Integrated approach to sustain biogas production in anaerobic digestion of chicken manure under recycled utilization of liquid digestate: Dynamics of ammonium accumulation and mitigation control

• Ammonium dynamics and control in anaerobic digestion of chicken manure was investigated.
• Organic and inorganic compounds significantly accumulated after direct slurry recirculation.
• Accumulated VFAs and ammonium resulted in decrease of biogas production of 43%.
• Integration of air stripping before recirculation shows to be effective for ammonium mitigation.

The dynamics of ammonium accumulation and mitigation control in anaerobic digestion of chicken manure under the recycled utilization of liquid digested slurry were investigated by using an integrated approach in two laboratory-scale semi-continuously stirred tank reactors. In the reactor with direct recycled utilization of the anaerobic digested liquid slurry, total volatilized fatty acids (in CH3COOH) and NH4+-N increased from 1600 mg/L to 8000 mg/L and from 2600 mg/L to 5000 mg/L, respectively. The daily volumetric biogas production decreased from 1.4 ± 0.1 L/(L·d) to 0.8 ± 0.1 L/(L·d) with a reduction efficiency of 43 ± 4%. Air stripping was integrated for ammonium mitigation of recycled liquid digested slurry and was shown to effectively reduce the ammonium to 3000 mg/L. Correspondingly, the biogas production was recovered back to 1.4 ± 0.1 L/(L·d). This indicated the potential of the integration of air stripping for ammonium mitigation in an anaerobic digestion process with liquid digested slurry recirculation.

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