Anaerobic Co-digestion Of Kitchen Greases And Nutrient-deficient Sludge

Based on the low methane yield production of nutrient-deficient activated sludge?NDAS?, treatment of kitchen dewatered greases?KDG? is difficult, NDAS and KDG can lead to secondary pollution and other issues, anaerobic co-digestion of NDAS and KDG is studied, such as the optimal dosing rate?the grease tolerance?the relationship between NDAS and KDG?different pretreatment technologies which can increase methane yields were studied. In addition, EPS and microbial community structure were analyzed, from the angle of microbiology to study the mechanism of codigestion system between NDAS and KDG.When KDG loading was 50%?G/S=1? and 66.7%?G/S=2?, methane yield of co-digestion system was 724.52 m L CH4 / g VS and 809.33 m L CH4 / g VS, VS removal rate of G/S=0?0.5?1?2?4 were 35.9%, 36.2%, 54.5%, 39.8% and 23.4%, respectively. VFA concentration was always below 5000 mg / L, acidification phenomenon does not appear. G/S=4, methane yield production of G/S=4 stagnated because of LCFAs inhibition. Grease tolerable limits of anaerobic co-digestion was 80% grease loading. Methane yield of NDAS and KDG alone was 133.84 m L CH4 / g VS and 505.02 m L CH4 / g VS, but methane yield of co-digestion between NDAS and KDG reach up to 770.56 m L CH4 / g VS, so during the anaerobic co-digestion system, the relationship between NDAS and KDG was synergistic relationship rather than simple sum “1+1=2”.Before and after anaerobic digestion, sludge CST increased from 0.84 s / mg VS to 1.80 s / mg VS?G / S = 0?, 1.88 s/mg VS?G / S = 0.5?, 8.15 s / mg VS?G / S = 1?, 12.33 s / mg VS?G / S = 2? and 12.86 s / mg VS?G / S = 4?, respectively. Dewatering performance became bad. EPS increased from 46.83 mg / g VSS increased to 55.57 mg / g VSS?G / S = 0?, 60.30 mg / g VSS?G / S = 0.5?, 57.35 mg / g VSS?G / S = 1?, 49.88 mg / g VSS?G / S = 2? and 47.03 mg / g VSS?G / S = 4?. Soluble proteins and polysaccharides increase significantly, which also leaded to dewatering performance.H₂O₂ pretreatment and Alkali pretreatment can significantly improve methane yield production and VS removal rate. When G/S=1, after pretreatment, methane yield production increased from 718.38 m L CH4 / g VS to 754.19 m L CH4 / g VS and 769.27 m L CH4/g VS, VS removal rate increased from 51.65% to 58.62% and 64.17%. When G/S=2, methane yield production increased from 778.25 m L CH4 / g VS to 916.87 m L CH4 / g VS and 939.92 m L CH4/g VS, VS removal rate increased from 41.04% to 59.84% and 59.79%.When grease loading was high, alkali pretreatment was better than H₂O₂ pretreatment.454 high-throughput sequencing technology was used to analysis methanogenic bacteria of anaerobic co-digestion system, it found that dominant methanogens species of G/S=1?2?4 were different, when G/S=1, dominant methanogens species were Methanoculleus, Methanosaeta and Methanospirillum, when G/S=2, dominant methanogens species were Methanoculleus, Methanosarcina, Methanofollis and Methanomassiliicoccus, when G/S=4, dominant methanogens species were Methanoculleus, Methanolinea and Methanoregula. PCR-DGGE test results found that diversity and abundance of microbial populations in anaerobic co-digestion were higher than NDAS alone.Used KDG as conditioner, which can significantly improve methane productivity and can also realize resource utilization of KDG and NDAS.