Maria Hermínia Ferreira Tavares

Produção específica de biogás a partir de manipueira em reator de fase única

This article presents a study on biogas production from wastewater cassava considering the volume of a one-phase horizontal tubular flow reactor. The objective was to evaluate the biogas production, enlarging the organic loadings and feeding volums, resulting in minor hydraulic retention times (HRT). The reactor was continuously fed with organic charges corresponding to 1.18; 1.28; 1.57 and 2.68 g COD L-1r d-1 (grams of oxygen chemical demand per liter of reactor per day), resulting in hydraulic retention times 15; 13; 8.3 and 6.6 days. The correspondent specific biogas productions were, respectively, 0.52; 0.41; 0.65 and 0.63 L L-1rd-1 , emphasizing that the 13-day was the first HRT rated, followed by 8.3, 6.6 and 15 days. It was concluded that with the HRT decrease occurred larger biogas production per reactor volume. Therefore, with the correct selection for HRT, it is possible to make the best of the reactor volume, resulting in economy at the technology implantation in cassava starch industries.

Anaerobic reactors with biofilter and different diameter-length ratios in cassava starch industry wastewater treatment

A utilizacao de reatores anaerobios com meio suporte no tratamento de efluentes liquidos, provenientes das fecularias de mandioca, tem-se apresentado como uma opcao viavel, uma vez que possibilita a aplicacao de cargas orgânicas elevadas e uma reducao consideravel do TDH necessario para o tratamento. O objetivo do trabalho consistiu no estudo do processo de biodigestao, em dois reatores anaerobios, com meio suporte de bambu, no tratamento de efluente de fecularia de mandioca, por meio da avaliacao do desempenho dos mesmos. Foram utilizados dois reatores com relacoes diâmetro:comprimento 1:6 e 1:3. As cargas orgânicas aplicadas aos sistemas foram 0,519; 1,156; 1,471; 3,049; 4,347; 4,708 e 5,601 g.L-1d-1. Com relacao a eficiencia de remocao de DQO, ST e STV, nao foram obtidas diferencas estatisticas entre os reatores. Os dois sistemas avaliados apresentaram comportamento estavel em relacao a AV/AT (acidez volatil/alcalinidade total) para todas as cargas submetidas. Os reatores apresentaram tendencia a manutencao da producao de biogas em funcao da DQO consumida, para as tres ultimas cargas orgânicas aplicadas, indicando uma capacidade de suportar cargas orgânicas mais elevadas.

Selecting statistical models to study the relationship between soybean yield and soil physical properties

Statistical models allow the representation of data sets and the estimation and/or prediction of the behavior of a given variable through its interaction with the other variables involved in a phenomenon. Among other different statistical models, are the autoregressive state-space models (ARSS) and the linear regression models (LR), which allow the quantification of the relationships among soil-plant-atmosphere system variables. To compare the quality of the ARSS and LR models for the modeling of the relationships between soybean yield and soil physical properties, Akaikes Information Criterion, which provides a coefficient for the selection of the best model, was used in this study. The data sets were sampled in a Rhodic Acrudox soil, along a spatial transect with 84 points spaced 3 m apart. At each sampling point, soybean samples were collected for yield quantification. At the same site, soil penetration resistance was also measured and soil samples were collected to measure soil bulk density in the 0-0.10 m and 0.10-0.20 m layers. Results showed autocorrelation and a cross correlation structure of soybean yield and soil penetration resistance data. Soil bulk density data, however, were only autocorrelated in the 0-0.10 m layer and not cross correlated with soybean yield. The results showed the higher efficiency of the autoregressive space-state models in relation to the equivalent simple and multiple linear regression models using Akaikes Information Criterion. The resulting values were comparatively lower than the values obtained by the regression models, for all combinations of explanatory variables.

Cassava starch extraction effluent treatment in a one phase tubular horizontal pilot reactor with support medium

The cassava starch industries generate a large volume of wastewater effluent that, stabilized in ponds, wastes its biogas energy and pollutes the atmosphere. To contribute with the reversion of this reality, this manipueira treatment research was developed in one phase anaerobic horizontal pilot reactor with support medium in bamboo pieces. The reactor was excavated into the ground and sealed with geomembrane in HDPE, having a volume equal to 33.6 m3 and continuous feeding by gravity. The stability indicators were pH, volatile acidity/total alkalinity ratio and biogas production. The statistical analyses were performed by a completely randomized design, with answers submitted to multivariate analysis. The organical loads in COD were 0.556; 0.670; 0.678 and 0.770 g L-1 and in volatile solids (VS) of 0.659; 0.608; 0.570 and 0.761 g L-1 for the hydraulic retention times (HRT) of 13.0; 11.5; 10.0 and 7.0 days, respectively. The reductions in COD were 88; 80; 88 and 67% and for VS of 76; 77; 65 and 61%. The biogas productions relatively to the consumed COD were 0.368; 0.795; 0.891 and 0.907 Lg-1, for the consumed VS of 0.524; 0.930; 1.757 and 0.952 Lg-1 and volumetric of 0.131; 0.330; 0.430 and 0.374 L L-1 d-1. The reactor remained stable and the bamboo pieces, in visual examination at the end of the experiment, showed to be in good physical conditions.

Electrical conductivity of soil irrigated with swine wastewater estimated by time-domain reflectometry¹

A aplicacao de agua residuaria no solo e uma forma alternativa de fertilizacao do solo e de reuso da agua. Entretanto, deve-se dar especial atencao a tecnica, devido ao fato de que sucessivas aplicacoes podem provocar a salinizacao do solo. A reflectometria no dominio do tempo (TDR) permite nao apenas o monitoramento simultâneo e continuo do teor de agua e da condutividade eletrica aparente do solo, como tambem a determinacao indireta da condutividade eletrica de sua solucao. O presente trabalho teve por objetivo avaliar a viabilidade do emprego da TDR na determinacao indireta da condutividade eletrica de um extrato de solo saturado (CEse), empregando-se uma equacao empirica para o equipamento TDR Trase® modelo 6050X1. O experimento foi conduzido utilizando-se amostras deformadas de solo saturadas com agua residuaria da suinocultura nas proporcoes de 0, 0,45, 0,90, 1,80, 2,70 e 3,60 m3 m-3 de solo. As sondas utilizadas eram equipadas com tres hastes de 0,20 cm de comprimento, montadas artesanalmente. O modelo empirico que associou valores da condutividade eletrica mensurado por meio da TDR (CETDR) com CEse propiciou excelente ajuste, indicando a viabilidade da tecnica na determinacao da condutividade eletrica da solucao do solo.

Optimization of the pretreatment of wastewater from a slaughterhouse and packing plant through electrocoagulation in a batch reactor

ABSTRACT The purpose of this study is to evaluate the removal of chemical oxygen demand (COD), turbidity and color of wastewater from a pig slaughterhouse and packing plant through the electrochemical technique and to optimize the ΔV (electric potential difference) and HRT (hydraulic retention time) variables in an electrocoagulation batch reactor using aluminum electrodes. The experimental design used was rotatable central composite design. For turbidity, the values for removal efficiency obtained varied from 92.85% to 99.28%; for color, they varied from 81.34% to 98.93% and for COD, they varied from 58.61% to 81.01%. The best optimized conditions of treatment were at 25 min for the HRT and 25 V for the ΔV, which correspond to electrical current of 1.08 A and a current density of 21.6 mA cm−2. The aluminum residue varied from 15.254 to 54.291 mg L−1 and the cost of the treatment was US

Construction and calibration of TDR probes for volumetric water content estimation in a Distroferric Red Latosol

4.288 m−3. The novelty of the work was the simultaneous optimization of three response variables using the desirability function applied to the treatment of wastewater from slaughterhouses.

Optimization of the nitrification process of wastewater resulting from cassava starch production

A determinacao da umidade volumetrica de solos e fator importante no manejo da irrigacao. Dentre os metodos indiretos para a estimativa, a tecnica da reflectometria no dominio do tempo (TDR) vem recebendo significativo enfoque. Como toda tecnica, apresenta vantagens e desvantagens, entre elas a maior desvantagem e a necessidade de calibracao e alto custo de aquisicao. O objetivo principal deste trabalho foi estabelecer um modelo de calibracao para o equipamento de TDR, Trase System Modelo 6050X1 para a estimativa da umidade volumetrica em um Latossolo Vermelho distroferrico tipico. A calibracao foi realizada em condicoes de laboratorio, utilizando amostras deformadas do solo em estudo, acondicionadas em colunas de PVC com volume de 0,0078 m3. As sondas de TDR, fabricadas artesanalmente com tres hastes e 0,20 m de comprimento, foram instaladas verticalmente nas colunas de solo, em um total de cinco sondas por coluna, totalizando dezesseis colunas. Realizaram-se as pesagens com balanca digital e leituras diarias da constante dieletrica com o equipamento TDR. O modelo linear θv =0,0103Ka + 0,1900 para estimativa da umidade volumetrica do solo em estudo apresentou excelente coeficiente de determinacao (0,93), viabilizando o uso das sondas na estimativa indireta da umidade do solo.

Concepts and importance of mathematical modeling of water quality for water resources management

ABSTRACT The present study has the objective of optimizing operational conditions of an aerated reactor applied to the removal of ammoniacal nitrogen from wastewater resulting from the production of cassava starch. An aerated reactor with a usable volume of 4 L and aeration control by rotameter was used. The airflow and cycle time parameters were controlled and their effects on the removal of ammoniacal nitrogen and the conversion to nitrate were evaluated. The highest ammoniacal nitrogen removal, of 96.62%, occurred under conditions of 24 h and 0.15 L min−1 Lreactor−1. The highest nitrate conversion, of 24.81%, occurred under conditions of 40.92 h and 0.15 L min−1 Lreactor−1. The remaining value of ammoniacal nitrogen was converted primarily into nitrite, energy, hydrogen and water. The optimal operational values of the aerated reactor are 29.25 h and 0.22 L min−1 Lreactor−1. The mathematical models representative of the process satisfactorily describe ammoniacal nitrogen removal efficiency and nitrate conversion, presenting errors of 2.87% and 3.70%, respectively. GRAPHICAL ABSTRACT

Influence of hydraulic retention time on the anaerobic treatment of cassava starch extraction effluent using a one-phase horizontal reactor

O acelerado desenvolvimento das atividades humanas, aliado aos impactos causados ao meio ambiente e a pressao pela preservacao dos recursos naturais, evidencia a necessidade da busca constante por novas ferramentas de apoio ao processo de tomada de decisoes pelo poder publico. Dentre as varias ferramentas desenvolvidas ao longo dos anos, os modelos matematicos de qualidade da agua merecem especial destaque e sao amplamente encontrados na literatura nacional e internacional, como tecnicas eficientes de apoio a gestao dos recursos hidricos. Partindo dessas premissas, o presente artigo tem como objetivo apresentar uma revisao bibliografica sobre a utilizacao de modelos matematicos de qualidade da agua, com enfoque aos principais conceitos e modelos relacionados. A modelagem matematica possibilita gerar cenarios futuros, estimando custos e, principalmente, as principais medidas preventivas a serem tomadas na execucao das atividades humanas. Sendo assim, existe a necessidade de estudos constantes, a fim de diminuir as limitacoes da aplicabilidade dos modelos de qualidade da agua como forma de atender a legislacao vigente.