Anaerobic treatment of agro-food industry wastewater: process progression, biogas production and kinetic modelling

Anaerobic processes are widely applied for the treatment of agro-industrial wastes, enabling both pollution control and resource recovery through energy production. Among agro-industries, bulgur-producing wheat processing facilities generate wastewater rich in rapidly hydrolysable biodegradable organic matter. In this study, the anaerobic treatment of bulgur processing wastewater was investigated under batch mesophilic conditions, with a focus on energy and resource recovery supported by kinetic modelling. The process achieved more than 95% total COD (tCOD) removal, confirming the high biodegradability of the wastewater. Cumulative biogas production reached approximately 0.22 m³/kg tCODfed, with a methane yield of 0.13 m³ CH₄/kg tCODfed. Process progression was governed by rapid acidification during the early stages of treatment, followed by system recovery and stabilization. Volatile fatty acid (VFA) production peaked within the first days of operation, with a dominant acid sequence of butyric > acetic > propionic acids. The substantial VFA production further highlights the potential of bulgur wastewater for dual resource recovery, supporting both biogas generation and polyhydroxyalkanoate (PHA) production within a biorefinery framework. Methane production kinetics were successfully described using the Modified Gompertz model, which showed excellent agreement with experimental data and provided quantitative insight into methane production potential, lag phase duration, and maximum methane production rate. Overall, the integration of experimental results with kinetic modelling demonstrated that bulgur processing wastewater can be effectively managed through anaerobic treatment while serving as a flexible platform for both biogas generation and PHA production.