NO₃^--N Removal From Wastewater Based On Sulfur-based Autotrophic Denitrification

Nitrates are elaborated the most common pollutants in groundwater and surface and pose a significant threat to human health.Therefore,it is essential to reduce nitrates from water resources for well-being of humanity.Thus,it is an urgent issue to development better techniques to purify nitrogen-containing pollutants in wastewater.It is well known that autotrophic denitirification has been recognized as one of the most promising processes for its cost-economical and eco-friendly.In this study,we compared the treatment performance of sulfur-based autotrophic denitrification(SAD)and sulfur-based mixotrophic denitrification(SMD).The microbial community and diversity among these two processes were also examined by High throughput Illumina sequencing technology.Sulfur is economically viable and non-toxic nature,and it can act as fillers to remove particles in the fixed bed packed reactor.In the process of SAD,the removal efficiency of nitrate has reached 77.8%,and the accumulation rate of residual nitrite reached 12 mg/L.As the nitrate removal efficiency was not high in the process of SAD,Heterotrophic denitrification was combined with SAD(here designated as SMD)to treat nitrate by adding glucose as carbon source.The reaction conditions of mixed autotrophic denitrification match the reality well and speed up the rate of nitrogen removal,so it can improve the adaptability of the system.Optimum running parameters of the process were determined.The removal efficiencies of both nitrate and nitrite were above 98%.The results indicated that the SMD with glucose as organic source was feasible and applicable for the nitrate removal.The relative abundances of the main functional genus in the SAD stage were Thiobacillus and Sulfurimonas,which accounted for 31.9%and 17.7%,respectively.At the SMD stage,the relative abundances of the two species decreased,and Gemmobacter and Trichococcus began to play an increasingly important role in polyculture conditions.The microbial analysis of the stable operation of the sulfur-based fixed bed reactor showed that the relative abundance of the denitrifying bacteria was the most abundant.