RESUMEN
The removal of hydrogen sulfide from biogas by microaeration was studied in Up-flow Anaerobic Sludge Blanket (UASB) reactors treating synthetic brewery wastewater. A fully anaerobic UASB reactor served as a control while air was dosed into a microaerobic UASB reactor (UMSB). After a year of operation, sulfur balance was described in both reactors. In UASB, sulfur was mainly presented in the effluent as sulfide (49%) and in biogas as hydrogen sulfide (34%). In UMSB, 74% of sulfur was detected in the effluent (41% being sulfide and 33% being elemental sulfur), 10% accumulated in headspace as elemental sulfur and 9% escaped in biogas as hydrogen sulfide. The efficiency of hydrogen sulfide removal in UMSB was on average 73%. Microaeration did not cause any decrease in COD removal or methanogenic activity in UMSB and the elemental sulfur produced by microaeration did not accumulate in granular sludge.
Asunto(s)
Bacterias Anaerobias/fisiología , Reactores Biológicos/microbiología , Sulfuro de Hidrógeno/aislamiento & purificación , Metano/metabolismo , Aguas del Alcantarillado/microbiología , Aguas Residuales/microbiología , Purificación del Agua/instrumentación , Diseño de Equipo , Análisis de Falla de Equipo , Sulfuro de Hidrógeno/metabolismo , Contaminantes Químicos del Agua/aislamiento & purificación , Contaminantes Químicos del Agua/metabolismoRESUMEN
Utilization of crude glycerol (CG) from the biodiesel industry in the production of biogas offers a perspective of further energy generation, which may result into the drop of biodiesel costs on the developing world market. This contribution is focused on anaerobic treatment of CG as a single substrate in mixed laboratory reactors. Experiences from long-term operation of mixed reactors processing either untreated or acidulated CG are discussed. The possibility of cofermentation of washing water (WW) from biodiesel production with CG was also attempted. It was demonstrated that long-term mesophilic anaerobic treatment of CG as the only substrate is possible. Except for nitrogen, and possibly phosphorus, the addition of other nutrients is unnecessary. Processing of both non-acidulated and acidulated CG in laboratory mixed reactors inoculated with suspended sludge resulted in a stable operation with high specific methane production (0.328 L/g chemical oxygen demand (COD) for non-acidulated CG and 0.345 L/g COD for acidulated CG), regarding organic loading rate of up to 4 g COD/(L x d). Due to the considerable content of dissolved inorganic salts in CG it is recommended to dilute this substrate with water to prevent the accumulation of salts and inhibition of the biomass activity. WW was proved to be a problematic substrate for anaerobic cofermentation with CG because its addition to the reactor caused a decrease in the pH value and biogas production.
Asunto(s)
Biocombustibles , Reactores Biológicos , Glicerol/química , Glicerol/metabolismo , Aguas del Alcantarillado/química , AnaerobiosisRESUMEN
The aim of this study was to discuss the experience from long-term operation of a laboratory UASB reactor inoculated with suspended or granulated biomass for the treatment of different kinds of crude glycerol in undiluted or diluted state. The UASB reactor was operated under mesophilic conditions. It was demonstrated that the anaerobic treatment of crude glycerol as the only substrate in the UASB reactor is feasible, although the specific inhibition effects and requirements resulting from the nature and composition of the g-phase have to be considered. Deficient concentrations of nutrients had to be compensated by their supplementation into the digester. Long-term microbiological treatment of undiluted crude glycerol led to the process inhibition due to the accumulation of dissolved inorganic salts. When dosing diluted g-phase previously treated by acidulation, very good removal efficiency of COD, stable biogas production and high share of methane in the biogas were observed at the organic loading rates of up to 12kg/(m(3)d).
Asunto(s)
Biocombustibles , Glicerol/metabolismo , Biomasa , Reactores Biológicos , Aguas del AlcantarilladoRESUMEN
This contribution reviews the possibility of using the by-products from biodiesel production as substrates for anaerobic digestion and production of biogas. The process of biodiesel production is predominantly carried out by catalyzed transesterification. Besides desired methylesters, this reaction provides also few other products, including crude glycerol, oil-pressed cakes, and washing water. Crude glycerol or g-phase is heavier separate liquid phase, composed mainly by glycerol. A couple of studies have demonstrated the possibility of biogas production, using g-phase as a single substrate, and it has also shown a great potential as a cosubstrate by anaerobic treatment of different types of organic waste or energy crops. Oil cakes or oil meals are solid residues obtained after oil extraction from the seeds. Another possible by-product is the washing water from raw biodiesel purification, which is an oily and soapy liquid. All of these materials have been suggested as feasible substrates for anaerobic degradation, although some issues and inhibitory factors have to be considered.