Carlos Dinamarca

Metabolic divergence in simultaneous biological removal of nitrate and sulfide for elemental sulfur production under temperature stress

The simultaneous removal of NO3- and HS- at temperature stress (25-10°C) is evaluated here. An expanded granular sludge bed (EGSB) reactor was run over 120days at N/S molar ratio of 0.35 (for S0 production) under constant sulfur loading rate of 0.4kgS/m3d. The simultaneous removal of NO3- and HS-, was achieved at applied conditions. Average HS--S removal varied from 98 (25°C) to 89.2% at 10°C, with almost complete NO3- removal. Average S0 yield ranged from 83.7 at 25°C to 67% at 10°C. The temperature drop caused a decrease in granular sludge accumulated S0 fraction by nearly 2.5 times. Decreased temperature caused metabolic pathway change observed as higher SO42- production, apparently allowing the biomass to obtain more energy per HS- consumed. It is hypothesized that the metabolic shift is a natural response to compensate for temperature-induced changes in energy requirements.

Biogasification of Waste Monoethanolamine Generated in Post Combustion CO2 Capture

Publisher Summary This chapter intends to investigate the suitable operating conditions for converting waste Monoethanolamine (MEA) into a CH4 rich biogas through anaerobic biogasification. MEA contaminated liquid waste generated in post combustion CO2 captures poses a disposal issue. Anaerobic biogasification potential of waste MEA is evaluated in a series of laboratory experiments conducted under different operating conditions. Provision of a limited amount of oxygen may enhance the methane potential of waste MEA. Codigestion of MEA together with a readily biodegradable substrate is found to be a solution to overcome ammonia and pH inhibition caused by low C/N ratio and high alkalinity. Substrate inhibition caused by waste MEA can be overcome by acclimatization. MEA degradation pathways via acetic and ammonium, with and without oxygen, are included in an anaerobic digestion model (ADM 1-Ox). MEA degradation to methane by anaerobic digestion with no or small quantities of free oxygen is adequately predicted by model simulations. Micro-aeration has a favorable effect on the methane generation potential. A cosubstrate approach is required to obtain stable biogasification of waste MEA in a continuous flow reactor, in order to increase the low C/N ratios typical for amine wastes and hence to avoid the ammonia and pH inhibition.

Effects of psychrophilic storage on manures as substrate for anaerobic digestion.

The idea that storage can enhance manure quality as substrate for anaerobic digestion (AD) to recover more methane is evaluated by studying storage time and temperature effects on manure composition. Volatile fatty acids (VFA) and total dissolved organics (CODs) were measured in full scale pig manure storage for a year and in multiple flasks at fixed temperatures, mainly relevant for colder climates. The CODs generation, influenced by the source of the pig manure, was highest initially (0.3 g COD L−1d−1) gradually dropping for 3 months towards a level of COD loss by methane production at 15°C. Methane emission was low (<0.01 g COD L−1d−1) after a brief initial peak. Significant CODs generation was obtained during the warmer season (T > 10°C) in the full scale storage and almost no generation at lower temperatures (4–6°C). CODs consisted mainly of VFA, especially acetate. All VFAs were present at almost constant ratios. The naturally separated manure middle layer without sediment and coarser particles is suitable for sludge bed AD and improved further during an optimal storage time of 1–3 month(s). This implies that high rate AD can be integrated with regular manure slurry handling systems to obtain efficient biogas generation.