3 research outputs found
Effect of operating pressure on direct biomethane production from carbon dioxide and exogenous hydrogen in the anaerobic digestion of sewage sludge
Producción CientíficaThe development of biological Power-to-Methane in-situ technologies aimed at producing biomethane directly in a single anaerobic digestion unit by the supply of external hydrogen, find its limiting step in the gas-to-liquid mass transfer of poorly soluble hydrogen. Increasing the operating pressure with an exogenous hydrogen supply could enhance transfer rates of hydrogen and carbon dioxide (enriching gas phase with methane) and simultaneously control the liquid media pH because the methanation of hydrogen and carbon dioxide prevents the acidification caused by carbon dioxide/bicarbonate equilibrium displacement. Thus, the feasibility of operating the anaerobic digestion of sludge at a pressure higher than the atmospheric pressure with an exogenous hydrogen supply to improve the solubilisation of hydrogen and subsequent bioconversion of hydrogen and carbon dioxide into methane by methanogenic archaea was studied. A mesophilic sludge digester (35 L) was operated at variable absolute pressure up to 300 kPa. Hydrogen was continuously supplied through the sludge recirculation stream, coupled to a static mixer. Hydrogen conversion increased with the operating pressure (up to 99%), and the methane concentration in the digester off-gas averaged 92.9 ± 2.3% at 300 kPa (maximum of 95.2%). pH approached 7 under such conditions, and the efficiency of organic matter removal was similar to that observed during conventional anaerobic digestion at atmospheric pressure without a detrimental accumulation of volatile fatty acids. This study confirmed that increasing the system pressure (mass transfer driving force) can be a viable alternative to high energy-consuming mixing methods to enhance the hydrogen gas-liquid mass transfer.Junta de Castilla y León, programa EU-FEDER (CLU 2017-09 y UIC 071
Biochar: Production, Application and the Future
Biochar, or carbon obtained from biomass, is a particularly rich source of carbon created by thermal burning of biomass. There is a rise of interest in using biochar made from waste biomass in a variety of disciplines to address the most pressing environmental challenges. This chapter will provide an overview on the methods employed for the production of biochar. Biochar has been considered by a number of analysts as a means of improving their ability to remediate pollutants. Process factors with regards to biochar properties are mostly responsible for determining biomass production which is discussed in this present chapter. Several characterization techniques which have been employed in previous studies have received increasing recognition. These includes the use of the Fourier transform infrared spectroscopy and the Scanning electron microscope which duly presented in this chapter. This chapter also discusses the knowledge gaps and future perspectives in adopting biochar to remediate harmful contaminants, which can inform governmental bodies and law-makers to make informed decisions on adopting this residue
Emerging Trends in Wastewater Treatment Technologies: The Current Perspective
The quality of freshwater and its supply, particularly for domestic and industrial purposes are waning due to urbanization and inefficient conventional wastewater treatment (WWT) processes. For decades, conventional WWT processes have succeeded to some extent in treating effluents to meet standard discharge requirements. However, improvements in WWT are necessary to render treated wastewater for re-use in the industrial, agricultural, and domestic sectors. Three emerging technologies including membrane technology, microbial fuel cells and microalgae, as well as WWT strategies are discussed in this chapter. These applications are a promising alternative for manifold WWT processes and distribution systems in mitigating contaminants to meet acceptable limitations. The basic principles, types and applications, merits, and demerits of the aforementioned technologies are addressed in relation to their current limitations and future research needs. The development in WWT blueprints will augment the application of these emerging technologies for sustainable management and water conservation, with re-use strategies