Methanogens, sulphate and heavy metals: a complex system

Anaerobic digestion (AD) is a well-established technology used for the treatment of wastes and wastewaters with high organic content. During AD organic matter is converted stepwise to methane-containing biogasa renewable energy carrier. Methane production occurs in the last AD step and relies on methanogens, which are rather sensitive to some contaminants commonly found in wastewaters (e.g. heavy metals), or easily outcompeted by other groups of microorganisms (e.g. sulphate reducing bacteria, SRB). This review gives an overview of previous research and pilot-scale studies that shed some light on the effects of sulphate and heavy metals on methanogenesis. Despite the numerous studies on this subject, comparison is not always possible due to differences in the experimental conditions used and parameters explained. An overview of the possible benefits of methanogens and SRB co-habitation is also covered. Small amounts of sulphide produced by SRB can precipitate with metals, neutralising the negative effects of sulphide accumulation and free heavy metals on methanogenesis. Knowledge on how to untangle and balance sulphate reduction and methanogenesis is crucial to take advantage of the potential for the utilisation of biogenic sulphide as a metal detoxification agent with minimal loss in methane production in anaerobic digesters.The research was financially supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013 under REA agreement 289193

Wetlands for wastewater treatment and subsequent recycling of treated effluent : a review

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used

Lake sediment fecal and biomass burning biomarkers provide direct evidence for prehistoric human-lit fires in New Zealand

Deforestation associated with the initial settlement of New Zealand is a dramatic example of how humans can alter landscapes through fire. However, evidence linking early human presence and land-cover change is inferential in most continental sites. We employed a multi-proxy approach to reconstruct anthropogenic land use in New Zealand’s South Island over the last millennium using fecal and plant sterols as indicators of human activity and monosaccharide anhydrides, polycyclic aromatic hydrocarbons, charcoal and pollen as tracers of fire and vegetation change in lake-sediment cores. Our data provide a direct record of local human presence in Lake Kirkpatrick and Lake Diamond watersheds at the time of deforestation and a new and stronger case of human agency linked with forest clearance. The first detection of human presence matches charcoal and biomarker evidence for initial burning at c. AD 1350. Sterols decreased shortly after to values suggesting the sporadic presence of people and then rose to unprecedented levels after the European settlement. Our results confirm that initial human arrival in New Zealand was associated with brief and intense burning activities. Testing our approach in a context of well-established fire history provides a new tool for understanding cause-effect relationships in more complex continental reconstructions

Chlorinated and brominated polycyclic aromatic hydrocarbons in ambient air: seasonal variation, profiles, potential sources, and size distribution

Chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs, respectively) are a new derivative group of PAHs. These halogenated PAHs (Halo-PAHs) have been reported to be carcinogenic and are considered emerging persistent organic pollutants. Gaining a clear understanding of the distribution and behavior of these ubiquitous organic pollutants is essential for the control and mitigation of their emission into the environment. However, research into the characteristics of Halo-PAHs in the atmosphere has been somewhat limited. This review paper thus aims to provide an overview of the seasonal patterns, profiles, potential sources, and particle-size distributions of atmospheric ClPAHs and BrPAHs with 3-5 rings. Most previous studies have focused on particulate Halo-PAHs and reported that their levels are higher during the cold season than during the warm season, with this seasonal variation more apparent for ClPAHs than for BrPAHs. In terms of their phase distribution, ClPAHs and BrPAHs share a similar trend, with their gaseous concentrations highest in summer and lowest in winter and their particulate concentrations exhibiting the opposite trend. Halo-PAH profiles have been shown to differ between sampling locations, possibly reflecting differences in the potential sources present at these sites, e.g., coal burning, traffic emissions, and industrial activity. The majority of Halo-PAHs tend to accumulate as ultrafine particles with an aerodynamic diameter of less than 1.0 mu m. Overall, a detailed understanding of the characteristics of Halo-PAHs in the atmosphere has yet to be achieved; hence, further research on atmospheric Halo-PAHs is necessary

Transcriptome-Wide Association Study Reveals Potentially Candidate Genes Responsible for Milk Production Traits in Buffalo

Identifying key causal genes is critical for unraveling the genetic basis of complex economic traits, yet it remains a formidable challenge. The advent of large-scale sequencing data and computational algorithms, such as transcriptome-wide association studies (TWASs), offers a promising avenue for identifying potential causal genes. In this study, we harnessed the power of TWAS to identify genes potentially responsible for milk production traits, including daily milk yield (MY), fat percentage (FP), and protein percentage (PP), within a cohort of 100 buffaloes. Our approach began by generating the genotype and expression profiles for these 100 buffaloes through whole-genome resequencing and RNA sequencing, respectively. Through comprehensive genome-wide association studies (GWAS), we pinpointed a total of seven and four single nucleotide polymorphisms (SNPs) significantly associated with MY and FP traits, respectively. By using TWAS, we identified 55, 71, and 101 genes as significant signals for MY, FP, and PP traits, respectively. To delve deeper, we conducted protein–protein interaction (PPI) analysis, revealing the categorization of these genes into distinct PPI networks. Interestingly, several TWAS-identified genes within the PPI network played a vital role in milk performance. These findings open new avenues for identifying potentially causal genes underlying important traits, thereby offering invaluable insights for genomics and breeding in buffalo populations

Pretreatment of Miscanthus × giganteus using aqueous ammonia with hydrogen peroxide to increase enzymatic hydrolysis to sugars

BACKGROUND: Miscanthus×giganteus (M.×giganteus) is a potential source for bioethanol or other useful products. Pretreatment of lignocellulosic biomass is an essential step prior to enzymatic hydrolysis to sugars and fermentation to bioethanol. RESULTS: In this work, a one-step process uses aqueous ammonia with or without hydrogen peroxide; a proposed two-step process uses aqueous ammonia in the first step and hydrogen peroxide in the second step. In the two-step process, overall 89.5% lignin is removed. The pretreated biomass is followed by using cellulase and β-glucosidase to convert cellulose and hemicellulose from the recovered solid to fermentable sugars. The conversion of cellulose to glucose is 90.2% and to xylose is 73.4%. Characterization data are obtained for the recovered solid using scanning electron microscopy (SEM), attenuated total reflection-infrared spectroscopy (ATR-IR), and X-ray diffraction (XRD) for better understanding of the two-step process. CONCLUSION: Results from the two-step process using aqueous ammonia and hydrogen peroxide separately are much better than those from the one-step process for removing lignin and for enhancing conversion to sugars by enzymatic hydrolysis. © 2013 Society of Chemical Industry

Pretreatment of Miscanthus × giganteus using aqueous ammonia with hydrogen peroxide to increase enzymatic hydrolysis to sugars

BACKGROUND: Miscanthus×giganteus (M.×giganteus) is a potential source for bioethanol or other useful products. Pretreatment of lignocellulosic biomass is an essential step prior to enzymatic hydrolysis to sugars and fermentation to bioethanol. RESULTS: In this work, a one-step process uses aqueous ammonia with or without hydrogen peroxide; a proposed two-step process uses aqueous ammonia in the first step and hydrogen peroxide in the second step. In the two-step process, overall 89.5% lignin is removed. The pretreated biomass is followed by using cellulase and β-glucosidase to convert cellulose and hemicellulose from the recovered solid to fermentable sugars. The conversion of cellulose to glucose is 90.2% and to xylose is 73.4%. Characterization data are obtained for the recovered solid using scanning electron microscopy (SEM), attenuated total reflection-infrared spectroscopy (ATR-IR), and X-ray diffraction (XRD) for better understanding of the two-step process. CONCLUSION: Results from the two-step process using aqueous ammonia and hydrogen peroxide separately are much better than those from the one-step process for removing lignin and for enhancing conversion to sugars by enzymatic hydrolysis. © 2013 Society of Chemical Industry