Characterization of dissolved organic matter and carbon release from wetland plants for enhanced nitrogen removal in constructed wetlands for low C-N wastewater treatment

The effects of pretreatment methods on the structure of functional groups and denitrification promotion capacity of solid carbon sources derived from reeds and cattails were elucidated. Alkaline treatment improved the relative content of carbon in the plant tissues, as well as prolonged the high denitrification rate of 0.40 mg/(L.h) from 6 days up to circa 28 days. Moreover, alkaline-heated cattails (ALH-C) showed high denitrification promotion capacity, and increased the removal rate of TN, NO3--N and NH4+-N in the CW by 24.41%, 31.80% and 8.80%, respectively. Furthermore, the quantity, quality and migration of dissolved organic matter (DOM) released from ALH-C in CW analyzed via fluorescence excitation-emission matrix spectrophotometry showed mainly humic acid-like, tyrosine-like, and tryptophan-like components. These DOM components were highly bioavailable and had minimal effects on COD removal. These results provide insights into the preparation and environmental applications of plant carbon sources. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrates that alkaline treatment and alkaline-heated treatment significantly enhance the denitrification promotion capacity of plant carbon sources, prolong the duration of high denitrification rate, and increase nitrogen removal rates in constructed wetlands. The main components of dissolved organic matter released from the treated carbon sources are humic acid-like, tyrosine-like, and tryptophan-like, which are highly bioavailable.