Denitrification efficiency analysis of sulfur autotrophic constructed wetlands for low C/N wastewater
Sulfur-autotrophic constructed wetlands(SCW)could efficiently and stably denitrify low C/N wastewater for denitrification,featuring no requirement for additional carbon sources,minimal sludge production,and phosphorus removal functions.Three sets of SCW pilot devices(an upflow SCW(SCW-1),an upflow plant-free SCW(SCW-2),a downflow SCW(SCW-3))and a conventional upflow constructed wetland(CW-1)were established,the denitrification performance of these four pilot devices without external carbon sources was evaluated and compared.The results showed that with an influent nitrate nitrogen concentration of approximately 12 mg/L and an ammonium nitrogen concentration of about 3 mg/L,the average removal rates of nitrate nitrogen by CW-1,SCW-1,SCW-2,and SCW-3 were 38.4％,93.7％,87.7％,and 88.4％,respectively,while the average removal rates of ammonium nitrogen were 81.1％,71.3％,56.6％,and 60.1％,respectively.SCW-1 demonstrated superior denitrification effectiveness.Analysis of the effluent from different outlets along SCW-1 revealed that ammonium nitrogen removal primarily occurred in the bottom support layer,heavily influenced by dissolved oxygen(DO);nitrate nitrogen removal was mainly through the sulfur-autotrophic denitrification(SAD)process,which took place in the functional layer containing sulfur-filled packing.The dominant microbial genera in SCW-1 were Acidithiobacillus,Thiomonas,Sulfuricurvum and Sulfurovum,all of which were associated with SAD functions.SCW could enhance the denitrification performance in wastewater with low C/N and had broad application potential.
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