Alternative statistical modeling for radical prostatectomy data.

Several statistical models have been proposed in recent years, among them is the semiparametric regression. In medicine, there are several situations in which it is impracticable to consider a linear regression for statistical modeling, especially when the data contain explanatory variables that present a nonlinear relationship with the response variable. Another common situation is when the response variable does not have a unimodal shape, and it is not possible to adopt distributions belonging to the symmetric or asymmetric classes. In this context, a semiparametric heteroskedastic regression is proposed based on an extension of the normal distribution. Then, we show the usefulness of this model to analyze the cost of prostate cancer surgery. The predictor variables refer to two groups of patients such that one group receives a multimodal local anesthetic solution (Preemptive Target Anesthetic Solution) and the second group is treated with neuraxial blockade (spinal anesthesia/traditional standard). The other relevant predictor variables are also evaluated, thus allowing for the in-depth interpretation of the predictor variables with a nonlinear effect on the dependent variable cost. The penalized maximum likelihood method is adopted to estimate the model parameters. The new regression is a useful statistical tool for analyzing medical data.

A new flexible regression model with application to recovery probability Covid-19 patients.

The aim of this study is to propose a generalized odd log-logistic Maxwell mixture model to analyze the effect of gender and age groups on lifetimes and on the recovery probabilities of Chinese individuals with COVID-19. We add new properties of the generalized Maxwell model. The coefficients of the regression and the recovered fraction are estimated by maximum likelihood and Bayesian methods. Further, some simulation studies are done to compare the regressions for different scenarios. Model-checking techniques based on the quantile residuals are addressed. The estimated survival functions for the patients are reported by age range and sex. The simulation study showed that mean squared errors decay toward zero and the average estimates converge to the true parameters when sample size increases. According to the fitted model, there is a significant difference only in the age group on the lifetime of individuals with COVID-19. Women have higher probability of recovering than men and individuals aged ≥60 years have lower recovered probabilities than those who aged <60 years. The findings suggest that the proposed model could be a good alternative to analyze censored lifetime of individuals with COVID-19.

Exploring fishery waste potential as antifouling component.

Marine biofouling is a global issue with economic and ecological implications. Existing solutions, such as biocide-based antifouling paints, are toxic for the environment. The search for better antifouling agents remains crucial. Recent research focuses on eco-friendly antifouling paints containing natural compounds like enzymes. This study evaluates enzymatic extracts from fishery residues for antifouling potential. Extracts from Pleoticus muelleri shrimp, Illex argentinus squid, and Lithodes santolla king crab were analyzed. Proteolytic activity and thermal stability were assessed, followed by bioassays on mussel byssus thread formation and barnacle cypris adhesive footprints. All three extracts demonstrated proteolytic activity and 24-h stability at temperate oceanic temperatures, except I. argentinus. P. muelleri extracts hindered cyprid footprint formation and mussel byssus thread generation. Further purification is required for L. santolla extract to assess its antifouling potential activity. This study introduces the use of fishery waste-derived enzyme extracts as a novel antifouling agent, providing a sustainable tool to fight against biofouling formation.

Evaluación de las propiedades psicométricas de la Escala de Curiosidad Epistémica de Litman en hispanohablantes

La Curiosidad Epistémica (CE) es el deseo que motiva a las personas a adquirir nuevo conocimiento. La escala de CE de Litman fue desarrollada para operacionalizar este constructo, y aunque su estructura latente ha sido validada en varios estudios, estos se han realizado en su mayoría en Alemania, EE. UU. y los Países Bajos, que son sociedades educadas, industrializadas, ricas y democráticas. Por consiguiente, el presente estudio evaluó las propiedades psicométricas de la escala de CE, en una muestra de adultos del noroeste de México (N = 334) con edades de 18 a 50 años. Al igual que en investigaciones previas, se compararon dos modelos: unidimensional y bidimensional, mediante análisis factoriales confirmatorios. Adicionalmente, se incluyeron los residuales correlacionados significativos, como parte de ambos modelos, y se examinó si el instrumento tiene invarianza de medición. Los resultados muestran que el modelo bifactorial presentó el mejor ajuste. La consistencia interna fue aceptable, y se comprobó que la escala posee invarianza configural, métrica, escalar y estricta. Usos potenciales de este constructo emergente incluyen su estudio como un factor motivacional relevante, en el nivel de involucramiento y las estrategias de formación de los estudiantes, así como su papel mediador en varios tipos de ansiedad en el aprendizaje.

Epistemic Curiosity (EC) is the desire that motivates people to acquire new knowledge. Litman's EC scale was developed to operationalize this construct, and although its latent structure has been validated in several studies, these have been conducted mostly in Germany, the Netherlands, and the United States, which are educated, industrialized, wealthy, and democratic societies. Therefore, the present study evaluated the psychometric properties of the EC scale in a sample of adults from northwestern Mexico (N = 334) aged 18 to 50 years. As in previous research, two models were compared: one unidimensional and one bidimensional, using Confirmatory Factor Analysis. Additionally, significantly correlated residuals were included as part of both models, and it was examined whether the instrument has measurement invariance. The results show that the bifactor model presented the best fit. The internal consistency was acceptable, and the scale was found to have configural, metric, scalar, and strict invariance. Potential uses of this emerging construct include its study as a relevant motivational factor in students' level of engagement and study strategies, as well as its mediating role in various types of learning anxiety.

Joint regression modeling of location and scale parameters of the skew t distribution with application in soil chemistry data.

In regression model applications, the errors may frequently present a symmetric shape. In such cases, the normal and Student t distributions are commonly used. In this paper, we shall be concerned only to model heavy-tailed, skewed errors and absence of variance homogeneity with two regression structures based on the skew t distribution. We consider a classic analysis for the parameters of the proposed model. We perform a diagnostic analysis based on global influence and quantile residuals. For different parameter settings and sample sizes, various simulation results are obtained and compared to evaluate the performance of the skew t regression. Further, we illustrate the usefulness of the new regression by means of a real data set (amount of potassium in different soil areas) from a study carried out at the Department of Soil Science of the Luiz de Queiroz School of Agriculture, University of São Paulo.

Challenges and opportunities for drinking water treatment residuals (DWTRs) in metal-rich areas: an integrated approach.

The physicochemistry and production rate of drinking water treatment residuals (DWTRs) depends on the raw water composition and the plant operational parameters. DWTRs usually contain Fe and/or Al oxyhydroxides, sand, clay, organic matter, and other compounds such as metal(oids), which are relevant in mining countries. This work proposes a simple approach to identify DWTRs reuse opportunities and threats, relevant for public policies in countries with diverse geochemical conditions. Raw water pollution indexes and compositions of DWTRs were estimated for Chile as a model case. About 23% of the raw drinking water sources had moderate or seriously contamination from high turbidity and metal(loid) pollution If the untapped reactivity of clean DWRTs was used to treat resources water in the same water company, the 73 and 64% of these companies would be able to treat water sources with As and Cu above the drinking water regulations, respectively. Integrating plant operational data and the hydrochemical characteristics of raw waters allows the prediction of DWTRs production, chemical composition, and reactivity, which is necessary to identify challenges and opportunities for DWTRs management.

First characterization of the probiotic potential of lactic acid bacteria isolated from Costa Rican pineapple silages.

BACKGROUND: Agro-industrial waste from tropical environments could be an important source of lactic acid bacteria (LAB) with probiotic potential. METHODS: Twelve LAB isolates were isolated from pineapple silages. The species identification was carried out considering 16S rRNA and pheS genes. Experiments to evaluate the probiotic potential of the isolates included survival under simulated gastrointestinal environment, in vitro antagonistic activity (against Salmonella spp. and Listeria monocytogenes), auto-aggregation assays, antibiotic susceptibility, presence of plasmids, adhesiveness to epithelial cells, and antagonistic activity against Salmonella in HeLa cells. RESULTS: Lacticaseibacillus paracasei, Lentilactobacillus parafarraginis, Limosilactobacillus fermentum, and Weissella ghanensis were identified. Survival of one of the isolates was 90% or higher after exposure to acidic conditions (pH: 2), six isolates showed at least 61% survival after exposure to bile salts. The three most promising isolates, based on survivability tests, showed a strong antagonistic effect against Salmonella. However, only L. paracasei_6714 showed a strong Listeria inhibition pattern; this isolate showed a good auto-aggregation ability, was resistant to some of the tested antibiotics but was not found to harbor plasmids; it also showed a high capacity for adhesion to epithelial cells and prevented the invasion of Salmonella in HeLa cells. After further in vivo evaluations, L. paracasei_6714 may be considered a probiotic candidate for food industry applications and may have promising performance in acidic products due to its origin.

Modeling Mortality Based on Pollution and Temperature Using a New Birnbaum-Saunders Autoregressive Moving Average Structure with Regressors and Related-Sensors Data.

Environmental agencies are interested in relating mortality to pollutants and possible environmental contributors such as temperature. The Gaussianity assumption is often violated when modeling this relationship due to asymmetry and then other regression models should be considered. The class of Birnbaum-Saunders models, especially their regression formulations, has received considerable attention in the statistical literature. These models have been applied successfully in different areas with an emphasis on engineering, environment, and medicine. A common simplification of these models is that statistical dependence is often not considered. In this paper, we propose and derive a time-dependent model based on a reparameterized Birnbaum-Saunders (RBS) asymmetric distribution that allows us to analyze data in terms of a time-varying conditional mean. In particular, it is a dynamic class of autoregressive moving average (ARMA) models with regressors and a conditional RBS distribution (RBSARMAX). By means of a Monte Carlo simulation study, the statistical performance of the new methodology is assessed, showing good results. The asymmetric RBSARMAX structure is applied to the modeling of mortality as a function of pollution and temperature over time with sensor-related data. This modeling provides strong evidence that the new ARMA formulation is a good alternative for dealing with temporal data, particularly related to mortality with regressors of environmental temperature and pollution.

A non-parametric statistic for testing conditional heteroscedasticity for unobserved component models.

When prediction intervals are constructed using unobserved component models (UCM), problems can arise due to the possible existence of components that may or may not be conditionally heteroscedastic. Accurate coverage depends on correctly identifying the source of the heteroscedasticity. Different proposals for testing heteroscedasticity have been applied to UCM; however, in most cases, these procedures are unable to identify the heteroscedastic component correctly. The main issue is that test statistics are affected by the presence of serial correlation, causing the distribution of the statistic under conditional homoscedasticity to remain unknown. We propose a nonparametric statistic for testing heteroscedasticity based on the well-known Wilcoxon's rank statistic. We study the asymptotic validation of the statistic and examine bootstrap procedures for approximating its finite sample distribution. Simulation results show an improvement in the size of the homoscedasticity tests and a power that is clearly comparable with the best alternative in the literature. We also apply the test on real inflation data. Looking for the presence of a conditionally heteroscedastic effect on the error terms, we arrive at conclusions that almost all cases are different than those given by the alternative test statistics presented in the literature.

Modelos estadísticos para las predicciones de la COVID-19 en Cuba

RESUMEN Introducción: Los estudios basados en modelos estadísticos juegan un papel importante para las predicciones sobre la COVID-19. Objetivo: Realizar un análisis de modelación estadística combinando 6 modelos de pronósticos para predecir la aparición de casos positivos diarios, activos y fallecidos por COVID-19 en Cuba. Métodos: Se utilizaron los datos reportados diariamente del 11 de marzo al 25 de mayo publicados en el sitio web CUBADEBATE. A los modelos propuestos se les calculó el desempeño mediante los estadísticos: MAE, RMSE, MAPE y ME así como el análisis de residuales. Resultados: Los modelos A y B dan una tendencia constante de 8 y 9 casos positivos respectivamente para el día 22 de julio. El modelo C indica una ligera disminución de los casos con 4 ese mismo día y el modelo D una tendencia al aumento con 19 casos. . El modelo E refleja un mínimo de 126 casos el día 3 de junio y luego un aumento de los casos hasta alcanzar el 22 de julio un valor de 374 casos activos hospitalizados. En el modelo F se apreció una tendencia a mantenerse constante el número de fallecidos por encima de 80 casos en la primera quincena de julio. Conclusiones: Los 6 modelos estudiados cumplen con las pruebas estadísticas, de desempeño y residuales. Sus datos proporcionan un pronóstico para la COVID-2019, representando una herramienta válida.

ABSTRACT Introduction: Studies based on statistical models play an important role for predictions about COVID-19. Objective: To carry out a statistical modeling analysis combining 6 forecast models to predict the appearance of daily positive cases, active and deceased by COVID-19 in Cuba. Method: Data reported daily from March 11 to May 25 from the CUBADEBATE website were used, which were processed and analyzed. The performance of the models was calculated: Mean absolute error (MAE), root of the mean square error (RMSE), percent of mean absolute error (MAPE) and the mean error (ME) as well as the residual analysis. Results: Models A and B gave a constant trend between 8 and 9 cases of until July 22. Model C indicated a decrease in cases with 4 that same day and model D indicated a raise to 19 cases. Model E indicated a minimum of 126 cases on June E and then a raise to 374 hospitalized cases. Deceases cases had a constant tendency in deceases numbers above of 80 cases in first 15 days of July. Conclusions: The 6 models studied meet the statistical , performance and residual tests. Their data provides a forecast for COVID2019, representing a valid tool.

Physiological damages of Sargassum cymosum and Hypnea pseudomusciformis exposed to trace metals from mining tailing.

The damages of Mariana's mining mud in the physiology of the brown algae Sargassum cymosum and its main epiphytic, the red algae Hypnea pseudomusciformis, were evaluated by controlled essays. Seaweeds were exposed to presence or absence of mud, isolated or in biological association, for 5 and 15 days. Measured parameters were growth rates, biochemical descriptors, and the chemical investigation of concentration and metal profile of the mud dissolved in seawater. Results showed that the highest values for metals were Al > Fe > Mn > Zn in both exposure periods. The mud also affected the growth rate with lethality in both isolated and associative treatments with H. pseudomusciformis after 15 days. According to our redundancy analysis (RDA), the profile and concentration of all metallic elements can induce different physiological responses of the organisms. We were able to observe a higher physiological adaptive ability of S. cymosum against the long-term presence of metals by the synthesis of phenolic compounds, while the deviation of metabolic routes in H. pseudomusciformis can be addressed as the main responsible for its lethality. Moreover, the presence of Hypnea in associative treatments reduces Sargassum's detoxification ability. The present results reinforce the importance of biological interaction studies in a context of physiological resilience against mining mud pollution and mutual influences of species over the individual ability to avoid oxidative stress.

Correlación entre residuales en análisis factorial confirmatorio: una breve guía para su uso e interpretación / Correlation between residuals in confirmatory factor analysis: a brief guide to their use and interpretation

Introducción: La inclusión de correlaciones entre residuales en modelos de medición es una práctica común en la investigación psicométrica y está orientada, predominantemente, a la mejora estadística del modelo por medio del aumento (e.g., CFI) o disminución (e.g., RMSEA) de la magnitud de determinados índices de ajuste, más a que a comprender la naturaleza de dichas asociaciones. El presente reporte metodológico tiene como objetivo presentar al lector el modelamiento, manejo e interpretación de los residuales correlacionados en un marco de análisis factorial confirmatorio y malas especificaciones. Método: Se utilizando los datos de un estudio presentado anteriormente de 521 estudiantes de psicología en una universidad privada de Lima Metropolitana (75.8% mujeres). Se utiliza la Escala de Florecimiento para realizar los análisis. Resultados y Discusión: Esas especificaciones no tendrían un impacto real en la relación de los ítems con el constructo que evalúan, por lo que no aportarían sustancialmente a la comprensión del modelo. Por tanto, especificar correlaciones entre residuales podría enmascarar un modelo mal especificado, o con falencias internas, mediante el incremento espurio de los índices de ajuste.

Introduction: The inclusion of correlations between residuals in measurement models is a common practice in psychometric research and is predominantly oriented to the statistical improvement of the model through increase (for example, IFC) or decrease (for example, RMSEA) of the magnitude of certain adjustment indices, rather than understanding the nature of these associations. This methodological report aims to present to the reader the modeling, management, and interpretation of correlated residuals in a framework of confirmatory factor analysis and poor specifications. Method: Using data from a previously presented study of 521 psychology students at a private university in Metropolitan Lima (75.8% women). The Flowering Scale is used to perform the analyses. Results and Discussion: These specifications would not have a real impact on the relationship of the elements with the construct they evaluate, so they do not contribute modifications to the understanding of the model. Therefore, specifying correlations between residuals could mask a poorly specified model, or with internal failures, by increasing spurious adjustment rates.

Multiparametric Monitoring in Equatorian Tomato Greenhouses (III): Environmental Measurement Dynamics.

World population growth currently brings unequal access to food, whereas crop yields are not increasing at a similar rate, so that future food demand could be unmet. Many recent research works address the use of optimization techniques and technological resources on precision agriculture, especially in large demand crops, including climatic variables monitoring using wireless sensor networks (WSNs). However, few studies have focused on analyzing the dynamics of the environmental measurement properties in greenhouses. In the two companion papers, we describe the design and implementation of three WSNs with different technologies and topologies further scrutinizing their comparative performance, and a detailed analysis of their energy consumption dynamics is also presented, both considering tomato greenhouses in the Andean region of Ecuador. The three WSNs use ZigBee with star topology, ZigBee with mesh topology (referred to here as DigiMesh), and WiFi with access point topology. The present study provides a systematic and detailed analysis of the environmental measurement dynamics from multiparametric monitoring in Ecuadorian tomato greenhouses. A set of monitored variables (including CO2, air temperature, and wind direction, among others) are first analyzed in terms of their intrinsic variability and their short-term (circadian) rhythmometric behavior. Then, their cross-information is scrutinized in terms of scatter representations and mutual information analysis. Based on Bland⁻Altman diagrams, good quality rhythmometric models were obtained at high-rate sampling signals during four days when using moderate regularization and preprocessing filtering with 100-coefficient order. Accordingly, and especially for the adjustment of fast transition variables, it is appropriate to use high sampling rates and then to filter the signal to discriminate against false peaks and noise. In addition, for variables with similar behavior, a longer period of data acquisition is required for the adequate processing, which makes more precise the long-term modeling of the environmental signals.

Tratamiento de agua contaminada con metales pesados utilizando como medios filtrantes biorresina intercambiadora de cationes de la cáscara y tallo de guineo y carbón activado de endocarpo de coco / Treatment of contaminated water with heavy metals, utilizing as filtering media a cation exchanger bio-resin from the banana peel and bush and activated carbon from coconut endocarp

En este trabajo de desarrollo experimental, la Escuela de Ingeniería Química de ITCA-FEPADE se propuso comprobar la efectividad de las cáscaras y pseudotallo de guineo y el endocarpo de coco, previamente tratados, para remover la contaminación por metales pesados en una muestra de agua. Para tal objeto, se procesaron dichas biomasas para ser utilizadas como medios filtrantes, los cuales se caracterizaron por medio de pruebas físicas: densidad y tamaño de partícula. Se evaluó su efectividad para remover metales, filtrando agua contaminada con cantidades conocidas de metales pesados tales como hierro, cromo y níquel (Fe3+Cr6+ y Ni2+), variando el tiempo de contacto y el tipo de medio filtrante. La cuantificación de los metales en el agua tratada se llevó a cabo por espectrofotometria de absorción atómica: para el níquel (λ = 232.0 nm); hierro (λ = 24830 nm) y cromo hexavalente (λ = 357.9 nm). Además, se determinó el color en los filtrados por el método de platino-cobalto. Se llegó a la conclusión que las biomasas utilizadas en este estudio resultaron efectivas para la disminución de metales pesados y color en la muestra de agua sintética elaborada en el laboratorio.

In this experimental development work, the Escuela de Ingeniería Química ITCA-FEPADE set out to verify the effectiveness of previously treated banana peels and pseudostem and endocarp to remove heavy metal contamination in a water sample. For this purpose, said biomasses were processed to be used as filter media, which were characterized by means of physical tests: density and particle size. Its effectiveness to remove metals was evaluated, filtering water contaminated with known amounts of heavy metals such as iron, chromium and nickel (Fe3 + Cr6 + and Ni2 +), varying the contact time and the type of filter medium. The quantification of the metals in the treated water was carried out by atomic absorption spectrophotometry: for nickel (λ = 232.0 nm); iron (λ = 24830 nm) and hexavalent chromium (λ = 357.9 nm). In addition, the color in the filtrates was determined by the platinum-cobalt method. It was concluded that the biomasses used in this study were effective in reducing heavy metals and color in the synthetic water sample prepared in the laboratory.

Caracterização de solos residuais para infiltração de efluente de estação de tratamento de esgoto / Characterization of residual soils for infiltration of reclaimed water

RESUMO Os efeitos das alterações climáticas e a crescente demanda de água para os variados consumos vão levar ao reúso de águas residuárias tratadas (ART). A recarga de aquíferos com ART pode constituir uma alternativa para o restabelecimento de volumes de água subterrânea que poderão ser utilizados para satisfazer parte daquelas atividades, especialmente em regiões de escassez de água ou onde sua qualidade não é adequada para uso. Uma pesquisa de dois anos realizada na estação de tratamento de esgoto de Vila Fernando (Guarda, Portugal) mostrou que as caraterísticas das ART são adequadas para que o efluente seja infiltrado no solo visando à recarga de aquífero. Como a área em estudo é vasta e dada a necessidade de considerar várias restrições técnicas, ambientais e econômicas, foi aplicada uma análise multicritério baseada em Sistemas de Informação Geográfica para encontrar o local mais adequado para a infiltração de ART. Recolheu-se uma amostra de solo para análise, na Quinta de Gonçalo Martins (Guarda, Portugal), tendo os resultados indicado que tal solo apresentava características favoráveis à infiltração de ART.

ABSTRACT The effects of climate change and the increasing demand of water for domestic, industrial and agricultural uses will lead to the use of treated wastewater (reclaimed water). The aquifer recharge with reclaimed water can be an alternative for restoring volumes of water to aquifers, which may afterwards be used to satisfy those demands, especially in regions with water scarcity or where water presents poor quality. A two-year research conducted in the sewage treatment plant of Vila Fernando (Guarda, Portugal) has shown that the characteristics of reclaimed water are adequate to be infiltrated into the soil for aquifer recharge. As the study area for infiltration was very large and it was necessary to consider several technical, environmental and economic constraints, a multi-criteria analysis based on Geographic Information Systems was used in order to find the most suitable site for reclaimed water infiltration. Soil sample was collected at Quinta Gonçalo Martins (Guarda, Portugal) for analysis, and the results have indicated that the site has favorable characteristics for reclaimed water infiltration.

Biochemical methane potential of oil-extracted microalgae and glycerol in co-digestion with chicken litter.

The objective of this work was to evaluate the technical feasibility of using both oil-extracted microalgae (M) and glycerol (G) in co-digestion with chicken litter (CL), thereby improving biochemical methane potential (BMP). Different feedstock ratios of M (0-30%), G (0-3%) and CL (67-100%) were investigated to determine the best co-digestion condition under mesophilic conditions. According to the modified Gompertz model, the best BMP (131.1mLCH4gVSfed-1) was obtained with the triple co-digestion (M:G:CL) in a proportion of 30:3:67. This yielded a methane production rate (µm) of 3.3mLCH4gVSfed-1d-1 and a lag time (λ) of 17.4d. This treatment reduced chemical oxygen demand (COD) by 91.02% and increased the methane yield 15.8% with respect to the CL control.

Elaboración de bio-resina intercambiadora de cationes a partir de cáscara de plátano o guineo para eliminar metales pesados en agua contaminada / Manufacture of cation exchange bio-resin from banana peel to remove heavy metals in contaminated water

Esta investigación tuvo por objetivo obtener una bio-resina intercambiadora de cationes utilizando cáscaras de guineo o plátano, la cual reduzca la concentración de metales pesados en agua contaminada. A esta bio-resina se le realizaron pruebas fisicoquímicas: densidad seca aparente, pH y solubilidad en agua y solventes orgánicos. Se evaluó su efectividad filtrando agua contaminada con metales pesados, tales como hierro, cromo y níquel (Fe3+, Cr6+ y Ni2+), variando las condiciones de tiempo de contacto, temperatura y el tipo de cáscara. La cuantificación de la concentración de los metales en el agua filtrada se llevó a cabo por espectrofotometría visible. Se llegó a la conclusión que la bio-resina obtenida es efectiva para disminuir la concentración de metales pesados en agua, teniendo especial afinidad química por el cromo hexavalente; metal pesado que logró remover arriba del 90%. Las condiciones óptimas de operación de la bio-resina son a 30°C y 90 minutos de tiempo de contacto con la muestra. Además, las pruebas fisicoquímicas, permitieron tipificarla preliminarmente como una resina de intercambio catiónico débil con un grado de entrecruzamiento bajo.

The objective of this research was to obtain a cation exchange bio-resin using banana peels, which reduces the concentration of heavy metals in contaminated water. Physicochemical tests were carried out on this bio-resin: apparent dry density, pH and solubility in water and organic solvents. Its effectiveness was evaluated by filtering water contaminated with heavy metals, such as iron, chromium and nickel (Fe3 +, Cr6 + and Ni2 +), varying the conditions of contact time, temperature and the type of shell. The quantification of the metal concentration in the filtered water was carried out by visible spectrophotometry. It was concluded that the bio-resin obtained is effective in reducing the concentration of heavy metals in water, having a special chemical affinity for hexavalent chromium; heavy metal that was able to remove over 90%. The optimal operating conditions for the bio-resin are at 30 ° C and 90 minutes of contact time with the sample. Furthermore, physicochemical tests allowed it to be preliminarily typified as a weak cation exchange resin with a low degree of crosslinking.

Quantificação da produção de lodo de estações de tratamento de água de ciclo completo: uma análise crítica / Quantification of complete cycle water treatment plant sludge production: a critical assessment

RESUMO Grande parte do lodo gerado em estações de tratamento de água (ETAs) no Brasil ainda é disposta em rios ou em aterros sanitários. Contudo, principalmente em grandes centros urbanos, legislações ambientais restritivas e custos logísticos crescentes têm levantado interesse em usos benéficos para esse resíduo. Para uma avaliação dos possíveis usos, além do conhecimento das características qualitativas do lodo, operadores e projetistas de ETAs devem ser capazes de prever, com algum grau de confiabilidade, sua massa e volume. Os objetivos deste trabalho são: comparar o desempenho de dois dos principais métodos quantitativos de estimativa de produção de lodo - o método de fórmulas empíricas e o de balanço de massa; investigar a prática disseminada de se estimar a concentração de sólidos em suspensão totais na água bruta por meio de modelos de regressão linear com a turbidez como variável independente e delinear condições para a aplicação dessa correlação.

ABSTRACT Most of the water treatment plant (WTP) residuals generated in Brazil are still discharged into water bodies, or disposed in landfills. However, especially in large urban areas, ever-stringent environmental legislation and rising logistical costs have put focus into beneficial uses for those residuals. To evaluate the possible beneficial uses, beyond the knowledge of qualitative characteristics of the residuals, operators and designers should be able to predict, with some degree of certainty, its mass and volume. The objectives of this work are: to compare the performance of two of the main quantitative estimation methods for residuals production - the empirical formulas and the mass balance; to investigate the widespread practice of estimating the concentration of total suspended solids using turbidity as a surrogate; and to identify the conditions under which such procedure is acceptable.

Riesgo químico en el Laboratorio de Análisis del Centro de Estudios de Biotecnología Industrial / Chemical risk in the analysis laboratory of the Industrial Biotechnology Studies Center

Se llevó a cabo un ensayo clínico para evaluar el riesgo químico en el laboratorio de análisis del Centro de Estudios de Biotecnología Industrial de la Facultad de Ciencias Naturales de la Universidad de Oriente, con vista a lo cual se identificaron, entre otros aspectos, las características generales del local y de las 20 técnicas establecidas para el análisis de aguas residuales y residuales agroindustriales (11 de estas se aplican 200 veces al año como promedio), frecuencia de los análisis, reactivos químicos empleados y su categoría de peligro (fundamentalmente ácidos minerales, álcalis, solventes orgánicos y oxidantes fuertes), así como se evaluaron los riesgos químico-físicos y las medidas laborales de seguridad, incluido el tratamiento de los residuos antes de ser eliminados. Se observó que los analistas están expuestos a fuentes de calor y vapores de solventes y ácidos a través de la piel y el sistema respiratorio, pero en un trienio solo se produjeron 3 accidentes leves y no hubo certificados médicos por enfermedades ocupacionales en este tipo de instalación

A clinical trial to evaluate the chemical risk was carried out at the analysis laboratory of the Industrial Biotechnology Studies Center in the Natural Sciences Faculty at Oriente University. For this purpose, aspects such as the general characteristics of the site and of the 20 established techniques for the analysis of waste waters and agroindustrial residual were identified, (11 of these were applied 200 times a year as average), frequency of the analyses, chemical reagents used and their danger category (fundamentally mineral acids, alkalis, organic solvents and strong oxidizers), as well as the chemical-physical risks and the security working measures were evaluated, including the treatment of residuals before being eliminated. It was observed that the analysts are exposed to sources of heat and steam of solvents and acids through the skin and the respiratory system, but just 3 mild accidents took place in a triennium, and there were no medical certifications due to occupational diseases in this type of facility

Análisis cuantitativo y efecto de residuos en procesos esterilización química a bajas temperaturas / Quantitative analysis and effect of residuals in low temperature chemical sterilization processes

Se desarrolló un estudio comparativo donde se emplearon 3 métodos químicos que permiten cuantificar residuos del agente esterilizante y determinar su efecto acumulativo en ciclos sucesivos de esterilización. Se utilizó un esterilizador modelo 130 LF marca Matachana, de fabricación española, cuyo principio de funcionamiento se basa en el uso de temperaturas bajas, empleando formaldehído 2 % en fase de vapor, como agente esterilizante químico. La tecnología de referencia emplea una mezcla de CO2 con óxido de etileno. Las muestras fueron tomadas del área de trabajo y de catéteres compuestos químicamente por cloruro de polivinilo y fluoroetileno propileno o teflón. Los niveles de residuos obtenidos dentro del área de trabajo y en los dispositivos resultaron por debajo del valor límite permisible para la primera esterilización y las 4 reesterilizaciones realizadas. Se eliminó el agente esterilizante dentro del propio proceso, permitiendo el uso inmediato de los materiales. La compatibilidad del agente esterilizante resultó excelente, sin riesgo de pérdida de funcionalidad del material.

A comparative study was conducted by using 3 chemical methods that allow to quantify residuals of the sterilizing agent and to determine their accumulative effect on succesive cycles of sterilization. It was used a Matachana sterilizer 130 LF made in Spain, whose functioning principle is based on the use of low temperatures and steam formaldehyde 2 % as a chemical sterilizing agent. This technology uses a mixture of CO2 with ethylene oxide. The samples were taken from the working area and from catheters chemically composed of polyvynil chloride and fluoroethylene propylene or teflon. The residual levels obtained within the working area and in the devices were under the permisible limit level for the first sterilization and the 4 resterilizations performed. The sterilizing agent was eliminated in the own process, allowing the immediate use of the materials. The sterilizing agent’s compatibility was excellent, without risk for losing the material’s functionality.