Nitrogen removal effect of six common wetland plant biomass as denitrification carbon source and residual organic components in effluent
Wetland plant biomass is a potential denitrification external carbon source for treating tail water with low carbon-nitrogen ratio,but it is limited by plant species,dosage and excessive release of organic components during use.In this study,six kinds of common wetland plant biomass were selected,and the nitrogen removal performance of each plant biomass with different dosages as denitrification carbon source was studied and analyzed by batch experiments,and the characteristics of residual organic components in the effluent of high-efficiency denitrification treatment group were deeply explored.The results showed that the liquid-solid ratio of Typha orientalis,Cyperus involucratus and Arundo donax treated with 1％NaOH could be reduced to 50:1 and below,and the longest periods of efficient denitrification for Typha orientalis,Cyperus involucratus,Arundo donax,and Potamogeton crispus were achieved at solid-liquid ratios of 33∶1,25∶1,25∶1,and 100∶1,respectively.The continuous high-efficiency denitrification treatment system needs to go through 1～5 batches of denitrification start-up period(the denitrification effect was poor or even the removal rate was negative)before entering the high-efficiency denitrification stage,and the first 1～2 batches effluents had ultra-high COD(1000～7 000 mg·L-1)residuals.The analysis of the characteristics of organic components in the ultra-high COD effluent of four plants showed that the organic components of Typha orientalis,Cyperus involucratus and Potamogeton crispus were mainly humic acid humus,while Arundo donax was mainly benzene ring protein and soluble microbial metabolites.In the effluent of Typha orientalis,Cyperus involucratus and Potamogeton crispus,the macromolecular organic components of≥1 kDa were dominant,accounting for more than 60％,while the small molecular organic components of＜1 kDa were dominant in the effluent of Arundo donax,accounting for more than 60％.The aromatic components in the effluent of Potamogeton crispus and Arundo donax had better photodegradation characteristics,and the photodegradation effect of ultraviolet light was better than that of photodegradation,while that of the other two plants was poor.From the perspective of denitrification effect and growth cycle,Typha orientalis and Potamogeton crispus are more suitable as external carbon sources for denitrification of tail water.Their biomass dosages have the best continuous and efficient denitrification effect in the range of liquid-solid ratio of 33∶1 and 100∶1,respectively.In practical application,a large number of refractory organic components in the effluent during the start-up period should be removed by pretreatment or advanced treatment of effluent.This study provides a scientific basis for the feasibility of using plant biomass as a carbon source for denitrification in effluents with low carbon-to-nitrogen ratios.
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