Novel lanthanum-iron oxide nanoparticles alleviate the inhibition of anaerobic digestion by carbamazepine through adsorption and bioaugmentation.

Several reports have shown that pharmaceuticals and personal care products (PPCPs) have some negative effects on anaerobic digestion (AD), yet there are no convenient and efficient strategies for mitigating the adverse influences. The typical PPCPs of carbamazepine have a strong negative effect on lactic acid AD process. Therefore, in this work, novel lanthanum-iron oxide (LaFeO) nanoparticles (NPs) were used for adsorption and bioaugmentation to weak the negative effects of carbamazepine. The adsorption removal of carbamazepine increased from 0 to 44.30% as the dosage of LaFeO NPs was increased from 0 to 200 mg/L, providing the necessary prerequisites for bioaugmentation. Adsorption reduced the probability of direct contact between carbamazepine and anaerobes, partly alleviating the inhibition of carbamazepine on microbes. The highest methane (CH) yield induced by LaFeO NPs (25 mg/L) was 226.09 mL/g lactic acid, increasing by 30.06% compared to the control yield with a recovery to 89.09% of the normal CH yield. Despite the ability of LaFeO NPs to restore normal AD performance, the biodegradation rate of carbamazepine remained below 10% due to its anti-biodegradability. Bioaugmentation was primarily reflected in the enhanced bioavailability of dissolved organic matter, while the intracellular LaFeO NPs promoted coenzyme F420 activity through binding to humic substances. Under the mediation of LaFeO, a direct interspecies electron transfer system with Longilinea and Methanosaeta as functional bacteria was successfully constructed and the corresponding electron transfer rate was accelerated from 0.021 s to 0.033 s. LaFeO NPs eventually recovered AD performance under carbamazepine stress in an adsorption and bioaugmentation manner.