Preliminary Study On The Coupling Mechanism Of Carbon,Nitrogen,Sulfur Cycles In A Hybrid Constructed Wetlandand

In order to study the effects of different substrate concentration on the microorganism,biochemical reactions and substances transformation in the constructed wetland,artificial sewage and the activated sludge which comes from the Jiulongpo BaiShiyi Qinghe area of artificial wetland treatment plant were employed.By using high-throughput sequencing technology,analysis of microbial diversity was carried out,and the bacteria involved in the transformation of C,N and S cycles were also analyzed.At the same time,the potential of sulfur autotrophic denitrification in wetlands was tested,the results show that:?1?The results of microbial diversity analysis show that the heterotrophic denitrifying bacteria were dominant microbes related C,N and S cycles,which account for 6.2-11.9%,sulfur-oxidizing bacteria?1.03-3.85%?,ammonia-oxidizing bacteria?0.49-1.66%?,aerobic nitrifying bacteria.?0.99-4.18%?were less than that.The relative abundance of sulfate-reducing bacteria,autotrophic denitrifying bacteria as well as the anaerobic ammonia oxidation?anammox?bacteria were less than 2%,meawhile,we found that there were a small amount of simultaneous nitrification and denitrification bacteria,dissinilatory nitrate reducing to ammonium?DNRA?bacteria,methane-oxidizing bacteria,but the methanogens was not detected in this study.?2?From the changes of substrate concentration,the correlation analysis of nitrogen,total organic carbon?TOC?consumption and analysis of microbial diversity,main known biochemical processes in the anaerobic reaction system were heterotrophic denitrification,sulfate reduction,sulfur autotrophic denitrification,anaerobic ammonium oxidation,and the good correlation with nitrogen and TOC consumption of up to 0.98?p<0.05?showed that heterotrophic denitrification was the dominant reaction.?3?Competition of limited organic carbon source between heterotrophic denitrification and sulfate reduction is very common in constructed wetlands,by analyzing the change of substrate concentration change,the TOC balance calculation and microbial diversity,Compared with denitrification,the sulfate reducing reaction is less competitive for organic carbon source,it was even completely suppressed when the temperature goes up.?4?The concentration of nitrite of the system can be up to 23 mg/L,which was almost the sum of nitrite and nitrate.There is no doubt that increasing carbon nitrogen ratio?such as increasing the concentration of ammonia,nitrite and nitrate?can be beneficial to denitrification and lower peak nitrite concentraion,but it cannot completely relieve this phenomenon,that means whether carbon source is adequate,nitrite will be accumulated during denitrification and then fade away,besides,the nitrite is nearly maximized when nitrate was exhausted.The correlation analysis of C/N and nitrite accumulation shows that when the temperature is higher than 21?,the correlation coefficient can reach up to 0.78.In addition,microorganism,temperature and pH can also influence the nitrite accumulation.?5?Sulfide inhibition was more remarkable in anaerobic environment,the removal rate of TOC and NO₃^-degradation was lower while the concentration of sulfide increased,and it can soonly recoverd under derepression.Anaerobic Sulfur autotrophic denitrification can significantly relieve the sulphide inhibition,the reaction potential was 0.06-0.91mgS/?L*d?approximately and it was greatly influenced by the relative ratio of all related bacteria.