Recycled Filling Materials for Enhancing Anaerobic Treatment of Wastewater

The use of recycled materials in environmental engineering is an important approach supporting circular economy, resource efficiency, and sustainable waste management. In anaerobic wastewater treatment systems, recycled filling materials may serve as low-cost functional components that improve biomass retention, support the development of attached microbial communities, and enhance process stability. This study presents the application of recycled filling in a vertical anaerobic labyrinth-flow bioreactor for the treatment of high-strength industrial wastewater. The proposed system combines anaerobic granular sludge with a fixed-bed zone based on recycled filling, creating a hybrid configuration that integrates suspended and attached biomass. This design is intended to improve the biodegradation of organic pollutants, support biogas production, and enhance the separation of suspended solids from treated wastewater. The study focuses on evaluating the role of recycled filling under different organic loading conditions and identifying operational indicators associated with stable anaerobic digestion. The results showed that the incorporation of recycled filling contributed to efficient wastewater treatment and stable reactor performance within the optimal loading range. The hybrid system supported effective organic matter removal, favorable biomethane production, and improved clarification of the effluent. However, excessive organic loading reduced process stability, which was reflected in changes in pH, the FOS/TAC - ratio of volatile organic acids to total inorganic carbonate alkalinity, and methane concentration in the biogas. The findings indicate that recycled filling materials can be successfully used as functional support media in anaerobic wastewater treatment technologies. Their application provides a practical example of integrating material recycling with biological wastewater treatment and renewable energy recovery. This approach may contribute to the development of circular and sustainable solutions for the treatment of industrial wastewater while reducing the demand for conventional reactor filling materials.