No abstract

No abstract

No abstract

Zero-discharge constructed wetland environments are more prone to the accumulation of pollutants. The relationship between filter media and microbial communities in this type of environment is still poorly known. We conducted bench-scale studies of different filter media (polyurethane foam, blast-furnace slag, and loofah) in these systems by simulating the batch operation with light greywater for 433 days. Physicochemical and microbiological analyses (scanning electron microscopy and polymerase chain reaction electrophoresis denaturing gradient gel) were used. In all systems, anoxic environments prevailed. These environments were crucial for methanogenesis and sulfidogenesis processes, which are primarily responsible for organic material conversion. The chemical oxygen demand/sulfate (COD/SO) ratio was the limiting factor in the competition of microorganisms involved in these processes. This condition, combined with the neutral-alkaline pH, also allowed Chloroflexi phylum bacteria to oxidize sulfide to sulfate and elemental sulfur in all studied media. The results showed strong evidence supporting that the microbial community formed in the present study is more related to operational/environmental conditions than to the different tested filter media. Thus, this demonstrates that the control of interactive effects between pH, redox potential, and the COD/SO ratio can prevent the accumulation and/or release of sulfide in anoxic environments.

The aim of this article is to characterize the current situation of family farmers or smallholders in Brazil and establish a connection with the rural public policies that exist in the country. This study analyzed the most current available data regarding family farming in Brazil, which included almost 4.7 million smallholders and their characteristics. Two analytical tools for unsupervised learning were combined, Principal Component Analysis (PCA) and K-means clustering, which enabled the analysis of such a large database and the extraction of information concerning this sector. It was found that cooperative smallholders are considerably more likely to achieve higher incomes. A family farmer's income and productivity are related to their region and are higher in the South and Southeast and lower in the Northeast region. Crop diversification presented a negative impact on family farming activity, although this practice is considered highly important for agricultural sustainability. These results confirm, based on the data, empirical findings regarding the sector and also reveal new information such as the negative impact that rural assistance services are demonstrated to have on smallholders' income. Therefore, this study provides essential information to support policy makers in the process of formulating better and more efficient policies in order to strengthen smallholders in Brazil and guarantee food security in the future.

Surfactants are among the main chemical contaminants in greywater (GW) and can cause severe health issues in humans and aquatic organisms. We assessed the performance of a multistage constructed wetland system (EvaTAC) for GW treatment and capacity of the microbial community in linear alkyl benzene sulfonate (LAS) biodegradation. Physicochemical analyses were performed over 497 d, and biomass samples were collected for high-throughput DNA sequencing. The system was predominated by anaerobic conditions and received an average chemical oxygen demand (COD) and LAS of 374 and 32 mg·L−1, with removal rates of 66% and 43%, respectively. A positive correlation between COD and LAS suggested COD as a design parameter for LAS removal. We identified microbial genera participating in hydrolysis, fermentation, syntrophy, acetogenesis, methanogenesis, surfactant degradation, and sulphate reduction. Among the 15 surfactant-degrading genera, Pseudomonas was predominant. Community richness and diversity indices were comparable between subsystems, with a slight decrease in diversity observed towards the outlet. Among the LAS degraders, Rhodopseudomonas palustris had the highest relative abundance of operational taxonomic unit (OTU)s in all samples and the highest richness in the anaerobic chamber. The patterns in microbial community composition and environmental conditions suggest that LAS biodegradation occurred throughout the EvaTAC system.