) neutral solutions of hydrogen peroxide can be safely obtained by the direct reaction of H 2and O 2gas mixtures in the presence of Pd-loaded sulfonic acid resins and (ii) low molecular weight olefins can be successfully epoxidized using aqueous solutions of H 2O 2in the presence of amorphous Ti/SiO 2catalysts. Against this background, this paper seeks to go one step further in our on-site H 2O 2strategy by combining the direct synthesis of nonacidic H 2O 2solutions with the catalyzed epoxidation of alkenes with hydrogen peroxide. In a first step, we optimized the reaction conditions for the direct synthesis of H 2O 2working in a semibatch reactor. Aqueous solutions of 9 wt % H 2O 2were then used in the epoxidation of oct-1-ene on a Ti-loaded amorphous silica catalyst, and reaction conditions were optimized. Finally, the propene epoxidation reaction was conducted in a continuous mode under the optimum reaction conditions selected (343 K, H 2O 2/catalyst ratio = 1:4, propene/catalyst ratio = 25, residence time 45 min). At steady-state, the conversion level of H 2O 2reached 96% with a selectivity of hydrogen peroxide to propene oxide of 95%. After 135 h of reaction time, a slight decrease in the selectivity of H 2O 2to epoxide was observed, with a decrease of H 2O 2conversion from 96 to 80%. This catalyst deactivation is reversible, as original activity is fully recovered upon regeneration in air at 873 K. [ABSTRACT FROM AUTHOR]

The article reports on the study concerning the effectiveness of switching disinfectants for nitrification control. The study shows that one-month switch from chloramines to free chlorine is effective for terminating nitrification, but nitrification is likely to return within several months after the return to chloramines. It found that ammonia-oxidizing bacteria (AOB) were attached to pipe-wall specimens removed from a distribution system at the end of the free-chlorination period, suggesting AOB persisted during free chlorination.

Abstract: DNA methylation is considered to play an essential role in cellular senescence. To uncover the mechanism underlying cellular senescence, we established the model of premature senescence induced by hydrogen peroxide (H2O2) in human embryonic lung fibroblasts and investigated the changes of genome methylation, DNA methyltransferases (DNMTs) and DNA-binding domain proteins (MBDs) in comparison with those observed during normal replicative senescence. We found that premature senescence triggered by H2O2 exhibited distinct morphological characteristics and proliferative capacity which were similar to those of replicative senescence. The genome methylation level decreased gradually during the premature as well as replicative senescence, which was associated with the reduction in the expression of DNMT1, reflecting global hypomethylation as a distinct feature of senescent cells. The levels of DNMT3b and methyl-CpG binding protein 2 (MeCP2) increased in both mid-aged and replicative senescent cells, while DNMT3a and MBD2 were upregulated in the mid-aged cells. Only DNMT3b was elevated in the cells in the premature senescence persistence status. Additionally, the expression for DNMTs, MBD2 and MeCP2 was increased rapidly upon H2O2 treatment. These results indicate that H2O2-induced premature senescence share some features of replicative senescence, such as basic biological characteristics and global hypomethylation while there are slight differences in the profile of methylation-associated enzyme expression. Oxidative damage may hence be a causative factor in epigenetic alteration partly responsible for cellular senescence. [Copyright &y& Elsevier]

This study investigated the characteristics of natural organic matter (NOM) in two different raw surface water sources that respond differently to ozonation: one for which ozonation decreases the disinfection by-product (DBP) formation potentials (i.e., Capilano Reservoir, Vancouver, Canada), and one for which ozonation does not (i.e., South Thompson River, Kamloops, Canada); and evaluated the effect of ozonation on these characteristics and on the DBP formation potential of the different size and polar fractions of the NOM. Although the South Thompson River and the Capilano Reservoir waters had relatively similar total organic carbon concentrations, the characteristics of the NOM (e.g., size and polar distribution, specific UV absorption), in these water sources differed significantly. In general, no clear and consistent trend was observed with respect to the tendency of different size and polar fractions of NOM to generate DBPs. Nonetheless, the results from the present study suggest that hydrophobic NOM has a higher tendency to form DBPs. In addition, when considering individual size and polar fractions, specific UV absorption was a good overall indicator of the DBP formation potential for a given water source. The effect of ozonation on South Thompson River and Capilano Reservoir waters also differed significantly. For both source waters, ozonation appeared to have a greatest effect on the more hydrophilic fractions, generally increasing the DBP formation potential of the smaller more hydrophilic NOM, while generally decreasing that of the larger more hydrophilic NOM. The beneficial effect of ozonation on reducing haloacetic acid (HAA) formation potentials was due to a reduction in both the dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) formation potentials, while the negative effect of ozonation on increasing HAA formation potentials was due to an increase in the DCAA formation potentials. The results from the present study clearly indicate that the use of ozone as a primary disinfectant does not necessarily reduce the DBP formation potential of NOM in all water sources, further demonstrating the complex structure of NOM and the fact that NOM from different sources cannot be simply treated as one entity and compared with one another. [ABSTRACT FROM AUTHOR]

Abstract: Standards for radiation sterilization of health care products require evaluation of the potential for induced radioactivity for electron beam energies greater than 10MeV. Measured energy for a 10MeV accelerator may be slightly higher, which could fall under the requirement. The evaluation method in this paper uses a pathways analysis method to estimate individual dose, which is compared against the estimate of induced activity. Based on this comparison, the amount of induced activity at 10.4MeV beam energy does not present a significant individual risk from exposure to the irradiated device. [Copyright &y& Elsevier]

Formaldehyde resins at various molar ratios of monomers (aniline/o-cresol/cyclohexanone) were synthesized under acid catalysis. The resultant resins were reacted with a large excess of epichlorohydrin, and multifunctional epoxy formaldehyde resins were obtained. These resins were reacted with monoallyl ester of maleic acid in the presence of benzyltriethylammonium bromide as catalyst, and multiallyl maleate resins were obtained. The resins were characterized by elemental analysis and by spectroscopic methods (IR and NMR). The curing and decomposition behavior of cross-linked resins were studied by DSC and TGA techniques. The presence of allyl maleate as pendant groups on polymeric chains confers on them the improvement of the possibilities for obtaining thermosetting resin systems based on bismaleimide derivatives. The cross-linked products showed good thermal properties, high glass transitions, and low water absorption. [ABSTRACT FROM AUTHOR]

An innovative approach to minimize bromate formation using sequential chlorine and ammonia (Cl2-NH3 process) was developed at pilot scale and validated in a full-scale drinking water facility. Pilot-scale results showed the Cl2-NH3 process minimized bromate formation by 65-95% compared to 40-70% using ammonia only. A 90-day full-scale evaluation confirmed the Cl2-NH3 process could prevent bromate concentrations from exceeding 10 μg/L. Full-scale implementation of the Cl2-NH3 process allowed an increase in ozone exposure level from 3.0 mg-min/L to 8.6 mg-min/L at 15.1°C. The increased exposure level is important as drinking water utilities strive to meet more stringent drinking water regulations such as Cryptosporidium inactivation. [ABSTRACT FROM AUTHOR]

The photodegradation of chlorine-based disinfectants NH2Cl, HOCl, and OCl− under UV irradiation from low-(LP) and medium-pressure (MP) Hg lamps was studied. The quantum yields of aqueous chlorine and chloramine under 254nm (LP UV) irradiation were greater than 1.2molEs−1 for free chlorine in the pH range of 4–10 and 0.4molEs−1 for monochloramine at pH 9. Quantum yields for MP (200–350nm) ranged from 1.2 to 1.7molEs−1 at neutral and basic pH to 3.7molEs−1 at pH 4 for free chlorine, and 0.8molEs−1 for monochloramine. Degradation of free chlorine was enhanced under acidic water conditions, but water quality negatively impacted the MP Hg lamp degradation of free chlorine, compared to the LP UV source. The production of hydroxyl radical via chlorine photolysis was assessed along with the rate of reaction between OH and HOCl using radical scavengers (parachlorobenzoic acid and nitrobenzene) in chlorinated solutions at pH 4. The quantum yield of OH radical production from HOCl at 254nm was found to be 1.4molEs−1, while the reaction of HOCl with OH radical was measured as 8.5×104 M−1 s−1. NH2Cl was relatively stable in all irradiated solutions, with <0.3mgL−1 increase in nitrate following a UV dose of 1000mJcm−2. For water treatment plants, no significant changes in chlorine concentration would be expected under typical pH levels and UV doses; however, the formation of OH could have implications for chlorinated byproducts or decay of unwanted chemical contaminants. [Copyright &y& Elsevier]

Abstract: This paper presents a novel cleaner production process for producing sodium chlorite by reducing sodium chlorate with hydrogen peroxide. In the new process, chlorine dioxide is generated by reducing chlorate ions with hydrogen peroxide in the presence of sulfuric acid: it then reacts with aqueous sodium hydroxide solution and hydrogen peroxide to produce sodium chlorite. The reaction conditions that were experimentally investigated included: reaction temperatures, concentrations of sodium chlorate solution, molar ratio of NaClO3:H2SO4:H2O2, and acidity. Waste acid in the chlorine dioxide generator is dramatically reduced with recycling in the new process. The by-produced sodium sulfate in sulfuric acid is minimized and reclaimed. [Copyright &y& Elsevier]

Seven diverse natural waters were collected and treated in the laboratory under five oxidation scenarios (chlorine, chloramine, both with and without preozonation, and chlorine dioxide). The impact of these disinfectants on the formation of disinfection byproducts was investigated. Results showed that preozonation decreased the formation of trihalomethanes (THMs), haloacetic acids (HAAs) and total organic halogen (TOX) for most waters during postchlorination. A net increase in THMs, HAAs and TOX was observed for a water of low humic content. Either decreases or increases were observed in dihaloacetic acids and unknown TOX (UTOX) as a result of preozonation when used with chloramination. Chloramines and chlorine dioxide produced a higher percentage of UTOX than free chlorine. They also formed more iodoform and total organic iodine (TOI) than free chlorine in the presence of iodide. Free chlorine produced a much higher level of total organic chlorine (TOCl) and bromine (TOBr) than chloramines and chlorine dioxide in the presence of bromide. [Copyright &y& Elsevier]

Salty taste with or without chlorine or chloramine flavour is one of the major consumer complaints to water utilities. The flavour profile analysis (FPA) taste panel method determined the average taste threshold concentration for salt (NaCI) in Milli-Q water to be 640 ± 3 mg/L at pH 8, Chlorine and chloramine disinfectants have no antagonistic or synergistic effects on the taste of NaCI, salt, in Milli-Q water. The flavour threshold concentrations for chlorine or chloramine in Milli-Q water alone or in the presence of NaCl could not be estimated by the Weber-Fechner curves due to the chlorine or chloramine flavour outliers in the 0.2-0.8 mg/L concentration range. Apparently, NaCI is not equilibrated with the concentration of ions in the saliva in the mouth and the concentration of free chlorine or chloramines cannot be tasted correctly. Therefore, dechlorinated tap water may be the best background water to use for a particular drinking water evaluation of chlorine and chloramine thresholds. Laboratory FPA studies of free chlorine found that a 67% dilution of Central Arizona Project (CAP) (Tucson, AZ) water with Milli-Q water was required to reduce the free chlorine flavour to a threshold value instead of a theoretical value of 80% (Krasner and Barren, 1980). No synergistic effect was found for chlorine flavour on the dilution of CAP water with Milli-Q water. When Central Avra Valley (AVRA) groundwater was used for the dilution of CAP water, a synergistic effect of the TDS present was observed for the chlorine flavour. Apparently, the actual mineral content of drinking water, and not just NaCI in Milti-Q water, is needed for comparative flavour tests for chlorine and chloramines. [ABSTRACT FROM AUTHOR]

Mixed chlorobromoanisoles have recently been recognized as new potential odorous compounds in tap water. The odour threshold concentrations (OTCs) of these compounds are close to the sub ng/L (ppt) and associated descriptors are "earthy, musty, rubber". During a "swampy, musty" episode in water of the Norrtälje district (Sweden), 2,4,6-mixed chlorobromoanisoles and their phenolic precursors were identified. These compounds were synthesised in order to quantify them in different types of waters, Samplings were performed during two different seasons. Results show that whatever the season, mixed haloanisoles and their precursors were present. Chlorination, biofilm activity and residence time in the distribution system seem to be critical factors for the appearance of such compounds. [ABSTRACT FROM AUTHOR]

Taste and odour problems of tap water in Seoul are attributed to 2-methylisoborneol (2-MIB) and trans-1, 10-dimethyl-trans-9 decalol (geosmin), which are the result of metabolism of algae and chlorine for disinfection. This study was carried out to measure 2-MIB and geosmin in the raw water from the Han River, to investigate removal efficiency of GAC and BAG integrated with post-ozonation, and to minimise and quantify the required chlorine concentration as a final disinfectant through the candidate process. [ABSTRACT FROM AUTHOR]

Bladder cancer has been associated with exposure to chlorination by-products in drinking water, and experimental evidence suggests that exposure also occurs through inhalation and dermal absorption. The authors examined whether bladder cancer risk was associated with exposure to trihalomethanes (THMs) through ingestion of water and through inhalation and dermal absorption during showering, bathing, and swimming in pools. Lifetime personal information on water consumption and water-related habits was collected for 1,219 cases and 1,271 controls in a 1998–2001 case-control study in Spain and was linked with THM levels in geographic study areas. Long-term THM exposure was associated with a twofold bladder cancer risk, with an odds ratio of 2.10 (95% confidence interval: 1.09, 4.02) for average household THM levels of >49 versus ≤8 μg/liter. Compared with subjects not drinking chlorinated water, subjects with THM exposure of >35 μg/day through ingestion had an odds ratio of 1.35 (95% confidence interval: 0.92, 1.99). The odds ratio for duration of shower or bath weighted by residential THM level was 1.83 (95% confidence interval: 1.17, 2.87) for the highest compared with the lowest quartile. Swimming in pools was associated with an odds ratio of 1.57 (95% confidence interval: 1.18, 2.09). Bladder cancer risk was associated with long-term exposure to THMs in chlorinated water at levels regularly occurring in industrialized countries. [ABSTRACT FROM AUTHOR]

The article discusses on the different methods used for water and wastewater disinfection, in the U.S. The first methods is the traditional residual monitoring and testing procedures, which measures the quantity of chlorine present in water. The second method is the oxidation-reduction potential (ORP), which looks at the qualitative measurement of chlorine, and the last method is the dual oxidation control, which combines the quantitative value of the residual measurement with the qualitative measurement of the efficacy of the disinfection program.

This paper describes the findings of a study to develop a ‘Disinfectant Demand Sensor’. The aim was to determine the 3- or 7-day demand of a water sample in a shorter period of time, such as a few hours. Three approaches were taken to achieve this: (i) assessment of water quality surrogate parameters, (ii) ‘short’ disinfection demand assessment, and (iii) temperature elevation approaches. All these methods can be used for the prediction of chlorine, but only temperature elevation and short demand assessment can be used for the prediction of chloramine with good accuracy. Water quality data (prior to disinfection) was used to identify surrogate water quality parameters for disinfectant demand. The study found that the surrogate parameters of major interest were UV254, DOC, and colour with R2 values of 0.94, 0.91 and 0.83, respectively for chlorine demand prediction. A rapid fractionation technique using ion-exchange resins to separate the organic component into various fractions demonstrated that the VHA (Very Hydrophobic Acid/humic acid) fraction showed the best relationship with chlorine demand and was also identified as a possible surrogate parameter with an R2 value of 0.88. Chloramine demand did not behave similarly. Other factors influencing chloramine decay make it more difficult to predict than chlorine decay. The possibility of using the demand of a shorter time span to predict demands of a longer time was also investigated. This technique was proved to work well for both chlorine and chloramine and results have shown that a 3-h chlorine demand correlated well with the 3-d demand (R2 = 0.97). Also, the 1-d chloramine demand correlates with the 3-d demand (R2 = 0.92). Thirdly, the temperature investigation used the concept of raising the temperature of a sample thereby reducing the time taken to reach the 3-d demand equivalent. This method was found to be suitable for both chlorine and chloramine demand prediction. For example the 3-d chlorine/chloramine demand at 20°C equivalents of Myponga water can be determined after just 5.3/5.5 h respectively when the sample is incubated at 40°C. [ABSTRACT FROM AUTHOR]

Abstract: In a water distribution system (WDS), chlorine disinfection is important in preventing the spread of waterborne diseases. The ability to forecast chlorine residuals at strategic points in the WDS would be a significant aid to water quality managers in helping them to ensure the satisfaction and safety of their customers. In this research, general regression neural networks (GRNNs) are developed for forecasting chlorine residuals in the Myponga WDS, to the south of Adelaide, South Australia, up to 72 h in advance. A number of critical model issues are addressed including: the selection of an appropriate forecasting horizon; the division of the available data into subsets for modelling; and the determination of the inputs relevant to the chlorine forecasts. To determine if the GRNN is able to capture any nonlinear relationships that may be present in the data set, a comparison is made between the GRNN model and a multiple linear regression (MLR) model. Additional investigations are also performed to simulate the effects of a reduced sampling frequency, and to estimate model performance for longer lead-time forecasts. When tested on an independent validation set of data, the GRNN models are able to forecast chlorine levels to a high level of accuracy, up to 72 h in advance. The GRNN also significantly outperforms the MLR model, thereby providing evidence of the existence of nonlinear relationships in the data set. [Copyright &y& Elsevier]

The present study investigates environmentally safe pretreatments for wool fabric to improve its printing with acid and reactive dyes. Wool fabric was pretreated either with activated hydrogen peroxide using tetraacetylethylenediamine or with lipase enzyme under specified conditions. Some acid and reactive dyes were applied for wool printing using normal techniques. These treatments were found to improve the colour intensity of the printed fabrics to a level comparable with those of prechlorinated wool fabrics. [ABSTRACT FROM AUTHOR]

This work addresses the problem of using seawater for cooling and the associated environmental problems caused by the usage and discharge of biocides. The discharged biocide and its byproducts are toxic to aquatic lives and must be decreased below certain discharge limits on load prior to discharge. The conventional approach has been to add biocide removal units as an end-of-pipe treatment. This work introduces an integrated approach to reducing biocide discharge though a set of coordinated strategies for in-plant modifications and biocide removal. In particular, process integration tools are used to reduce heating and cooling requirements through the synthesis of a heat-exchange network. Heat integration among process hot and cold streams is pursued economically by reconciling cost reduction in utilities versus any additional capital investment of the heat exchangers. Other strategies include maximization of the temperature range for seawater through the process and optimization of biocide dosage. This new approach has the advantage of providing cost savings while reducing the usage and discharge of biocides. A case study is used to illustrate the usefulness of this new approach and the accompanying design techniques. [ABSTRACT FROM AUTHOR]

No abstract available. [ABSTRACT FROM AUTHOR]

There are several concerns associated with the use of chlorine for potable water disinfection. These are the resistance of certain pathogens, the formation of toxic disinfection by-products and the adverse effects on aesthetic water quality, Owing to these concerns the water industry is continually reviewing alternative disinfection technologies. A methodology has been devised that will aid the water industry in evaluating the potential of these technologies. The methodology uses seven criteria to evaluate the technologies, these are: inactivation efficiency, disinfection by- product (DBP) formation, toxicity, aesthetic water quality, cost, scalability and residual maintenance. Each criterion is assessed by associated questions in order of importance in accordance with a protocol. The criteria are evaluated using UK water quality regulations as standards. Ultraviolet (UV) disinfection was used as an example to demonstrate the methodology. UV was shown to meet all the criteria apart from the provision of a residual disinfectant. Several other disinfection technologies were evaluated using the methodology. Direct electrochemical disinfection and mixed oxidant generators were identified as having the most potential for replacing chlorination. [ABSTRACT FROM AUTHOR]

Inactivation of Yersinia enterocolitica by chlorine (0.6 to 20 ppm) was investigated in distilled water and in tryptic soy broth (TSB, 0.015%) at different temperatures (4, 20, and 40°C). In distilled water, chlorine inactivation of Y. enterocolitica was enhanced by increasing the temperature from 4 to 20°C, and survival curves were described by a model that assumed first-order kinetics followed by tailing in which the microbial concentration remained constant. The presence of TSB increased chlorine resistance of Y. enterocolitica, and survival curves were concave downward. These survival curves were described by a model based on the Weibull distribution. Chlorine decay in distilled water was independent of temperature and of the initial concentration of available chlorine and was modeled by first-order reaction kinetics. Chlorine decay in TSB was independent of the initial chlorine concentration but depended on the treatment temperature and was modeled by the addition of two first-order decay equations. The increased resistance of Y. enterocolitica to chlorine in TSB was not due only to the chlorine demand by the TSB components. These components protected Y. enterocolitica ceils from the antimicrobial effect of chlorine. [ABSTRACT FROM AUTHOR]

A laboratory scale system, partially reproducing dairy plant conditions, was developed to quantify the effectiveness of chlorine and alternative sanitizers in reducing the number of viable bacteria attached to stainless steel surfaces. Stainless steel tubes fouled in a continuous flow reactor were exposed to a standard clean-in-place regime (water rinse, 1% sodium hydroxide at 70°C for 10 min, water rinse, 0.8% nitric acid at 70°C for 10 min, water rinse) followed by exposure to either chlorine (200 ppm) or combinations of nisin (500 ppm), lauricidin (100 ppm), and the lactoperoxidase system (LPS) (200 ppm) for 10 min or 2, 4, 8, 18, or 24 h. There was significant variation in the effectiveness of the alkaline-acid wash steps in reducing cell numbers (log reduction between 0 and 2). Following a 10-min treatment, none of the sanitizers significantly reduced the number of attached cells. Two hours of exposure to chlorine, nisin + the LPS, or lauricidin + the LPS achieved 2.8, 2.2, and 1.6 log reductions, respectively. Exposure times >2 h did not further decrease the number of viable bacteria attached to the stainless steel. The effectiveness of combinations of nisin, lauricidin, and the LPS was similar to that of chlorine (P > 0.05), and these sanitizers could be used to decontaminate the surfaces of small-volume or critical hard-to-clean milk processing equipment. [ABSTRACT FROM AUTHOR]

Malaysia, like any other country has experienced a number of chemical accidents in the past, hence the necessity to undertake thorough consequence analysis to mitigate similar occurrences in future. The water treatment plant in question keeps more than 18.6 MT (metric tonnes) of chlorine to disinfect water for the community in municipal area. However, chlorine is a hazardous chemical that can cause serious injuries, loss of life and damage to properties and environment if not handled properly. Hence using the Environmental Protection Agency (EPA) methodology an offsite consequence analysis was conducted to determine the potential impacts in the event of catastrophic release of chlorine at the water treatment plant. A “worst-case release scenario” and 7ldquo;alternative scenario” were developed for the treatment plant. The results obtained from the use of TRACE software showed that a potential hazard exists, even under average annual weather conditions. Within a 6 km radius, an estimated number of 102000 people within the zone for a 3 ppm chlorine exposure may be affected due to a worst-case release. The consequence isopleth for the respective chlorine concentration indicates that the chlorine plume is directed towards the administration building and process unit facilities of the plant. Hence, it is critical to ensure that all personnel within the plant are provided with sufficient training on the emergency response plan and the application of the relevant personnel protective equipment (PPE) in the event of accidental releases. Although the hazard exists, the risk to the public may be low. An alternative release scenario would be limited due to the use of safety and mitigation systems incorporated into the chlorinating system, but the plant requires other supporting safety measures to supplement the existing facility's inherent safety. Such measures are essential to ensure that in the event of a potential incident at the plant onsite and offsite effects could be minimised to ensure the risk is as low as reasonably practicable (ALARP). [ABSTRACT FROM AUTHOR]

The bioassays assimilable organic carbon (AOC) and coliform growth response are better indexes than biological oxygen demand to determine water quality and water's ability to support the growth of bacteria. Ozonated (5 mg/liter) and chlorinated tap water were used to wash alfalfa seeds for 30 min. After washing in the ozonated tap water, the AOC concentration increased 25-fold, whereas the dissolved ozone decreased to undetectable levels. The AOC levels for the chlorinated water after washing the seeds also increased. These increases are due to ozone's strong oxidizing ability to break down refractory, large-molecular-weight compounds, forming smaller ones, which are readily used as nutrient sources for microorganisms. This same phenomenon was observed when using ozone in the treatment of drinking water. The AOC value increased from 1,176 to 1,758 µgC-eq/liter after the reconditioned wastewater was ozonated. When the ozonated wastewater was inoculated with Salmonella serotypes, the cells survived and increased generation times were observed. The increased nutrients would now become more readily available to any pathogenic microorganisms located on alfalfa seed surface as seen with the increase in the inoculated levels of Salmonella in the ozonated wastewater. If the washing process using ozonated water is not followed by the recommended hypochlorite treatment or continually purged with ozone, pathogen growth is still possible. [ABSTRACT FROM AUTHOR]

The elimination of Listeria monocytogenes inoculated onto a piece of cut iceberg lettuce (3.8 by 3.8 cm) by treatment with chlorinated water (200 µg/ml free chlorine) and a 0.5% (wt/vol) solution of FIT Professional Line Antibacterial Cleaner (FIT) was investigated. The efficacy of the two sanitizers was not influenced by the composition of the medium used to culture the L. monocytogenes used in the inocula, the number of strains in the inoculum, or the recovery medium used to enumerate the pathogen on lettuce after treatment. Drying inoculum on lettuce for 45 min at 37°C caused more cells to die or not be retrieved compared with drying inoculum for 30 min at 25°C. However, the percentage of cells in the inoculum recovered from lettuce treated with chlorine or FIT was not significantly different, regardless of the drying method. Stomaching, homogenizing, or stomaching followed by homogenizing lettuce treated with sanitizers resulted in recovery of similar numbers of L. monocytogenes, indicating that stomaching and homogenizing are equivalent in extracting cells; the sequential use of both processing methods did not substantially increase the efficiency of recovery. Washing lettuce with water or treating lettuce with 200 µg/ml chlorine or FIT resulted in decreases in populations of 0.60, 1.76, and 1.51 log CFU per lettuce piece, respectively, regardless of variations in test parameters. Reductions caused by sanitizers were significantly greater (α = 0.05) than that observed for water but not significantly different from each other. It is concluded that evaluation of sanitizers for their efficacy in killing L. monocytogenes on lettuce can be determined by spot inoculating 50 µL of a five-strain mixture of cells from 24-h cultures suspended in 5% horse serum albumen, followed by drying the inoculum for 45 min at 37°C, treatment by submerging in 50 ml of sanitizer for 5 min, stomaching samples in 50 ml of Dey-Engley neutralizing broth for 2 min, and enumerating survivors on modified Oxford medium. [ABSTRACT FROM AUTHOR]