Influence of temperature on kinetics and hydraulic retention time in discontinuous and continuous anaerobic systems

Anaerobic digestion (AD) is a biological treatment susceptible to temperature variations. The Arrhenius model and the Van´t Hoff-Arrhenius relationship analyze the temperature effect in AD first-order kinetic constant (k). Kinetic data is relevant for estimating the hydraulic retention time (HRT) in continuous reactors. This research aimed to evaluate the behavior of kinetic constants concerning temperature using the Arrhenius model and Van´t Hoff-Arrhenius relationship and analyze the influence of kinetic constants as estimators of the HRT. The evaluation of the temperature effect in AD analyzed k fit to the Arrhenius model and Van’t Hoff-Arrhenius relationship. The research used data of AD methane yield (B0) kinetics from the literature, corresponding to macroalgae (MA) (25, 35, 45oC), swine manure (SM) (25, 30, 35oC), and co-digestion of chicken manure with sawdust and miscanthus (CM) (35, 40, 42oC). The Arrhenius model and Van´t Hoff-Arrhenius relationship fitted the data with reduced temperature intervals (∆T = 5°C). The HRT analysis used a mass balance model considering 80% of the maximum B0 compared with the technical digestion time at 80 (T80) and 90% (T90) of the maximum B0. The results indicate that the HRT calculation is sensitive for k below 0.13 d-1.