RCAAP Repository

Abstract Upflow Anaerobic Sludge Blanket (UASB) reactors are widely used for domestic sewage treatment in Brazil, and generate sludge and biogas as by-products. Typically, the sludge is sent to sanitary landfills, and the biogas is burned in flares. This study assessed the energy potential of these by-products in sewage treatment plants (STPs) located in the state of Paraná, Brazil. First, an overview of biogas energy recovery potential in a full-scale STP based on UASB reactors was carried out. Afterwards, a total of 239 STPs in the state of Paraná were assessed, and the energy potential of the by-products was estimated by a mathematical model. Data were spatially classified using ArcGIS®, taking into account the different effluent characteristics (worst, typical and best scenario), sludge dehydration systems (drying bed and centrifuge) and sizes (small, medium and large). Among the states in Brazil, Paraná presented the highest biogas potential, although nowadays it exploits only 0.4% of its capacity. Biogas was the main by-product generated by UASB reactors in Paraná, and if used in the entire state, it could supply the energy demands of a city with 111,000 inhabitants. Biogas corresponded to 65, 64 and 74% of the total potential (sludge and biogas) for small, medium and large STPs, respectively. The study of the energy potential of the by-products associated with GIS tools positively contributes to the decision-making process in sanitation management and to improve energy sustainability.

Abstract This study developed a method for furosemide quantification through high performance liquid chromatographic technique. Special attention was given to solute loss and storage stability due to furosemide’s low solubility and photosensitivity, respectively. The performance of Nylon and PVDF filters was tested in a 2 mg.L-1 furosemide solution. PVDF filters showed better recovery capacity and therefore are more suitable for furosemide filtration. Over eight days, three different storage conditions were studied to access furosemide degradation susceptibility: (i) exposure to light at room temperature, (ii) storage at room temperature without exposure to light, and (iii) storage at 4ºC without exposure to light. The study demonstrated that after 48 h under natural light exposure furosemide was completely degraded. Furosemide solution stored in the dark was stable. Storage temperature did not seem to affect furosemide concentration. The study shows that the selection of more suitable filter and storage conditions for furosemide determination is crucial to avoid underestimation errors.

Abstract The search for better living conditions has led the residents of the Brazilian semi-arid region to plant forage crops, leading to a gradual decrease in the native vegetation (Caatinga) of this region. The effects caused by the replacement of Caatinga with palm, for example, have been little studied, especially with regard to the physical and hydraulic properties of the soil. The objective of this study was to compare the physical-hydraulic characteristics of a litholic neosol in two areas having different vegetation cover: one area cultivated with forage palm (O. ficus-indica) and the other covered by native Caatinga. Differences in soil structure, especially in porosity, between the natural and cultivated soils were observed to control the hydrodynamic processes, resulting in changes in water retention curves and hydraulic conductivity. Natural soil presents low values of hydraulic conductivity when compared to those of cultivated soil. This increase is probably due to soil management required for forage palm cultivation. The natural soil structure, characterized by relatively low saturated hydraulic conductivity values, presents an infiltrability that favors surface runoff. Human activities in the study area have promoted changes in the soil’s physical attributes, decreasing density and increasing porosity. Consequently, there is an increase in water infiltration into the soil and a reduction of runoff in cultivated areas, confirming results obtained in previous studies.

Abstract The differentiated effects of the provision of environmental services in a watershed are due to the capacity of regularization of outflows in its mouth. In impacted areas, this environmental function is affected, and in some situations, it ceases to exist completely. This study characterized the soil and the production of sediments in anthropic watersheds, with the purpose of describing and evaluating the environmental services offered by a watershed undergoing anthropic transformation. The analyses show that the water flow in the remaining watersheds was preferably horizontal in the transmission zone, and these areas represent almost all areas. The values of hydraulic conductivity suggest that the infiltration decreases with soil depth; this fact is corroborated by the values of bulk density. The natural regions of water accumulation, the floodplains or outcrops zones, are small and do not have direct contact with the main floodplain present in the Guandu River Basin, making it impossible to recharge through other areas. Even so, water balance shows that the set of measures implemented ensured that the deficit water demand was supplied during the years of operation, even in times of water deficit. Likewise, the retention of solids in the settling tanks and in the drainage system prevented some 29,000 t of sediment from being carried between the years of 2012 and 2015.

Abstract There is great concern with soil and plant contamination by heavy metals due to the use of polluted water in agricultural irrigation. In this study, areas irrigated with Vieira River water were evaluated as to contamination by As, Cr, Cu, Ni, Pb and Zn. The Vieira River receives effluent from Montes Claros city, state of Minas Gerais, Brazil. To do so, two irrigated areas were selected, one upstream and one downstream of the Montes Claros city. Wastewater discharge increased the concentration of As and Ni in the water of Vieira River, and consequently, of As, Cr, Cu, Ni, Pb and Zn in the soil and of As and Zn in forage grasses. However, the content of heavy metals in the soil did not exceed the internationally recommended limits. Pollution load index (PLI) and contamination factor (CF) indicated the existence of pollution and moderate contamination in downstream soils of the city of Montes Claros. Potential ecological risk index (RI) and ecological risk factor (Er) indicated a low ecological risk, but these indicators were higher in downstream soils of Montes Claros. Arsenic (As) was the only heavy metal that featured a transfer factor (TF) higher than the widespread values found in literature and positive geoaccumulation index (Igeo), indicative of anthropogenic pollution.

Abstract Considering the current importance watercourses quality conservation, it is important to establish relationships between parameters that enable evaluation of the origins of changes in water quality, allowing actions to mitigate them. However, it is important to improve the association of different variables and to take sufficient samples. This study associates usual techniques and parameters to analyse the water quality of an urban river from Paraná State, Brazil. For this, we used biological indicators (aquatic macroinvertebrates), physical-chemical (temperature, turbidity, true colour, pH, DO and BOD5,20) indicators and microbiological (faecal and total coliforms) indicators. These indicators were related to land use and occupation classes obtained from high resolution QuickBird 2 images. For this association, the surroundings (450 meters buffer) of three distinct points of the river were considered: I. Near the spring; II. In the downtown city; and III. In a residential neighbourhood. Different values of physical, chemical and microbiological variables were detected along the river, showing evident relationships between them and with the use and occupation of the urban and peri-urban space in the characterization of surface waters. The association design was able to detect the landscape effect on water quality in a coherent way and that these connections were mainly related to suppression of the riparian forest present in the surroundings, further demonstrating the importance of this vegetation for the maintenance of watercourse quality.

Abstract Inefficiency of sanitation companies’ operation procedures threatens the population’s future supplies. Thus, it is essential to increase water and energy efficiency in order to meet future demand. Optimization techniques are important tools for the analysis of complex problems, as in distribution networks for supply. Currently, genetic algorithms are recognized by their application in literature. In this regard, an optimization model of water distribution network is proposed, using genetic algorithms. The difference in this research is a methodology based on in-depth analysis of results, using statistics and the design of experimental tools and software. The proposed technique was applied to a theoretical network developed for the study. Preliminary simulations were accomplished using EPANET, representing the main causes of water and energy inefficiency in Brazilian sanitation companies. Some parameters were changed in applying this model, such as reservoir level, pipe diameter, pumping pressures, and valve-closing percentage. These values were established by the design of experimental techniques. As output, we obtained the equation of response surface, optimized, which resulted in values of established hydraulic parameters. From these data, the obtained parameters in computational optimization algorithms were applied, resulting in losses of 26.61%, improvement of 16.19 p.p. with regard to the network without optimization, establishing an operational strategy involving three pumps and a pressure-reducing valve. We conclude that the association of optimization and the planning of experimental techniques constitutes an encouraging method to deal with the complexity of water-distribution network optimization.

Abstract Soil is a fundamental natural resource for subsistence and development of humanity, exploited mainly for agriculture. Agricultural practices, though, are improperly performed, compromising edaphic conditions and favoring erosive processes, which mainly culminate in the loss of soil and nutrients. Water erosion represents the main form of soil degradation, given that the impact of raindrops on the soil results in the detachment of particles, a process favored by factors such as climate, relief, soil vegetation and use and occupation. The objective of the study was to classify four gullies based on their evolutionary turns and to judge the physical-chemical classifications of the soil at the internal and external faces of the gullies. The morphology of the gullies was classified by aerial images generated by drones. The gullies were mapped using Google Earth images from 2016. The qualitative assessment was performed using the digital field-elevation curvature (MDESC) model with field validation. Deformed samples were collected at depths of 0-10 and 10-20 cm, while non-deformed samples were collected at depths of 0.0-0.10 cm to evaluate their chemical and physical attributes. A nonparametric 5% Kruskal-Wallis statistical analysis was performed on the resulting data. The chemical and physical attributes of the soil differed according to the evolutionary stage of the surfaces (internal and external) at depths of 0 to 10 cm, while the faces showed differences in depth of 10 to 20 cm.

Abstract Population growth has contributed to increasing poultry production, entailing a high waste loading, mainly poultry litter. One of the alternatives to treat such residues is anaerobic digestion, in which digester startup and generated-digestate quality are related to the material to be digested and to operation conditions, wherein inoculum use is one of the factors. This study therefore aimed to investigate how digestates, such as inocula, influence poultry litter (PL) anaerobic digestion, as well the reduction of solids and chemical oxygen demand (COD). For this, two inocula (bovine and swine digestates) were tested in the digestion process. The inocula were added at loads of 0.67, 1.00 and 1.67 gVS.L-1day-1. A split-plot design was developed and data underwent analysis of variance with means compared by the Tukey's test at 5% significance. Concerning bovine and swine inocula, it was concluded that both are indicated in the process. However, swine inoculum is better indicated because it had a better removal of total solids (TS), volatile solids (VS) and COD.

Abstract The present work evaluated the influence of filling substrate material (crushed PET bottles or fine gravel) on the efficiency of pollutant removal in horizontal subsurface flow constructed wetlands (HSSF-CWs). They were cultivated with a consortium of elephant grass cv. Napier (Pennisetum purpureum Schum) and Tifton 85 (Cynodon spp.) to treat wastewater from a common milk cooling tank (WWMT). For this, six HSSF-CWs were used which had dimensions of 0.6 m tall x 1.0 m wide x 2.5 m long. In order to investigate possible efficiency loss in the removal of pollutants from the system, operation was divided into two periods: Period I (from April to December 2015) and Period II (April to December 2016). Thus, the removal efficiencies of BOD5, solids and total nitrogen (TN), total phosphorus (TP), potassium (K) and sodium (Na) from WWMT were statistically compared. Results indicated that the efficiency of the HSSF-CWs for removing pollutants increased or remained similar after one year and nine months of their operation; and PET bottles were a viable alternative substrate in HSSF-CWs based on the efficient removal of pollutants from WWMT during the one year and nine months of monitoring. Crushed PET bottles constitute a viable substrate for filling HSSF-CWs. Altering the cultivation positions of the plant species did not change pollutant removal efficiencies, but indicates the importance of species arrangement to maximize system performance.

Abstract Population growth has led to occupation and housing near rivers and lakes. This contributes to the increase of water pollution. The industrial laundry sector, for example, consumes a large quantity for its processes and pollutes water bodies due to the improper disposal of its effluents which contain numerous harmful compounds. This study employed electroflocculation in effluent treatment and evaluated its efficiency by analyzing turbidity, chemical oxygen demand, and pH levels. It used aluminum and zinc plates as sacrificial electrodes and principal component analysis (PCA) as a statistical tool. A maximum electroflocculation time of 40 min was utilized in order to obtain efficient results from the study. The experiment showed significant improvement in the water quality in the physicochemical aspects, primarily concerning the reduction of organic matter in the effluent. The efficiency of this treatment increased with higher current; however, both the aluminum and zinc plates reacted differently to pH, COD, and turbidity. Two principal components were generated to explain 86.90% of the data variance in the experiment. The principal component analysis indicated that the aluminum electrode showed the best correlation (|>0.5|) for pH, COD, and turbidity in the effluent treatment.

Abstract Malls concentrate a large number of people in a relatively small area, and thus generate concentrated urban wastewater. This study evaluated the performance of a membrane bioreactor (MBR) as an alternative for the treatment of mall wastewater. Wastewater samples without any previous treatment were collected from a medium-size mall and showed a high chemical oxygen demand (COD) near 2,000 mg L-1. The MBR operated with a constant pressure of 40 kPa during 60 days with a sludge age of 30 days. Concentration of biomass was 3,738±930 mg L-1 and average permeate flux was 7.0 L h-1 m-2. The MBR was able to remove 91.2% and 97.2% of color and turbidity, respectively. Furthermore, COD removal was approximately 90% and biochemical oxygen demand (BOD) 88%. In addition, the MBR produced a phosphorus removal near 50%, and for nitrogen, 80%. The MBR system proved to be an efficient process for the removal of the pollutants, remaining stable even with the oscillation of the characteristics of the raw sewage, presenting great potential for application in the treatment of sewage from malls and effluents with high organic loads.

Abstract Wastewater from textile industries is loaded with synthetic dyes. These effluents are often not adequately treated, affecting the soil and groundwater quality and leading to environmental contamination. The Agreste mesoregion of the state of Pernambuco is home to one of the largest textile centers in Brazil. This work therefore aims to study the behavior of Remazol Black B (RB5) dye in subsurface mediums in this region. The kinetics and isotherm sorption experiments allowed an evaluation of RB5 retention capacity in two layers of alluvial soil of the dry riverbed of the Capibaribe Basin. The maximum sorption rate was 81.81 mg kg-1 and 21.7 mg kg-1 for the loamy sand and sand layers, respectively. The Pseudo-second order kinetic model described more appropriately the sorption kinetics for both soils. The isotherms behavior was nonlinear, and Freundlich model was the most suitable to describe this process for both soils, presenting KF values of 8.6407 L kg-1 for loamy sand and 0.1868 L kg-1 for sand. The isotherm parameters confirm a more significant interaction of RB5 with the loamy sand layer than with the sand layer, indicating lower leaching in the first layer, which is less mobile for RB5 contamination. Furthermore, the different sorption rates for both soils indicate the importance of studying the soil as a heterogeneous profile.

Abstract The water hyacinth (Eichhornia crassipes) is listed among the 100 worst invasive plants and was ranked as the 11th worst invasive species in Europe, being a threat to aquatic biodiversity and water-provision. Predicting species distribution is the first step to understanding niche suitability, forecasting the invasion impact and building resilience against this species. In this study, we used a potential distribution model to assess the global risk of water hyacinth invasion by overlapping maps of highly suitable areas for water hyacinth occurrence and areas of biological importance and water scarcity. The MaxEnt - Maximum Entropy algorithm was used in the construction of the model and included five global bioclimatic layers and one of urbanized areas. Among the variables used, occurrence is mainly explained by urban areas, highlighting the importance of cities as a source or dispersion mechanism of the water hyacinth. Global biodiversity hotspots are predominantly situated in high suitability regions for the species. Ramsar sites and global protected areas are at a lower risk level compared to hotspots; however, future climate change and urban growth scenarios could put these areas at higher risk for invasion. Threats posed by the water hyacinth are possibly more acute in regions suffering from current or chronic drought. The results suggest that niche models that do not consider anthropic variables may be underestimating potential distribution of invasive species. Furthermore, the ecological plasticity of the water hyacinth and its close association with cities increase the concern about the impact of this species on the environment and on water security.

Abstract Although the analyses of characteristic hydraulic times are important diagnostic tools for studying water mass exchanges and identifying areas prone to stagnation that are potentially subjected to eutrophication effects, their concepts and uses are often misinterpreted. This paper compares similarities and differences between widely used characteristic hydraulic times, CHT, known as Residence Time, Times of Water Renewal Rates and Water Age. A proper definition for each of these characteristic hydraulic times is stated to avoid the existing confusion with multiple concepts in the literature. Methodologies to compute these CHT through hydrodynamic modelling systems are presented and, in order to enhance understanding, applied to three idealized cases in steady flow channels: (1) Channel with uniform flow; (2) Channel with a lateral inflow; and (3) Channel with a lateral embayment. Finally, a practical example is discussed by applying the methodologies to the Patos Lagoon (RS). The results for the idealized channel cases are non-intuitive and this theoretical discussion clarifies the interpretation and uses of different timescales and outlines the Water Age as the more versatile and multifunctional timescale if compared to the others addressed here. The results for the Patos Lagoon exemplify the valuable information that CHT can offer for environmental management in natural water bodies.

Abstract Chemical contamination of the water supply system caused by anthropic activities can cause adverse health effects. This study determined the presence of toxic metals, organic substances, pesticides and trihalomethanes in the water supply systems of the urban area of Ibague City. The economic and sanitary activities located in the 25 surface streams of the 32 water supply systems of the municipality were characterized. A total of 25 water samples were taken from the surface streams, and 35 samples in the water network of each drinking water service provider for the identification of pesticides (carbamates, organochlorines, organophosphorus), mercury, arsenic, cyanide, lead, cadmium, antimony, cobalt, selenium, silver, nickel and hydrocarbons. The presence of trihalomethanes was sampled after the treatment process given. A total of 775 economic and sanitary activities were detected in the surface streams of the water supply systems, highlighting the human settlements, agricultural and tourist activities impact on the water sources. Organochlorine pesticides (0.009-0.109 mg/L), mercury (0.001-0.004 mg/L) were identified in the water supply system in concentrations higher than those permitted by local regulation. Concentrations of trihalomethanes (0.064-1.260 mg/L) were detected in 68.7% of the water supply systems with treatment. The presence of chemical contaminants occurs mainly in communities with water supply systems of low complexity with high anthropic affectation. It is necessary to strengthen the assessment of hazards and risk by health surveillance, as well as intersectoral intervention for the protection of water sources and the improvement of water treatment technologies.

Abstract Recently, the Poti river mouth region has experienced environmental impacts that resulted in a change of landscape in its dry season, highlighting the eutrophication and proliferation of phytoplankton, algae, cyanobacteria and aquatic plants. Considering the aspects related to water-quality monitoring in the semiarid region of Brazil from remote sensing, this study aimed to evaluate the performance of Sentinel-2A satellite data in the retrieval of chlorophyll-a concentration in Poti River in Teresina, Piaui, Brazil. The chlorophyll-a concentration retrieval and mapping methodology involved the study of the water surface reflectance in Sentinel-2A images and their correlation with the chlorophyll-a data collected in situ during the years 2016 and 2017. The results generated by the Chl-1, Ha et al. (2017), Chl-2, Page et al. (2018), and Chl-3, Kuhn et al. (2019) equations show the need for calibrating the algorithms used for the Poti River water components. However, the empirical algorithm Chl-2 shows a correlation has been established to identify the spatiotemporal variation of chlorophyll-a concentration along the Poti River broadly and not punctually. The spatial distribution of this pigment in maps derived from Sentinel-2A is consistent with the pattern of occurrence determined by the in situ data. Therefore, the MSI sensor proved to be a tool suitable for the retrieval and monitoring of chlorophyll-a concentration along the Poti River.

Abstract Density of phytoplankton in stabilization ponds influences treatment performance. The study hypothesized that the phytoplankton community structure varies according to local and temporal changes and consequently influences the treatment of the effluent. Phytoplankton community structure in facultative and maturation ponds in central Brazil was analyzed to provide guidance on system operation and maintenance. Further, species density, abundance, diversity, richness, dominance and beta diversity were measured. The efficiency of the treatment was evaluated based on Biochemical Oxygen Demand (BOD). Additionally, a Canonical Correspondence Analysis (CCA) was used to investigate how physical and chemical variables influenced the composition of the most abundant species in the dry and rainy seasons and the microalgae that were most related to the removal of BOD. One hundred and sixty-eight taxa were recorded, and the most abundant classes in both ponds were Chlorophyceae and Cyanophyceae (40% potentially toxic). The maturation pond had greater adaptability in the rainy season, while the facultative pond was more flexible in the dry season. The best period of growth varied among species. In both ponds, Chlorella minutissima was the one which most contributed to the optimization of the treatment. Thus, identifying phytoplankton species and relating them to water quality parameters and weather can help to understand the ecological dynamics of wastewater treatment and provide useful information for the operation and maintenance of stabilization ponds.

Abstract This study aimed to regionalize maximum (Qmax), minimum (Q95), and long-term mean (Qltm) streamflows in the Juruena River Basin to further water-resource planning and management, especially regarding water-use grant rights, streamflow regulation, and hydraulic designs. To do that, a traditional method was used, which relates the interest streamflows with sub-basin physiographic parameters by linear and nonlinear regressions. In summary, the traditional method was efficient for regionalization of Q95, Qltm, and Qmax streamflows for the Juruena River Basin. Moreover, the explanatory variables able to provide the best results for regionalization of Q95 and Qltm stream flows are drainage area, total watercourse length, and sub-basin mean altitude. For Qmax regionalization, the best results were provided by explanatory variables like drainage area, perimeter, and total watercourse length.

Abstract Pork production involves the generation of wastewater containing a high pollutant load. Although the biological systems show satisfactory efficiency for the treatment of these effluents, they demand an elevated area for installation and high production of biological sludge. Alternatively, oxidative processes are an alternative for treating such effluents, requiring minor areas and increasing the efficiency of the treatment. We studied the Fenton process assisted with ultrasound for the treatment of swine slaughterhouse wastewater. Nails used in civil construction were used as the iron source. We evaluated the influence of pH, contact time, nail mass, and hydrogen peroxide concentration on color removal, turbidity, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5). The removal of nutrients and oils and greases was also evaluated. The best results using the ultrasound-assisted Fenton process were obtained at pH 3, hydrogen peroxide concentration 90 mg L-1, and a nail unit (2.7g). In these conditions, color, turbidity, COD, and BOD5 removal of 98, 98.2, 84.6, and 98%, respectively, were achieved. The reduction in the other parameters evaluated was above 70%. Catalytic activity maintained above 90% until the sixth cycle of use. In general, the ultrasound-assisted Fenton process using the nail as a catalyst would be an alternative for the treatment of swine slaughterhouse wastewater. This alternative is responsible for the higher removal of organic load and nutrients in a shorter time when compared with biological systems.