RCAAP Repository

Abstract Biological wastewater treatment processes with biological nitrogen removal are potential sources of nitrous oxide (N2O) emissions. It is important to expand knowledge on the controlling factors associated with N2O production, in order to propose emission mitigation strategies. This study therefore sought to identify the parameters that favor nitrite (NO2 -) accumulation and its influence on N2O production and emission in an anaerobic/aerobic/anoxic/aerobic sequencing batch reactor with biological nitrogen removal. Even with controlled dissolved oxygen concentrations and oxidation reduction potential, the first aerobic phase promoted only partial nitrification, resulting in NO2 - build-up (ranging from 29 to 57%) and consequent N2O generation. The NO2 - was not fully consumed in the subsequent anoxic phase, leading to even greater N2O production through partial denitrification. A direct relationship was observed between NO2 - accumulation in these phases and N2O production. In the first aerobic phase, the N2O/NO2 - ratio varied between 0.5 to 8.5%, while in the anoxic one values ranged between 8.3 and 22.7%. Higher N2O production was therefore noted during the anoxic phase compared to the first aerobic phase. As a result, the highest N2O fluxes occurred in the second aerobic phase, ranging from 706 to 2416 mg N m-2 h-1, as soon as aeration was triggered. Complete nitrification and denitrification promotion in this system was proven to be the key factor to avoid NO2 - build-up and, consequently, N2O emissions.

Abstract The objective of this work was to evaluate the bioaccumulation of mercury in 13 species of fish with different eating habits, captured in the Três Marias Reservoir, São Francisco Basin, from March 2012 to April 2013. The results obtained showed that the species with carnivorous eating habit presented the highest average concentrations of mercury in muscle, especially Serrasalmus brandtii (pirambeba) and Pygocentrus piraya (piranha), with concentrations of 0.4147 ± 0.2744 μg g-1 and 0.17774 ± 0.2980 μg g-1, respectively. Considering the average concentrations, all the species studied showed levels of mercury below the maximum limit of 0.5 μg g-1 in non-predatory fish and 1.0 μg g-1 in predatory fish, established by the Agência Nacional de Vigilância Sanitária. Taking each species into account, the minimum and maximum values of mercury in the muscular and hepatic tissues showed a wide dispersion. In 4% of the specimens of pirambeba and 7% of piranha, the contents of mercury in muscle exceeded the limit established by ANVISA for predatory fish, and therefore, were unfit for human consumption. The other species did not present muscle samples with Hg content above that established by law. Due to its carnivorous eating habit and its wide distribution in the São Francisco Basin, Serrasalmus brandtii can be considered a biomonitor, capable of bioaccumulating mercury, thus indicating the level of contamination in the aquatic environment in which it lives.

Abstract A challenge for the design of drip irrigation systems with non-pressure compensated emitters is to increase the maximum length of the lateral lines without significantly reducing water application uniformity. This work evaluated the effect of the flow-rate variation and the local head loss in the maximum length of drip tape with a non-pressure compensated flat emitter. The tests were carried out in a laboratory, using a collapsible drip tape non-pressure compensated in three 50-meter segments. The production line was configured to generate drip tapes without insertion of emitters and with closed emitters (0.30 m spacing). The experimental local head loss was compared with the Darcy-Weisbach equation's estimates using the Blasius friction factor. In the sequence, simulations were generated for the flow-rate variations of 10 and 20% for the emitter spacings of 0.30, 0.40, and 0.50m. The results showed that the local head loss had little influence on the lateral line's maximum length, generating variations of 2.5% on average. However, increasing the allowable flow rate variation from 10 to 20% resulted in a 34% increase in the lateral line maximum length. Also, the reduction in uniformity coefficients was less than 5%, enabling the indexes to remain above 90%. The adoption of higher flow rate variation values ​​allowed gains in the lateral line length with a small decrease in uniformity, making it an alternative to reduce design and operational costs.

Abstract The Mundaú-Manguaba Estuary Lagoon Complex is located on the coast of Alagoas state in Northeastern Brazil, and consists of two shallow lagoons, Mundaú and Manguaba, that form a system of choked lagoons which are connected to the Atlantic Ocean by a series of narrow channels with a single outlet which dynamically alters its position. This study uses the Hydrodynamic Environmental System, SisBaHiA® to investigate how variations in river discharge and wind influence hydrodynamic circulation, water renewal, salinity and temperature in the lagoons. The free surface positions, obtained by model, were compared with the free surface positions measured at two points of the complex, showing good agreement. The analyses were carried out for dry and wet seasons and extreme events with very high freshwater discharge. The channel system of the lagoons is an efficient filter in reducing tidal variability inside the lagoons. The tidal ranges in the Manguaba and Mundaú Lagoons are 90% and 80% lower, respectively, as compared with the values in the open boundary. The residence time calculated varied between 11 and 365 days and between 2 and 180 days for the Manguaba and Mundaú Lagoons, respectively, making it possible to identify possible stagnation areas. The results from the salt and heat transport model show a prolonged period with low salt concentrations and slow salinity recovery after the rainy season; the water temperature in the lagoons shows little spatial and temporal variation.

Abstract Superior productivity of genotypes in forest plantations depends on the supply, capture and use-efficiency of resources. In this context, knowledge regarding the nutritional efficiency of Eucalyptus influences farmers and researchers in decision-making and in the management of forest ecosystems. The aim of this research was to estimate nutrient-use efficiency in Eucalyptus genotypes planted in the state of Rio Grande do Sul, Brazil. We evaluated six potential genotypes at 43-month-old stands. Nutrient-use efficiency was calculated using the ratio of biomass and the amount of nutrients for each component of the biomass. Results here presented confirmed that there is synergism and antagonism between nutrients at the shoot level in the Eucalyptus genotypes. For stemwood, E. saligna showed the best utilization efficiency of N, P, K, S, and Mn; and E. urophylla × E. globulus for Mg, B, and Zn. Metabolic pathways control the production of biomass synthesized by each genotype and the differences between genotypes groups were on the basis of their nutrient-use efficiency in the biomass components. Stemwood was the component that showed the highest nutrient-use efficiency, while leaves presented the lowest nutrient-use efficiency. Additionally, our analyses identified how different each Eucalyptus genotype is and these traits may be used for clone allocation according to soil fertility.

Abstract In view of the water crises historically experienced by Brazil’s semi-arid region, it is necessary to search for methodological tools that allow us to propose efficient alternatives for managing water demand. In this regard, the present study developed and applied a hybrid approach of flow network modeling and the Analytic Hierarchy Process (AHP) combined with Shannon’s entropy for simulating and prioritizing water demand management alternatives in the Epitácio Pessoa Reservoir in the Brazilian semiarid region. The approach initially performed simulations of the hydro system flow network to explore rational alternatives that evaluated the following criteria: meet the demands of human supply, meet the demands for irrigation, maintain the reservoir above the target volume, and reduce consumption. Subsequently, Shannon's entropy was used to assess the importance of the criteria and the multicriteria analysis of ranking of alternatives was built. Finally, a sensitivity analysis of the model was performed regarding the dependence on respective weights of the criteria. The results made enabled evaluation of the hydro system’s water security, highlighting insufficient supply by the single measure of water management transposition of the São Francisco River, and based on the hierarchy of alternatives, suggesting actions to improve the sustainability of water use, such as reuse of water, reduction of losses in supply systems and increasing irrigation efficiency. The proposed hybrid approach permitted the synthesis of the simulation’s results, which may simplify and support the decision-making process in water-demand management.

Abstract Irrigated rice (Oriza sativa L.) pre-germinated production systems occupy approximately 100 thousand ha, annually cultivated in Rio Grande do Sul State, mainly in poorly drained areas, and with infestation of competing plants, especially red rice (Oriza sativa L.). This system constitutes the main technologic resource for rice crops produced on an ecological basis, by means of soil tillage and water management. Despite this, water outlets, specifically after seeding, have outstanding agronomic and environmental implications. Loss of nutrients and the physical and chemical quality of drained water have been questioned by public research and environmental institutions. This work evaluated the effects of different soil tillage systems and retention time of water in irrigated rice frames. The experiment was conducted in Viamão town, Rio Grande do Sul State. Two different soil tillage systems and four different times of frame drainage after seeding were investigated. Results showed that the main limiting attributes of water quality were turbidity, biochemical oxygen demand (BOD) and phosphorus (P) content, reaching 1800 TNU, 115 mg L-1, and 1.6 mg L-1, respectively. These attributes showed values higher than established environmental thresholds. Water quality was inappropriate to discharge directly into water courses, regardless of treatments.An alternative is the immediate placement in rice production areas, in more advanced development stages of plants. Pre-germinated rice crops require a system framework to avoid nutrient loss and consequent reduction of soil fertility.

Abstract The quality of water for human consumption has been a concern for large organizations and researchers, since the disinfection process, a step of great importance in water treatment plants, has not achieved its proper purpose. There have been frequent reports of the ineffectiveness of bacteria inactivation by the use of chlorine, which is the most used in Brazil, and also due to the formation of by-products such as trihalomethanes and haloacetic acids that are considered toxic to human health. The method of disinfection by ultraviolet radiation (UV) has been widely explored, due to its effectiveness in inactivating a wide variety of pathogens, in addition to the absence of by-product formation. The combined chlorine+UV process as chemical and physical disinfectants, respectively, is complementary and essential when looking for the safety of water for human consumption. The objective of this research was to statistically analyze the performance of disinfectants, chlorine and UV radiation, both separately and together, by inactivating the bacteria Escherichia coli and Pseudomonas aeruginosa and then incubating for 48 hours after having received the treatments. The statistical method showed that chlorine and UV obtained the same significance of 100% bacteria inactivation, and that within the determined time of 48 hours after the treatments the bacteria did not show reactivation. Thus, the study affirmed the usefulness of applying UV radiation as a complement to systems that use chlorine, with a special focus on residential water systems and supply.

Abstract The aim of this study was to derive a methodology for calculating a sequential water balance that accurately estimates the occurrence of excess water in soybeans cultivated in lowlands. We tested four calculation strategies of water balance associated with the simulation of soybean development, which differed on the calculation of rainfall and time of water drainage from the soil macropores. Data of volumetric moisture monitored in three soil layers throughout the soybean cycle in the 2014/15 agricultural year were used as a reference. Microporosity was used as a lower limit for the occurrence of excess water in the area. Excess water was considered to be whenever the daily volumetric soil moisture in the 0-100 mm layer was greater than 0.39 mm3 mm-3. Over the 111 days of measurement, soil moisture indicated the presence of excess water in 38 days. The traditional calculation strategy of water balance underestimated the occurrence of excess water, as well as the other strategies that considered effective precipitation in their formulas. The calculation strategy that considers that all the rainfall infiltrates in the soil and that the water from macropores is removed only by crop evapotranspiration exhibited good performance and indicated 35 days of excess water, being the most appropriate and recommended for determining excess water in lowland soybeans.

Abstract In this work, a flow photoreactor was designed and set up using low-cost and recyclable parts to develop chemical treatments based on advanced oxidation processes (AOP) of highly colored textile wastewater. To evaluate this sustainable system´s efficiency, we investigated and compared the performance of three types of destructive methods (UV/H2O2, Fenton, and photo-Fenton) on the decolorization of aqueous solutions of Reactive Black 5 dye (RB5). We also analyzed the effect of the oxidant and dye concentrations on the rate of color removal in each one of the three methods. The results showed that, regardless of the initial operating conditions, the photo-Fenton process achieved the highest degradation rates, particularly when the highest ratio between the oxidant and dye concentrations was used ([H2O2]: [RB5] = 24.5 mg L-1: 25 mg L-1), leading to complete color removal within only 10 minutes of reaction. With the same initial condition, the Fenton and UV/H2O2 processes were also capable of removing the color entirely, even though they demanded more extended runs of 25 min. and 45 min., respectively. The effect of pH on the decolorization by the photo-Fenton process was also investigated, showing the same high performance at pHs 3 and 4. The degradation profile achieved by the photo-Fenton treatment was appropriately fitted by a pseudo-first-order kinetic. The non-expensive photoreactor proved to be quite useful for the degradation of the RB5, mainly when this azo dye underwent the photo-Fenton process.

Abstract Intensive management of forest stands can increase biomass production, as well as increase the removal of nutrients from the site. This study therefore sought to simulate different harvest intensities and to calculate the nutrient-use efficiency of Eucalyptus urograndis in different types of soil. The study was carried out in a plantation of seven-year-old hybrid E. urograndis in the city of Telêmaco Borba, Paraná, Brazil. The study site included two sub areas with sandy soil and clayey soil (Cambisols Inceptisol and Ferralsols Oxisols, respectively). Using biomass and nutrients stock data, nutrient removal was simulated under five different harvest scenarios. Nutrient-use efficiency was obtained from the relation between the amount of biomass and nutrients of each tree component. Harvesting the whole tree resulted in the removal of approximately 61% of the nutrients from the site in sandy soil, while in clayey soil 57% of the nutrients were removed. With harvesting of only the commercial stemwood, only 22% of the nutrients were removed from the sandy soil, and 21% from the clayey soil. Stemwood was the component that had the highest nutrient-use efficiency values for all the analyzed nutrients. In conclusion, to achieve nutritional sustainability of E. urograndis stands, the best harvesting system involves the removal of only commercial stemwood. For the production of stemwood, sandy soils have a greater biological efficiency of calcium and magnesium when compared to clayey soil.

Abstract This study evaluated changes in the structure for remnant Mixed Ombrophilous Forest recovering from logging, which ceased over 40 years ago. Regarding the dynamics of the floristic composition of natural regeneration, 18 species remained (23.38% of the total) and 27 new species entered (35.06% of the total). The greatest increases were observed for Allophylus edulis, Myrsine umbellata, and Miconia cinerascens. When analyzing the dynamics of regeneration in ecological groups, it was observed that pioneer species had a similar value in both surveys (29.4% and 29.6%); secondary species decreased from 56.6% to 52.8%, and late-successional species increased from 0.2% to 6.0%. Therefore, the forest fragment studied is in a healing phase after disturbance, characterized by the increased regeneration of pioneer species as a result of sufficient light entering the interior of the forest.

Abstract Brazil has experienced a rise in the use of agrochemicals in recent years, representing a potential threat to nearby ecosystems. The Volta Grande Reservoir (Minas Gerais/São Paulo, Brazil) has about 87% of its area surrounded by agricultural systems, and many compounds used in agriculture end up being carried into nearby water bodies. Given the potential ecological risk, our purpose was to assess pesticides in the reservoir. We collected specimens of two bivalves and three gastropods using bottom dredging and visual investigation in three different sites within the reservoir. The sampling sites were classified according to their distance from the dam, and all were close to agricultural lands. The samples were processed and frozen for qualitative toxicological analysis using mass spectrophotometry. Eight pesticides were identified, including four organochlorines (Aldrin, p,p’-DDE, Heptachlor epoxide, and Endrin) and organophosphates (Disulfoton, Malathion, Parathion- methyl, and Parathion-ethyl). All five studied species (Limnoperna fortunei, Corbicula fluminea, Melanoides tuberculata, Aylacostoma tenuilabris, and Pomacea aff. canaliculata) presented traces of pesticides in their bodies. Of the eight pesticides found in our analysis, six are illegal in Brazil, raising awareness about the continuous use of forbidden pesticides, and also the ecological risk in the Volta Grande Reservoir area. Our results suggest stricter control by environmental agencies regarding the use and commercialization of these illegal toxic compounds.

Abstract This study aimed to undertake an environmental life cycle assessment (LCA) of a sewage treatment plant (STP) equipped with low-rate trickling filters (TFs) as post-treatment of upflow anaerobic sludge blanket (UASB). The STP is located in South Brazil and uses landfill and agriculture as sludge-disposal alternatives. The evaluation was performed using the LCA technique and SimaPro® 9 software. The results revealed that the gases methane (CH4) and sulfur dioxide (SO2), emitted into the atmosphere after the partial burning of the biogas in flares, are mainly responsible for impacts in the categories of global warming (GW) and terrestrial acidification (TA), respectively. Due to the low rate of hydraulic sewage application in TFs, nitrous oxide (N2O) emissions stood out due to their high impact in the category of stratospheric ozone depletion (SOD). The use of sludge in agriculture obtained a greater potential for environmental impact compared to landfills in five of the eight categories evaluated. The main impacts of agricultural use were in the category of human toxicity (HT), due to the high concentration of zinc present in the sludge, and in the category TA, due to the emission of ammonia (NH3) during hygienization of the sludge. In turn, the main positive aspects were avoided products, such as urea, phosphate fertilizer and limestone. The results contribute to a greater discussion of sewage-treatment processes, as well as sludge-management alternatives used in developing countries.

Abstract Effluent from a fish tank with Nile tilapia (Oreochromis niloticus) was treated in a system of two parallel fixed-bed anaerobic reactors followed by a suspended stirred, anoxic reactor for solids, organic matter and nitrogen removal. Microbial community structure was compared between the reactors and an enriched anammox culture originated from anaerobic sludge by using the PCR (Polymerase Chain Reaction) and DGGE (Denaturing Gradient Gel Electrophoresis) techniques. DGGE analysis revealed three large microbial clusters, namely, the biomass in the inoculum, the biomass growing in the reactors, and the enriched anammox culture. The similarity between the microbial community recovered from the anaerobic reactors and the anammox community was considered low (32.7%), suggesting differentiation of the bacterial community as a function of the selection of specific anammox groups. The last step in the anoxic reactor had worsened the effluent quality. The potential of organic matter and ammonia removal in a single anaerobic reactor was demonstrated.

Abstract Computational methods based on machine learning have had extensive development and application in hydrology, especially for modelling systems that do not have enough data. Within this problem, there are data series that are missing, and that should not necessarily be discarded; this is achieved by means of the imputation of the same ones, obtaining complete sets. For this reason, this research proposes a comparison of computer-learning techniques to identify those best suited for hydrographic systems of the Pacific of Ecuador. For the elaboration of this investigation, the hydro-meteorological records of the monitoring stations located in the watersheds of the Esmeraldas, Cañar and Jubones Rivers were used for 22 years, between 1990 and 2012. The variables that were imputed were precipitation and flow. Automatic learning machines of the Python Scikit_Learn module were used; these modules integrate a wide range of automated learning algorithms, such as Linear Regression and Random Forest. Finally, results were obtained that led to a minimum useful mean square error for Random Forest as an automatic machine-learning imputation method that best fits the systems and data analyzed.

Abstract The active sludge process is one of the most-used techniques for the biodegradation of organic compounds present in effluents from an assortment of wastewaters. This study investigated the bacterial community structure of a petroleum industry’s activated sludge and its physical and chemical parameters using high-throughput sequencing. Samples were collected over one year: autumn 2015 (C1), winter 2015 (C2), spring 2015 (C3), and summer 2016 (C4). Total DNA was extracted, and the primers targeting the V4 region of the 16S rRNA gene were used for amplicon sequencing. The majority of the detected microorganisms were considered rare microbiota, presenting a relative abundance below 1% of the total sequences. All of the sequences were classified at the phylum level, and up to 55% of the ASVs (Amplicon Sequence Variants) were associated with known bacterial genera. Proteobacteria was the most abundant phylum in three seasons, while the phylum Armatimonadota dominated in one season. The genus Hyphomicrobium was the most abundant in autumn, winter and summer, and an ASV belonging to the family Fimbriimonadaceae was the most abundant in the spring. Canonical Correspondence Analysis showed that physicochemical parameters of SS, SD and TSS are correlated, as well as ammoniacal nitrogen. Sample C3 presented the highest values of COD, AN and solids (SS, SD and TSS). The highest COD, AN, and solids values are correlated to the high frequency of the phylum Armatimonadota in C3.

Abstract This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µmax) and generation time (tg), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µmax and the consequent decrease in tg. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L-1) and Nannochloropsis sp. (1237.05 mg.L-1), both at a concentration of 4.0 g.L-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.

Abstract This study investigated the demographic, socioeconomic, and municipal health indicators related to the quality of water fluoridation. An ecological study was carried out in Espirito Santo state (ES), based on data from the Drinking Water Quality Surveillance Information, from 2014 to 2017. The non-parametric Mann-Whitney and Spearman tests were applied to compare municipal indicators with the availability of information and the quality of fluoridation, respectively. Fluoridation quality was calculated to define the percentage of fluoride concentration values in each municipality within the range of the optimal level corresponding to the maximum benefit for preventing dental caries and minimum risk for the occurrence of dental fluorosis. The proportion of 80% or more samples were defined as a compliance criterion. In 2014, 62.8% of the municipalities had information available, and 16.7% performed analyses of fluoride concentration. The percentage of available data increased about 30%, in 2017, with 3.8% referring to fluoride. The quality of fluoridation remained high (> 80%) in ES in almost every year, except in 2014. The municipalities with the largest population, the highest GDP per capita, and the lowest coverage of the oral health team exhibited a greater availability of information about fluoride (p <0.05). The child mortality rate showed a strong negative correlation with the quality of fluoridation. The findings reinforce the importance of directing public policies that ensure the correct practices for monitoring and maintaining the quality of fluoridation.

Abstract Measurement and evaluation of soil erosion and consequent sediment yield are fundamental in the planning and management of watersheds, as they allow the identification of critical areas susceptible to erosive processes. This study analyzed the sediment yield generated by water erosion in the Indaia River Basin, Alto São Francisco, Minas Gerais, by using the SWAT hydrological model. From a regional/local scale, the initial simulation of the variables (flow and solid discharge) was performed on a monthly scale from 1988 to 2017. Then, parameter-sensitivity analysis, calibration, and validation of the model were executed. In the monthly calibration (1988 to 2007), the performance of the simulations for flow was R2=0.92 and NSE=0.91 and for total solid discharge R2=0.51 and NSE=0.50. In the monthly validation (2008 to 2017) for flow, R2=0.85 and NSE=0.82 was obtained and for total solid discharge R2=0.19 and NSE=0.16. Despite the unsatisfactory result in the validation stage, the model was able to analyze the distribution of sediment production by sub-basins or even by the Hydrologic Response Unit (HRU). Therefore, a sediment-yield map was generated which qualitatively indicated a tendency for greater erosive processes in the central portion of the basin. The results will support public policies mitigating environmental degradation of the Indaia River Basin.