Dissolved Organic Matter In Wastewater Research Articles

Development and application of the UVC LED-based spectrophotometer for high frequency online monitoring of nitrate concentration in municipal wastewater

Developing a fast, sensitive and stable sensor for online monitoring nitrate concentration is an urgent need for the optimization of denitrification processes in wastewater treatment plants (WWTPs). In this study, the miniaturized spectrophotometric nitrate sensor was developed using UVC light-emitting diodes (LEDs) coupled with AlGaN or SiC-based photodiodes. The use of novel SiC photodiodes could effectively eliminate UVB and UVA light in the 230 nm LED emission spectra. Replacing 235 nm UVC-LED with 230 nm UVC-LED could effectively increase the detection sensitivity but not the linear range that follows the Lambert-Beer's law. The influences of dissolved organic matter (DOM) on nitrate analysis could be corrected by a unified coefficient α across the NO3--N concentration ranging in 0–50 mg/L. Across the investigated WWTP samples, the correction coefficient α was mainly determined by the fractions of humic substances with apparent molecular weight (MW) of 1.5–9.0 kDa, while the degradation of the large MW proteinaceous biopolymer resulted in dramatic variations of correction coefficient α along the WWTP A/A/O process. Microfiltration membranes with pore sizes ≤ 30 µm could sufficiently eliminate the influences of particles in effluents on photometric nitrate analysis. The ultrafiltration and enhanced coagulation treatment could effectively remove the biopolymer fractions of DOM in wastewater, and thus alleviate its influences on sensitivity and accuracy of nitrate analysis. The spectrophotometric nitrate sensors were successfully applied for on-line monitoring NO3--N concentrations in the influent and effluent of denitrifying biofilter in a municipal WWTP, providing high-frequency feedback signals to precise control of feeding external carbon source.

Dynamic relationship between dissolved organic matter and soluble microbial products during wastewater treatment

Dynamics of the dissolved organic matter (DOM) and soluble microbial products (SMP) significantly affected the sustainability of wastewater treatment plants and effluent qualities. In this study, the origin, transformation, and seasonal variation of DOM components in the anaerobic/anoxic/oxic (A2O) units were illustrated with fluorescence analysis. Results show that the anaerobic process transformed humic acid-like substances (HA) and SMP into fulvic acid-like substances (FA) and aromatic proteins (AP), which indicated the decomposition of macromolecules. In cold seasons, the anoxic process turned AP to HA, SMP, and FA; but the oxic process reversed the transformation. In warm seasons, 6.0% of AP decreased while 3.1% of HA, 1.8% of SMP, and 1.0% of FA increased during the oxic process. Proteobacteria strains were isolated from the activated sludge to stimulate the SMP generation, it was found higher temperature facilitated the transformation of FA and HA (humics) to SMP and AP (proteins), which resulted more proteins presented in the wastewater DOM. These findings indicated that the treatment efficiency and DOM quality in A2O processes were influenced by influent quality and/or temperature conditions, and highlighted the generation of SMP by sludge microorganisms, based on which the corresponding strategies considering the seasonal DOM/SMP dynamics were recommended for the stringent regulation of effluents and the sustainability of the receiving water bodies. Besides, the overall fluorescence intensity was positively correlated with the quantified biopolymer contents in SMP, implying the potential of using the fluorescence-derived information to indicate more quantified DOM properties.

Role of precursors in the formation of trihalomethanes during chlorination of drinking water and wastewater effluents from a metropolitan region in western India

Dissolved organic matter (DOM) is the primary precursor that reacts with chlorine to form potentially carcinogenic/mutagenic disinfection byproducts (DBPs). The prime objective of this study was to compare the nature of DOM in samples collected from drinking water and wastewater treatment plants in western India and to relate their nature and concentration to trihalomethane (THM) formation. The effects of chlorine dose, bromide ion, contact time, and pH on THM formation were also studied. The surrogate parameters, such as UV absorbance at 254 nm and dissolved organic carbon (DOC) were monitored for each experiment to understand their correlation with THM formation in the selected water and wastewater systems. Fluorescence spectroscopy revealed that DOM in wastewater was dominated by protein-like components, while DOM in water samples consisted mostly of humic-like components, which exhibited greater THM formation potential. Fractionation of DOM into various fractions followed by reaction with chlorine revealed that the hydrophobic acid and neutral fractions of DOM were primarily responsible for THM formation. Thus, methods that target removing these fractions before chlorination would have maximum impact on reducing THM formation.

Electrochemically modified dissolved organic matter accelerates the combining photodegradation and biodegradation of 17α-ethinylestradiol in natural aquatic environment

The photochemical conversion and microbial transformation of pollutants mediated by dissolved organic matter (DOM), including 17α-ethinylestradiol (EE2), are often accompanied in natural water. However, there are few studies to explore the connection and mechanism between the two processes. This research aims to investigate the mechanism of DOM after electrochemically modification mediated EE2 combining photodegradation and biodegradation in the environment and it want to explain the natural phenomena of DOM after electrochemical advanced treatment entering the water environment mediated EE2 natural degradation. The results showed that combining photodegradation with biodegradation rates of EE2 mediated by DOM and electrochemically modified DOM (E-DOM) were promoted obviously. The efficiency of EE2 biodegradation was shown to be strongly correlated with electron accepting capacity (EAC) of DOM. Electrochemical modification can increase the EAC of DOM leading to EE2 biodegradation accelerated, and it also can form more triplet-state DOM moieties to promote the EE2 photodegradation in irradiation conditions, due to the increasing of quinone-type structures in DOM. Moreover, cell polymeric secretion (CPS) secreted from the microorganism could be stimulated to an excited state by irradiation, and that also accelerated EE2 degradation. Photolysis combined with biochemical degradation yielded less toxic degradation products. This study shows that the emission of DOM in wastewater after electrochemical treatment could accelerate estrogen degradation and play a positive role on the pollutant transformation in the environment.

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 CH2 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.

HPLC-SEC: a new approach to characterise complex wastewater effluents

ABSTRACTThis work investigates the use of HPLC-SEC to characterise dissolved organic matter (DOM) of complex wastewater effluents. A silica-based column, sodium acetate eluent and multiple detections were employed: UV-254 absorbance for humictype, and tryptophan-like (Ex/Em = 270/355) and tyrosine-like (Ex/Em = 270/310) fluorescence for protein type compounds. Effects of eluent pH, eluent ionic strength and injection volume on separation efficiency were tested. Humic-type and protein-type fractions were clearly differentiated and eluted within and out of calibration range. Eluent ionic strength had the greatest influence on global resolution; the lowest eluent concentration of 0.01 M produced the best separation for all wastewater effluents tested at any detection. UV-254 absorbance was higher at neutral and basic eluent pH while tryptophan-like fluorescence depended on the sample composition rather than on the eluent pH or ionic strength. Tyrosine-like fluorescence decreased significantly with the increase of eluent ionic strength. Accurate molecular weight measurements could not be done, the separation being influenced by secondary interactions, but could be approximated using separate calibrations with sodium salts of polystyrene-sulfonates and protein standards. The results show that this method is suitable for determining DOM in wastewater at low eluent concentrations (up to 0.03 M), at neutral or slightly basic pH.

Interactions of Soluble and Solid Organic Amendments with Priming Effects Induced by Glucose

In this work, the effects of various dissolved organic matter (DOM) sources (piggery effluent [PigE], dairy effluent [DE], sewage effluent [SE], and stormwater [SW]) on the priming effect (PE) of soil C as affected by solid organic amendments (biochar [BC], biosolids [BS], compost, and poultry manure [PM]) and microbial activity were quantified using landfill, arable, and metal‐contaminated field and spiked soils. The BC‐amended soil caused significantly lower PEs than BS‐, compost‐, or PM‐amended field soils due to its low DOM. A strong positive correlation was observed between the dissolved organic C content and glucose‐induced PE of soil C. However, a negative correlation between the PE and dissolved N in different sources of DOM suggested that the PE may also be influenced by the quality of added C sources in the soils. The DE‐treated soil with the highest dissolved N resulted in significantly lower PE than PigE‐, SE‐, and SW‐treated soils. Compared with the uncontaminated soils, microbial activity as CO2 evolution and PE decreased markedly in the metal‐contaminated soils, which may be attributed to the heavy metal toxicity. However, the distinct increase in microbial activity in the wastewater‐treated contaminated soils suggests the capacity of wastewater to reduce metal toxicity in soils. The findings of this study suggest that although wastewater DOM may reduce the toxic effect to microorganisms, it can have an important effect on the source of CO2 by stimulating the decomposition of native soil organic matter.

Assessing removal efficiency of dissolved organic matter in wastewater treatment using fluorescence excitation emission matrices with parallel factor analysis and second derivative synchronous fluorescence

To assess removal efficiency of dissolved organic matter (DOM) in the wastewater treatment plant (WWTP), fluorescence excitation emission matrices (EEM) with parallel factor analysis (PARAFAC) and second derivative synchronous fluorescence (SDSF) were used for the characterization of DOM in wastewater. In A(2)/O process, tryptophan-like and tyrosine-like materials were removed to the much greater extent than that of fulvic-like. The protein-like material might be mostly decomposed by anaerobic and aerobic bacteria in anaerobic/anoxic and oxic zones. C1, C2, I276, I286, AP1 and AP2 were much better in tracing variations of tryptophan-like and tyrosine-like materials than C3, I329 and AF1 in tracing fulvic-like. The number of sampling sites should be reduced, as concentration variations of DOM components were subtle among sampling sites in the oxic zone and secondary sedimentation tank. SDSF may be a useful tool as PARAFAC to monitor removal efficiency of DOM fractions from wastewater in the WWTP.