Kinetic parameter estimation model for anaerobic co-digestion of waste activated sludge and microalgae

•Kinetic parameter estimation models were proposed for anaerobic co-digestion.•The models considered co-substrate ratios and single substrate kinetic parameters.•The models were used to determine the first-order kinetic and Monod coefficients.•The models could estimate kinetic parameters for the microalgae-WAS co-digestion.

Anaerobic co-digestion has a potential to improve biogas production, but limited kinetic information is available for co-digestion. This study introduced regression-based models to estimate the kinetic parameters for the co-digestion of microalgae and Waste Activated Sludge (WAS). The models were developed using the ratios of co-substrates and the kinetic parameters for the single substrate as indicators. The models were applied to the modified first-order kinetics and Monod model to determine the rate of hydrolysis and methanogenesis for the co-digestion. The results showed that the model using a hyperbola function was better for the estimation of the first-order kinetic coefficients, while the model using inverse tangent function closely estimated the Monod kinetic parameters. The models can be used for estimating kinetic parameters for not only microalgae-WAS co-digestion but also other substrates' co-digestion such as microalgae-swine manure and WAS-aquatic plants.