Karina Querne de Carvalho

Chitosan, a biopolymer derived from chitin, boasts a broad spectrum of industrial and environmental applications. Owing to its porosity, amino and hydroxyl groups, and other inherent characteristics, this polymer presents a promising option for various applications, particularly in the adsorption of emerging pollutants and the fabrication of bioplastics and biosensors. However, chitosan faces limitations concerning polymer swelling, low mechanical strength, and solubility. These drawbacks can be overcome by incorporating composites into the chitosan matrix, thereby enhancing the overall strength of the polymer and expanding its environmental utility. Thus, this review explores the environmental applications of chitosan, mainly in pollutant removal from air, soil, and water, its utilization in bioplastics and biosensors, as well as an exploration of supplementary materials such as diatomaceous earth, zeolite, and bentonite, which, when combined with chitosan, exhibit remarkable efficacy in environmental decontamination.

O comércio internacional de resíduos é central no debate sobre sustentabilidade, governança ambiental e economia circular. Este estudo analisa a literatura científica global sobre o tema, com ênfase nas dinâmicas econômicas, institucionais e ambientais associadas à importação desses materiais. Metodologicamente, realizou-se uma revisão semi-sistemática da literatura nas bases Scopus, Web of Science e Google Scholar, considerando publicações de 2016 a 2026. Os resultados indicam que a política chinesa National Sword esteve associada à redistribuição dos fluxos e, segundo a literatura, a impactos ambientais nos países receptores, evidenciando assimetrias na economia circular. Enquanto resíduos de alto valor (mineração urbana) operam em redes estruturadas, materiais de baixo valor (plásticos mistos) migram para “zonas cinzentas” regulatórias devido a lacunas na Convenção de Basileia. Diante da rigidez dos modelos preditivos e do caráter reativo das alfândegas, os achados indicam a necessidade de desenvolvimento e avaliação de um modelo de indicadores integrados (ambientais, logísticos e aduaneiros) em tempo real, fortalecendo o papel dos portos como barreiras potenciais de monitoramento e triagem preliminar contra o dumping ambiental.

Países com economias frágeis enfrentam maiores desafios no manejo de resíduos sólidos, e a Guiné-Bissau não foge a essa realidade, apresentando limitações no tratamento dos resíduos orgânicos. A expansão demográfica e econômica não foi comboiada pela ampliação dos serviços de coleta e tratamento, resultando no acúmulo de resíduos nas áreas urbanas. Este estudo tem como objetivo avaliar o gerenciamento de resíduos sólidos orgânicos no Mercado de Caracol, em Bissau. Trata-se de um estudo de caso exploratório-descritivo, com abordagem qualitativa, fundamentado em pesquisa bibliográfica e entrevistas semiestruturadas com usuários do mercado e representantes da Câmara Municipal de Bissau, além de questionários abertos e de múltipla escolha. Para análise dos dados, empregou-se a técnica de análise de conteúdo de Bardin cujos resultados foram sistematizados em gráficos. Os resultados demonstraram que o gerenciamento de resíduos sólidos orgânicos no Mercado de Caracol ocorre de maneira inadequada, pois não existe um sistema de coleta seletiva, sendo os resíduos sólidos orgânicos e inorgânicos descartados conjuntamente. Foram identificadas possíveis causas para a ausência deste necessário gerenciamento de resíduos, dentre as quais a ausência de leis e normas sobre o tema, bem como propostas medidas de auxílio neste processo, tais como instalação de recipientes adequados, capacitação dos usuários do mercado e promoção de atividades educativas, realizando-se a correta destinação desses resíduos.

The estimation of construction and demolition waste (CDW) generation is essential for sustainable planning and effective waste management on construction sites. However, conventional methods often fail to meet the practical demands of the sector. This study investigated the use of artificial neural networks (ANN) as a predictive tool for CDW quantification. Simulations were performed with samples of 5,000 data points (A) and 10,000 data points (B), followed by validation with a sample of 360 data points (R) collected from construction sites in Curitiba, Paraná state, Brazil. This approach allowed for a comprehensive evaluation of the predictive accuracy and practical applicability of the ANN. The best performance was obtained with sample B, using an ANN configured with two input variables, ten neurons in the hidden layer, and three training cycles. In the simulations, the model presented a coefficient of determination (R²) of 1.00, a root mean squared error (RMSE) of 6.55 kg, and a mean absolute percentage error (MAPE) of 0.00013%. In the validation, an R² of 0.83 was obtained, along with an RMSE of 4,337.69 m³, and accurate estimates in over 60% of cases (MAPE). The results demonstrated the viability of using ANNs to improve CDW estimation, contributing to decision-making and the development of more efficient waste reduction strategies in civil construction.

The support media of upflow anaerobic hybrid reactors (UAHB) facilitates the formation and retention of microbial biofilm and the contact between the influent and microorganisms. Previous studies demonstrated the importance of support media height (SMH) to organic matter removal; however, the influence of this parameter in the UAHB reactor performance under varying conditions is still a gap. The Central Composite Design (CCD) method was applied to optimize the removal of organic matter by varying the cross-sectional area and height of the reactor based on 42 studies. The modelling indicated 72-87% COD removal efficiencies with 0.007 m² cross-sectional area and 0.75 m height, with 5.5 L total volume. Thus, three pilot-scale UAHB reactors, filled with Corrugated Polyvinyl Chloride (PVC) rings at different heights (6, 15, and 24 cm), were operated with a hydraulic retention time of 10 h, treating synthetic effluent with a COD of 490 mgO₂ L^-1. Unlike previous studies, this study evaluated identical UAHBs operating in parallel under controlled conditions. The UAHB reactors presented stability, buffering capacity, and neutral pH during the operation. The reactor with higher SMH (24 cm) achieved higher removal efficiencies of turbidity (90%), COD (72.6%), and TS (63%). Variations in SMH affected reactor performance, as corroborated by the negative and 'very strong' correlation for turbidity, COD, and TS and a 'moderate' correlation for fixed and volatile solids. The novelty of this study lies in its comprehensive assessment of how varying SMH affects UAHB reactor performance, guiding future advancements in its design for efficient wastewater treatment.

The objective of this research was to evaluate the influence of the recirculation rate on nutrient removal and on the hydrodynamic behavior of a fixed-bed anaerobic-aerobic reactor, operated on a bench scale, in the treatment of sanitary effluent. Different recirculation ratios (0.5, 1.0 and 1.5) were tested with a constant air flow of 10 L min-1. During the operation period, the physicochemical parameters were analyzed. Hydrodynamic tests were also carried out using pulse stimulus-response tests with the eosin Y tracer, to evaluate the hydrodynamic behavior and investigate anomalies. The 50% recirculation ratio proved to be the condition with the highest removal efficiency for total solids (83%). The 100% recirculation ratio was the most efficient for TKN (97%) and Nammon (99%). For the recirculation ratio of 150%, the highest removal efficiency was for phosphorus (33%). As for hydrodynamic behavior, according to the correlation of the theoretical uniparametric models tested, it is possible to state that the recirculation ratios of 50%, 100% and 150% presented correlation coefficients that indicate complete mixing, with good hydraulic efficiency for recirculation. of 100%. By varying these factors, it was possible to verify the influence of the recirculation ratio on the removal of nitrogen and phosphorus, as well as on the hydrodynamic behavior of the reactor.

O objetivo deste trabalho foi avaliar o desempenho de um sistema combinado utilizado na remoção de nitrogênio e fósforo, com variação do tempo de detenção hidráulica (TRH) e da taxa de recirculação (R). O sistema foi composto por três reatores sequenciais operados em série, composto por um reator anaeróbio (20 L), um reator aeróbio de leito fixo (19 L) e um filtro percolador (16 L). Foram testadas as razões de recirculação de 150, 100 e 50% e TDH de 9, 7 e 5 h, com vazão de aeração constante de 10 L min-1. Para avaliação do sistema foram analisados temperatura do líquido, pH, alcalinidade total, alcalinidade do bicarbonato, ácidos voláteis, oxigênio dissolvido, demanda química de oxigênio, nitrogênio total Kjeldahl, nitrogênio amoniacal, nitrito, nitrato e fósforo total. O sistema combinado atingiu eficiências de remoção de matéria orgânica de 99%, 98% e 98% para as taxas de recirculação de 50, 100 e 150%, respectivamente. Sob as mesmas taxas de R, as eficiências de remoção de NTK resultaram em 96, 89 e 87%, e as eficiências de remoção de PT em 78, 82 e 77%, respectivamente. Quando operado com TDH de 9, 7 e 5 h, o sistema combinado atingiu eficiências de remoção de 86, 96 e 98% para DQO, 90, 93 e 94% para NTK e 74, 89 e 95% para PT, respectivamente. A melhor condição operacional foi estabelecida experimentalmente com a taxa de recirculação de 150% e TDH de 5 h. Entretanto, após a validação experimental por DCCR (por desejabilidade), a condição operacional ótima resultou na taxa de recirculação de 123% e TDH de 5 h para eficiências de remoção de NTK e TP.

This study investigated the influence of hydraulic retention time (HRT) variation and the presence of macrophytes on the efficiency of two pilot-scale hybrid-constructed wetlands (HCWs) treating urban streamwater contaminated with nontreated sanitary sewage contributions from the surrounding communities. Each HCW comprises a vertical unit (VF) and a horizontal unit (HF) filled with sand and gravel. HCW-P was planted withEichornia crassipes onto the filtering media, and HCW-C was set up as a control unit with no macrophytes. The novelty of this study consists of evaluating the combination of these factors (HRT and macrophytes) in the operation of HCWs for removing organic matter and nutrients. The operation of the HCWs was divided into step I, with a hydraulic retention time (HRT) of 9 days for 133 days, and step II, with an HRT of 5 days for 131 days. Neither HRT variation (p-value = 0.7691) nor the presence of macrophytes (p-value = 0.0941) influenced the COD removal, as the HCWs achieved high removal efficiencies (>87%) during the operation. HCW-P achieved higher total nitrogen (TN) removal efficiencies in steps I and II (56% and 78%) compared to HCW-C (31% and 48%) during the operation, demonstrating the improvement in removing TN due to the presence of macrophytes (p-value ≤ 0.05). In addition, the shorter HRT promoted an increase of 22% in TN removal for HCW-P (p-value ≤ 0.05). The macrophytes and longer HRT enhanced total ammonia nitrogen (TAN) removal, as HCW-P (46% and 88%) achieved higher removal efficiencies than HCW-C (29% and 72%) in steps I and II, respectively (p-value ≤ 0.05). Regarding total phosphorus (TP), HCW-C and HCW-P achieved removal efficiencies of 63% and 89% in step I and 69% and 96% in step II, confirming the influence of HRT and macrophytes on TP removal. Finally, macrophytes demonstrated adaptability and resilience to the operational conditions, even when fixed in HCWs, which presented robustness in removing organic matter and nutrients from the urban streamwater via biofilm assimilation and adsorption under HRT variations.