Effects Of Carbon Source And Bio-Augmentation On The Production Of Elemental Sulfur In Denitrifying Sulfide Removal Process

Sulfur and nitrogen-containing organic industrial wastewater mainly comes from Pharmaceutical,slaughter,papermaking,petrochemical and other processes,and is a typical refractory wastewater.High concentration of sulfur compounds in wastewater can be converted into elemental sulfur through specific methods to realize resource utilization.A lot of research home and abroad indicated that Denitrifying Sulfide Removal（DSR）process can effectively recovery elemental sulfur through biological sulfide oxidation.However,due to the complexity of organic matter（carbon source）in the real wastewater and the toxicity inhibition to microorganisms by sulfide with high-concentration,it is difficult for the DSR process to maintain a high elemental sulfur yield,which has become a difficult problem restricting the application of the DSR process.This article first discussed the effect of carbon sources on the DSR process by analyzing the elemental sulfur production with three common denitrification carbon sources,and clarified the low efficiency of glucose as a carbon source for DSR process by explaination of the distribution law of functional bacteria.And then,the DSR functional bacteria Pseudomonas sp.gs1 was obtained under high sulfide concentration,and the functional microbial Inoculant was prepared to enhance the production efficiency of elemental sulfur in the DSR system under high sulfide load,and the effect of bio-enrichment on promotion of DSR process efficiency was clarified.Furthermore,the Bio-augmentation effect under complex carbon source was studied by adding fillers,analyzing the structure and function of the microbial community on the surface of the fillers,and revealing the internal reasons for the increased efficiency of elemental sulfur generation.Through the construction and stable operation of the DSR process,the effect of carbon sources（sodium acetate,ethanol and glucose）on the DSR process was revealed,and the dominant functional flora was analyzed.It was found that when glucose was the carbon source,the elemental sulfur yield was the lowest,and the dominant bacteria were Azoarcus,Geoalkalibacter and Mangroviflexus.When glucose was the carbon source,the sqr gene activity was much lower than that of acetate and ethanol.It is speculated that when glucose was the carbon source,intense compition was happened between autotrophic and heterotrophic denitrifying bacteria,leading to the lack of sufficient carbon source to drive the sulfur oxidation reaction.Pseudomonas sp.gs1 Inoculant was used to bioenhance the DSR system,which effectively shortened the start-up time of the process,improved the tolerance of microorganisms to sulfide concentration,and relieved the toxic effect of high concentration of sulfide on microorganisms in the DSR process system.Studies showed that Pseudomonas sp.gs1 could tolerate 400mg/L of sulfide,and most of the sulfide was converted into elemental sulfur in the 4th hour.Two reactors were operated in parallel for a total of 60 days.One group started normally（without adding microbial inoculants）,and the other group was added with inoculants.The reactor with inoculants achieved a good treatment effect on the third day,with an effluent elemental sulfur concentration of 342.6 mg/L,and then the effluent elemental sulfur concentration was maintained between 245.3～333.8 mg/L.However,the reactor without inoculation achieved the same operating effect on the 50th day.Through high-throughput sequencing,it was found that when the influent NO₃^--N,acetate and sulfide concentration were 210 mg/L,450mg/L and 400 mg/L,respectively,Pseudomonas and Azoarcus were the dominant bacterial genera.Functional gene analysis proved that the addition of microbial inoculants can quickly increase the sulfur oxidation and carbon metabolism activities of the activated sludge in the reactor.Adding fillers to the DSR system further promoted the bio-augmentation effect of the inoculants,and improved the efficiency of the denitrification and desulfurization.The study showed that elemental sulfur generation was raised to1.5 times that of the control group by adding fillers.The dominant bacteria in the biofilm on the filler surface were Pseudomonas and Azoarcus,and the polysaccharide and protein content on the biofilm surface was also enhanced.Elemental sulfur generation was raised to 2 times that of the control group by adding fillers and microbial inoculants together.It was discovered that after the bio-augmentation of bacteria was found,the abundance of Pseudomonas on the biofilm significantly occupied the dominant position,and Arcobacter replaced Azoarcus to become the dominant functional bacteria genus.Bio-augmentation improved the polysaccharides and proteins on the surface of the biofilm on the filler surface,making the surface more adhesive,which was conducive to the adhesion of the biofilm.The addition of inoculants had little effect on the expression of sulfur oxidation genes.The filler provided a place for microbial attachment in which the stability of the microbial community structure and the expression of sulfur oxidation genes were promoted,which was an important internal cause for the increase of the elemental sulfur yield of the filler-assisted and bio-augmentation system.Based on the analysis of the superior functional flora of the DSR process system,this study explored the regulatory effects of bio-augmentation and addition of filler on the system performance,and provided theoretical guidance for the regulation of the functional flora of the DSR process and the increase in elemental sulfur yield under complex carbon sources.