Figure 1. Layout of the lab-scale GCC reactor. 1. Anaerobic compartment. 2. Headspace. 3. Aerobic compartment. 4. Gas deflector. 5. Water cycling pump. 6. Influent pumps. 7. Biogas collection system. 8. Gravel bed. 9. Sludge bed. 10. Anaerobic effluent. () Liquid flow. () Gas flow.