Spectroscopic and Chromatographic Characterization of Wastewater Organic Matter from a Biological Treatment Plant

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation

Assessment of the Analytical Potential of HPLC-SEC for the Characterization of DOM and Nutrients in Various Types of Water

This study focused on high performance size exclusion liquid chromatography (HPLC-SEC) combined with two ultraviolet (UV, 254 nm and 224 nm) detection wavelengths to detect humic-like compounds and two fluorescence (FLU) excitation/emission (tyrosine-like and tryptophan-like) wavelengths to detect protein type compounds in water samples. Targeted particularly were further possibilities of this method, such as finding suitable chromatographic surrogates for organic matter and nutrient indicators for water types such as catchment surface waters, well waters, and onsite wastewater effluents, which have been studied little before. It was thus necessary to determine the optimum analytical conditions for exacting wastewater effluent analysis in term of eluent strength, eluent pH, and sample injection volume. Additionally, this study provided valuable information on the spatial and temporal behavior of dissolved organic matter along a catchment area and on the quality of onsite wastewater effluent and well water in sparsely populated areas. A TSK-GEL G3000SW column, Na-acetate of 0.01 M at pH=7 eluent, and an injection volume of 30 μL guaranteed good separation of dissolved organic matter (DOM) in surface and well water samples up to 8 fractions and further up to 11 fractions in complex onsite black water effluents. For systematic analysis of high strength onsite wastewater effluents, we chose, based on calculations of global resolution at various eluent conditions, Na-acetate of 0.02 M at pH=7 eluent and an injection volume of 20 μL. DOM concentration dropped along the catchment, as 35-75% of dissolved organic carbon (DOC) was eliminated. DOM in drains had up to 80% high molecular weight (HMW) fraction and lakes only 50-60% HMW. Drains had high DOC in summer and lakes in winter and spring with seasonal increase in DOC resulting from increased HMW fractions in these waters. The water treatment plant eliminated HMW fractions from raw water up to 100%, intermediate MW (IMW) fractions up to 87%, and low LMW fractions up to 66%. A seasonal increase in raw water DOM was detected in drinking water samples as increased IMW and appearance of HMW fractions. Of the two protein-type detections, tryptophan-type signals were clearly measured in surface water. Tryptophan-like FLU, as sum of peak height (SPH), was consistently higher in the drain affected by agriculture than in the drain in the mire area. The study on well waters showed that, on average, shallow and deep well water differ little in quality in the sparsely populated agricultural areas studied. According to HPLC-SEC-UV254, high-DOC well water samples had clear and often dominant HMW fractions and low-DOC samples hardly any HMW fractions but dominant IMW fractions. The LMW fraction, correlating with nitrate, indicates anthropogenic influence. Nitrate was precisely calculated from the peak height (PH) of the LMW fraction detected by UV-224. Our study on onsite blackwater effluent (BWE) and greywater effluent (GWE) disclosed the overall quality of onsite wastewater effluents with BWEs having higher mean values than GWEs for all the conventional indicators measured. The chromatograms (UV-254, tyrosine, and tryptophan) of onsite wastewater effluents showed the regular peaks for surface and well waters and extra peaks eluted over the permeation volume. Dividing the chromatograms into 3 regions helped identify the best possible surrogates for conventional indicators. Region 3 comprising the late peaks eluted over the permeation volume in the tyrosine- and tryptophanchromatograms correlated best with biochemical oxygen demand (BOD-7), showing that these fractions are biodegradable. Tyrosine-like chromatograms assess best DOC and BOD-7, trytophan-like chromatograms best total nitrogen (TN), and UV254 and tyrosine-like chromatograms best the chemical oxygen demand (COD) of wastewater effluents. Regression equations corresponding to the best correlations between the chromatographic and conventional indicators are given in the study for reliable calculation of DOC, COD, and BOD-7 and rough assessment of the TN. This study highlights the fact that secondary interactions, unwanted in SEC can be exploited in nitrate measurement of well waters and BOD assessment of high strength wastewater effluents

13C NMR study of the effect of aerobic treatment of olive mill wastewater (OMW) on its lipid-free content

Olive mill wastewater was treated by an aerobic bio-process at different values of pH (with or without addition of lime), for 45 days on a laboratory scale, to evaluate the reduction of the organic load. The lipid content showed an appreciable change in relation to the applied treatment both for total lipids and for the different fractions (neutral lipids, monoglycerides and phospholipids). 13C NMR spectroscopy was performed on initial and final samples both raw and after lipid extraction. The main spectral differences were observed in the C-alkyl region (0–50 ppm), in the C O-alkyl/N-alkyl region (50–110 ppm), and in the C-carboxylic (160–200 ppm) region, providing information on the alterations occurring in the different biochemical entities composing this complex biomatrix (e.g. lipids and carbohydrates) according to the treatment

A non-targeted high-resolution mass spectrometry data analysis of dissolved organic matter in wastewater treatment

The dissolved organic matter (DOM) in wastewater is typically described by a limited number of concentration measurements of select DOM fractions or micro-contaminants, which determine the removal efficiency in a wastewater treatment. Current methods do not necessarily reflect the true performance of the treatment with regard to environmental and public health risk. Herein we describe the development and application of a non-targeted liquid chromatography-high resolution mass spectrometry (LC-HRMS) data analysis for the evaluation of wastewater treatment processes. Our data analysis approach was applied to a real wastewater system with secondary biological treatment and tertiary treatment consisting of sand filtration, UV-treatment, and chlorination. We identified significant changes in DOM during wastewater treatment. The secondary treatment removed 1617 of 2409 (67%) detected molecular features (grouped isotopologues belonging to the same molecule) from the influent while 255 of 1047 (24%) new molecular features appeared in the secondary effluent. A reduction in the number of large molecules (>450 Da) and an increase in unsaturated molecular features of the effluent organic matter was observed. Van Krevelen plots revealed the distribution of unsaturation and heteroatoms and Kendrick mass defect plots uncovered single bondCH2- homologous series implying a removal of heavy constituents in that fraction. The demonstrated approach is a step towards a more comprehensive monitoring of DOM in wastewater and contributes to the understanding of current treatment technologies

Effect of cytostatic drug presence on extracellular polymeric substances formation in municipal wastewater treated by membrane bioreactor

The effect of the cyclophosphamide and its mean metabolites on extracellular polymeric substances (EPS) formation was investigated. Two lab-scale membrane bioreactors were followed in parallel (one with the cytostatic drugs, the second without). Chromatographic and spectroscopic studies (UV–Vis spectroscopy and IR spectroscopy) showed that the presence of CPs induced an increase in EPS concentration in the biological sludge, especially of soluble substances, mainly polysaccharides and proteins. Size exclusion chromatography analysis revealed that in the presence of CPs, macromolecular EPS were formed (polysaccharides corresponding to about 6 KDa and proteins to about 18 KDa). The formation of EPS seemed to be a protection mechanism. More important membrane fouling in reactor with CPs seemed to be related to the retention of an increased amount of soluble substances

Characterization and fate of EfOM during ozonation applied for effective abatement of recalcitrant micropollutants

Alterations occurring in the effluent organic matter (EfOM) during ozonation could be detrimental depending on the final application of the treated effluent. In this work, the fate of EfOM in different ozonized wastewaters was assessed through the monitoring of general water quality parameters and organic fractions determined through size-exclusion chromatography combined with organic carbon detection (SEC-OCD) analysis. These different components of EfOM were distinguished based on relative molecular weights and assigned to fractions named as biopolymers, humic substances, building blocks and low molecular weight neutrals and acids. The significant abatement (60-90%) of an ozone-refractory micropollutant (MP) was employed as reference to simulate potential scenarios in which also the presence of these species is wanted to be attenuated. Ultraviolet absorbance at 254 nm (UVA254) and chemical oxygen demand (COD) reductions ranged from 40 to 80% and from 10 to 45%, respectively, for ozone doses between 0.6 and 1.0 mM, depending on the organic matter content (both dissolved and suspended) and alkalinity of the effluents. Dissolved organic carbon (DOC) analysis showed 21-27% reductions in Membrane bioreactor (MBR) effluents, whereas for conventional activated sludge (CAS) samples this value increased (6-35%) during the oxidative treatment. This was attributed to the continuous solubilization of humic substances, according to SEC-OCD results. Moreover, accumulation of lower molecular weight fractions such as building blocks or acids was observed in all the tested effluents, and attributed to the breakdown of largest EfOM fractions, mainly humic substances. Relationships proposed in this work between humic substances evolution, water quality (UVA254) and process parameters (immediate ozone demand (IOD), IOD-normalized hydroxyl radical exposure (∫[¿OH]dt/IOD) and transferred ozone dose (TOD)) might be useful for EfOM variations estimations along ozonation

Estimation of Biological Oxygen Demand and Chemical Oxygen Demand for Combined Sewer Systems Using Synchronous Fluorescence Spectra

Real-time monitoring of water quality for sewer system is required for efficient sewer network design because it provides information on the precise loading of pollutant to wastewater treatment facilities and the impact of loading on receiving water. In this study, synchronous fluorescence spectra and its first derivatives were investigated using a number of wastewater samples collected in sewer systems in urban and non-urban areas, and the optimum fluorescence feature was explored for the estimation of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations of sewer samples. The temporal variations in BOD and COD showed a regular pattern for urban areas whereas they were relatively irregular for non-urban areas. Irrespective of the sewer pipes and the types of the areas, two distinct peaks were identified from the synchronous fluorescence spectra, which correspond to protein-like fluorescence (PLF) and humic-like fluorescence (HLF), respectively. HLF in sewer samples appears to be associated with fluorescent whitening agents. Five fluorescence characteristics were selected from the synchronous spectra and the first-derivatives. Among the selected fluorescence indices, a peak in the PLF region (i.e., Index I) showed the highest correlation coefficient with both BOD and COD. A multiple regression approach based on suspended solid (SS) and Index I used to compensate for the contribution of SS to BOD and COD revealed an improvement in the estimation capability, showing good correlation coefficients of 0.92 and 0.94 for BOD and COD, respectively

Nylon 6 and nylon 6,6 micro- and nanoplastics: a first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

A novel procedure for nylon 6 and nylon 6,6 polyamide (PAs) microplastics (MPs) quantification is described for the first time. The overall procedure, including quantification of poly(ethylene terephthalate) (PET), was tested on wastewater treatment plant (WWTP) sludges. The three polymers account for the largest global share of synthetic textile microfibers, being possibly the most common MPs released upon laundering in urban wastewaters. Therefore, measuring their content in WWTP sludges may provide an accurate picture of the potential risks associated with both the inflow of these MPs in natural water bodies and the practice of using WWTP sludges as agricultural soil amendment. The novel procedure involves PAs depolymerization by acid hydrolysis followed by derivatization of the monomers 6-aminohexanoic acid (AHA) and hexamethylene diamine (HMDA) with a fluorophore. Reversed-phase HPLC analysis with fluorescence detection results in high sensitivities for both AHA (LOD = 8.85·10–4 mg/L, LOQ = 3.73·10–3 mg/L) and HMDA (LOD = 2.12·10–4, LOQ = 7.04·10–4 mg/L). PET quantification involves depolymerization, in this case by alkaline hydrolysis, followed by HPLC analysis of its comonomer terephthalic acid. Eight sludge samples from four WWTPs in Italy showed contamination in the 29.3–215.3 ppm and 10.6–134.6 ppm range for nylon 6 and nylon 6,6, respectively, and in the 520–1470 ppm range for PET

Facilitated Transport of Triclosan in the Receiving Environment of an Onsite Wastewater Treatment System: Agent of Aquatic Concern

Triclosan (TCS) is an antibacterial found in a host of consumer products ranging from toothpaste to textiles. While initially confined to health care settings, the increased popularity of antimicrobial products has resulted in a surge of products containing this compound and can currently be found in over 700 consumer products. The fate of TCS in wastewater treatment plants (WWTPs) and loss mechanisms once exposed to the environment is a topic that has gained much attention over recent years. However, similar research in onsite systems, where its presence and subsequent persistence can have similar adverse environmental effects, is lacking. It is the objective of this study to examine the interaction of TCS to a sorbing medium in the presence of treated effluent from an onsite wastewater treatment system (OWTS). Experiments conducted to examine factors that govern this behavior were centered around three main points of interest: 1) the interaction of TCS to the sorbing medium in the presence and absence of DOM, 2) the mobility of TCS in the presence and absence of DOM, and 3) the effect DOM with a high and low organic carbon concentrations on sorption and mobility. Laboratory scale batch sorption equilibrium and column transport studies were used to observe the solution interaction of TCS in the presence of a sorptive material, 100% quartz sand. Treatments consisted of three solutions: 1) low organic content (LOC) wastewater filtrate (\u3c0.45µm), 2) high organic content (HOC) wastewater filtrate (\u3c0.45µm), and 3) 5 mM CaCl2 serving as the organic free control (NOC). Human derived wastewater from OWTSs was collected for wastewater treatment solutions. Sorption data fit to the Freundlich isotherm model indicates the greatest amount of TCS sorption to sand in the presence of CaCl2 as compared to LOC and HOC treatments. The Freundlich sorption coefficient (KF) revealed the least amount of sorption in the LOC treatment. Statistical analysis showed significant differences (P\u3c0.001) between all three treatment means. Based on isotherm results, TCS has the potential to be preferentially transported by DOM. Column transport experiments also indicate the potential for facilitated transport by DOM in both LOC and HOC treatments. Breakthrough curves demonstrate earlier breakthrough in DOM treatments as compared to NOC. Although DOM treatments (LOC and HOC) were not found to be significantly different from each other, both were significantly different from the NOC treatment (P\u3c0.001). Batch and transport results indicate potential for the facilitated transport of TCS by DOM. However, predicted (batch sorption) and calculated (CXTFIT v2.0) retardation factors did not correlate well with each other. Equilibrium effects were expected to be the dominant factor behind this discrepancy