TY - JOUR
T1 - Relieving the inhibition of humic acid on anaerobic digestion of excess sludge by metal ions
AU - Li, Ji
AU - Hao, Xiaodi
AU - van Loosdrecht, Mark C.M.
AU - Liu, Ranbin
PY - 2021
Y1 - 2021
N2 - Anaerobic digestion (AD) is an effective approach to recovering chemical (organic) energy from excess sludge, but the conversion efficiency for energy is usually not very high. One of the obstacles comes from the severe inhibition of humic acid (HA) on both hydrolytic and methanogenic process on the AD. Therefore, it is necessary to ascertain some effective approaches to relieving the inhibition of HA for obtaining a high methane (CH4) yield. With the “clean” sludge (cultured by synthetic wastewater) containing almost no HA and metal ions, the inhibition of HA on the AD process was designed by dosing HA at 15% VSS, and relieving the inhibition by metal ions was also designed by dosing the different amounts of Ca2+ and Al3+. Based on the batch AD experiments, solo Ca2+=100 mg /L or Al3+=70 mg/L added realized the highest relieved efficiency of 65%, respectively. Interestingly, dual metal ions added at the low concentrations (Ca2+=50 mg/L and Al3+=10 mg/L) could reach up to 80 % of the relieved efficiency, which was attributed to the synergistic effect of 1+1>2. The mechanisms behind the phenomena could be that metal ions might interact with HA via electrostatic force, cation exchange and sweep flocculation. Thus, some key hydrolytic and methanogenic enzymes could indirectly be reactivated and degradation of organic substances could be enhanced in the AD process. In wastewater treatment plants, metal ions contained in excess sludge would “inherently” relieve the inhibition of HA to an extent, which depends on the effective and/or optimal concentration of metal ions at a free (unabsorbed and/or unwrapped) state.
AB - Anaerobic digestion (AD) is an effective approach to recovering chemical (organic) energy from excess sludge, but the conversion efficiency for energy is usually not very high. One of the obstacles comes from the severe inhibition of humic acid (HA) on both hydrolytic and methanogenic process on the AD. Therefore, it is necessary to ascertain some effective approaches to relieving the inhibition of HA for obtaining a high methane (CH4) yield. With the “clean” sludge (cultured by synthetic wastewater) containing almost no HA and metal ions, the inhibition of HA on the AD process was designed by dosing HA at 15% VSS, and relieving the inhibition by metal ions was also designed by dosing the different amounts of Ca2+ and Al3+. Based on the batch AD experiments, solo Ca2+=100 mg /L or Al3+=70 mg/L added realized the highest relieved efficiency of 65%, respectively. Interestingly, dual metal ions added at the low concentrations (Ca2+=50 mg/L and Al3+=10 mg/L) could reach up to 80 % of the relieved efficiency, which was attributed to the synergistic effect of 1+1>2. The mechanisms behind the phenomena could be that metal ions might interact with HA via electrostatic force, cation exchange and sweep flocculation. Thus, some key hydrolytic and methanogenic enzymes could indirectly be reactivated and degradation of organic substances could be enhanced in the AD process. In wastewater treatment plants, metal ions contained in excess sludge would “inherently” relieve the inhibition of HA to an extent, which depends on the effective and/or optimal concentration of metal ions at a free (unabsorbed and/or unwrapped) state.
KW - Anaerobic digestion (AD)
KW - Humic acid (HA)
KW - Hydrolysis
KW - Inhibition
KW - Metal ions
KW - Methanogenesis
KW - Relieved efficiency
UR - http://www.scopus.com/inward/record.url?scp=85096471031&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2020.116541
DO - 10.1016/j.watres.2020.116541
M3 - Article
C2 - 33142119
AN - SCOPUS:85096471031
SN - 0043-1354
VL - 188
JO - Water Research
JF - Water Research
M1 - 116541
ER -