EEM Spectra Research Articles

Removal of refractory humic acid-like components from UF filtrate of landfill leachate through pH adjustment and coupled electrochemical process

Mature landfill leachate contains large quantities of a wide range of hazardous and refractory pollutants, especially humic acid-like (HA) and fulvic acid-like (FA) substances. These have poor biodegradability and a considerable ultraviolet-light quenching capacity, severely inhibiting the performance of wastewater treatment and post ultraviolet-light disinfection, but this aspect has attracted little previous research. The Fenton reaction has proved to be a feasible method for removing ultraviolet-quenching substances (UVQSs) but in conventional systems it is unable to completely mineralize organic contaminants. In this study, a novel electro-oxidation process was developed consisting of a flow-through reactor with a Cu2O cathode to catalyze Fenton-type reactions, and oxidation at a RuO2 anode. The combination of pH adjustment and electro-oxidation was evaluated for the treatment of real ultrafiltration (UF) filtrate of mature landfill leachate. A series of analytical techniques were used to determine the performance for the removal of HA and FA. Under optimal conditions, the elimination of fluorescence characteristics of HA and FA reached 100 % and 99.3 %, respectively, according to PARAFAC results based on EEM spectra. TOC was removed by 25.5 %∼30.4 % during the pH adjustment step and 51 % by electrochemical oxidation. Changes in the molecular weight distribution and fluorescence content showed that pH adjustment played an important and significant role in removing UVQSs, and the remaining TOC after electrochemical oxidation was attributed to bioavailable amino acid-like substances. Overall, the results have demonstrated the successful development of an effective method of treating the UF filtrate from mature landfill leachate, with particular respect to the removal of the problematic HA and FA content.

Optical and molecular insights into dissolved organic matter release in soils induced by downward migration of biochar colloids

The frequent wildfires and extensive biochar application accumulate biochar colloids in soils. The transport of biochar colloids may influence the release of soil dissolved organic matter (DOM) due to their high mobility and active surface, posing a detrimental impact on carbon cycle, pollutants behaviors, and water quality. Here, we examined the effect of pristine and aged biochar colloids on soil DOM release in three types of soils (black soil, fluvisol, and paddy soil) through adsorption and column experiments combined with fluorescence excitation/emission matrix spectroscopy (EEM) and fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Adsorption experiment showed that biochar exhibited little effect on soil DOM release, while transport experiment indicated that the downward movement of both pristine and aged biochar colloids significantly enhanced the release of soil DOM, especially black soil and fluvisol. EEM spectra indicated that a humic acid-like substance with large molecular weights was the primary DOM that enhanced release from black soil (10.9–12.0% enhancement) and fluvisol (6–8% enhancement) during biochar colloid transport. Condensed aromatic-like (22.8% and 19.4%) and tannin-like (18.4% and 18.9%) compounds are the primary molecules correlated to the enhanced release of humic acid-like substances. Although chemical aging resulted in a more negative surface of aged biochar colloids and slightly enhanced biochar colloid transport (up to 7.0%), it showed no distinct effect on the release of soil DOM. This study indicates that biochar colloids may cause an increase in DOM release when irrigation and rainfall occur, and more attention should be paid to the environmental impacts of biochar colloids from intensive biochar application and wildfires.Graphical

Gas-liquid contact evaporation of concentrate leachate from disk-tube reverse osmosis treatment in waste incineration plant

In order to utilize waste heat such as exhaust steam and hot air passing through air preheater in the waste incineration plant to heat air used for evaporating leachate concentrate (LC) by gas-liquid contact evaporation technology, hot air of 600 °C, 450 °C and 250 °C was used to evaporate LC in a laboratory-scale evaporator to obtain purified condensate used for supplying water for circulating cooling water system. The influence of pH, hot air temperature and evaporation rate on COD and NH3–N in condensate were investigated to identify the optimum operation of this technology. The results showed that COD concentration in condensate obviously decreased with increase in hot air temperature. Higher hot air temperature led to higher initial evaporation temperature, and evaporation rate of water was significantly greater than that of small molecular organic matter with lower boiling point than water with increasing hot air temperature. Reduction in contents of phenol, ketone and benzene was responsible for COD decreasing in condensate. COD in condensate decreased with increase in pH, as the amount of volatile organic matter such as fatty acids escaped from LC to condensate decreased. The pH had little influence on the DOM in condensate according to EEM spectra analysis. Evaporation rate had little influence on COD in the condensate water. NH3–N concentrations in condensate in all experimental groups were far away from the limit value (10 mg/L) in the water quality standard. Under the premise of meeting water quality standard, the lowest temperature (450 °C) of hot air was selected to save energy and use lower grade waste heat. Therefore, the optimum condition was 450 °C of hot air, pH = 7 of LC and CF = 10. At this condition, molecular weight of DOM in the condensate was smaller and humification degree and aromaticity of DOM were lower according to UV–visible absorption spectrum analysis.

Enhanced membrane fouling by microplastics during nanofiltration of secondary effluent considering secretion, interaction and deposition of extracellular polymeric substances

Microplastic (MP) has been found to influence membrane fouling during microfiltration/ultrafiltration processes in direct and indirect ways by acting as fouling components and changing microbial activities, respectively. However, there is no relevant research about the contribution of MPs to nanofiltration membrane fouling. In this study, for the first time, the impacts of MPs on membrane fouling during the nanofiltration of secondary effluent (SE) were systematically investigated from the perspective of bacterial extracellular polymeric substances (EPS) secretion, their interaction with coexisting pollutants and also deposition. Membrane flux behaviors indicate that MPs simultaneously aggravated the short-term and long-term membrane fouling resistance of nanofiltration by 46 % and 27 %, respectively. ATR-FTIR, XPS and spectrophotometry spectra demonstrate that the deteriorated membrane fouling by MPs directly resulted from the increased accumulation of protein-like, polysaccharides-like and humic-like substances on membranes. EEM spectra further confirmed that MPs preferred to induce serious cake layers, which dominated membrane flux decline but hindered pore fouling. According to CLSM and SEM-EDS mappings, MPs in SE could stimulate microbial activities and then aggravate EPS secretion, after which their interaction with Ca2+ was also enhanced in bulk solution. The cross-linker nets could promote the deposition of other unlinked pollutants on membranes. Besides, MPs could weaken the rejection of certain dissolved organic matters (from 57 % to 52 % on the 50th day of filtration) by aggravating cake-enhanced concentration polarization (CECP), but improved the average removal of inorganic salts from 58 % to 63 % by improving their back diffusion through cake layers. Based on these analyses, the mechanisms of MP-enhanced membrane fouling during the nanofiltration of SE can be thoroughly revealed.

Indium removal by Aspergillus niger fungal pellets in the presence of selenite and tellurite

The feasibility of simultaneous removal of indium, selenite and tellurite using biological reduction by Aspergillus niger fungal pellets is explored. Initially, batch experiments were conducted to study the capability of A. niger pellets to remove indium, selenium and tellurium in different combinations. The indium removal efficiency ranged between 52.3 and 65.6 % at 10 mg/L, with a maximum removal (~65 %) in incubations with only indium or indium with tellurite. The tellurium removal efficiency was maximum (76.7 %) in experiments with indium, but dropped drastically to 47.2 and 33.7 %, respectively, when selenite and indium were incubated together. The selenite removal efficiencies of the A. niger pellets were more consistent (50.2–59.5 %) for different experimental combinations and were not affected by either indium or tellurium. Further characterization of fungal biomass showed accumulation of mainly elemental Se and Te nanoparticles within the pellets. In addition, XRD analysis showed the formation of indium selenide and indium telluride during their simultaneous removal. The EPS production by A. niger increased in the presence of these elements along with changes in the polysaccharide and protein content of the EPS. The fluorescence EEM spectra revealed that the EPS produced by A. niger during pollutant removal was mostly composed of soluble microbial products and humic acid like substances. This study demonstrated recovery of elemental chalcogen and indium chalcogenide nanoparticles can be achieved using fungal pelleted systems.

Optical Properties of the Suwannee River Fulvic Acid Complexation with Thorium Using 3D Fluorescence Spectroscopy

The relationship between the complexation amount of thorium (Th) and Suwannee River fulvic acid (SRFA) and the changes in Th concentration and pH were studied using differential spectroscopy and 3D excitation-emission matrix fluorescence spectroscopy (3D EEM). Experiments were performed at different Th concentrations and pH values. In the differential spectra at different concentrations, four bands of aromatic components appeared, and thorium was complexed with the carboxyl groups in SRFA. The 3D EEM spectra showed a fulvic acid-like fluorescence region, a visible-light fulvic acid region, and the blueshift phenomenon. The fluorescence intensity decreased with increasing thorium concentration and increased with increasing pH. The results showed that the amount of complexation of thorium and SRFA increased with increasing thorium concentration, and high pH was not conducive to the complexation of thorium and SRFA.

Methods for unsupervised contribution analysis of raw EEM data in water monitoring. Contaminant identification and quantification

Fluorescence EEM spectra provide the “fingerprint” of water contamination and is a very efficient way to access the quality of water bodies. These multivariate datasets correspond to complex mixtures and are very rich in information. Graphical approaches have been used for decades to characterize and quantify different contamination sources. It is very important to resolve mixed signals in raw EEM spectra in terms of signal sources and respective composition profiles – signal sources allow the identification of contamination type, while concentration profiles quantify the respective contribution inside the mixtures. In order to be able to use robust modeling algorithms, the first task is to accurately estimate the number of contributions that are present. We demonstrate the ability of Singular value Decomposition (SVD) in accessing this information content in raw EEM datasets. To decompose raw EEM information, several algorithms are tested: PARAFAC, MCR-ALS and ICA. In this work we suggest a systematic unsupervised algorithm to process raw EEM spectra of water samples.

Reverse osmosis concentrate treatment by microbubble ozonation-biological activated carbon process: Organics removal performance and environmental impact assessment

Reverse osmosis (RO) is being used in many water reclamation facilities to produce high quality water that can be reused for different purposes. As a part of the RO process, a reject stream is produced as the reverse osmosis concentrate (ROC), which contains elevated levels of contaminants compared to the source water. Effective treatment and safe disposal of ROC via cost-effective means is very challenging. This study aims to develop a robust microbubble ozonation–biological process for industrial ROC treatment with a target effluent chemical oxygen demand (COD) lower than 60 mg/L. As compared to macrobubble ozonation, microbubble ozonation exhibited better ozone dissolution and 29% higher COD removal efficiency with the same ozone dosage. Under the optimum operating conditions with ozone dosage of 30 mg/L, ROC natural pH of 8.67 and ozonation duration of 1 h, microbubble ozonation achieved 42% COD removal efficiency while increasing the BOD5/COD ratio (ratio of biological oxygen demand over 5 days to the corresponding chemical oxygen demand) in ROC from 0.042 to 0.216. A biological activated carbon (BAC) column with an empty bed contact time (EBCT) of 120 min was combined with microbubble ozonation for continuous ROC treatment. Over the 100-day operation, the combined system performed consistent organics removal with an average effluent COD of 45 mg/L. Both LC-OCD data and fluorescence EEM spectra confirmed humic substances were the dominant organic species in ROC. Ozone pre-treatment could achieve significant removal of humic substances in raw ROC. ATP analysis found that ozone pre-treatment enhanced BAC biofilm activity by around 5 folds. 5 min acute toxicity assessment with Aliivibrio fischeri showed 4 times reduction of bioluminescence inhibition in ozone treated ROC. From the environmental point of view, Life cycle assessment (LCA) results demonstrated that Ozone-BAC system had significant environmental burdens on climate change and human toxicity due to the electricity production process. These environmental impacts can be mitigated by optimizing the ozonation process with reduced ozone dosage or utilizing renewable energy sources for electricity generation.

Variations of disinfection byproduct precursors through conventional drinking water treatment processes and a real-time monitoring method

In this investigation, raw water (RW), settled water (SW), and filtered water (FW) collected from a drinking water treatment plant were fractionated into 24 natural organic matter (NOM) fractions with varying molecular weights and hydrophobicity. The yields of disinfection byproducts (DBPs) obtained during the chlorination of the NOM fractions were explored. Results revealed that the 0–1 kDa, 5–10 kDa, and hydrophobic DBP precursors dominated RW. Hydrophobic fractions cannot be effectively removed, which contributed to the high DBP precursors remaining in the FW. The optional optical parameters, including UVA (UV340, UV360, and UV380), UVB (UV280, UV300, and UV310), and UVC (UV254, UV260, and UV272), were analyzed to determine the DBP yields during chlorination of different NOM fractions. Results revealed that UVC could be applied to indicate the regulated DBP yields of the humified precursors. Contrary to the generally accepted view, for biologically derived precursors, their regulated DBPs and dichloroacetonitrile correlated better with UVA (e.g. UV340). Moreover, PARAFAC analysis was applied to decompose an array of 24 EEM spectra. Good linear correlations were found between the PARAFAC components and most DBP yields. Furthermore, four fluorescence parameters were proposed via a modified fluorescence picking method, which can serve as excellent surrogates of PARAFAC components. These fluorescence parameters were found to be effective in indicating most DBP yields. Finally, the fluorescence intensity at excitation wavelength/emission wavelength = 310/416 nm was found to be a promising built-in parameter for the real-time monitoring of DBP precursors, regardless of the humification degree of the precursors.

Spatiotemporal variations of DOM components in the Kushiro River impacted by a wetland.

Dissolved organic matter (DOM) has been recognized as a serious water quality problem in natural water bodies receiving pollution loads from point and nonpoint sources. The present study investigates the spatiotemporal variability of DOM composition in the Kushiro River and its tributaries (Eastern Hokkaido, Japan) impacted by the Kushiro wetland. Water samples were collected in the wet and dry seasons from several locations of the river and analyzed for DOM characteristics by UV-visible and excitation-emission matrix fluorescence spectroscopy techniques and by developing water quality index. Rather than the spatial effect, significant seasonal impacts on DOM pollution in the Kushiro River were observed. Overall concentrations of DOM decreased during the dry season. The increase of specific ultraviolet absorbance in the dry season indicated an increasing trend of humification, aromaticity and molecular weight of DOM. Five fluorescent peaks, including peaks A, C, M, B, and T were predicted by EEM spectra. Peaks A and C were found to be the most dominating peaks in both the seasons and indicated enrichment of humic-like matters in river water. The intensities of poly-aromatic humic substances as well as DOM components of microbial origin increase in the wet season and proteins like autochthonous DOM increase during the dry season. The study recognized the contribution of freshly produced DOM component by the decomposition of wetland plants in wet season and effect of snowfall in the dry season. Analysis of three fluorescence indices revealed that the river water primarily contains terrestrially dominated DOM. A significant impact of the adjacent WWTPs and wetland to the river water DOM were also observed. The water quality index of river water DOM showed low to medium levels of DOM pollution in the Kushiro River.

Insight into the cadmium and zinc binding potential of humic acids derived from composts by EEM spectra combined with PARAFAC analysis

AbstractTo investigate the characteristics of humic acids (HAs) and the combined effects of HAs on heavy metals, three HAs derived from kitchen waste compost (KW), pig manure compost (PM), and green waste compost (GW) were exposed to Cd(II) and Zn(II). The elemental contents and functional groups of HAs were different due to different raw materials. Fulvic-, humic-like content C1, humic-like content C4, and two protein-like contents C2 and C3 were identified in three HAs by EEM-PARAFAC analysis. The effects of HAs on heavy metals were associated with the metal species and HA source. Our results reveal that titrating Cd(II) caused stronger fluorescence quenching compared to titrating Zn(II) for all HAs. C1 and C4 of KW-HAs and PM-HAs showed fluorescence quenching after Cd(II) was added, whereas negligible fluorescence quenching was found when Zn(II) was added. In addition, C1 and C4 in the GW-HAs did not show obvious fluorescence quenching regardless of whether Cd(II) or Zn(II) was added. C3 in all HAs caused significant fluorescence quenching, suggesting that C3 plays an important role affecting the mobility of heavy metals. Consequently, these results suggest that HAs from KW and PM have greater potential for Cd-contaminated soil remediation than those from GW.

Insights into solubility of soil humic substances and their fluorescence characterisation in three characteristic soils

Soil humic substances (HS) are involved in almost all biogeochemical processes and functions in soils, thus their extraction from aiming to their characterization is very important. However, many factors that influence HS extraction from soil still need further studies. The aim of this work was to assess and quantify comparatively the solubility of soil HS as a function of extraction time, various extractants, solid to liquid ratio and sequential extraction. In this work three different soils, i.e. a forest, a maize and a paddy soil, were examined to assess the solubility of soil HS based on their fluorescence (excitation-emission matrix, EEM) features and changes in nutrient (NO3−-N, PO43−-P and dissolved Si) contents using multiple extraction approaches (time-dependent, various extractants, solid to liquid ratio, and sequential extraction). Three fluorescent components, i.e. humic acids-like (HA-like), fulvic acids-like (FA-like), and protein-like fluorophores (PLF), were identified by parallel factor (PARAFAC) analysis of EEM spectra of the various soil extracts. The solubility of HS, dissolved organic carbon (DOC) and nutrients were shown to increase with extraction time, except for PLF. The FA-like fraction disappeared completely in KCl extracts of all three soils, suggesting the inefficiency of salt extraction. Conversely, HS and nutrients solubility substantially increased in alkaline extracts, and dissolved Si was correlated significantly with the fluorescent intensities of HA-like and FA-like, thus confirming the well-known typical process of alkaline dissolution of HS bound to phytolith and silicate minerals. The relative solubility of HS and nutrients was higher at lower solid to liquid ratio (1:250–1:100), whereas their maximum yields was achieved at high solid to liquid ratio (1:10) for all three soils. Sequential extraction results showed that the first water extraction step contributed 42–55% of HS, which suggested that a single extraction was insufficient to recover HS. In conclusion, water and alkaline extraction could provide, respectively, the labile and insoluble complexed HS existing in soil.

Potential of combined advanced oxidation – Biological process for cost-effective organic matters removal in reverse osmosis concentrate produced from industrial wastewater reclamation: Screening of AOP pre-treatment technologies

While reverse osmosis (RO) technology is playing an important role in industrial wastewater reclamation, safe and cost-effective RO concentrate (ROC) disposal becomes challenging due to high levels of organic pollutants. The present study assessed the feasibility of combined advanced oxidation – biological process for organics removal in real ROC. Four advanced oxidation processes (AOPs) were evaluated for ROC pre-treatment, including UV/H2O2, UV/Persulfate (PS), Fenton and Fluidized bed reactor (FBR)-Fenton processes. Based on the results of process optimization and cost evaluation, FBR-Fenton was identified as the most cost-effective pre-treatment technology with a chemical cost of S$0.519/m3. Under the optimum operating conditions with 10 mM H2O2, 1.25 mM Fe2+, pH 3 and HRT of 1 h, continuous FBR-Fenton process increased the BOD5/COD ratios in ROC by 4.2–10.0 times, while the COD removal efficiency was in the range of 30.9–59.8%. A biological activated carbon (BAC) column with EBCT of 120 min was combined with FBR-Fenton for continuous treatment of ROC. Over the 120-day operation, the combined system performed consistent organics removal in ROC with an average COD removal efficiency of 69%. The average effluent COD level in ROC was observed to be 26 mg/L. Both LC-OCD data and fluorescence EEM spectra suggested humic substances to be the dominant organic species in ROC, FBR-Fenton could achieve significant humic substances removal and biodegradability enhancement in ROC. High-throughput sequencing demonstrated Planctomycetes to be top dominant phylum in BAC media with high salinity influent, and FBR-Fenton process promoted its proliferation for higher COD removal efficiency in ROC.

Intensifying ozonation treatment of municipal secondary effluent using a combination of microbubbles and ultraviolet irradiation.

Ozonation treatment of municipal secondary effluent is complicated by the low solubility of ozone and inefficient production of hydroxyl free radicals from ozone decomposition. To resolve these problems, this study investigated methods for intensifying ozonation treatment, using a combination of microbubbles and ultraviolet (UV) irradiation (UV/MBO). The high efficiency of the method was illustrated by treating river water containing refractory components derived from secondary effluent in a wastewater treatment plant. The results showed that the ozone mass transfer coefficient in a microbubble system was an order of magnitude compared with a conventional macrobubble system at the initial stage. The amount of ·OH generated during the treatment was quantified using a fluorescent probe analysis. The amount of ·OH in the UV/MBO system was almost 2-6 times more than the amount found with conventional ozonation using macrobubbles (CO), CO with UV irradiation (UV/CO), and microbubble ozonation (MBO) units. The UV/MBO system achieved chemical oxygen demand (COD), UV254, and UV400 removal performance rates of up to 37.50%, 81.15%, and 94.74% respectively. These levels were 2-36% higher than those in other systems. The coupling UV/MBO treatment significantly reduced all five categories of substances according to EEM spectra and fluorescence regional integration. The distribution of fractions with different molecular weights (MW) was altered and the UV254 of MW (< 500Da) increased by 15.8%. The biodegradability of the water was significantly improved, as indicated by the TOC/UV254. This is ascribed to the enhanced degradation of refractory organics in the water. The combination of the UV/microbubble technique with ozonation could provide an efficient approach for advanced wastewater treatment. Graphical abstract.

Assessing Fluorescent Organic Matter in Natural Waters: Towards In Situ Excitation–Emission Matrix Spectroscopy

Natural organic matter (NOM) is a key parameter in aquatic biogeochemical processes. Part of the NOM pool exhibits optical properties, namely absorption and fluorescence. The latter is frequently utilized in laboratory measurements of its dissolved fraction (fluorescent dissolved organic matter, FDOM) through excitation–emission matrix spectroscopy (EEMS). We present the design and field application of a novel EEMS sensor system applicable in situ, the ‘Kallemeter’. Observations are based on a field campaign, starting in Norwegian coastal waters entering the Trondheimsfjord. Comparison against the bulk fluorescence of two commercial FDOM sensors exhibited a good correspondence of the different methods and the ability to resolve gradients and dynamics along the transect. Complementary laboratory EEM spectra measurements of surface water samples and their subsequent PARAFAC analysis revealed three dominant components while the ‘Kallemeter’ EEMS sensor system was able to produce reasonable EEM spectra in high DOM concentrated water bodies, yet high noise levels must be addressed in order to provide comparable PARAFAC components. Achievements and limitations of this proof-of-concept are discussed providing guidance towards full in situ EEMS measurements to resolve rapid changes and processes in natural waters based on the assessment of spectral properties. Their combination with multiwavelength FDOM sensors onboard autonomous platforms will enhance our capacities in observing biogeochemical processes in the marine environment in spatiotemporal and spectral dimensions.

Identification of textile wastewater in water bodies by fluorescence excitation emission matrix-parallel factor analysis and high-performance size exclusion chromatography

Identifying the causes of water body pollution is critical because of the serious water contamination in developing countries. The textile industry is a major contributor to severe water pollution due to its high discharge of wastewater with high concentrations of organic and inorganic pollutants. In this study, fluorescence excitation emission matrix-parallel factor (EEM-PARAFAC) analysis was applied to characterize textile industry wastewater and trace its presence in water bodies. The EEM spectra of textile wastewater samples collected from 12 wastewater treatment plants (WWTPs) revealed two characteristic peaks: Peak T1 (tryptophan-like region) and Peak B (tyrosine-like region). Two protein-like components (C1 and C2) were identified in the textile wastewater by PARAFAC analysis. The components identified from different textile WWTPs were considered identical (similarity >0.95). C1 and C2 were not sensitive to changes in pH, ionic strength, or low humic acid concentration (TOC < 4 mg/L). Therefore, C1 combined with C2 was proposed as a source-specific indicator of textile wastewater, which was further demonstrated by conducting high-performance size exclusion chromatography analysis. These results suggested that EEM-PARAFAC analysis is a reliable means of identifying textile wastewater pollution in water bodies and may also enable the identification of other industrial wastewater.

Short-term exposure effects of magnetic Fe3O4 nanoparticles on anaerobic granular sludge performance

Effects of magnetic Fe3O4 nanoparticles (Fe3O4 NPs) on the decontamination performance and the EPS components of sludge were studied during short-term exposure experiments. Results showed that compared with the control, the COD removal efficiency reduced from 92.8% to 84.5% with the abrupt short-term addition of excessive Fe3O4 NPs. The content of TB-EPS increased from 64.8 mg/gVSS to 74.5 mg/gVSS. The absorption peak of amine in LB-EPS became sharp in the FTIR spectra. In the EEM spectra, the intensity of coenzyme F420 peak in LB-EPS was slightly enhanced.

The Organic Pollutant Characteristics of Lurgi Coal Gasification Wastewater before and after Ozonation

The effluent of distilled and extracted Lurgi coal gasification wastewater has been found to have low biodegradability and high toxicity, which inhibits further biodegradation. However, ozonation enhances the biodegradability and reduces the toxicity of this effluent, enabling further biological treatment and increased removal of organic materials. In this study, the dissolved organic matters in Lurgi coal gasification wastewater were isolated into six classes by resin adsorbents, after which TOC, UV254, UV-Vis, and 3D EEM were employed to quantitatively and qualitatively analyze organic materials in each part of the fractionated samples. The HoA and HiN fraction accounted for large amounts of the Lurgi coal gasification wastewater, and their TOC values were about 380.21 mg·L−1 and 646.84 mg·L−1, respectively. After ozonation, the TOC removal rates of HoA and HiN reached 42.85% and 67.13%, respectively. The UV254 of HoA was basically stable before and after ozonation, while that of HiN increased continuously because a portion of the humic macromolecular organic materials in HoA was oxidized to HiN. Additionally, UV-Vis analysis revealed that the larger molecular organics of HoA were oxidized during ozonation, resulting in high biodegradability. Finally, the 3D EEM spectra indicated that the macromolecular organics were oxidized to smaller molecules with the degradation of soluble microbial by-products.

Effects of sepiolite addition on removing contaminants in anaerobic reactor for treatment landfill leachate

The effects of adding sepiolite in the performance of an anaerobic reactor for treating landfill leachate were investigated. Responses of SMP and EPS of the R1 (without sepiolite) and R2 (with sepiolite) reactors were evaluated by EEM and FTIR spectra. Results showed that addition of sepiolite increased the removal of COD removal by 10%. The highest removal rate of ammonia nitrogen was also observed reaching 69.8% in R2 reactor. In the EEM spectra, humic- and fulvic acid-like substances were present in the EPS of the R1 reactor. The peak was located at the excitation/emission wavelength (Ex/Em) of 280/350 nm in the R2 reactor, attributed to tryptophan-like proteins. Meanwhile, dehydrogenase activities were higher than in the R1 reactor, similar with observations on COD removal rate.

Correlating fluorescence spectral properties with DOM molecular weight and size distribution in wastewater treatment systems

By systematically exploring the EEM spectra, some fluorescence variables are found to correlate with the molecular weight/size (MW) levels of DOM and may usefully reflect the MW in wastewater treatment systems.