Aproximação usando dinâmicas de sistemas para estimar e manejar os recursos hídricos em bacias hidrográficas

As Bacias Hidrográficas dos Rios Piracicaba, Capivari e Jundiaí (BH-PCJ) estão localizadas, nos Estados de Minas Gerais e São Paulo, Brasil. Em 2005 produziu 5.8% do PIB brasileiro. Este desenvolvimento econômico demanda grandes volumes de água. Com o Modelo para a Gestão dos Recursos Hídricos das BH-PCJ (MRH-PCJ), desenvolvido em dinâmica de sistemas, cinco cenários para 50 anos foram simulados. O MRH-PCJ foi desenvolvido para ser uma ferramenta de gestão do Comitê de Bacia Hidrográfica. O modelo estima a oferta e demandas de água, e a carga contaminante dos diversos consumidores. No cenário Business as Usual, para 2054, as demandas de água incrementaram em 76%, 39% da água disponível terá origem em águas de reuso, e a carga contaminante incrementará 91%. O Índice de Falkenmark, que em 2004 era de 1403 m³ pessoa-1 ano-1, será 734 m³ P-1 ano-1 em 2054; o Índice de Sustentabilidade de Xu iniciou em 0.44 e chegou até 0.20; quando consideradas as Fases de Desenvolvimento das Bacias Hidrográficas, propostas por Keller, iniciou-se na Fase II, e terminou-se na Fase III, de Aumento. Os três critérios utilizados para avaliar os recursos hídricos mostraram que as BH-PCJ encontram-se num ponto de tomada de decisões importante. O MRH-PCJ mostrou-se uma excelente ferramenta para avaliar a disponibilidade de recursos hídricos.The Piracicaba, Capivari and Jundiaí River Basins (RB-PCJ) are located in the States of Minas Gerais and São Paulo, Brazil. By 2005, 5.8% of Brazil's General National Product-GNP was produced there. Such economic development has created a huge demand for water resources. The availability of water resources was assessed by running a dynamic systems simulation model to manage these resources in the RB-PCJ (WRM-PCJ), considering five 50-year simulations. WRM-PCJ was developed as a tool to aid the RB-PCJ Watershed Committee. The model computes water supply, demands, and contamination load from several consumers. When considering a Business-as-Usual scenario, by 2054, water demands will have increased up to 76%, 39% of the available water will come from wastewater reuse, and the contamination load will have increased by 91%. The Falkenmark Index started at 1403 m³ person-1 year-1 in 2004, ending at 734 m³ P-1 yr-1 in 2054; the Xu Sustainability Index started at 0.44 and ended at 0.20; and Keller's River Basin Development Phases started as Phase II, and ended at final Phase III, of Augmentation. The three criteria used to evaluate water resources showed that RB-PCJ is at a crucial management turning point. The WRM-PCJ performed well, and proved to be an excellent tool to assess water resources availability

Assessment of availability water at Boi Branco watershed through the water climate balance and growing

The water resources are fundamental to the development of several economic activities. Concerning the agriculture production, the water can represent close to 90% of the physical constitution of the plant. The low water supply during the growing stage of vegetables can make the agricultural production not viable and can even seriously affect the balance of the ecosystem

Domestic wastewater solar disinfection for reuse in family agriculture

Um sistema piloto para desinfetar o esgoto doméstico usando a radiação solar (SODIS) foi construído na Estação Experimental para Tratamento de Águas Residuárias Domésticas para Uso na Agricultura (EETARD-UA) do Departamento de Engenharia Agrícola da Universidade Federal de Viçosa, estado de Minas Gerais, Brasil. A Estação Experimental encontra-se a 20º45 14 S, 42º52 53 W, na altitude de 648,74 m acima do nível do mar. No reator, construído com blocos de concreto, foi aplicada água residuária doméstica tratada (ARDT) a qual passou por: a) tratamento preliminar; e b) tratamento primário em tanque séptico, com tempo de detenção de aproximadamente 14 horas. No reator solar, o efluente do tanque séptico permaneceu durante oito horas, em sistemas de tratamento em batelada. Amostras da água residuária foram retiradas a cada duas horas. As análises nelas realizadas foram: oxigênio dissolvido, turbidez, demanda química de oxigênio (DQO), sólidos suspensos totais (SST), coliformes totais e Escherichia coli (E. coli). A temperatura da água no reator solar foi medida a cada hora. Uma estação meteorológica automática, instalada na área da EETARD-UA, foi usada para coletar os dados de radiação solar. Todos os dados foram analisados estatisticamente e foi proposto um modelo para estimar a população final de E. coli, a partir da população inicialmente presente na água residuária, da lâmina de ARDT a ser tratada no reator solar e da quantidade de radiação. Usando esse modelo e os valores de horas de insolação de 202 estações meteorológicas distribuídas por todo o Brasil, foi determinado o tempo de exposição necessário para desinfetar a ARDT, objetivando o seu uso posterior como fertirrigação em agricultura familiar, com garantias de que a exposição à radiação solar reduz a população de E. coli a níveis recomendados pela Organização Mundial da Saúde (OMS) para água a ser usada sem nenhuma restrição sanitária na irrigação de culturas agrícolas. Assim, foram elaborados 48 mapas da distribuição mensal dos tempos de exposição para quatro profundidades (0,05; 0,10; 0,15 e 0,20 m) de ARDT a serem tratadas no Brasil. A viabilidade financeira do projeto foi avaliada considerando-se um núcleo familiar de quatro pessoas. Foram destacados na análise: o investimento inicial, os custos (manutenção, sementes, implementos, o pagamento da dívida, etc.), e as entradas geradas pela produção de alimentos na horta familiar. Foi detectado que o valor presente líquido (VPL), a taxa interna de retorno (TIR), a taxa de retorno do capital (TRC) e a relação custo/benefício (C/B) foram favoráveis à implantação do projeto, quando foi considerado como fonte de financiamento o Programa Nacional de Fortalecimento da Agricultura Familiar Mulher (PRONAF - Mulher), nos quatro cenários analisados.A pilot study to disinfect domestic wastewater using solar radiation was built in the Experimental Station for Domestic Wastewater Treatment for Use in Agriculture (ESDWT-UA) of the Departamento de Engenharia Agrícola at Universidade Federal de Viçosa, Minas Gerais, Brazil. The experimental station is located at 20º45'14" S, 42º52'53" W, altitude 648.74 meters above sea level (masl). The effluent from a residential development was used as supply; this treated domestic wastewater (TDWW) passed through a pretreatment unit, and primary treatment in septic tank with detention time of 14 hours. After that, in the solar reactor, the septic tank s effluent was exposed to solar radiation for eight hours in a batch system treatment. Samples of water were collected every two hours. The samples were analyzed for: dissolved oxygen, turbidity, chemical oxygen demand (COD), total suspended solids (TSS), total coliforms and Escherichia coli (E. coli). Water temperature in the solar reactor was taken every hour. An automatic meteorological station, installed at ESDWT-UA, was used to collect solar radiation data. All data were statistically analyzed, and a model was proposed to estimate the final E. coli population given the initial E. coli population in the TDWW, the TDWW depth to be treated at the solar reactor and the dose accumulated. Using the model proposed in this work, and the insolation values for 202 meteorological stations distributed throughout Brazil, the time of exposure necessary to disinfect the TDWW was determined reducing the E. coli population to values recommended by World Health Organization (WHO) for irrigation water to be used without any sanitary restriction in agriculture. 48 maps with the exposure times for monthly distribution were elaborated for four depths (0.05, 0.10, 0.15, 0.20 m) of TDWW to be used in Brazil. The financial viability of this project was evaluated considering a family of four people. The analysis considering: the initial investment, costs (maintenance, seeds, implements, debt payments, etc.), and incomes generated by the production of food in the family vegetable garden. It was found that the present value (VPL), the capital rate of return (TRC), internal rate of return (TIR) and cost/benefit (C/B) relationship were all favorable to the implantation of the project when Programa Nacional de Fortalecimento da Agricultura Familiar Mulher PRONAF - Mulher), for four scenarios analyzed was considered as source of financing.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Efficiency of domestic wastewater solar disinfection in recatos with different colors

The aim of this study was to evaluate the efficiency of domestic wastewater solar disinfection for agriculture reuse in solar reactors with different colors: black, white and raw concrete. After passing through a septic tank, the wastewater was conducted to the reactors until the water depth reaches 10 cm and it was exposed to sunlight for three consecutive days. The disinfection efficiency was evaluated by the concentration of E. coli, chemical oxygen demand, effluent temperature, global radiation, UV radiation, pH and total suspended solids and the data was analyzed by regression analysis. The results show that the effluent in different reactors had distinct temperatures: the highest rates were observed in the black reactor and the smallest in the white, however these differences were slight (on average 2 ºC) and the statistical analysis did not show a significant difference (p ≤ 0.05) between the efficiency in the reactors. The collected data allowed the development of a mathematical model that represents the remaining population of fecal coliforms in wastewater after being exposed to a certain dose of solar radiation. In conclusion, the reactor color does not alter the disinfection efficiency and the most important process variables are the UV-A radiation and total suspended solids concentration

Desinfecção solar: uma solução de baixo custo para o tratamento de águas residuárias

In the last decades, many studies have shown the efficiency of UV rays in the removal of pathogens from water. Solar radiation has an important component of UV radiation which affects the DNA chains of the microorganisms causing the loss of its biological activity resulting in reproduction incapacity and cell death. There are several models and ways to carry out solar disinfection. In brief, the system consists of a container which allows water exposure to solar radiation. For so, it might be used either PET or glass bottles, concrete containers, reactors, etc. These characteristics explain its low costs of installation and maintenance and, therefore, makes this technology suitable to be adopted by developing countries and/or low-income rural communities. SODIS is, therefore, a great alternative for regions with higher UV radiation incidence, where are located most part of the developing countries. Besides being an inexpensive and simple technology, SODIS does not produce toxic byproducts.Nas últimas décadas diversos estudos mostraram a eficiência dos raios UV para a remoção de patógenos das águas. A radiação solar, que tem um componente importante de radiação UV, afeta as cadeias do DNA dos microorganismos causando a perda da sua atividade biológica seguida da morte celular, pela incapacidade de se reproduzir. Existem diversos modelos e maneiras de realizar a desinfecção solar. De modo geral, o sistema é composto apenas por um recipiente que permita a exposição da água à radiação solar. Para isso, podem ser utilizadas garrafas PET, garrafas de vidro, reatores, caixas de concreto, etc. Estas características justificam seu baixo custo de instalação e manutenção e, portanto, torna essa tecnologia adequada para ser adotada por países em desenvolvimento e/ou comunidades rurais de baixa renda. A SODIS é, portanto, uma ótima alternativa para regiões entre as latitudes com maior incidência de raios UV, onde está localizado grande parte dos países em desenvolvimento. A desinfecção solar, além de ser uma tecnologia simples e barata, não produz subprodutos tóxicos

Optimal moment to change pressure regulator and sprayer kit on center pivot irrigation machines: application to a study case

A theoretical model developed by the authors for determining the optimal moment to substitute sprayer and pressure regulator kit on a center pivot irrigating potatoes and beans has been applied. The methodology compares the sum of the costs due to additional consumption of water and energy, maintenance and labor, as well as yield losses associated to areas with deficit or over irrigation to the costs due to buy and install a new sprinkling set on the pivot. The results showed that for a reduction of 3.07% of the Hermann and Hein’s Uniformity Coefficient (UCh), the substitution of the sprinkling module on the pivot is justified when potatoes and beans are cultivated

No-till and direct seeding agriculture in irrigated bean: Effect of incorporating crop residues on soil water availability and retention, and yield

Brazil is one of the top world producers of the staple commodity common bean (Phaseolus vulgaris L.). Irregular distribution of rainfall and the lack of rain during the crop reproductive phases affect its yield and increase the demand of water for irrigation. However, in recent years, water resources have decreased and water saving has become an issue. Thus, soil management techniques, which reduce evaporation, and efficient irrigation programming, through the monitoring of soil water content, could be adopted in water scarcity scenarios. This study assesses the effect of crop residues management (incorporated IR or left on soil surface NR) in soil water availability (and its retention in the soil pore space), and yield in common beans cultivated under no-till and directly seeded in an irrigated farm located southwest of São Paulo state. Soil water content was monitored with TDR probes installed within the 0–20 cm layer and its retention was assessed through the soil water retention curve. For the same irrigation management, the IR led to soil water content was lower than NR but both soil managements had similar available water and their demand of water for irrigation was similar. For the same soil water content, NR soils could hold it tightly in the pore space and the root plant system would require higher energy to absorb it. Then, it is foreseen that the root system in IR soils will be shallower than in NR soils, since it will withdraw water easily within the first 20 cm, however, in NR, the roots will extend deeper searching for available water. Considering 40 kPa as a threshold value, the plants suffered water stress during all crop cycle at the same physiologic stages in both soils. The variables studied to assess yield presented no-statistical significance in the T test at significance level of 0.05