Characterization of Hydrolysis Kinetics in Staged Anaerobic Digestion of Wastewater Treatment Sludge

Abstract

The hydrolysis of mixed primary and secondary sludges in two-stage anaerobic digestion was evaluated and compared with conventional single-stage digestion, using various temperature-phased configurations of M1-M2, M1-T3, T1-T2, and T1-M3. A dual hydrolysis model best described the hydrolysis in all tests. This model was also able to consistently estimate the readily and slowly fractions of particulate chemical oxygen demand (COD) of raw sludge used in the tests. The hydrolysis kinetic coefficients (Khyd_s and Khyd_r) estimated for the mesophilic digesters were significantly greater in the short hydraulic retention time (HRT) M1 digester than those of the extended HRT digesters. Conversely, at thermophilic temperatures only Khyd_r was greater in short HRT T1 digester when compared to the extended HRT digesters. The increased Khyd_r and reduced Khyd_s values due to staging effect were explained with surface reaction models and endogenous decay. The temperature dependency of Khyd_s and Khyd_r was also explored in the staged digesters.

Volatile Fatty Acids (VFA) Production and Recovery from Chicken Manure Using a High-Solid Anaerobic Membrane Bioreactor (AnMBR)

“…Compared to the alkaline condition provided in AnMBR2, the activity of methanogens was inhibited by about 50% at pH 6.0 (AnMBR1). This result was consistent with the result in methane producing processes [43]. Consequently, the hydrogenesis activities under the condition of pH 6.0 was higher by 12-53% compared with that under weak alkaline conditions (Table 4).…”

“…These yields, no matter with or without pH control, were much higher than those of many other organic wastes, such as cow manure (0.39-0.15 g-VFA/g-VS at OLR from 0.8-4.7 gVS/(L•d)) [16], food waste (0.54 g-VFA/g-VS at OLR of 2 gVS/(L•d) or 0.52 g-VFA/g-VS at OLR of 6 gVS/(L•d)) [29,35]. However, stability in VFA production was only maintained for 16 d (day 32-47) for AnMBR1 and 11 d (day [35][36][37][38][39][40][41][42][43][44][45] for AnMBR2. VFA concentration dropped rapidly to 6.1 and 8.5 g/L in AnMBR1 and AnMBR2 after a stable phase while the reactors still operated at OLR 2 g-VS/(L•d).…”

Modeling, instrumentation, automation, and optimization of water resource recovery facilities (Review of 2018 Literature) DIRECT

“…SRT above 13 days enhanced the prediction of effluent chemical oxygen demand (COD), volatile solids removal, and biogas production, and at SRT below 20 days, it predicted volatile fatty acids (VFA) concentration. A dual hydrolysis model was used by Zamanzadeh and Parker (2018) to describe the hydrolysis of a mixed primary and waste activated sludge under both mesophilic and thermophilic conditions in single‐ and two‐stage digestion systems. The mesophilic hydrolysis kinetic coefficients for slowly and rapidly hydrolyzed COD in the first stage of the two‐stage system were significantly greater than the values for the extended hydraulic residence time (HRT) digesters.…”