Study On The Efficacy Of Fe(?) In Producing Hydrogen Sulfide By Anaerobic Digestion Of Excess Sludge

Biogas is the main target product of anaerobic digestion of sewage sludge.The calorific value is 19075-21800 kJ/m³,which has great energy utilization value.Nowadays,the energy recovery rate of sludge treatment process resources is low,and the H₂S content in biogas is high,which limits the application and development of biogas.This paper proposes the idea of adding iron ions to control H₂S in sludge anaerobic system,adding Fe³⁺in anaerobic digestion system to improve anaerobic digestion gas production performance,effectively inhibiting H₂S production,and measuring different stages of anaerobic digestion.The formation of sulfur and iron forms,and the addition of Fe³⁺at different stages of anaerobic digestion,the determination of the presence of sulfur in the state of the determination of the mechanism of Fe³⁺inhibition of anaerobic digestion of H₂S.Firstly,Fe³⁺with different concentration gradients?0-250 mg/L?was added to the residual sludge anaerobic digestion system to determine the gas production performance and digestion effect of sludge anaerobic digestion.The methane volume fraction,H₂S inhibition effect and organic matter removal efficiency of anaerobic digestion of different concentration reactors were compared.It was determined that the gas production performance and digestion effect were the best when Fe³⁺dosage was 150 mg/L.Among them,the methane content in biogas can reach 62%,which is7%higher than 55%in the blank group;the removal effect on H₂S is obvious,from1.5 mg/L in the blank group to 0.5 mg/L;effectively promote bacterial lysis and organic matter removal.The rate?in terms of TCOD?was 42.6%,which was 5.9%lower than the 36.7%in the blank group.Secondly,after adding 150 mg/L Fe³⁺in the reactor,the changes of the content of sulfur and iron in the anaerobic digestion process were observed.It was found that the total inorganic sulfur content increased significantly after anaerobic digestion,from 34.9 mg/L in the blank group to 44.2 mg/L,and 98.7%?62.64 mg/L?of the converted inorganic sulfide was converted into sulfide.Precipitation,1.3%?0.84mg/L?into biogas,98%?52.4 mg/L?in the blank group was converted to sulfide precipitation,2%?1.14 mg/L?into biogas;solid Fe²⁺content increased,by blank The175.2 mg/L of the group increased by 286.8 mg/L;the H₂S content of biogas decreased from 1.14 mg/L to 0.84 mg/L in the blank group,indicating that most of the sulfide ions combined with Fe²⁺to form FeS precipitate,which reduced the H₂S content.Finally,the change of the percentage of sulfur in each form was studied by adding 150 mg/LFe³⁺at different stages of anaerobic digestion.From the point of view of the conversion effect of sulfur form,the best addition in the hydrolysis acidification stage,and the worst effect in the methanogenesis stage.Compared with the original excess sludge,Fe³⁺was added during the hydrolysis acidification stage,and the H₂S emission was significantly reduced,and the final percentage was 0.1%;the inorganic sulfur emission increased by about 7%;the organic sulfur content was significantly reduced by about 6.6%.In other stages,the addition of Fe³⁺is lower than that in the hydrolysis and acidification stage,the amount of organic sulfur dissolved is lowered,the sulfate reduction rate is lowered,the H₂S inhibition rate is also lowered,and the effect is the worst in the methanogenesis stage.It is indicated that Fe³⁺mainly plays a role in the hydrolysis acidification stage.