Thermophilic anaerobic digestion of coffee grounds with and without waste activated sludge as co-substrate using a submerged AnMBR: System amendments and membrane performance

- Lack of nitrogen and trace metals caused the failure of coffee grounds digestion.
- A long-term operation was established by using sludge as co-substrate.
- Additions of NH4HCO3 and trace metals overcame the unstable problem.
- Stable operation of membrane was successful with TS in reactor up to 75 g/L.