水热预处理对猪粪厌氧消化系统中磺胺嘧啶降解的影响

Effects of hydrothermal pretreatment on the sulfadiazine degradation in anaerobic digestion system of pig manure

为进一步了解水热预处理对猪粪连续厌氧消化过程中磺胺嘧啶(sulfadiazine,SDZ)降解机制的影响,以及对厌氧消化系统性能的影响效果。该研究以猪粪为对象,对比研究了水热预处理对厌氧发酵模式下SDZ的降解变化规律与途径及其对猪粪产气性能的影响。研究结果表明:水热预处理(150℃)使中温连续厌氧反应器中的SDZ的综合去除率显著提升(P<0.05),由40.5%~58.5%提高到54.4%~75.2%;并且通过中间降解产物推测SDZ的生物降解途径主要包括SDZ水解、羟基化、硫脱氧、氨基氧化、嘧啶环裂解等;在厌氧消化性能方面,水热预处理使稳定运行后反应器的日产沼气量提高了约34.05%(P<0.05)。此外,对反应器中微生物群落分析后,发现Syntrophomonas、Sedimentibacter与SDZ的降解高度相关,并且经过水热预处理后Sedimentibacter的相对丰度较未水热预处理显著提升。因此,水热预处理耦合厌氧消化工艺具有同步提高SDZ降解和厌氧消化性能的作用,有助于进一步提高沼液的生态安全性。

Hydrothermal pretreatment(HTP)can be used to decompose the sulfadiazine(SDZ)during continuous anaerobic digestion(AD)of pig manure.This study aims to explore the effect of HTP on the SDZ degradation and performance of AD system.Pig manure with SDZ was taken as the research object.A comparison was made on the degradation regular,SDZ paths and products,as well as the gas production performance of pig manure with/without HTP during AD.The results showed that the HTP(150°C)significantly increased the comprehensive removal rate of SDZ in the mesophilic continuous AD reactor(P<0.05),particularly from 40.5%~58.5%to 54.4%~75.2%.Moreover,the biodegradation paths of SDZ were inferred through intermediate degradation products,including SDZ hydrolysis,hydroxylation,thiodeoxidation,amino oxidation,nitroation,amidation and pyrimidine ring cleavage.HTP enhanced the degradation products and paths of SDZ,biodegrade SDZ from different degradation paths,and the removal rate of SDZ.There were four paths of degradation in pig manure with HTP,while there was only one degradation path without HTP.In terms of AD performance,the system was stabilized after 25 days,the daily gas production in the R0 reactor was stable at 5.14 L/d,and the cumulative VS gas production rate was 16.64 L/g;In the R0h reactor,the daily gas production was stable at 6.89 L/d,and the cumulative VS gas production rate was 22.31 L/g.The daily biogas yield of the reactor and the volume production rate increased by about 34.05%(P<0.05),and 34.00%,respectively,after stable operation with HTP.There was little difference in the methane content between the two reactors after two SRTs.The average contents of methane in R0 and R0h reactors were 61%and 59%,respectively.Thus,the AD process was stable in the two groups of reactors over the whole operation stage,according to the biogas production rate and methane content.The degradation of organic matter was also enhanced for the high concentration of VFAs after HTP.The substrate was provided for the subsequent stage of methane production,in which the acetic acid content accounted for 25.3%~46.1%.In addition,the microbial communities showed that Firmicutes and Bacteroidota were the dominant phylum bacteria in the reactors during anaerobic fermentation.Their relative abundance was beneficial to the degradation of antibiotics.A comparative analysis was also made on the microbial community at the class level.It was found that Clostridia and Bacteroidia were the main microorganisms in the two reactors.The relative abundance of Proteiniphilum increased after HTP.The full hydrolysis of pig manure was also realized for the better performance of methane production.Meanwhile,it was found that Syntrophomonas and Sedimentibacter were highly correlated with the degradation of SDZ,and the relative abundance of Sedimentibacter after HTP was significantly higher than that without HTP,indicating the better degradation of antibiotics.Therefore,the HTP coupled with the AD process can be expected to simultaneously improve the degradation of SDZ and AD performance,particularly for the ecological safety of biogas liquor.