Enhancement of autothermal thermophilic aerobic digestion by chemical approach: Dosage of ferric nitrate on disinhibition of excessive volatile fatty acids

• Ferric nitrate was used to remove excessive volatile fatty acids in sludge digestion.
• The contents of total VFA and VFAs in the proper dosing digester were lowest of all.
• The digester with optimal dosage achieved stabilization 7 days earlier than control.
• VS removal of optimal dosing one was 6.83% higher than that of control on 21st day.

Ferric nitrate was utilized to remove inhibition of excessive volatile fatty acids (VFAs) in autothermal thermophilic aerobic digestion (ATAD) by chemical precipitation in this study. The dosage of Fe(NO3)3 had a significant effect on performance of the ATAD process and a dosage gradient of Fe(NO3)3 equivalent to 500, 1000, 1500, 2000 mg/L for the removal of acetic acid was adopted. The lowest concentrations of total VFA (TVFA) and VFAs but highest content of ATP were found in the digester with a dosage of Fe(NO3)3 equivalent to 1000 mg/L removal of acetic acid (D2) and VS removal of 40.28% was obtained in D2 after 14 days digestion, which achieved stabilization 7 days earlier than the digester without any additions. Furthermore, VS removal of 45.51% was observed after 21 days digestion in D2. Hence, chemical precipitation with Fe(NO3)3 was an effective method for disinhibition of VFAs in ATAD when dosage of Fe(NO3)3 equivalent to 1000 mg/L removal of acetic acid was added on the 6th day.

Figure optionsDownload as PowerPoint slide