Double-edged effect of tar on anaerobic digestion: Equivalent method and modeling investigation

Abstract

This study investigated the influence of real tar (RT) and synthetic tar (ST) on anaerobic digestion (AD). Mapping relationship was built effectively between ST set and RT set through equivalent method. Both sets performed the double-edged effect on AD: low dosage of tar performed stimulated effect and high dosage caused inhibited effect. Anaerobic Digestion Model No.1 (ADM1) was modified and extended by introducing kinetic parameters (inhibition constant: KI, Monod maximum uptake rate: km, Monod half saturation constant: Ks) of tar to describe related degradation process. Model calibration with ST set data achieved accurate simulation of methane production with satisfactory R2 (0.80–0.97), and model validation was conducted with RT set data. The linkage between kinetic parameters and microbial community was further bridged. The decrease of km_H2 (km of hydrogen) value was less than km_ac (km of acetate) value, corresponding to the less sensitivity of hydrogenotrophic methanogenesis to tar toxicity as reflected by 16S rRNA. Modified ADM1 could help in understanding AD system macroscopically and microscopically.