Transformation of dissolved organic matter in a constructed wetland: A molecular-level composition analysis using pyrolysis-gas chromatography mass spectrometry

Abstract

This study investigated the transformation of dissolved organic matter (DOM) in a free-water surface flow constructed wetland. Pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) coupled with preparative high-performance liquid chromatography (prep-HPLC) was used to analyze the compositions of biopolymers (polysaccharides, amino sugars, proteins, polyhydroxy aromatics, lipids and lignin) in DOM according to the molecular size at three sampling points of the water flow: inflow, midflow, and outflow. The prep-HPLC results verified the decomposition of DOM through the decrease in the number of peaks from three to one in the chromatograms of the sampling points. The Py-GC/MS results for the degradable peaks indicated that biopolymers relating to polysaccharides and proteins gradually biodegraded with the water flow. On the other hand, the recalcitrant organic fraction (the remaining peak) in the outflow showed a relatively high concentration of aromatic compounds. Therefore, the ecological processes in the constructed wetland caused DOM to become more aromatic and homogeneous. This indicated that the constructed wetland can be an effective buffer area for releasing biochemically stable DOM, which has less influence on biological water quality indicators, e.g., biochemical oxygen demand, into an aquatic ecosystem.

Onsite Chlorination of Greywater in a Vertical Flow Constructed Wetland—Significance of Trihalomethane Formation

“…The relative abundance of these moieties can be related to two sources: (1) It is expected that following microbial activity, labile molecules will be favorably consumed, increasing the relative abundance of more complex recalcitrant compounds. In agreement with this general expectation, Park et al [47] showed an increase in aromaticity throughout a constructed wetland receiving secondary treated wastewater (shown for a free-water surface flow constructed wetland with a retention time of seven days). (2) Vegetation can serve as an important additional source of wetland organic matter, as in the RVFCW systems studied here.…”

Influence of pH on the release of colloidal and dissolved organic matter from vertical flow constructed wetland surface sludge deposits

“…The specific ultraviolet absorbance at 254 nm (SUVA 254 , L.mgOC -1 .m -1 ), defined as the ratio of the absorbance at 254 nm to the organic carbon concentration was used as an indicator of the degree of aromaticity of the molecules [37,38]. Values of SUVA 254 above 4 and below 2 were considered to reveal highly aromatic and poorly aromatic molecules, respectively [31].…”

“…The surface sludge layer is the siege of numerous reactions which induce the evolution of organic matter [26,28] that could in turn influence the quantity and the chemical nature of the DOM. Some studies have already monitored the concentration of DOM in VFCW systems, from inflow to outflow [29][30][31]. Kania et al [25] showed that SDs were sources of DOM and reported a pH-dependent leaching pattern.…”

“…During the operation of a wastewater treatment plant unit, the SD layer is usually submitted to pHs ranging between 6 and 9 [31,32]; However, more acidic conditions (pH below 6) can be observed with winery effluents for example [33]. A better description of the leaching of organic compounds from the SDs may also provide useful information regarding the final use of the sludge material in land applications where it would be submitted to pHs ranging from 5 to 9 [34].…”

Investigating Influence of Hydrological Regime on Organic Matters Characteristic in a Korean Watershed

“…In general, terrestrial DOM, originating from plant litter and soil humus, contains mostly carbohydrates and lignin while autochthonous DOM, derived from algae and macrophyte, has a relatively high percentage of protein [8,9]. However, characteristics of DOM cannot be classified into two groups (terrestrial and autochthonous) because DOM is affected by various environmental factors such as source material, microbial community, and temperature [10][11][12].…”