Impact of Storage Conditions on the Methanogenic Activity of Anaerobic Digestion Inocula

The impact of storage temperature (4, 22 and 37 °C) and storage time (7, 14 and 21 days) on anaerobic digestion inocula was investigated through specific methanogenic activity assays. Experimental results showed that methanogenic activity decreased over time with storage, regardless of storage temperature. However, the rate at which the methanogenic activity decreased was two and five times slower at 4 °C than at 22 and 37 °C, respectively. The inoculum stored at 4 °C and room temperature (22 °C) maintained methanogenic activity close to that of fresh inoculum for 14 days (<10% difference). However, a storage temperature of 4 °C is preferred because of the slower decrease in activity with lengthier storage time. From this research, it was concluded that inoculum storage time should generally be kept to a minimum, but that storage at 4 °C could help maintain methanogenic activity for longer.

Improving Biomethanation of Chicken Manure by Co-Digestion with Ethanol Plant Effluent

As the global production of chicken manure has steadily increased, its proper management has become a challenging issue. This study examined process effluent from a bioethanol plant as a co-substrate for efficient anaerobic digestion of chicken manure. An anaerobic continuous reactor was operated in mono- and co-digestion modes by adding increasing amounts of the ethanol plant effluent (0%, 10%, and 20% (v/v) of chicken manure). Methanogenic performance improved significantly in terms of both methane production rate and yield (by up to 66% and 36%, respectively), with an increase in organic loading rate over the experimental phases. Correspondingly, the specific methanogenic activity was significantly higher in the co-digestion sludge than in the mono-digestion sludge. The reactor did not suffer any apparent process imbalance, ammonia inhibition, or nutrient limitation throughout the experiment, with the removal of volatile solids being stably maintained (56.3–58.9%). The amount of ethanol plant effluent appears to directly affect the rate of acidification, and its addition at ≥20% (v/v) to chicken manure needs to be avoided to maintain a stable pH. The overall results suggest that anerobic co-digestion with ethanol plant effluent may provide a practical means for the stable treatment and valorization of chicken manure.

Optimization and Modelling of Denitrification and Methanogenic Activity in Start up of Mixotrophic Anammox Reactor

In the present study, the SDA (specific denitrification activity) and SMA (specific methanogenic activity) in Start up of mixotrophic anammox reactor was optimized by applying the response surface method (RSM). The purpose of this work was to find the optimal combination of C/N ratio, influent ammonium (NH4+-N) and volatile suspended solid (VSS) with respect to minmum the SDA and SMA. Based on the RSM results, the quadratic model developed for the responses indicated that optimal conditions were C/N ratio of 0.5, influent NH4+-N content of 200mg L-1, and VSS content of 59.31g L-1. Under this conditions, the SDA and SMA were minimize and found to be 0.05 mmol N2 (g VSS d)-1, 0.017 mmol N2 (g VSS d)-1, respectively

Optimization of the thermophilic anaerobic co-digestion of pig manure, agriculture waste and inorganic additive through specific methanogenic activity

The anaerobic co-digestion of three wastes (manure, rice straw and clay residue, an inorganic additive) at different concentration levels and their interactive effects on methanogenic activity were investigated in this work at thermophilic conditions in order to enhance hydrolytic activity and methane production. A central composite design and the response surface methodology were applied for the optimization of specific methanogenic activity (SMA) by assessing their interaction effects with a reduced number of experiments. The results showed a significant interaction among the wastes on the SMA and confirmed that co-digestion enhances methane production. Rice straw apparently did not supply a significant amount of substrate to make a difference in SMA or methane yield. On the other hand, clay residue had a positive effect as an inorganic additive for stimulating the anaerobic process, based on its mineral content and its adsorbent properties for ammonia. Finally, the optimal conditions for achieving a thermophilic SMA value close to 1.4 g CH4-COD/g VSS · d−1 were 20.3 gVSS/L of manure, 9.8 gVSS/L of rice straw and 3.3 gTSS/L of clay.