Si no cuentas con agua segura para consumo humano, no olvides desinfectar el agua, principalmente durante la pandemia de COVID-19 [infografía]

Si no cuenta con agua segura para consumo humano, no olivdes desinfectar el agua, principalmente durane la pandemia de COVID-19

Variability of residual chlorine in swimming pool water and determination of chlorine consumption for maintaining hygienic safety of bathers with a simple mass balance model.

Trial-and-error chlorination as a conventional practice for swimming pool water disinfection may fail to consistently maintain the pool's residual chlorine within regulatory limits. This study explored the variability of residual chlorine and other common water quality parameters of two sample swimming pools and examined the potential of using a mass balance model for proactive determination of chlorine consumption to better secure the hygienic safety of bathers. A lightly loaded Pool 1 with a normalized bather load of 0.038 bather/m3/day and a heavily loaded Pool 2 with a normalized bather load of 0.36 bather/m3/day showed great variances in residual free and combined chlorine control by trial-and-error methods due to dynamic pool uses. A mass balance model based on chemical and physical chlorine consumption mechanisms was found to be statistically valid using field data obtained from Pool 1. The chlorine consumption per capita coefficient was determined to be 4120 mg/bather. The predictive method based on chlorine demand has a potential to be used as a complementary approach to the existing trial-and-error chlorination practices for swimming pool water disinfection. The research is useful for pool maintenance to proactively determine the required chlorine dosage for compliance of pool regulations.

Análise da concentração de cloro ativo em sanitizantes industrializados comercializados em Maceió, AL

No Brasil, do ano de 2000 a 2017, ocorreram 12.503 surtos de origem alimentar e os locais que sobressaíram como os mais frequentes na ocorrência destes surtos foram restaurantes e residências tendo como uma das causas principais, as superfícies de equipamentos, utensílios e objetos mal higienizados. O produto mais usado para realizar a higiene é o hipoclorito de sódio (água sanitária), sendo este utilizado tanto para serviços de alimentação como para uso residencial. O hipoclorito é comercializado industrialmente e este pode ser fabricado de forma impropria não correspondendo ao percentual de cloro contido em sua rotulagem. O objetivo deste estudo foi analisar o teor de cloro das marcas comerciais de águas sanitárias industrializadas comercializadas na cidade de Maceió/ AL. A metodologia utilizada para determinação de Cloro Ativo foi o método volumétrico, em solução de hipoclorito de sódio. Duas marcas comerciais apresentaram valores menores que 2% de cloro, sete com valores acima e três com valores entre 2 e 2,5%, valores estes preconizados pela legislação. Os resultados mostram que a fabricação deste produto precisa de fiscalização por órgãos competentes para que o teor de cloro esteja dentro do padrão da Legislação. Com essa inadequação a população será prejudicada, pois estará comprando um produto adulterado.

In Brazil, from the year 2000 to 2017, 12,503 foodborne outbreaks have occurred, and the other important local as the more frequent occurrence of these outbreaks was restaurants and residences having as one of the main causes, the surfaces of equipment, utensils and objects poorly sanitized. The product used to perform hygiene is sodium hypochlorite (bleach), which is used for both food service as for residential use. The hypochlorite is sold industrially and this can be manufactured in a manner unbecoming not corresponding to the percentage of chlorine contained in your labelling. The aim of this study was to analyze the chlorine content of the trademarks of sanitary water marketed in the industrialised city of Maceió/AL. The methodology used for the determination of active chlorine, was using the volumetric method, solution of sodium hypochlorite. Two trademarks presented values less than 2% chlorine, seven with values above and 3 with values between 2 and 2.5%, these values provided by the legislation. The results show that the manufacture of this product needs supervision by competent bodies so that the chlorine content is within the pattern of legislation. Whit this inadequacy to population will suffer, as will be buying and adulterated product.

Whole-head washing, prior to cutting, provides sanitization advantages for fresh-cut Iceberg lettuce (Latuca sativa L.).

The efficacy of two leafy produce wash methods, the traditional cutting-before-washing process and a new washing-before-cutting method, on reduction of Escherichia coli O157:H7 inoculated on Iceberg lettuce was compared. The washing tests were conducted in a pilot-scale washer using combinations of water, chlorine, peroxyacetic acid, and ultrasound. The washing-before-cutting process recorded an E. coli O157:H7 count reduction 0.79-0.80 log10 CFU/g higher than that achieved with the cutting-before-washing process in treatments involving only a sanitizer. When ultrasound was applied to the washing-before-cutting process, a further improvement of 0.37-0.68 log10 CFU/g in microbial count reduction was obtained, reaching total reductions of 2.43 and 2.24 log10 CFU/g for chlorine and peroxyacetic acid washes, respectively.

Physicochemical quality and chemical safety of chlorine as a reconditioning agent and wash water disinfectant for fresh-cut lettuce washing.

Chlorine was assessed as a reconditioning agent and wash water disinfectant in the fresh-cut produce industry. Artificial fresh-cut lettuce wash water, made from butterhead lettuce, was used for the experiments. In the reconditioning experiments, chlorine was added to artificial wash water inoculated with Escherichia coli O157 (6 log CFU/ml). Regression models were constructed based on the inactivation data and validated in actual wash water from leafy vegetable processing companies. The model that incorporated chlorine dose and chemical oxygen demand (COD) of the wash water accurately predicted inactivation. Listeria monocytogenes was more resistant to chlorine reconditioning in artificial wash water than Salmonella spp. and Escherichia coli O157. During the washing process with inoculated lettuce (4 log CFU/g), in the absence of chlorine, there was a rapid microbial buildup in the water that accumulated to 5.4 ± 0.4 log CFU/100 ml after 1 h. When maintaining a residual concentration of 1 mg/liter free chlorine, wash water contamination was maintained below 2.7, 2.5, and 2.5 log CFU/100 ml for tap water and artificial process water with COD values of 500 and 1,000 mg O2/liter, respectively. A model was developed to predict water contamination during the dynamic washing process. Only minor amounts of total trihalomethanes were formed in the water during reconditioning. Total trihalomethanes accumulated to larger amounts in the water during the wash water disinfection experiments and reached 124.5 ± 13.4 µg/liter after 1 h of execution of the washing process in water with a COD of 1,000 mg O2/liter. However, no total trihalomethanes were found on the fresh-cut lettuce after rinsing.

APMP comparison of measurement of surface emission rate of 36Cl large area source (APMP.RI(II)-K2.Cl-36).

An international comparison of measurement of beta particle surface emission rate from a (36)Cl large area source (APMP.RI(II)-S1.Cl-36) was carried out within the framework of the Asia-Pacific Metrology Program (APMP). Participants from APMP were NMIJ (Japan), KRISS (Korea) and INER (Chinese Taipei). Participants from the other RMOs were NIST (United States), PTB (Germany), NMISA (South Africa) and VNIIM (Russia). All the results of the participants agreed within ±1%. This was the first international comparison of measurement of surface emission rate of beta particle from a large area source.

Compound-specific chlorine isotope analysis: a comparison of gas chromatography/isotope ratio mass spectrometry and gas chromatography/quadrupole mass spectrometry methods in an interlaboratory study.

Chlorine isotope analysis of chlorinated hydrocarbons like trichloroethylene (TCE) is of emerging demand because these species are important environmental pollutants. Continuous flow analysis of noncombusted TCE molecules, either by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) or by GC/quadrupole mass spectrometry (GC/qMS), was recently brought forward as innovative analytical solution. Despite early implementations, a benchmark for routine applications has been missing. This study systematically compared the performance of GC/qMS versus GC/IRMS in six laboratories involving eight different instruments (GC/IRMS, Isoprime and Thermo MAT-253; GC/qMS, Agilent 5973N, two Agilent 5975C, two Thermo DSQII, and one Thermo DSQI). Calibrations of (37)Cl/(35)Cl instrument data against the international SMOC scale (Standard Mean Ocean Chloride) deviated between instruments and over time. Therefore, at least two calibration standards are required to obtain true differences between samples. Amount dependency of δ(37)Cl was pronounced for some instruments, but could be eliminated by corrections, or by adjusting amplitudes of standards and samples. Precision decreased in the order GC/IRMS (1σ ≈ 0.1‰), to GC/qMS (1σ ≈ 0.2-0.5‰ for Agilent GC/qMS and 1σ ≈ 0.2-0.9‰ for Thermo GC/qMS). Nonetheless, δ(37)Cl values between laboratories showed good agreement when the same external standards were used. These results lend confidence to the methods and may serve as a benchmark for future applications.

Factorial analysis of the trihalomethanes formation in water disinfection using chlorine.

The factors that affect trihalomethane (THM) (chloroform, bromodichloromethane, chlorodibromomethane and bromoform) formation from the chlorination of aqueous solutions of hydrophobic fulvic acids (FA) were investigated in a prototype laboratorial simulation using factorial analysis. This strategy involved a fractional factorial design (16 plus 5 center experiments) of five factors (fulvic acids concentration, chlorine dose, temperature, pH and bromide concentration) and a Box Behnken design (12 plus 3 center experiments) for the detailed analysis of three factors (FA concentration, chlorine dose and temperature). The concentration of THM was determined by headspace analysis by GC-ECD. The most significant factors that affect the four THM productions were the following: chloroform-FA concentration and temperature; bromodichloromethane-FA concentration and chlorine dose; chlorodibromomethane-chlorine dose; and, bromoform-chlorine dose and bromide concentration. Moreover, linear models were obtained for the four THM concentrations in the disinfection solution as function of the FA concentration, chlorine dose and temperature, and it was observed that the complexity of the models (number of significant factors and interactions) increased with increasing bromine atoms in the THM. Also, this study shows that reducing the FA concentration the relative amount of bromated THM increases.

Effects of chlorine solutions on footwear.

Operating theatre personnel need to disinfect floors, other surfaces and sometimes their footwear with chlorine solutions in order to comply with Department of Health (DH) guidance on the safe method of dealing with blood spills. This study was designed to determine the effect of repeated applications of chlorine solutions to a new theatre clog manufactured from high density polyurethane.

Toxicity screening and evaluating in chlorination disinfection of wastewater reclamation processes.

Reclamation and re-use of wastewater is one of the most effective ways to alleviate the shortage of water resources, while the safety of reclaimed water becomes one of the critical problems for protecting human health and the ecosystem. While a toxicity test can vividly reflect biological effects of chemicals as a whole, in this study, the Microtox test was used to screen toxicity changes of wastewater during conventional reclamation processes. The results showed that toxicities of water samples decreased continuously along reclamation processes except chlorination/dechlorination in which the toxicity increased significantly. Furthermore, as for different forms of residual chlorine, toxicity of wastewater was quite different with increasing chlorine dosage. NH3-N had a trend to decrease toxicity of disinfected wastewater, while UV254 had a trend to increase toxicity. It was found that there was a good linear relationship between toxicity formation and UV254/NH3-N ratio for wastewater after disinfection with combined chlorine form before peak-point.

Analysis of physical and chemical parameters of bottled drinking water.

Seventeen different brands of bottled drinking water, collected from different retail shops in Amritsar, were analyzed for different physical and chemical parameters to ascertain their compliability with the prescribed/recommended limits of the World Heath Organization (WHO) and the United States Environmental Protection Agency (USEPA). It was found that the majority of the brands tested were over-treated. Lower values of hardness, total dissolved solids (TDS) and conductance than the prescribed limits of WHO showed that water was deficient in essential minerals. Minerals like magnesium, potassium, calcium and fluoride were present in some cases in such a low concentration that water seemed to be as good as distilled water. Samples showing fluoride lesser than 0.5 mg/l warranted additional sources of fluoride for the people consuming only bottled water for drinking purposes. Zero values for chlorine demand as shown by all the bottled water samples showed that water samples were safe from micro-organisms. In case of heavy metals, only lead had been found to be greater than the limit of 0.015 mg/l as prescribed by WHO and USEPA, in seven out of 17 samples. Lead even at such a low concentration can pose a great health hazard.

Material flow analysis of RDF-production processes.

The authors evaluate the possibilities of modifying the chemical characteristics of refuse-derived fuels (RDF) that are processed from residual household waste by mechanical operations to achieve and assure quality targets for relevant chemical concentrations, especially for heavy metals and chlorine. Quality assurance in the production of RDF demands that, together with an enrichment of the calorific value, highly toxic waste components are selectively separated and concentrated in a small stream to produce high yields of a relatively low polluted fuel. Based on the method of material flow analysis, a process evaluation is developed that considers the aspect of minimizing hazardous chemicals along with classical process data such as yield and product quality. Data on specific concentration of hazardous chemicals in waste components and their distribution in residual household waste as well as the results from large-scale test runs using different separation techniques demonstrate that mechanical operations alone are insufficient for separating hazardous chemicals. In the test runs, chemical compounds such as chlorine, cadmium and lead were often concentrated in the product. Even using optimized techniques, the ability to reduce hazards in the product is limited due to the distribution of the element concentration in the various components of the waste stream.

Absolute measurements of total-body calcium using prompt gamma neutron analysis and internal chlorine standardization: results in renal patients.

Measurement of total-body calcium (TBCa) is important in the study of several medical conditions. Neutron activation analysis (NAA) is sufficiently precise for serial measurements, but in order to provide single, absolute determinations of TBCa, it requires a correction for body habitus. A method is described for the absolute determination of TBCa by comparing the total-body chlorine, obtained by NAA, with that obtained by stable bromine dilution. The method is applied to a group of thirty patients who had been treated for chronic renal failure, and significant differences are found between measured values of TBCa and those predicted for 'normal' healthy subjects. The overall experimental error in the absolute determination of TBCa is estimated to be 8%, for a dose equivalent of 3.1 mSv (based on skin dose, and a quality factor of 10 for neutrons).

[Study od visual evoked potentials in employees of the Chemical Works in Bydgoszcz]. / Badanie wzrokowych potencjalów wywolanych u pracowników Zakladów Chemicznych w Bydgoszczy.

Examined was a group of 50 persons aged 25-60 years employed in the Chemical Works in Bydgoszcz. The time of professional contact counted from 4 month to 31 years. During this time the workers had contact with the following--at least 2--compounds: chlorine and its derivates, benzene, propylene, katolite, phosgene, isocyanianes, epichlorohydrine and others. In 33 among 50 examinees (66 p.c.) the authors detected a normal record of VEP. A pathological record was observed in 17 persons (34 p.c.). The greatest per cent of pathological records concerned a group of professional practice amounting 20-29 years as well as persons undertaking the work before the 25th year of life. The most frequent pathological record of VEP was a curve with reduced amplitude of the P wave; the least frequently seen was the debasement of the amplitude together with the elongation of the latent time of this wave.

Desinfección del agua / Desinfection of water

Contiene: generalidades sobre desinfección de aguas; microorganismos que se eliminan con la desinfección; teoría de la desinfección química y su cinética; formas de desinfección; formas de determinar la eficiencia de la desinfección y normas bacteriológicas del agua potable; desinfección con cloro; resultados de la desinfección con cloro; métodos de aplicación del cloro en plantas de tratamiento de agua y determinaciones previas; técnicas de evaluación y control de cloro residual; cloradores e hipocloradores; otros usos del cloro en la ingeniería sanitaria; abastecimiento de agua y su desinfección en casos de emergencia; precauciones en el uso del cloro y sus derivados; efectos potencialmente tóxicos de la cloración; control de trihalometanos; métodos analíticos para la determinación de trihalometanos en aguas de consumo humano; programa de vigilancia de la calidad del agua potable; glosario de términos

Energy-dispersive X-ray microanalysis of air-dried microdroplets containing a macromolecular solute.

In the preparation of microdroplets of biological fluids for X-ray microanalysis, we have found that incorporation of a macromolecular solute, dextran, to a final concentration of 1.5-2.5% retards crystal formation and produces sufficiently uniform deposits on thin films to allow droplets to be analysed without prior freeze-drying. Analyses have been carried out at 20 kV in a scanning electron microscope, using energy-dispersive spectrometry. Absorption of Na X-rays by the added solute can be significant but its effect is minimized by preparing droplets as thin as possible, and by using standards of similar composition. The minimum detectable concentrations are increased because of the extra background contribution, and for a single determination are about 6 mM for Na and 2 mM for Cl and K. These concentrations can be further reduced by measuring replicates. The reproducibility of analysis is significantly improved (to less than 5% for Na and K) over the use of calibration curves by calculating the element concentrations from a known element in the sample, chlorine. Under our analytical conditions loss of Cl did not occur. This method requires that the Cl is measured separately by microcoulometry, but eliminates the need for a range of standard droplets on the grid, and determination of the unknowns is then independent of droplet volume, beam current, counting time and magnification. We have compared, with biological samples, the results from using Cl as an internal standard with those obtained using an added standard element, cobalt. The reproducibility using Cl was approximately two-times better than that obtained with Co, probably because of unavoidable volumetric errors when the Co is pipetted separately.