Isabela da Silva Pedro Rochinha

Mining activities can generate effluent contamination with potentially toxic elements such as iron (Fe) and manganese (Mn), posing environmental and technological challenges, particularly during mine closure and the decommissioning of mining structures. Constructed wetlands have been proposed as a nature-based, passive, and low-cost alternative for treating mining effluents; however, the mechanisms, controlling factors, and performance patterns governing Fe and Mn removal remain insufficiently synthesized across different wetland configurations and effluent types. This study performs a systematic review combined with a meta-analysis to synthesize Fe and Mn removal mechanisms, quantify removal performance, and identify the operational, hydraulic, physicochemical, and biological factors influencing system performance. A total of 55 primary studies were analyzed, comprising 155 observations for Fe and 96 for Mn. The results indicate that Fe removal is generally high (median ln(RR)ln(RR) = −1.89), whereas Mn removal is more variable and less efficient (median ln(RR)ln(RR) = −0.59), highlighting the greater complexity of Mn removal processes. Fe removal was mainly associated with hydraulic retention time and pH, while Mn removal was more strongly influenced by redox conditions and the type of support material, particularly mineral substrates. Overall, wetland performance is governed by the interaction among hydraulic retention time, pH buffering, redox conditions, support media reactivity, vegetation-mediated rhizosphere processes, and influent geochemistry. A significant research gap remains regarding neutral mine drainage (NMD), since this effluent category was not explicitly reported in the primary studies and could not be robustly isolated as an independent subgroup, especially in relation to Mn removal efficiency.

Constructed wetlands are nature-based technologies widely used for the treatment of wastewater and contaminated surface water. This study evaluated the efficiency of free water surface (FWS) and horizontal subsurface flow (HSSF) constructed wetlands in reducing the turbidity of mine spoil rainwater using the w-C* model. Different hydraulic retention times (2, 4, and 6 days) were tested, and the influence of macrophyte type and substrate on the w parameter was investigated. Model calibration was performed based on correlation coefficients (R), coefficient of determination (R²), Nash–Sutcliffe efficiency (NSE), and root mean square error (RMSE). The results indicated a 99% reduction in turbidity, with average values of R = 0.87 ± 0.05 (FWS) and 0.87 ± 0.03 (HSSF), and NSE of 0.76 ± 0.04 (FWS) and 0.74 ± 0.07 (HSSF), demonstrating good agreement between observed and predicted data. The settling rate (w) ranged from 0.16 to 0.40 m·d⁻¹ in FWS and from 0.20 to 0.70 m·d⁻¹ in HSSF, with the lowest value recorded in the control (0.09 m·d⁻¹). The best performances were observed in FWS-P with Pistia stratiotes (0.40 m·d⁻¹) and HSSF with Typha domingensis (0.70 m·d⁻¹), demonstrating that vegetation, combined with the use of medium-grain substrate (9.5–19.0 mm), enhances turbidity removal. The w-C* model proved to be a robust tool for describing the kinetics of suspended colloidal particle removal in constructed wetlands, providing valuable insights for optimizing hydraulic parameters and design criteria for full-scale application.

This study investigated nutrient removal in tubular photobioreactors (PBR) illuminated by Light-Emitting Diodes (LEDs), treating the effluent from an Up-Flow Anaerobic Sludge Blanket (UASB) system followed by a Biological Percolator Filter (BPF). Designed as a tertiary treatment step, the PBRs aimed to minimize eutrophication while promoting microalgal growth through CO₂ assimilation released by bacterial activity—resulting in biomass with potential for value-added applications. The objective of this study was to elucidate the mechanisms responsible for nitrogen and phosphorus removal under a controlled environment. A key novelty of this work lies in the comparative evaluation of red and blue LED illumination in the pilot-scale PBRs used for wastewater treatment. All systems achieved >99% ammoniacal nitrogen removal, while soluble phosphorus removal achieved up to 95%. The highest nitrogen removal rate was observed under red light (10.60 mg L⁻¹ d⁻¹), although there was no difference for blue light, while blue light was more effective for phosphorus removal (3.28 mg L⁻¹ d⁻¹). Assimilation was the primary removal mechanism, supported by microalgae–bacteria interactions and artificial CO₂ injection. The research highlights distinct advantages of each light illumination: the blue-light photobioreactor was more suitable for tertiary treatment, whereas the red-light system showed potential for microalgal biomass-based co-product generation.

Surface runoff in mining areas transports dissolved and suspended particles into water bodies, known as mine spoil rainwater, contributing to increases in turbidity. The aim of this study was to evaluate the effectiveness of horizontal flow wetlands, free water surface (FWS), and subsurface flow (HSSF) in reducing turbidity >1500 NTU from a synthetic mine spoil rainwater. Macrophytes, support media, hydraulic retention time (HRT), and hydraulic loading rate (HLR) were analyzed. The HSSF T. domingensis in gravel #1 achieved a 99% reduction for 4-day HRT, with residual turbidity of 7 ± 3 NTU for 27.43 L m⁻² d⁻¹ HLR. The FWS P. stratiotes achieved a 99% reduction for 6-day HRT, with residual turbidity of 11 ± 5 NTU for 36.53 L m⁻² d⁻¹ HLR. P. stratiotes free root structures promoted interception of suspended colloidal particles, resulting in a better performance. The dense root structure of T. domingensis spreading through the pores of the substrate provided better efficiency than N. humboldtiana. However, N. humboldtiana proved to be promising as a native species. The use of small granulometry alkaline support media (9 to 19 mm) was highlighted. Therefore, this research proves the efficiency of constructed wetlands in reducing high turbidity and provides optimized parameters for this technology application.

A alimentação tem um papel de suma importância no processo de desenvolvimento dos seres vivos. Porém, observa-se que, para os seres humanos, o ato de se alimentar envolve, além dos aspectos nutricionais, a cultura, características socioeconômicas e o meio ambiente. Objetivou-se, então, avaliar os impactos ambientais gerados pelas escolhas alimentares em uma comunidade e analisar, no âmbito socioeconômico, a acessibilidade de indivíduos de baixa renda aos alimentos que melhor se enquadram na definição de dietas adequadas e sustentáveis. Tendo como base hábitos alimentares de um grupo de moradores da Comunidade de Manguinhos (RJ), foram analisadas as pegadas de carbono e hídrica, a partir de dois cardápios simulados. Considerando a caracterização socioeconômica da população, também foram analisados os fatores relacionados à acessibilidade à alimentação sustentável por famílias de baixa renda. Há um elevado consumo de alimentos ultraprocessados e de origem animal entre os indivíduos da Comunidade de Manguinhos. No cardápio simulado com padrão ocidental as refeições com carnes vermelhas e os alimentos ultraprocessados corresponderam a emissões de carbono de 46% e 39%, respectivamente, e pegadas hídricas de 39% e 34%, respectivamente. Há a necessidade de mudanças nos sistemas alimentares e em como ocorre a distribuição. Programas de educação nutricional e ambiental são necessários para famílias com menores rendas, visando a auxiliá las a terem acesso a alimentos seguros e a fazerem escolhas conscientes quanto à alimentação.