Aeration pre-treatment role in improving the performance of bio-conditioning dewatering of food waste anaerobic digestate.

Bio-conditioning dewatering followed by activated sludge process (BDAS) is a promising technology for purifying food waste anaerobic digestate (FWAD). However, the bio-conditioning dewatering efficiency is often affected by FWAD properties and ambient temperature. Here, we firstly reported that aeration pre-treatment of FWAD played an important role in improving the bio-conditioning dewatering performance of FWAD. The study found that the accumulated carbonate (CO ₃ ^2- ) in FWAD severely affected the flocculation of Fe-containing flocculant formed in microbial fermentation liquor due to the competitive consumption of the flocculant by CO ₃ ^2- . The capillary suction time (CST) and specific resistance to filtration (SRF) of the bio-conditioned FWAD increased from initial 77.8 s and 2.0 × 10 ¹² m/kg to 122.7 s and 3.4 × 10 ¹² m/kg, respectively, within 1 day of aeration. Prolonged aeration pre-treatment of FWAD could reduce its CO ₃ ^2- concentration and total alkalinity. Additionally, the aeration pre-treatment simultaneously decreased the proportion of macromolecular organic matter that hindered dewatering and the content of total solids (TS) and hydrophilic protein-like substances in FWAD. After 20 days of aeration followed by bio-conditioning, the CST and SRF reduced to final 36.5 s and 2.3 × 10 ¹¹ m/kg, respectively, indicating a substantial improvement in dewatering performance. Successive forced aeration combined with the addition of CaCl ₂ to eliminate adverse factors mainly CO ₃ ^2- was a feasible and cost-effective strategy to realize bio-conditioning dewatering of FWAD in less than 2 days and a lower reagents dose of bio-conditioning, which was helpful in the engineering application of the novel BDAS process for FWAD purification.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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