Anaerobic co-digestion of food waste and sewage sludge in anaerobic sequencing batch reactors with application of co-hydrothermal pretreatment of sewage sludge and biogas residue.

The effect of pretreatment technologies and reactor types on conversion efficiency and operating costs of anaerobic co-digestion of food waste and sewage sludge were investigated by 300-day continuous experiments. The volatile solids (VS) removal efficiency increased from 61% to 77% with the application of co-hydrothermal pretreatment of sewage sludge and biogas residue. Deep dewatering reduced the volume of hydrothermally pretreated biogas residue by 85%. When continuous stirred tank reactors (CSTRs) were converted to anaerobic sequencing batch reactors (ASBRs), vS removal efficiencies increased by 6%, attributed to a 1.4-1.6-fold increase in solids retention time (SRT). The bottom drainage of mineralized sludge every 40 days increased ASBR stability. Firmicutes and Methanosphaera dominated the bacterial and archaeal communities, respectively. Operating costs decreased by 14.9 US$/metric ton feedstock by applying ASBRs. Compared to CSTRs, ASBRs achieved higher organic matter conversion efficiency, smaller volume of biogas residue, and lower operating costs.

Combined hydrothermal treatment, pyrolysis, and anaerobic digestion for removal of antibiotic resistance genes and energy recovery from antibiotic fermentation residues.

A process combining hydrothermal treatment (HT), pyrolysis, and anaerobic digestion can efficiently treat antibiotic fermentation residues (AFR). The process characteristics and antibiotic resistance genes (ARGs) removal efficiencies of each unit have been investigated. HT of 180 °C improved the biodegradability and dewaterability of the AFR. Pyrolysis of 500 °C and upflow anaerobic sludge blanket (UASB) of 6.5 ± 0.5 kg COD•(m3•d)-1 recovered the organic matter in filter cake and filtrate of AFR. The biogas and pyrolysis gas can compensate the energy this system needs. HT of 180 °C could reduce 16S rRNA, ARGs, and mobile genetic elements (MGEs) by 2.3 to 7.4 logs. UASB increased the copy numbers of ARGs and MGEs, but the relative abundances of ARGs normalized against 16S rRNA were significantly declined. The ARGs and MGEs were enriched in suspended solids of digestate. The application of this process can promote the resources recycling of fermentation waste.

Analysis on integrated thermal treatment of oil sludge by Aspen Plus.

An integrated thermal treatment (coupled pyrolysis and combustion) of oil sludge (OS) was proposed for enhancing the OS resource utilization. According to the pyrolysis experiment results, the integrated thermal treatment process of OS was modeled and simulated using Aspen Plus. Carbon flow, heat distribution, energy flow, energy efficiency and exergy efficiency of the process were analyzed and discussed. The results indicated that the simulation values were consistent with the experimental ones within the pyrolysis temperature of 00-780 °C With the increase of pyrolysis temperature, the carbon flow of pyrolysis oil was firstly increased and then sharply decreased, and the maximum value was achieved at 600-650 °C. Carbon flow of pyrolysis gas was initially increased rapidly followed by a continuously decreasing growth rate, and then increased sharply above 650 °C. The maximum heating value of pyrolysis oil was obtained at 600 °C. When pyrolysis temperature exceeded 650 °C, both the pyrolysis gas production rate and the gas heating value were improved. The energy and the exergy efficiency of the system can reach values as high as 61-68% and 56-71%, respectively, and the maximum efficiencies were achieved at the pyrolysis temperature of 650 °C. The present work could provide valuable insights towards promoting the development of effective OS utilization processes in the near future.