Performance Of Denitrification Sulfur Resourcization Granular Sludge And Its Micro-Ecological Mechanism

In view of the technical bottleneck of biological denitrification desulfurization technology in the treatment of actual industrial wastewater,the effect of different S/N?molar?ratio on the pollutant removal performance and the production and recovery potential of elemental sulfur in the bio-denitrifcation sulfur resource granular sludge bed reactor was studied using anaerobic granular sludge as the inoculum.The results demonstrate that with the S/N ratio of 5:5?6:2,the average nitrate and sulfide removal rates of the reactor were 0.17 kgN·m^-1·d^-1 and 0.72 kgS·m^-1·d^-1,respectively.There is not any accumulation of nitrite,and the average conversion rate of elemental sulfur is low?45.8%?.At the S/N ratio of 7:2,the nitrate removal rate was slightly reduced to 0.15 kgN·m^-1·d^-1,and the nitrite accumulation ratio was 9.2%,but the sulfide removal performance is 96.3%,and the conversion rate of elemental sulfur is increased to 79.5%.When the S/N ratio was 8:2,the nitrate removal rate of the reactor further decreased to 0.05 kgN·m^-1·d^-1 with the nitrite accumulation rate of 41.5%,and the elemental sulfur conversion rate increase to 94.5%.The bio-sulfur produced in the system was recovered,and its purity was detected by elemental analysis and XPS techniques.The results showed that the sulfur purity was as high as 92.5%.16S rRNA gene analysis showed that with the increase of the influent S/N ratio,the abundance of Thiobacillus,Thauera,Thioalkalispira and Sulfurovum genus continued to increase,from the time of inoculation?all abundances were less than 0.I%?to the 7:2 stage increased to 10.5%,8.62%,4.75%and 3.43%respectively,which is likely the key to the process to obtain high elemental sulfur conversion rate.Meta-omics analysis showed that with the increase of S/N ratio,the gene abundance of napA,narG and nirS increased,but the expression levels were significant decline.This shows that although the denitrifying bacteria group is effectively enriched during the increase of the S/N ratio,the excessive S/N ratio may inhibit the expression of key genes during the reduction of nitrate and nitrite.On the other hand,as the S/N ratio increases,the expression level of the key gene?sqr?that produces elemental sulfur in the first step of the sulfide oxidation pathway?S²-?S⁰?SO₄²?increases significantly,while in the second step the expression level of the key genes sorA,dsrB,aprA,and sot that produces sulfate was not significantly changed.The expression level of key gene soxA in Sox pathway(S²-?SO₄^2-)decreased significantly.The above results indicates that the S/N ratio is the key operating parameter of the denitrification sulfur resourcization process,and the recovered biological sulfur has high purity and has the value of recovery and utilization.The denitrification sulfur resourcization technology based on anaerobic granular sludge inoculation has strong engineering development potential and practical value.