RESUMO

The aim of this work was to stabilize excess sludge (ES) coming from a wastewater treatment plant (WWTP) by vermistabilization and to evaluate ecotoxicological effects over the earthworm species Eisenia fetida. Three mixtures were made up in triplicate using different volume ratios of ES and soil (S) (100% ES, 70:30% ES:S and 30:70% ES:S in wet weight basis). Earthworms were added in order to compare vermicomposting vs. natural stabilization. The mixtures were monitored over 130 days through physical, chemical, pathological and biological analysis, following quality standards depicted in the US EPA 40 CFR Part 503, local regulations and background studies. Histopathological samples were processed as biomarkers of acute and chronic toxicity on earthworms, and germination assays were performed at the end of the experiment to assess phytotoxicity. In terms of pathogen depletion comparing initial and final values from each treatment, the mixtures with higher ES proportions (70 and 100%) with earthworms were the most efficient ones registering 64.8 and 75.5% of reduction of fecal coliforms (FC) respectively, while the lowest ES proportion with earthworms (30%) showed 54.7%. Final pathogens content in all the treatments with earthworms were significantly lower (ranged from 1360 to 1760 MPN g total solids-1) than the values registered in treatments without earthworms (ranged from 2400 to 4000 MPN g total solids-1) (p < 0.05). However, none of the treatments attained class A categorization (FC ≤ 1000 MPN g total solids-1) in terms of FC. Also, values of mean cocoon production and hatched juveniles along time were significantly higher in the treatments with 100 and 70% ES (p < 0.05), while the higher mean adult biomass was detected in the treatment with 30% ES. Volatile solids decrease ranged between 8.45 and 22.34% in treatments with earthworms and all values of specific oxygen uptake rate were below 1.5 mg O2 h -1 g total solids -1. There were not negative effects over behavior or reproduction of E. fetida adults, nor the presence of external and internal injuries. Final products from mixtures with earthworms presented a humus-like structure, were odorless and reached maturity values -presenting no phytotoxicity-with significant differences between germination index values of treatments with and without earthworms (p < 0.05). Vermistabilization is a successful eco-technology to sanitize excess sludge, acquiring an added-value material and contributing to its revalorization as organic amendments or fertilizers in soils within the circular economy framework and the United Nations' Sustainability Development Goals.

Assuntos

RESUMO

Mining activities put the Brazilian savannas, a global biodiversity hotspot, in danger of species and soil carbon losses. Experiments employing biosolids have been applied to rejuvenate this degraded ecosystem, but a lingering question yet to be answered is whether the microbiota that inhabits these impoverished soils can be recovered towards its initial steady state after vegetation recovery. Here, we selected an 18-year-old restoration chronosequence of biosolids-treated, untreated mining and native soils to investigate the soil microbiota recovery based on composition, phylogeny, and diversity, as well as the potential factors responsible for ecosystem recovery. Our results revealed that the soil microbiota holds a considerable recovery potential in the degraded Cerrado biome. Biosolids application not only improved soil health, but also led to 41.7 % recovery of the whole microbial community, featuring significantly higher microbiota diversity and enriched groups (e.g., Firmicutes) that benefit carbon storage compared to untreated mining and native soils. The recovered community showed significant compositional distinctions from the untreated mining or native soils, rather than phylogenetic differences, with physiochemical properties explaining 55 % of the overall community changes. This study advances our understanding of soil microbiota dynamics in response to disturbance and restoration by shedding light on its recovery associated with biosolid application in a degraded biodiverse ecosystem.

Assuntos

RESUMO

Sewage sludge contains plant nutrients and organic matter in its composition, making it a potential partial substitute for mineral fertilizers if it meets environmental, agronomic, and sanitary standards. The objective was to evaluate the content of nutrients and heavy metals in the sludge generated in four wastewater treatment stations (WWTPs) in Rio de Janeiro state and assess its potential value and usefulness. The samples of 19 batches from the WTTPs Alegria, Barra da Tijuca, Ilha do Governador, and Sarapuí were analyzed. The WWTPs differ in methods and processes used for treating sewage and sludge. The total contents of C, N, P, K, Ca, Mg, Fe, Al, Na, Co, Mn, As, Ba, Cd, Cr, Cu, Ni, Se, Pb, and Zn were evaluated, as well as the ratio C/N, pH, organic matter content, and electrical conductivity. The grouping of sludge samples was assessed using principal components (PCA) and cluster analysis. The economic valuation of sludge was conducted utilizing the substitute goods method, which compared the sludge's N-P-K contents with the prices of consolidated nutrient sources. All the evaluated sludge batches exhibited concentrations of heavy metals below the limits allowed by Brazilian law, along with high levels of nutrients and organic matter. Considering the chemical characteristics, all evaluated materials showed potential for agricultural use, but it is crucial to evaluate the microbiological characteristics of sludge batches before agriculture application. PCA and cluster analysis demonstrated that sludge samples from the same WWTP clustered close to each other, demonstrating higher similarity among themselves than with samples from other WWTPs. The sludge had an average added value of U$ 88.46 per megagram, considering the total contents of N, P, and K in its composition. Land application of sewage sludge can reduce the need to purchase mineral fertilizers, thereby supporting the feasibility of reusing this material in the agricultural sector.

Assuntos

RESUMO

The physical and chemical characteristics of the soil can influence plant growth. When sewage sludge (SS) is applied as a soil fertilizer, the accumulation of non-essential elements contained in it can be toxic for plants. The aim of this study was to understand the effect of SS dosage on the cell cycle of Lactuca sativa L. meristematic cells and on the initial growth of L. sativa and Passiflora alata Curtis. Nine concentrations of SS + distilled water (mg dm-3) corresponding to 0, 20, 40, 60, 80, 120, 160, 320, and 520 t ha-1 were tested in four replicates of 25 seeds. Chemical analysis showed an increase in pH of the sludge from 0 to 80 t ha-1 SS followed by its stabilization thereafter. The highest electrical conductivity was observed at 520 t ha-1 SS. SS negatively affected the germination and initial growth of seedlings from P. alata and L. sativa. Cytogenetic analysis on 6000 L. sativa meristematic cells for each treatment revealed that SS could adversely affect the genetic stability of this species. SS concentrations above 120 t ha-1 adversely affected the germination and early seedling growth of L. sativa and P. alata. At high concentrations (120 t ha-1), SS induced genetic lesions in L. sativa, along with chromosomal and nuclear alterations.

Assuntos

RESUMO

Wastewaters are nutrient-rich organic materials containing significant concentrations of different nutrients, dissolved and particulate matter, microorganisms, solids, heavy metals, and organic pollutants, including aromatic xenobiotics. This variety makes wastewater treatment a technological challenge. As a result of wastewater treatment, biosolids are generated. Biosolids, commonly called sewage sludge, result from treating and processing wastewater residuals. Increased biosolids, or activated sludge, from wastewater treatment is a major environmental and social problem. Therefore, sustainable and energy-efficient wastewater treatment systems must address the water crisis and environmental deterioration. Although research on wastewater has received increasing attention worldwide, the significance of biosolids treatments and valorization is still poorly understood in terms of obtaining value-added products. Hence, in this review, we established some leading technologies (physical, chemical, and biological) for biosolids pretreatment. Later, the research focuses on natural treatment by fungal enzymes to end with lignocellulosic materials and xenobiotic compounds (polyaromatic hydrocarbons) as a carbon source to obtain biobased chemicals. Finally, this review discussed some recent trends and promising renewable resources within the biorefinery approach for bio-waste conversion to value-added by-products.

Assuntos

RESUMO

Primary sludge (PS) is associated with public health and environmental risks, so regulations focus on reducing the pathogenic and heavy metal contents of the treated material (biosolids), intended for soil amendments and land reclamation. The regulations set limits for Escherichia coli (or fecal coliforms), Salmonella spp., helminth eggs and enterovirus. However, the potential risk due to antibiotic resistant bacteria (ARB) and other human potential pathogenic bacteria (HPB) are not considered. In this work, three sludge treatment processes, having in common an anaerobic digestion step, were applied to assess the removal of regulated bacteria (fecal coliforms, Salmonella spp), ARB and HPB. The treatment arrangements, fed with PS from a full-scale wastewater treatment plant were: 1) Mesophilic anaerobic digestion followed by alkaline stabilization post-treatment (MAD-CaO); 2) Thermophilic anaerobic digestion (TAD) and, 3) Pre-treatment (mild thermo-hydrolysis) followed by TAD (PT-TAD). The results address the identification, quantification (colony forming units) and taxonomic characterization of ARB resistant to ß-lactams and vancomycin, as well as the taxonomic characterization of HPB by sequencing with PacBio. In addition, quantification based on culture media of fecal coliforms and Salmonella spp. is presented. The capabilities and limitations of microbiological and metataxonomomic analyses based on PacBio sequencing are discussed, emphasizing that they complement each other. Genus Aeromonas, Acinetobacter, Citrobacter, Enterobacter, Escherichia, Klebsiella, Ochrobactrum, Pseudomonas and Raoultella, among others, were found in the PS, which are of clinical or environmental importance, being either HPB, HPB-ARB, or non-pathogenic ARB with the potentiality of horizontal gene transfer. Based on the analysis of fecal coliforms and Salmonella spp., the three processes produced class A (highest) biosolids, suitable for unrestricted agriculture applications. Mild thermo-hydrolisis was effective in decreasing ARB cultivability, but it reappeared after the following TAD. O. intermedium (HPB-ARB) was enriched in MAD and TAD while Laribacter hongkongensis (HPB) did persist after the applied treatments.

Assuntos

RESUMO

Abstract Sewage sludge (SS) has nutritional contents and has been implemented in the cultivation of seedlings. This study aimed to evaluate the quality of Malpighia emarginata DC. seedlings produced in different substrates with SS. Treatments were implemented with the addition of SS, and after 180 days seedling the characteristics were measured: aerial part and root system length, stem base diameter, number of leaves, fresh and dry mass of aerial part and root, and total biomass. The Dickson Quality Index (DQI) was calculated and the macro and micronutrient content of the aerial part and root. The accumulation of macronutrients in the root system followed the order of N>K>P>Ca>Mg>S, and aerial part of N>Ca>K>P>Mg>S, in the two vegetative structures N and S were in lower concentration. For micronutrients, the accumulation in the root system occurred with Fe>Zn>Mn>Cu>B, and aerial part with Fe>Mn>Zn>B>Cu. It was noted that in the two vegetative structures the Fe content was more concentrated. The use of SS in the substrate formulation proved effective in obtaining viable seedlings for field planting, being recommended the treatment with 60% SS + 40% organic compost.

Resumo O lodo de esgoto (LE) possui teor nutricional e tem sido aplicado no cultivo de mudas. Assim, o objetivo deste estudo foi avaliar a qualidade de mudas de Malpighia emarginata DC. produzidas em diferentes substratos com LE. Os tratamentos foram implantados com adição de LE, e após 180 dias de semeadura as seguintes características das mudas foram avaliadas: comprimento da parte aérea e do sistema radicular, diâmetro da base do caule, número de folhas, massa fresca e seca da parte aérea e da raiz, biomassa total. O Índice de Qualidade de Dickson (IQD) foi calculado junto aos teores de macro e micronutrientes da parte aérea e da raiz. O acúmulo de macronutrientes no sistema radicular seguiu a ordem de N>K>P>Ca>Mg>S, e parte aérea N>Ca>K>P>Mg>S, nas duas estruturas vegetativas N e S estiveram em menor concentração. Para os micronutrientes, o acúmulo no sistema radicular ocorreu Fe>Zn>Mn>Cu>B, e na parte aérea Fe>Mn>Zn>B>Cu. Observou-se que nas duas estruturas vegetativas o teor de Fe foi mais concentrado. A utilização de LE na formulação do substrato mostrou-se eficaz na obtenção de mudas viáveis para o plantio em campo, sendo recomendado o tratamento com 60% de LE + 40% de composto orgânico.

RESUMO

Biosolids are a by-product of wastewater treatment, and their nutritional composition makes them ideal for fertilizing crops. However, pre-treatments, such as conditioning and/or (vermi)composting, are often required to stabilize the product and remove pathogens. Biosolids, cow manure, and a 50-50% mixture were conditioned for 21 days, composted or vermicomposted with Eisenia fetida (Savigny 1826) for 28 days, and applied to soil cultivated with wheat (Triticum sp. L.), while emissions of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were monitored. Emissions of CH4 were large from the biosolid and N2O from the cow manure during conditioning. Emissions of CH4 remained high during (vermi)composting of the biosolids, while the emissions of N2O from the cow manure dropped. The addition of E. fetida did not affect the emissions of greenhouse gases during (vermi)composting. The emission of N2O was higher when (vermi)composted biosolid was applied to soil cultivated with wheat than when (vermi)composted cow manure was applied. The global warming potential (GWP) of the sum of the emitted greenhouse gases (GHG) during conditioning, (vermi)composting, and when the final product was applied to soil was 3 times larger from the cow manure than from the biosolid, but mixing biosolid with cow manure eliminated that difference. It was concluded that mixing biosolid with cow manure might be a simple way to reduce the GWP of the emitted GHG during storage, (vermi)composting, and when applied to soil.

Assuntos

RESUMO

Sewage sludge biochar (SSB) is a multi-nutrient fertilizer with very low K concentration. This study presents a novel K-enriched SSB fertilizer with the potential to increase K use efficiency by crops. The object of this work was therefore to evaluate the physical-chemical, morphological and mineralogical characteristics of a SSB organomineral fertilizer (OSSB) enriched with K. SSB was enriched with KCl and K2SO4 using three technological methods (granules, pellets and powders). The enrichment of SSB with K ensured a K2O content about 75 times higher than the pure SSB. Organominerals in powder form had higher levels of total nitrogen, calcium, sulfur, phosphorus and higher pH than granules and pellets. The morphology and physical characteristics of enriched OSSBs were more influenced by the form of the fertilizer than by the source of K. In general, the enriched OSSBs are influenced by the quantities of feedstocks and the enrichment technology.

Assuntos

RESUMO

ABSTRACT During the most recent decades, advances have been made to reduce the environmental impact by anthropogenic activities that constantly release toxic components into the environment, generating instability and damage to the health of biological communities. Among the different pollutants, heavy metals are important by virtue of their properties, which hinder their degradation or transformation into other less toxic compounds. Chromium is one of the metals of greatest global interest due to its use in multiple industries. Conventional methods using chromed materials in their processes, not only throw considerable amounts of waste into the environment, but also give little account of the fraction of hexavalent chromium (Cr6+) present in certain ecosystems. Bioremediation has been proposed as an economically viable and environmentally sustainable alternative. This work aimed to evaluate the chromium reduction capacity by bacteria isolated from a biosolids matrix obtained at the San Fernando Wastewater Treatment Plant (WWTP), located in Medellín (Colombia). Biosolids samples were grown in a nutrient agar enriched with different concentrations of Cr6+. The strains presenting the greater tolerance to chromium were isolated to perform reduction tests by triplicate, monitoring the concentration of the metal over time. Seven different bacterial species were obtained, among which Staphylococcus saprophyticus, Ochrobactrum anthropic, and Bacillus cereus showed the greatest ability to reduce Cr6+ (29.0%, 61.1 and 100%, at 96 h) respectively.

RESUMEN En las últimas décadas se ha trabajado activamente para reducir el impacto ambiental generado por las actividades antrópicas que constantemente liberan componentes tóxicos al ambiente generando inestabilidad y daños en la salud de las comunidades biológicas. Entre los diferentes contaminantes, los metales pesados revisten importancia en virtud de sus propiedades, que dificultan su degradación o transformación en otros compuestos menos tóxicos. El cromo es uno de los metales de mayor interés a nivel global por su uso en múltiples industrias. Los métodos convencionales que utilizan materiales cromados en sus procesos, no sólo arrojan cantidades considerables de residuos al ambiente, sino que dan poca cuenta de la fracción de Cr6+ presente en determinados ecosistemas. La biorremediación se ha propuesto como una alternativa económicamente viable y ambientalmente sostenible. El propósito del presente trabajo fue evaluar la capacidad de reducción de cromo por bacterias, aisladas de una matriz de biosólidos de la Planta de tratamiento de aguas residuales (PTAR) San Fernando en la ciudad de Medellín-Colombia. Muestras de biosólidos se cultivaron en Agar Nutritivo enriquecido con diferentes concentraciones de Cr6+. Las cepas que presentaron mayor tolerancia al cromo fueron aisladas para realizar ensayos de reducción por triplicado, monitoreando la concentración del metal en el tiempo. Se obtuvieron siete especies bacterianas diferentes dentro de las cuales se destacaron Staphylococcus saprophyticus, Ochrobactrum anthropi y Bacillus cereus por la capacidad de reducir Cr6+ a 96 h con eficiencias de 29.0%, 61.1% y 100%, respectivamente.