Long-term stability of thermophilic co-digestion submerged anaerobic membrane reactor encountering high organic loading rate, persistent propionate and detectable hydrogen in biogas

Comprehensive monitoring and management of a long-term thermophilic CSTR treating coffee grounds, coffee liquid, milk waste, and municipal sludge

“…Bicarbonate alkalinity, TAN, and pH were maintained at stable range with average value of 2.52 g/L, 0.79 g/L, and 7.5, respectively. Digester achieved COD removal by 54% and biogas conversion by 54% which is 275 mL-CH 4 /g-COD in and higher than previous experiment of 210 mL CH 4 /g-COD in under OLR 4.9 kg-COD/m 3 /d by Qiao et al (2013b). The CSTR performance under steady state are summarized in Table 4.…”

“…Laboratory and field-scale applications indicate that start-up periods ranging from three weeks to one year (Poggi-Valardo et al, 1997;Biey et al, 2003). The short period of start-up in this experiment was most probably attributed to the combination of two different seed sludge in which the sludge from AnMBR provided the reactor with well-adapted microorganism, while the new seed sludge served as a dilution agent of VFA, given the AnMBR had previously experienced an overload condition with VFA accumulation of up to 7 g/L (Qiao et al, 2013b). Fdéz-Güelfo et al (2010) highlighted the need for a seed sludge that is adapted to appropriate temperature as well as the type of feed in order to achieve fast start-up and stabilization, since the lack of acclimated seed sludge is often attributed to poor start-up condition.…”

“…Recent studies by Qiao et al (2013a,b) on thermophilic co-digestion of coffee grounds and sludge using anaerobic membrane reactor found a process instability during the first 115 days due to the lack of alkalinity, decreased pH, and deficiency of microelements, while a high concentration of propionic acid of 1-3 g/L and H 2 of 100-200 ppm was observed throughout the reactor operation time. The sufficiency of bicarbonate alkalinity, trace elements, and control of OLR were identified to play important roles in maintaining long-term stability of coffee grounds and sludge digestion (Qiao et al, 2013b).…”

Challenges in biogas production from anaerobic membrane bioreactors

“…psychrophilic (0-20°C) [18,31], mesophilic (20-42°C) [19,75] and thermophilic (42-75°C) [76]. Thermophilic AnMBRs are known to have a rate-advantage over the others due to a faster reaction time and higher volumetric loading rate, thus demonstrating higher biogas productivity [2].…”

Effect of Mild-Temperature Thermo-Alkaline Pretreatment on the Solubilization and Anaerobic Digestion of Spent Coffee Grounds

“…Generally, SCG is disposed of as general waste in landfills, although small amounts are used as boiler fuel [2] or a mushroom cultivation medium [3]. If SCG is improperly managed, serious pollution issues will develop due to the decomposition of easily degradable organic matter and the release of potentially toxic compounds such as caffeine, tannin, and polyphenols [1,4]. On the other hand, due to its high organic content, SCG has recently attracted increasing interest as a feedstock for biofuel production [5].…”