Three identical lab-scale TBRs were operated in parallel under thermophilic conditions (50 ± 2°C) over a period of 125 days. Each TBR was constructed from clear polyvinyl chloride (PVC) pipes and had an internal diameter of 4.3 cm, a height of 48 cm, and was packed with polyethylene Raschig rings (PE08, Tongxiang Small Boss Special Plastic Products Ltd.). Each TBR had an effective bed empty volume (𝑉) of 697 mL and could hold 480 mL of water when filled with the packing material.