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

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 ecosyste

Confirming anthropogenic influences on the major organic and inorganic constituents of rainwater in an urban area

Recently, rainwater composition affected by atmospheric pollutants has been the topic of intense study in East Asia because of its adverse environmental and human health effects. In the present study, the chemical composition and organic compounds of rainwater were investigated from June to December 2012 at Gwangju in Korea. The aim of this study is to determine the seasonal variation of rainwater chemical composition and to identify possible sources of inorganic and organic compounds. The volume-weighted mean of pH ranged from 3.83 to 8.90 with an average of 5.78. Of rainwater samples, 50 % had pH values below 5.6. The volume-weighted mean concentration (VWMC) of major ions followed the order Cl- > SO4 2- > NH4+ > Na+ > NO3- > Ca2+ > Mg2+ > K+. The VWMC of trace metals decreased in the order Zn > Al > Fe > Mn > Pb > Cu > Ni > Cd > Cr. The VWMCs of major ions and trace metals were higher in winter than in summer. The high enrichment factors indicate that Zn, Pb, Cu, and Cd originated predominantly from anthropogenic sources. Factor analysis (principal component analysis) indicates the influence of anthropogenic pollutants, sea salt, and crustal materials on the chemical compositions of rainwater. Benzoic acids, 1H-isoindole-1,3(2H)-dione, phthalic anhydride, benzene, acetic acids, 1,2-benzenedicarboxylic acids, benzonitrile, acetaldehyde, and acetamide were the most prominent pyrolysis fragments for rainwater organic compounds identified by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The results indicate that anthropogenic sources are the most important factors affecting the organic composition of rainwater in an urban area. © 2015 Author(s)open

Abundance and expression of denitrifying genes (narG, nirS, norB, and nosZ) in sediments of wastewater stabilizing constructed wetlands

As expected, the expression of denitrifying genes in a Typha wetland (relatively stagnant compared to other ponds), showing higher nitrogen removal efficiency in summer, was affected by temperature. The abundance and gene transcripts of nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductase (norB), and nitrous oxide reductase (nosZ) genes in seasonal sediment samples taken from the Acorus and Typha ponds of free surface flow constructed wetlands were investigated using quantitative polymerase chain reaction (Q-PCR) and quantitative reverse transcription PCR (Q-RT-PCR). Denitrifying gene copy numbers (10(5)-10(8) genes g(-1) sediment) were found to be higher than transcript numbers( 10(3)-10(7) transcripts g(-1) sediment) of the Acorus and Typha ponds, in both seasons. Transcript numbers of the four functional genes were significantly higher for Typha sediments, in the warm than in the cold season, potentially indicating greater bacterial activity, during the relatively warm season than the cold season. In contrast, copy numbers and expression of denitrifying genes of Acorus did not provide a strong correlation between the different seasons.close

Advanced characterization of organic foulants of ultrafiltration and reverse osmosis from water reclamation

Organic foulants obtained from ultrafiltration (UF) and reverse osmosis (RO) membranes of a large scale municipal water reclamation plant were rigorously characterized using conventional and advanced characterization analyses (e.g. pyrolysis and mass spectrometry) in order to identify major constituents of the organic foulants and investigate fouling characteristics in a large scale application of the UF and RO membranes. Although water qualities and characteristics of effluent organic matter in the feed water were slightly changed during the UF membrane, fouling characteristics of the UF and RO membranes used in a large scale municipal water reclamation plant were significantly different according to the type of membranes. Hydrophobic fractions comprising of carboxylic acids and aldehydes strongly contributed to the fouling formation of the UF membrane compared to that of the RO membranes whereas the RO membrane foulants mainly consisted of hydrophilic fractions comprising of amides and alcohols due to the repulsive electrostatic interaction between negatively charged RO membrane surfaces and hydrophobic fractions with a negative charge, indicating that the membrane characteristics could play an important role in the fouling formation of the tested UF and RO membranes. (C) 2012 Elsevier B.V. All rights reservedclose131

Humification of effluent organic matters through a surface-flow constructed wetland

Dominant fractions of wastewater effluent organic matter (EfOM) were changed from polysaccharides (PS) to polyhydroxyaromatics (PHA), throughout the constructed treatment wetland connected to a wastewater treatment plant, as measured using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The changes in the fractions were also identified, with respect to molecular weight (MW) distributions of the effluent organic matters, as measured using high performance size exclusion chromatography equipped with both UV and fluorescence detectors, for aromatic/hydrophobic and protein-like organic substances, respectively; organic matter, with MWs of approximately 2,500 and 20,000 Da, and approximately 38,000 Da, as measured by the UV and fluorescence detectors, respectively, were newly formed after the wetlands, especially for the samples of the Typha wetland in June and August against in December. Thus, with the above two different analyses, the humification type of transformation of EfOM through the treatment wetland, was believed to occur, probably due to biological transformation (from the comparison of results in June and August with those in December). It was anticipated that the humification of EfOM could reduce biodegradable organic portions of wastewater effluents even though total organic carbon levels were not reduced that much after the treatment wetlandopen0

Science Walden: new horizons of combined ecological sanitation with separated urine/feces and treatment wetlands

A new engineering concept, designed with separated urine/feces and graywater recovery, was proposed, and the first steps in taking this concept from the planning stage to implementation have been taken using pilot experiments within a small village. The village employs ecological toilet, equipped with 24 h ventilation, and constructed treatment wetlands consisting of both vertical and horizontal subsurface wetlands for graywater recovery. The quality of recovered graywater was similar to that of the water found in the adjacent stream, which is a concept of zero discharge system with graywater. Separated urine, in either fresh or stored form, was diluted with collected rainwater and with reused water without any detergent from a sink, to be supplied to vegetable garden as fertilizer. Separated dried feces were composted in the garden for approximately 3 months and then used as fertilizer. Dried and composted feces, together with stored urine, were characterized in terms of microbial community using pyrosequencing, to identify the presence of any potential pathogens, in order to confirm the system provides safe hygiene. Hypothesized idea of a micro-algae farm within the village might be proposed with separated urine serving as nutrients for algae that could in turn be cultivated as biofuel (diesel) produced from extracted lipids of algae. Through this pilot village test, we have taken a great stride towards practical realization of experimental concepts, in the form of this new urban water management model with ecological sanitationclose0

Developing organic fouling indices of microfiltration and nanofiltration membranes for wastewater reclamation

Wastewater reclamation processes, including membrane bio reactor (MBR) and nanofiltration (NF) membrane, have been built, and those processes were independently operated, under recycling conditions, to compare the performances, with respect to contaminants removal and fouling minimization. The hydrophilic fractions of organic matter were more effectively removed than the hydrophobic fraction through the system due to microbial activities in the MBR, as measured using three dimensional fluorescence excitation and emission spectra. Furthermore, levels of nitrogen compounds, micropollutants, metals, and metalloid were substantially reduced by the applied MBR and NF system. These observations were in good agreements with patterns in molecular weight distributions and fluorescence spectra. The major components of membrane fouling in the system for wastewater reclamation were the hydrophilic fractions; high-performance size-exclusion chromatography, fluorescence and infrared spectra, and XAD 8/4 resins revealed that the hydrophilic fractions (non-humic substances), comprising of protein-like substances and saccharide groups, are responsible for serious membrane fouling in the tested system for wastewater reclamationclose101

Role of a constructed wetland to humify effluent organic matter from a wastewater treatment plant

The degree of aromaticity or hydrophobicity in wastewater effluent organic matter (EfOM) increases during flow-through constructed wetlands connected directly to a wastewater treatment plant (WWTP), as identified using fractionation followed by analysis methods, with respect to major biopolymers (polysaccharides, amino sugars, protein, polyhydroxy aromatics, and lignins). In this study, WWTP effluent and wetland EfOM were fractionated using preparative high-performance liquid chromatography (prep-HPLC) with both UV and RI detectors, and then, their physical and chemical properties were characterized using UV/Vis, high-performance size exclusion chromatography (HPSEC), 3D fluorescence, and pyrolysis-GC/MS (Py-GC/MS). WWTP and wetland EfOM were separated into three fractions (peak #1-3), using prep-HPLC, through C-18 and size exclusion mechanisms. Results of specific UV absorbance (SUVA), 3D fluorescence, and Py-GC/MS analyses indicate that relative aromaticity/hydrophobicity of organic matter are in the order of peak #3 > peak #2 > peak #1, which also represents order of molecular weight (MW) (peak #1 > peak #2 > peak #3)close0