| Thermal hydrolysis technology has been widely used in wastewater treatment plants in recent years as a pretreatment of sludge to improve performance and in combination with anaerobic units.Sodium dodecylbenzene sulfonate(SDBS)is the most commonly used ingredient in detergents.With the impact of the epidemic,its usage has surged and eventually enriched in sewage treatment plant sludge.In this paper,the thermal hydrolysis pretreatment-anaerobic digestion experiment of sludge was carried out to analyze the change of thermal hydrolysis on the physical and chemical properties of sludge and the concentration and distribution of SDBS,and the effect of SDBS on the anaerobic digestion of thermal hydrolysis sludge was studied.The mechanism of sludge coping with SDBS was explored by detecting extracellular polymers and microbial community structure.First,the "stepped" thermal hydrolysis conditions were set to analyze the modification effect of the sludge.After thermal hydrolysis,the maximum loss rates of TS and VS of sludge were 21.6% and 23.7%,respectively,and the loss rate of organic components was higher than Inorganic components;the average particle size of the sludge decreased by 22.8%;more pore and gully structures appeared;the SCOD of the sludge increased significantly,with the fastest growth at 160 °C,with an increase of 77.9%;the SCOD/TCOD ratio increased from 18.0% to the highest increased to 40.0%;protein and polysaccharide increased by 44.2% and 478.2% at most,the proportion of protein in the sludge was larger and the increase of polysaccharide was higher.The concentration of VFA increases by 2.4 times,and the proportion of acetic acid will also increase;the extracellular polymer is transformed from a tightly bound state to a loose or dissolved state;heavy metals show a trend of transformation to a more stable state;The proportion of liquid phase of sludge SDBS gradually increased from 1.0% to 12.9%,and the temperature factor had a stronger influence on the solubilization than the time factor.Secondly,the thermal hydrolysis sludge was anaerobic digested to study the effect of different concentrations of SDBS on it.The anaerobic reaction reached the peak gas production on the 5th day;the experimental group added with 100 mg/LSDBS had the maximum daily gas production(282.5 m L)and methane(68.6%);thermal hydrolysis increased the gas production of sludge by 44.7%;with the increase of SDBS concentration,the cumulative gas production and SDBS reduction rate both increased first and then decreased,with the highest reduction rate of 26.8%,And more and more exist in the solid phase;VFA was dominated by acetic acid,and the concentration peak appeared around 4 days,and the addition of SDBS helped to improve the VFA production.Finally,the changes of EPS and microorganisms in anaerobic sludge were analyzed.The protein and polysaccharides in EPS increased in the first four days,and then gradually decreased;SDBS would promote the secretion of more EPS by sludge microorganisms.When the dosage of SDBS was 180mg/L,the EPS protein had a maximum value of 647.4 mg/L on the fourth day;when the SDBS addition amount was 100～140 mg/L,the EPS polysaccharide increased significantly,an increase of 50.4% compared with the control group;moderate addition of SDBS improved the microbial abundance and diversity.The stability of the microbial system helps to improve the effect of anaerobic digestion.More than half of the shared species,and the differences in microbial composition were small.Firmicutes were the dominant species.With the addition of SDBS,the abundances of Firmicutes and Bacteroidetes first increased and then decreased.At high concentration of SDBS(220 mg/L),the species of Proteobacteria and Actinobacteria were more abundant,and the addition of SDBS was not found to inhibit methanogens. |
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