Characteristics of two-phase mesophilic anaerobic digestion of co-substrates consisting of waste activated sludge and corn silage based on modified ADM1.

• Two-phase anaerobic digestion of co-substrates (TPADCSs) studied with modified ADM1. • Optimal feedstock ratio of WAS to corn silage was 2:1 during mesophilic TPADCSs. • Acetate maximum specific uptake rate was calibrated to 29 d−1 in acidification phase. • Hydrogen maximum specific uptake rate was calibrated to 23 d−1 in methanogenic phase. • Good agreements achieved between measured data and simulation with the modified ADM1. Two-phase anaerobic digestion of co-substrates is a promising process to alleviate environmental pollution, product valuable methane gas and renew energy. A modified anaerobic digestion model No. 1 (ADM1) was proposed to characterize the mesophilic two-phase anaerobic digestion at the feedstock ratios of waste activated sludge to corn silage 1:1, 2:1, 3:1, respectively. The sensitivity analysis of the modified ADM1 was operated on the platform AQUASIM 2.0 while the kinetic parameter estimation and simulation was implemented on the platform MATLAB 7.0. The Monod maximum specific uptake rate for acetate (k m,ac) was calibrated to 29.0 d−1, and the half-saturation value for acetate (k s,ac) 0.40 kgCOD/m3 in the acidification phase while k m,ac 35.0 d−1, Monod maximum specific uptake rate for hydrogen (k m,h2) 23.0 d−1 and k s,ac 0.70 kgCOD/m3 in the methanogenic phase in the modified ADM1. The results from the batch tests showed the optimal feedstock ratio of waste activated sludge to corn silage was 2:1. Under this condition, chemical oxygen demand could reach the largest removal at around 51.0%, while Ammonia-nitrogen and total phosphorous increased by the maximal 192.0% and 71.5%. Besides, volatile fatty acids were lowest at about 0.27 kgCOD/m3, and the biogas flow was highest at about 47.6 mL/d. The pH values were always maintained at 6.8–7.2. Good agreements could be achieved between the measured data and the simulation with the modified ADM1. Therefore, the optimal and preferable operating factors during two-phase anaerobic digestion of co-substrates could be obtained from the simulation. The modified model will contribute to further investigating and predicting the characteristics of the process. [ABSTRACT FROM AUTHOR]