• Energy Research

Inland water bodies (particularly ponds) emit a significant amount of greenhouse gases (GHGs), particularly methane (CH4), carbon dioxide (CO2), and a comparatively low amount of nitrous oxide (N2O) to the atmosphere. In recent decades, ponds (<10,000 m2) probably account for about 1/3rd of the global lake perimeter and are considered a hotspot of GHG emissions. High nutrients and waterlogged conditions provide an ideal environment for CH4 production and emission. The rate of emissions differs according to climatic regions and is influenced by several biotic and abiotic factors, such as temperature, nutrients (C, N, & P), pH, dissolved oxygen, sediments, water depth, etc. Moreover, micro and macro planktons play a significant role in CO2 and CH4 emissions from ponds systems. Generally, in freshwater bodies, the produced N2O diffuses in the water and is converted into N2 gas through different biological processes. There are several other factors and mechanisms which significantly affect the CH4 and CO2 emission rate from ponds and need a comprehensive evaluation. This study aims to develop a decisive understanding of GHG emissions mechanisms, processes, and methods of measurement from ponds. Key factors affecting the emissions rate will also be discussed. This review will be highly useful for the environmentalists, policymakers, and water resources planners and managers to take suitable mitigation measures in advance so that the climatic impact could be reduced in the future.

Dissolved arsenic typically results from chemical weathering of arsenic rich sediments and is most often found in oxidized forms in surface water. The mobility of arsenic is controlled by its valence state and also by its association with iron oxides minerals, the forms of which are both influenced by abiotic and biotic processes in aqueous environment. In this study, speciation methods were used to measure and confirm the presence of reduced arsenic species in the surface water of Frenchman creek, a gaining stream that crosses the Colorado-Nebraska border. Selective extraction analysis of aquifer and stream bed sediments shows that the bulk of the arsenic occurs with labile iron-rich oxy(hydroxide) minerals. Total dissolved arsenic in surface and groundwater ranged from ~3-18 µg L-1, and reduced arsenic species comprise about 41% of the total dissolved arsenic (16.0 µg L-1) in Frenchman creek. Leachable arsenic in the aquifer sediment samples ranged up to 1553 µg kg-1, while samples from Frenchman creek bed sediments contained 4218 µg kg-1. Dynamic surface and groundwater interaction sustains arsenite in iron-rich surface headwaters, and the implied toxicity of reduced arsenic in this hydrogeological setting, which can be important in surface water environments around the globe.

AbstractThe aim of the present investigation was to study the removal of total chromium from the electroplating industry effluent using Weathered Basalt Andesite Products (WBAP). The reduction of Cr (VI) to Cr (III) by hydrazinium sulfate (HS) was adopted. The sorbent WBAP before and after sorption, was characterized by FTIR, X‐ray diffraction, SEM, TEM, and TGA methods. The effects of various parameters such as hydronium ion concentration, shaking time, sorbent dose, initial metal ion concentration, and temperature on the removal of Cr (III) from aqueous solution was studied. Thermodynamic parameters (ΔH0, ΔS0, and ΔG0) for the sorption process were evaluated. Freundlich, Langmuir, and Dubinin‐Kaganer‐Radushkevich isotherm models were examined to describe the sorption isotherms. Analysis of sorption results obtained showed that the sorption pattern followed the Freundlich sorption isotherm. Langmuir maximum sorption capacity of WBAP for Cr (III) was found to be 12.07 mg/g. The process follows Pseudo second order rate and surface diffusion is identified as the predominating mechanism. The effluent having average discharge of total chromium 90 mg/L was successfully treated with the same sorbent with a removal of 85.65%. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Floating treatment wetlands (FTWs), also called constructed floating wetlands or floating islands, are a recent innovation in constructed wetlands (CWs) inspired by natural wetlands. In FTWs, emergent plants grown hydroponically on buoyant mats are used for wastewater treatment, which makes them far more economical than other CWs. The objective of this study was to evaluate the performance of FTWs for the treatment of municipal wastewater from an urban drain using native plant species Canna indica and Phragmites australis. A pilot-scale experiment was carried out using four FTW treatment cells with different plant coverages for pollutant removal: C1 (Canna indica, 100% coverage), C2 (Phragmites australis, 100% coverage), C3 (Phragmites australis, 50% coverage), and C4 (control). Overall, treatment cells with Canna indica and Phragmites australis showed reductions in BOD5, COD, EC, TDS, NO3−, and PO43− compared with the control. Maximum BOD5 and COD removal was 53% and 50%, respectively, at 50% coverage of Phragmites australis (C3). The maximum reduction in NO3− (61%) was achieved using Canna indica at 100% coverage (C1). Conversely, moderate removal of PO43− (27%) was obtained in the control (C4) with a visibly high amount of algal growth, indicating the influence of algae on pollutant removal. This study highlights the significance of Phragmites australis for organic matter removal and Canna indica for nutrient removal, mainly NO3− from municipal wastewater. Furthermore, this study suggests that FTWs perform well for BOD5 and COD removal at 50% plant coverage (Phragmites australis) and NO3− removal at 100% coverage (Canna indica).

Abstract Global warming, management of soil health, remediation of contaminated wastewater,and sustainable alternate source of energy are the major challenges of the 21st century. Biochar has an enormous potential in addressing these global issues and can act as a catalyst in achieving sustainable development goals (SDGs). Biochar produced from waste biomass (crop residues, algal biomass, municipal waste, etc.) has dual advantages of waste management along with its application in different sectors. The mineral contents and buffering capacity of biochar make it an ultimate catalyst for anaerobic digestion which significantly enhances bioenergy production. Supplementing anaerobic digestion with biochar can increase biogas and biological hydrogen production up to 57% and 118% respectively, over control. Biochar addition to soil improves soil health, porosity and aeration which mitigates greenhouse gas emission from soil. Addition of biochar at the optimum level in rice can reduce cumulative methane emission up to 60%. In this manuscript, the potential of biochar for bioenergy production (biogas and biological hydrogen production), greenhouse gases mitigation, carbon sequestration in soils, and waste water remediation is discussed in detail along with the challenges and future prospects of biochar. This review identifies the key issues which need to be addressed for sustainable utilization of biochar.