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Engenharia Agrícola, Volume: 38, Número: 6, Publicado: 2018
  • PERFORMANCE OF FUZZY INFERENCE SYSTEMS TO PREDICT THE SURFACE TEMPERATURE OF BROILER CHICKENS Scientific Paper

    Bahuti, Marcelo; Abreu, Lucas H. P.; Yanagi Junior, Tadayuki; Lima, Renato R. de; Campos, Alessandro T.

    Resumo em Inglês:

    ABSTRACT This study aimed to compare fuzzy systems with different configurations to predict the surface temperature (ts) of broiler chickens subjected to different intensities and durations of thermal challenges in the second week of life. Data on the ts of broiler chickens aged 8 to 11 days were acquired by infrared thermography and subjected to combinations of four dry-bulb temperatures (tdb) (24, 27, 30, and 33 °C) and four durations of thermal challenges (DTC) (1, 2, 3, or 4 days). The input variables of the fuzzy systems were tdb and DTC, and the output variable was ts. The Mamdani inference method involving five defuzzification methods [center of gravity (centroid), bisector of the area (bisector), largest of maximum (lom), middle of maximum (mom), and smallest of maximum (som)], and Sugeno inference with two defuzzification methods [weighted average (wtaver) and weighted sum (wtsum)] were evaluated. For both inference methods, triangular and Gaussian pertinence functions were tested for input and output variables, except for Sugeno inference, which used singletons functions as output variables. While developing fuzzy systems, different configurations must be compared, and the system with smaller simulation errors should be selected.
  • THERMAL INSULATION WITH RECYCLED MATERIAL IN CREEPS FOR PIGLETS Scientific Paper

    Sartor, Karina; Barros, Juliana de S. G.; Sarubbi, Juliana; Alonso, Jonas B.; Rossi, Luiz A.

    Resumo em Inglês:

    ABSTRACT In the swine intensive farming, one of the biggest problems is to meet the thermal requirements of piglets in heated creeps, which demand high consumption of electricity and increase in production costs. The aim of this study was to evaluate the thermal efficiency and the consumption of electric energy in heated and internal insulated creeps, made of recycled material, when compared to creeps without thermal insulation. The treatments were: control (TCON): creep heated through suspended electric resistance, controlled by thermostat; thermal insulation with recycled material (TPK). The experiment was carried out for 21 days. In the treatments, the temperature (°C) and relative humidity (RH) of the air, consumption of electric energy (kWh), specific consumption (kWh kg-1), specific cost (R$ kg-1), weight gain (kg) and daily weight gain (kg day-1) were measured. The indoor insulation creep kept the upper air temperature (33.05°C) to the control treatment without thermal insulation (32.6°C) and was more efficient in the use of electric energy (2.46 kWh) in comparison to the non-insulated creep (3.48 kWh). The heat-insulated creep shelter consumed the equivalent of 1.02 kWh more than the insulation treatment to maintain the thermal comfort condition of piglets between 30 and 34 ° C. The conclusion is that the use of recycled material as thermal insulation in heated creeps reduces heat losses and economy electricity.
  • AMBIENCE OF SHEEP SUBMITTED TO DIFFERENT BREEDING ENVIRONMENTS AND GLOBAL TEMPERATURES Scientific Paper

    Furtado, Dermeval A.; Santos, Luana de Fátima D. dos; Nascimento, José W. B. do; Lopes, Fernanda F. M.; Costa, José H. S.

    Resumo em Inglês:

    ABSTRACT The aim is to characterize and to compare the black (TBG) and gray (TGG) globe temperatures in the production of sheep in the Brazilian semi-arid, using Santa Inês and Doper breeds, distributed in two thermal environments (exposed to the sun and shaded), containing 10 animals in each picket. The experimental design was completely random, 2 x 2 factorial scheme (shaded environment and sun x black and gray globe) in 46 replicates (evaluation days). There was an increase of the TBG in relation to the TGG during the evaluation times, with maximum temperature (48.1°C) at 1p.m. in the environment exposed to the sun, concomitantly with elevation of the black globe temperature and humidity index - BGHI (96.7). The result was distinct for TGG, with a maximum temperature of 37.6°C and BGHI of 86.2 in the same environment. Regardless of the thermometer used, the BGHI values exceeded the considerable comfortable limit for sheep. Under shaded conditions, the globe temperatures showed similar behavior. In sunny conditions, these temperatures diverged, higher in the black, because of the absorption conditions of the thermal radiation of the different colors.
  • AXENIC CULTIVATION OF Pleurotus ostreatus var. Florida IN SUPPLEMENTED SUGARCANE BAGASSE BRIQUETTES Scientific Paper

    Magalhães, Anderson C.; Moreira, Bruno R. de A.; Zied, Diego C.

    Resumo em Inglês:

    ABSTRACT Articles on the applicability of briquetting to the production of mushrooms are rare. Therefore, this research provides the scientific community and, mainly, producers, unpublished technical information regarding the productive yield of oyster mushroom cultivated in sugarcane bagasse briquettes supplemented with bioproducts of cereals. In 30 days of axenic cultivation, 6 tons-force briquettes with 80% humidity resulted in higher productivity (30.4%), and generated the lowest physical volume of exhausted compound (44.8%), thus, overcoming the technical performance of the other briquetting matrices tested, and even of methods traditionally used for the preparation of substrate for P. ostreatus cultivation on a commercial scale. The conclusion is, therefore, that the axenic cultivation of P. ostreatus var. Florida in sugarcane bagasse briquettes, supplemented with bioproducts of cereals, has technically qualified as an original and efficient method for the production of high biological value protein by the recycling of agricultural residues and can therefore guarantee multiple economic benefits to the agribusiness of the oyster mushroom, in addition to allowing reduction of environmental impacts by the restricted generation of exhausted compound in the post-harvest stage.
  • ARTIFICIAL NEURAL NETWORKS FOR PREDICTING ANIMAL THERMAL COMFORT Scientific Paper

    Borges, Pedro H. M.; Mendoza, Zaíra M. S. H. de; Morais, Pedro H. M.; Santos, Ronei L. dos

    Resumo em Inglês:

    ABSTRACT The objective of this study was to develop artificial neural networks (ANNs) for predicting animal thermal comfort based on temperature and relative humidity of the air for each day of the year. The data on temperature and relative humidity for a 25-year historical series collected at the Padre Ricardo Remetter Conventional Meteorological Station, located in the city of Santo Antônio de Leverger - Mato Grosso (Brazil), were retrieved from the website of the National Institute of Meteorology. According to the day of the year, the temperature and humidity index was determined as a function of the climatic variables. Therefore, the day of the year was the input variable of the neural networks, and the temperature and humidity index (THI) was the output variable. The number of layers and neurons used for establishing different architectures was variable. Data were adjusted on the basis of mean square errors, performance and efficiency indexes, and normality tests. The values estimated by the networks and those obtained from the historical series did not differ significantly. The networks with the best performance were selected for graphical analysis of residuals. The ANNs developed in this study predicted animal thermal comfort with adequate reliability and precision.
  • UNCERTAINTY ANALYSIS OF A WEB-BASED DATA ACQUISITION SYSTEM FOR POULTRY MANAGEMENT WITH SENSOR NETWORKS Scientific Paper

    Yu, Ligen; Teng, Guanghui; Riskowski, Gerald L.; Xu, Xuzhang; Guo, Wenzhong

    Resumo em Inglês:

    ABSTRACT This paper presents a web-based data acquisition system developed by the LabVIEW software program for environment monitoring for poultry management. The measurement error and uncertainty analysis should be conducted accurately to maximize the reliability of this system. An algorithm was proposed for the uncertainty analysis to estimate the sensor networks, with the calibration and validation processes fulfilling the standards of the Guide to the Expression of Uncertainty in Measurement. For the different environmental sensors, the values of the uncertainties were calculated by the methods of type A and B evaluation through a case study. Environmental parameters including air temperature, relative humidity, and CO2 concentration of a compartment housing for a small group (n = 90) of laying hens were measured using a perch aviary system in a 24-h period with an interval of 5 min. The results showed that with the perch system for laying hens, the expanded uncertainty of the data acquisition system was above 1.02 °C, 5.54%, and 67.8 ppm over the sensor data of the air temperature, relative humidity, and CO2 concentration, respectively. Moreover, the relative uncertainty of this system was estimated as 15.9%. Therefore, because of its more reliable uncertainty analysis and data evaluation, the proposed web-based data acquisition system has considerable potential for ensuring correct decision-making when used in poultry production.
  • LOSS OF WATER AND NUTRIENTS IN DIFFERENT SOIL TILLAGE SYSTEMS SUBJECTED TO NATURAL RAINFALL IN THE STATE OF MATO GROSSO, BRAZIL Scientific Paper

    Leite, Marcelo H. S.; Couto, Eduardo G.; Amorim, Ricardo S. S.; Scaramuzza, José F.

    Resumo em Inglês:

    ABSTRACT The aim of this study was to evaluate the loss of water and nutrients by laminar runoff in different soil tillage systems subjected to natural rainfall. Five experimental plots were established for the cultivation of cotton in the city of Campo Verde - MT, with the following treatments: CTDP = conventional soil tillage and planting of the cotton in the direction of the slope; CTCP = conventional tillage and contour planting; CP = tillage of soil with a disk harrow and a leveling harrow, followed by contour planting; CoP = tillage by two passes of a leveling harrow followed by contour planting; MTCP = minimum tillage with contour planting. The losses of water by laminar runoff in were determined by the stored volume and samples were taken to quantify nutrient losses in water (nitrite, nitrate, phosphate and potassium). The losses of water by runoff were highest for the CTDP; intermediate for the treatments CTCP, CoP and MTCP, and lowest for the CP. Potassium (K) was the nutrient that had the highest concentrations and losses in water: the highest values were found in the CTDP and CTCP tillage systems, whereas the lowest were observed for the CP, CoP, and MTCP treatments. The concentrations and the losses by water erosion of phosphate (PO43-), nitrite (NO2–), and nitrate (NO3–) were low in all of the soil tillage systems compared to the losses of K in this study.
  • SIMULATION OF SODIUM AND POTASSIUM DYNAMICS BY THE HYDRUS 2D MODEL IN A HAPLIC PLANOSOL VIA RESIDUE WATER Scientific Paper

    Andrade, Carolyne W. L. de; Montenegro, Suzana M. G. L.; Miranda, Jarbas H. de; Montenegro, Abelardo A. de A.; Assis, Fred M. C. V. de

    Resumo em Inglês:

    ABSTRACT The application of chemical substances to the soil together with little attention given to the possible environmental impacts, transformed the environment into a recipient of waste. The aim of this study was to simulate the movement of water and solutes (sodium and potassium together) using the STANMOD and HYDRUS-2D models in a typical Haplic Planosol under the application of wastewater via surface irrigation under different flow rates. The experiment was conducted in the laboratory by miscible displacement tests, first using columns with deformed soil under saturation and steady water flow conditions, at a rate of 11.7 cm3 min-1, to obtain transport parameters of sodium and potassium ions, and in the applied residual water, the values of 475 and 76.6 mg dm-3, respectively. The transport parameters were estimated from the numerical adjustment of effluent distribution curves, using the STANMOD model. In a second step, the HYDRUS-2D model was applied to simulate the volumetric soil moisture distribution profiles, as well as the ion concentrations in the wet bulb. Considering the results obtained, we can see that there was considerable interaction between the solutes and the soil. The value of the delay parameter was higher for the sodium when compared to the potassium, reflecting its greater adsorption and the processes of exchange between the solute and the soil. The results suggested the need for adequate soil management in order to avoid future soil sodification and, in view of the application of HYDRUS-2D, it was verified that the model presented a satisfactory performance in the simulation of the displacement of the ions, after 1, 5 and 10 hours of wastewater application.
  • CONSUMPTION, EFFICIENCY AND WATER CONTENT OF ARUGULA UNDER DIFFERENT MANAGEMENT OF BRACKISH NUTRITIONAL SOLUTIONS Scientific Paper

    Campos Júnior, José E.; Santos Júnior, José A.; Silva, Ênio F. de F. e; Martins, Juliana B.; Rolim, Mário M.

    Resumo em Inglês:

    ABSTRACT The need to use strategies for using brackish water in agriculture, especially in semi-arid conditions, is evident. Based on this information, this study was developed with the aim of evaluating the consumption, efficiency and water content, as well as the dry mass of the arugula plants (cv. Broad Leaf) exposed to brackish nutrient solutions as a function of replacement strategies and circulation frequencies. The treatments consisted of six salinity levels of the nutrient solution (1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 dS m-1) and two circulation frequencies (twice a day 8 a.m. and 4 p.m., and three times a day at 8 a.m., 12 p.m. and 5 p.m.). In Experiment I, the evapotranspiration line was replaced with the respective brackish water used in the preparation of the solution, and in Experiment II, the water supply was used. In both treatments, the experimental design was completely randomized, in a 6 x 2 factorial scheme, with five replications. The conclusion is that it is technically feasible to circulate the nutrient solution twice a day and there were lower losses in the water relations, in the biomass production of the shoot and in the partition of photoassimilates when the replacement with water supply was adopted.
  • METROLOGICAL BEHAVIOUR OF BULK WATER METERS UNDER DIVERSE INSTALLATION CONFIGURATIONS Scientific Paper

    Palau, Carmen V.; Peralta, Iban B.; Manzano, Juan; Azevedo, Benito M. de; Bomfim, Guilherme V. do

    Resumo em Inglês:

    ABSTRACT As the correct measurement is an essential part of water management, this study describes the metrological behaviour of a range of bulk water meters under different installation configurations. The meters analysed included the horizontal and vertical Woltman, singlejet, tangential and proportional. Configurations included straight pipe lengths; gate and butterfly valves at different degrees of closure, rotations and distances from the meter; meter with volumetric and reducing valves; reverse installation; and meter rotated 90° from the horizontal setting. The metrological behaviour under different flow conditions was analysed by comparison with electromagnetic and volumetric meters (ISO-4064). The horizontal Woltman showed no permissible errors with reverse installation; gate valve closed 75% and placed alongside the meter; and with butterfly valve closed 30°, non-rotated, and rotated right or left. The vertical Woltman gave no permissible errors with reverse installation. The single-jet meter did not show any errors above the permitted limit. The tangential meter had no permissible errors with reverse installation and in almost all configurations with gate and butterfly valves. The proportional meter showed no permissible errors with a gate valve at any degree of closure.
  • PHOTOCHEMICAL AND PRODUCTIVE PERFORMANCE OF YELLOW PASSION FRUIT IRRIGATED IN THE BRAZILIAN SEMIARID Scientific Paper

    Dutra, Alexson F.; Melo, Alberto S. de; Brito, Marcos E. B.; Suassuna, Janivan F.; Dutra, Wellison F.

    Resumo em Inglês:

    ABSTRACT The drought stress is an important factor for crops in areas with low rainfall as in the semiarid regions and affects immediately the physiological processes and plant production. However, irrigation is an essential practice to minimize effects of drought stress since the appropriate management is done it can increase the farm income. This study aimed to analyze the photochemical and productive performance of passion fruit (Passiflora edulis) hybrid ‘BRS Gigante Amarelo' irrigated in a Brazilian semiarid region. It was studied four water replacement rates (33, 66, 100 and 133% of ETo) at field conditions. A randomized block design was used with five replications and the fluorescence of chlorophyll a, yield and fruit quality were evaluated. The photochemical efficiency of photosystem II has been changed along the day at high temperatures occurring evidential damage in PHS II. Water replacement between 100 and 133% of ETo (1032 mm year-1) promoted the best production rates and quality of the fruit, however the size of the fruit and bark thickness are reduced by over 100% ETo.
  • PARAMETERS OF OPERATIONAL PERFORMANCE OF SOIL PREPARATION AND SEMI-MECHANIZED TRANSPLANTATION OF COFFEE SEEDLING Scientific Paper

    Cunha, João P. B.; Silva, Fabio M. da; Andrade, Ednilton T.; Barros, Murilo M. de

    Resumo em Inglês:

    ABSTRACT In recent years, the coffee has undergone major changes, and in case of transplanting operation, the use of machinery has proved to be a viable alternative to producers. Prior knowledge of the influence of the variables that influence the operational capability of these machines can generate models to estimate precisely these parameters, thus enabling the optimization and management of mechanized operations. One of this tool is the use of the response surface methodology, which allows checking the influence of different independent variables and the response generated to allow a great value. This study aims to verify the use of the response surface method to determine parameters of mechanized operations in coffee plant implantation. The results show that the number of seedlings deposited increases with the increase in operating speed. In contrast, the adoption of higher speeds decreases the efficiency of the evaluated field operations. The response surface methodology was an important tool to check the effect of variables on performance parameters, and the generated models showed high significance allowing the identification of the effects of the operational speed and the average length of the cultivation line.
  • STATITIONARY ENGINE PERFORMANCE USING MIXTURE OF SOYBEAN AND CASTOR BEAN BIODIESEL TO DIESEL OIL Scientific Paper

    Cortez, Jorge W.; Guimarães, Camila C.; dos Santos, Vivianni M. L.

    Resumo em Inglês:

    ABSTRACT The use of alternative fuels in diesel engines has been the subject of research that seeks new fuels to expand the energy matrix. The aim of this study was to evaluate the performance of the stationary engine with the use of mixtures of biodiesel from soybean and castor bean added to diesel (S500) in two proportions (25% and 40%), evaluating the torque, effective power observed and specific consumption. The five biodiesel mixtures of soybean (S) and castor bean (C) analyzed were: S100C0, S75C25, S50C50, S25C75 and S0C100, which were added to the diesel in proportions B25 and B40, totaling ten treatments, plus the control with diesel S500 (B7). The stationary engine was subjected to the rotations of 3000, 2700, 2400, 2100, 1800 and 1500 rpm. The performance of the engine was similar for all biodiesel mixtures of soybean and castor bean, and commercial diesel (B7). The B40 S100C0 and B40 S75C25 provide better performance in terms of effective power observed and torque at 2700 rpm. The highest effective maximum power (3000 rpm) was obtained with the use of B7 diesel. In the lower rotations, it was possible to identify a similar performance result of the biodiesel mixtures with the B7, in addition to providing better torque and consumption performance compared to the commercial diesel.
  • DROPLET DISTRIBUTION AS A FUNCTION OF COTTON INTERROW SPACING AND ANGLES OF SPRAYER DISPLACEMENT Scientific Paper

    de Lima Junior, Izidro dos S.; Degrande, Paulo E.; de Souza, Cristiano M. A.; Viegas Neto, Antonio L.

    Resumo em Inglês:

    ABSTRACT Application technology factors may be influenced by changes in plant architecture, such as height and leaf area. This study aimed to evaluate which angle of sprayer displacement in the application of pesticides in relation to the direction of cotton sowing, cultivated in the ultra-narrow row, narrow row, and conventional systems, provides the best application quality characteristics in the different thirds of plants. The experiment was installed in a split-plot design with four replications in the 3 × 4 factorial scheme, composed of three cotton cultivation systems and four angles of sprayer displacement in relation to the direction of the sowing rows. The evaluated characteristics were mean volumetric diameter, density and coverage of droplets, number of droplets, and open area in the interrows without leaf. The upper third presented the highest values of mean volumetric diameter, number of droplets, and density and coverage of droplets for all interrow spacing and application angles. The angle of displacement of 30° in relation to the sowing row presented the best results in relation to the number and density of droplets. The spacing of 0.90 m in the interrows increased the number of droplets, droplet density, and coverage in the lower third of plants.
  • FERTILIZER METERING MECHANISM WITH HELICAL CONIC CYLINDRICAL THREAD FOR FAMILY AGRICULTURE Scientific Paper

    Galvão, Cezario B.; Albiero, Daniel; Garcia, Angel P.; Monteiro, Leonardo de A.

    Resumo em Inglês:

    ABSTRACT Small rural farms are important for Brazilian agribusiness, but equipment suitable for distributing fertilizers on these properties is scarce. We studied a new fertilizer metering mechanism for use on the family farm. It combines a helical conic thread with a conventional fertilizer meter in a cylindrical section. The experimental plan was created using a 24 factorial design. An analysis of variance (ANOVA) was also conducted. The mechanism showed a positive result with respect to the uniformity of fertilizer flow (with a coefficient of variation of 3.1-5.8%), longitudinal distribution (with a coefficient of variation of 4%), and different types of fertilizers (in which variations between 2.7 and 3.5% were found).
  • MOISTURE SORPTION ISOTHERMS OF QUINOA SEEDS: THERMODYNAMIC ANALYSIS Scientific Paper

    Bustos-Vanegas, Jaime D.; Corrêa, Paulo C.; Zeymer, Juliana S.; Baptestini, Fernanda M.; Campos, Renata C.

    Resumo em Inglês:

    ABSTRACT The present research aimed to study the water sorption behavior of quinoa seeds analyzing the hysteresis phenomenon and determining thermodynamic properties. Static gravimetric technique was used to obtain the equilibrium moisture content of quinoa seeds in different temperature conditions (15, 25, 35 e 50 °C) and relative humidity (between 11 and 96%). Equilibrium moisture content data were adjusted by eight mathematical models and the Modified Halsey model was the best one to describe the water sorption phenomena of quinoa seeds. Hygroscopic equilibrium moisture content of quinoa seeds is directly proportional to the water activity and decreases with increasing temperature. The hysteresis phenomena were observed throughout the range of water activity, showing more evident at low temperatures. Integral isosteric heat and differential entropy decreased with the increase of equilibrium moisture content. Gibbs free energy decreased with the increase of temperature and equilibrium moisture content. Compensation enthalpy-entropy theory was confirmed and the sorption mechanism is controlled by enthalpy.
  • STATISTICAL CONTROL OF THE PROCESS APPLIED TO THE MONITORING OF THE WATER QUALITY INDEX Scientific Paper

    Conceição, Ketllin Z. da; Boas, Marcio A. Vilas; Sampaio, Silvio C.; Remor, Marcelo B.; Bonaparte, Danilo I.

    Resumo em Inglês:

    ABSTRACT Analyzing the physical-chemical and biological characteristics allows the evaluation of the water quality of a water body. Thus, the objective of this study was to determine the water quality index of the Passaúna and Piraquara rivers, as well as to apply statistical quality control methodologies to evaluate the data resulting from the monitoring of water quality. Therefore, a database with physico-chemical and microbiological parameters of the Passaúna and Piraquara rivers, a watershed of the Iguaçu River, belonging to the cities of Araucária and Piraquara, respectively Paraná, Brazil, was used to carry out the research. The water quality index was determined with the time series and, subsequently, these data were submitted to the statistical control of the process, with the control charts of individual Shewhart, EWMA and CUSUM, in addition to the development of the process capacity index. The WQI detected that the rivers remained in average quality until the year 2000, however, from that year it was possible to see a decreasing trend in the water quality of the evaluated rivers. The control charts of Shewhart, EWMA, CUSUM and the process capability index were able to identify the decreasing trend in water quality, demonstrating that they are fast and efficient techniques for the evaluation of water quality control.
  • ANAEROBIC DIGESTION AND CO-DIGESTION OF POULTRY LITTER SUBMITTED TO DIFFERENT REUSES Scientific Paper

    Vicente Jr., Donizete J.; Costa, Monica S. S. de M.; Costa, Luiz A. M.; Pereira, Dercio C.; Santos, Francielly T. dos

    Resumo em Inglês:

    ABSTRACT Considering the constant increase in the waste generation from poultry and pigs’ husbandries, the main contributions of this study were to verify the potential of biogas production through the anaerobic digestion and co-digestion of the residues generated by these two activities, as well as to highlight the recovery of the nutrients contained in the obtained digestate. The wastes used were poultry litters after six, seven and eight production lots, as well as the sifted wastewater from one Piglets Producer Unit (PPU). Higher biogas production (p <0.05) was observed in the treatments in which anaerobic codigestion was used with the swine wastewater (SW): 0.179; 0.158 and 0.117 m3 per kg of total solids (TS) added for poultry litters with six, seven and eight lots, respectively. It was concluded that the anaerobic co-digestion between the poultry litter and sifted swine wastewater is the best option for energy and nutrient recycling. No positive relationships were observed in the increase in the number of reuses of litter in the production of biogas and in the concentration of nutrients in the digestate.
  • SWINE WASTEWATER NITROGEN REMOVAL AT DIFFERENT C/N RATIOS USING THE MODIFIED LUDZACK-ETTINGER PROCESS Scientific Paper

    Giongo, Adelcio; Bortoli, Marcelo; Prá, Marina Celant De; Veruck, Marcos; Kunz, Airton

    Resumo em Inglês:

    ABSTRACT The swine industry has been presented strong growth and thus is producing large volumes of effluents that must be correctly management. Nitritation/denitritation process can be used to improve system performance, saving the energy cost with aeration and with the external source of carbon due to the lower C/N requirement. The aim of this study was to evaluate swine wastewater Nitrification/Denitrification (NDF) and Nitritation/denitritation (NDT) processes at different C/N ratios, using the Modified Ludzack-Ettinger (MLE) process, in order to obtain a system with efficient nitrogen removal and low oxygen and carbon consumption. Four phases were conducted during the experiment: Phase I) DO between 2.0-3.0 mg L−1 of O2 and C/N 1.5 (NDF); Phase II) DO between 0.6-0.7 mg L−1 of O2 and C/N 1.5 (NDT); Phase III) DO between 0.6-0.7 mg L−1 of O2, C / N ratios of1.5, 0.9, 0.75 and 0.6 (NDT); Phase IV) DO between 2.0-3.0 mg L−1 of O2, C/N ratios of 1.5, 0.9, 0.75, and 0.6 (NDF). The best operational condition was found in the C / N ratio of 0.9 (Phase III) obtaining an optimum N removal of 86.3%. In this condition, the system saved around 26.8% in total organic carbon consumption and operated at conditions of 74% lower dissolved oxygen when compared to conventional process for N-removal. This strategy can be very useful for nitrogen removal for low carbon swine wastewater as digestate from anaerobic processes.
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