| Background: Nowadays,slaughterhouse waste（SHW）pollution is getting more serious.As one kind of recycling technology,anaerobic digestion has the advantages in environment protection and resource recovery in the treatment of SHW.However,there are still several problems in digestion of SHW,such as high inhibition risk and low resource recovery efficiency,and the optimal SHW load is uncertain and comparison between researches is difficult due to the difference in organic load index.Objectives: This study was integrated two organic loaded index,and committed to determine the optimal SHW loaded in anaerobic digestion system.Biochar was introduced as additive to improve reactor performance and recycling efficiency,and the optimal concentration of biochar was determined.Methods: Volatile solid,total solid,lipid/protein/carbohydrate content,carbon/hydrogen/nitrogen content,and p H were measured to characterize SHW,inoculum and biochar.Then the batch anaerobic digestion was conducted under various SHW loaded（0、2、4、6、8%）.On the basis,biochar was introduced as additive to study the influence of biochar addition（0、5、10、15 g/L）in AD with high SHW loaded on reactor performance and microbial dynamic.The biogas production was measured and the methane/CO2 content were detected by gas chromatograph every two days.The liquid analysis was conducted every five days with the total ammonia nitrogen（TAN）,which was measured by Narsh’s colorimetry method with water quality detector.The p H was measured via p H measuring instrument.The free ammonia nitrogen（FAN）was calculated by standard formula.The volatile fatty acids（VFAs）were detected by gas chromatograph.Meanwhile,the microbial dynamic in groups was revealed by 16 s r RNA high sequence technology.Results: The optimum SHW loading was 2% in anaerobic digestion system,which resulted in maximum biogas and biomethane production,a more stable reactor,and shorter reactor time.A higher SHW concentration（4% and 6%）resulted in a prolonged lag-phase and decreased biomethane production.High VFAs（28.88 g/L）and TAN（>4g/L）accumulation were observed at 8% SHW leading to permanent inhibition of biomethane and methanogenic archaea.An increase in ammonia and VFAs concentration,at 4% and 6% SHW loadings,shifted the methanogenic pathway from acetoclastic to hydrogenotrophic lead by Methanoculleus.Acetoclastic Methanosaeta（77.15%）dominated the reactors loaded with 2% SHW resulting in the highest biomethane production.The optimal biochar concentration was 5 g/L which resulted in maximum biogas production and volatile solid consumption in both 6% and 8% SHW loaded.A higher biochar concentration（10 and 15 g/L）resulted in decreased biogas production,indicating that suitable biochar addition can effectively enhance the reactor stability.Meanwhile,suitable biochar addition can reduce the TAN/FAN concentration and maintain a steady p H under 6% and 8% SHW loaded.Due to the alkaline properties of biochar,excess biochar addition may cause the increment of FAN and p H leading to negative impact on biomethanation.As the 16 s r RNA high sequence analysis result showed,the 5 g/L biochar addition effectively enhanced the bacteria richness and diversity,and the relative abundance of dominated archaeal under 6% and 8% SHW loaded groups,such as Methanosaeta,Methanosphaera,Methanobrevibacter,Methanosarcina.However,higher biochar concentration may reduce the relative abundance of dominated archaea.Moreover,correlation was observed between biochar addition and relative abundance of hydrogenotrophic methanogensis.Conclusions: As one kind of high organic waste rich in oil and protein,SHW can be well applied in anaerobic digestion technology.Although there are certain risks in the process of anaerobic digestion,the stability and resource conversion rate of the reactor can be effectively improved by controlling the organic loading and adding biochar with appropriate concentration.On this basis,it is helpful to realize the winwin of environmental protection and economic benefits. |
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