Wastewater Effluent Organic Matter Research Articles

Mechanistic Aspects of Photodegradation of Deoxynucleosides Induced by Triplet State of Effluent Organic Matter.

Excited triplet states of wastewater effluent organic matter (3EfOM*) are known as important photo-oxidants in the degradation of extracellular antibiotic resistance genes (eArGs) in sunlit waters. In this work, we further found that 3EfOM* showed highly selective reactivity toward 2'-deoxyguanosine (dG) sites within eArGs in irradiated EfOM solutions at pH 7.0, while it showed no photosensitizing capacity toward 2'-deoxyadenosine, 2'-deoxythymidine, and 2'-deoxycytidine (the basic structures of eArGs). The 3EfOM* contributed to the photooxidation of dG primarily via one-electron transfer mechanism, with second-order reaction rate constants of (1.58-1.74) × 108 M-1 s-1, forming the oxidation intermediates of dG (dG(-H)•). The formed dG(-H)• could play a significant role in hole hopping and damage throughout eArGs. Using the four deoxynucleosides as probes, the upper limit for the reduction potential of 3EfOM* is estimated to be between 1.47 and 1.94 VNHE. Compared to EfOM, the role of the triplet state of terrestrially natural organic matter (3NOM*) in dG photooxidation was minor (∼15%) mainly due to the rapid reverse reactions of dG(-H)• by the antioxidant moieties of NOM. This study advances our understanding of the difference in the photosensitizing capacity and electron donating capacity between NOM and EfOM and the photodegradation mechanism of eArGs induced by 3EfOM*.

Evaluation of the fate of wastewater effluent organic matter in receiving water: Effect of sequential photochemical and biological processes

Effluent organic matter (EfOM) discharged from wastewater treatment plants (WWTPs) carry substantial risks to river ecosystems. The fate and role of EfOM in the receiving water is affected by its exposure to sunlight and microbial processes, but the extent of these processes remains unclear. In this study, three-phase sequence of irradiation and microbial incubation with EfOM were conducted to compare the behavior of EfOM with that of natural organic matter in receiving rivers (RNOM). The dissolved organic carbon (DOC) in EfOM was degraded by 23% after three sequential phases, while that in RNOM was degraded by 19%. In the first phase, the irradiation of EfOM stimulated microbial respiration and growth by producing easily metabolizable less aromatic lignin-type molecules, leading to a 21% increase in biodegradation. Conversely, the irradiation of RNOM removed biodegradable lignin-type molecules, causing a 50% decreased in biodegradation. The second and third irradiation phases of EfOM and RNOM produced biodegradable lignin-type molecules, making their molecular compositions increasingly similar. The acute toxicity of EfOM decreased by 55%, and differences in microbial species composition between EfOM and RNOM waters decreased by 82% after the three-phase sequence. These findings can improve understanding of the fate of EfOM discharged into receiving rivers.

Photo-transformation of wastewater effluent organic matter reduces the formation potential and toxicity of chlorinated disinfection byproducts

Sunlight exposure can degrade and transform discharged wastewater effluent organic matter (EfOM) in aquatic systems, potentially enhancing the feasibility of reusing wastewater for drinking purposes. However, there remains a lack of comprehensive understanding regarding the sunlight-induced changes in the molecular-level composition, characteristics, and chlorine reactivity of EfOM. Herein, we investigated the impact of sunlight on the optical properties, chemical composition, and formation of disinfection byproducts of EfOM using multiple spectroscopic analyses, high-resolution mass spectrometry, chlorination experiments, and in vitro bioassays. Upon natural sunlight exposure, we observed significant decreases in ultraviolet–visible absorbance and fluorescence intensity of EfOM, indicating the destruction of chromophores and fluorophores. Photolysis generally yields products with lower molecular weight and aromaticity, and with higher saturation and oxidation levels. Moreover, a shift within the EfOM from condensed aromatic-like compounds to tannin-like components was observed. Furthermore, sunlight exposure reduced the reactivity of EfOM toward the formation of trihalomethanes and haloacetonitriles during chlorination, while there was a slight increase in the specific formation potential of haloketones. Importantly, the disinfection byproducts resulting from chlorination of the irradiated EfOM exhibited reduced microtoxicity. Overall, this study provides new insights into alterations in EfOM under sunlight exposure and aids in predicting the health risks of effluent discharge in water environments.

Adsorptive removal of propranolol under fixed-bed column using magnetic tyre char: Effects of wastewater effluent organic matter and ball milling

We investigated the competitive effects of different fractions of wastewater treatment plant effluent organic matter (EfOM) on adsorption of an organic micro pollutant (OMP), propranolol (PRO), in a fixed bed column packed with magnetic tyre char (MTC). The results showed that the presence of EfOM inhibited PRO adsorption in wastewater leading to decreased PRO adsorption capacity from 5.86 to 2.03 mg/g due to competitive effects and pore blockage by smaller EfOM fractions. Characterization of EfOM using size exclusion chromatography (LC-OCD) showed that the principal factor controlling EfOM adsorption was pore size distribution. Low molecular weight neutrals had the highest adsorption onto MTC while humic substances were the least interfering fraction. Effect of important parameters such as contact time, linear velocity and bed height/diameter ratio on MTC performance was studied in large-lab scale columns. Linear velocity and contact time were found to be effective in increasing adsorption capacity of PRO on MTC and delaying breakthrough time. Increase in linear velocity from 0.64 cm/min to 1.29 cm/min increased mass transfer and dispersion, resulting in considerable rise of adsorbed amount (5.86 mg/g to 22.58 mg/g) and increase in breakthrough time (15.8–62.7 h). Efficiency of non-equilibrium Hydrus model considering dispersion and mass transfer mechanism was demonstrated for real wastewater and scale up purposes. Ball milling for degradation of adsorbed PRO and regeneration of MTC resulted in 79% degradation of PRO was achieved after 5 h milling (550 rpm), while the addition of quartz sand increased the efficiency to 92%.

Kinetics and Transformations of Diverse Dissolved Organic Matter Fractions with Sulfate Radicals.

Dissolved organic matter (DOM) scavenges sulfate radicals (SO4•-), and SO4•--induced DOM transformations influence disinfection byproduct (DBP) formation when chlorination follows advanced oxidation processes (AOPs) used for pollutant destruction during water and wastewater treatment. Competition kinetics experiments and transient kinetics experiments were conducted in the presence of 19 DOM fractions. Second-order reaction rate constants for DOM reactions with SO4•- (kDOM,SO4•-) ranged from (6.38 ± 0.53) × 106 M-1 s-1 to (3.68 ± 0.34) × 107 MC-1 s-1. kDOM,SO4•- correlated with specific absorbance at 254 nm (SUVA254) (R2 = 0.78) or total antioxidant capacity (R2 = 0.78), suggesting that DOM with more aromatics and antioxidative moieties reacted faster with SO4•-. SO4•- exposure activated DBP precursors and increased carbonaceous DBP (C-DBP) yields (e.g., trichloromethane, chloral hydrate, and 1,1,1-trichloropropanone) in humic acid and fulvic acid DOM fractions despite the great reduction in their organic carbon, chromophores, and fluorophores. Conversely, SO4•--induced reactions reduced nitrogenous DBP yields (e.g., dichloroacetonitrile and trichloronitromethane) in wastewater effluent organic matter and algal organic matter without forming more C-DBP precursors. DBP formation as a function of SO4•- exposure (concentration × time) provides guidance on optimization strategies for SO4•--based AOPs in realistic water matrices.

Photodegradation-induced biological degradation of treated wastewater effluent organic matter in receiving waters

Effluent organic matter (EfOM) from wastewater treatment plants (WWTP) constitutes an important source of dissolved organic matter in receiving waters. Photodegradation may alter the properties of WWTP EfOM, thereby impacting its biodegradability and microbial respiration. However, whether and how natural sunlight exposure of EfOM affects its biodegradability and microbial oxygen consumption in the receiving waters are unclear. To address these knowledge gaps, incubation experiments of biodegradation, photodegradation, and bio-photodegradation were conducted with the effluent samples from a tertiary WWTP in Heifei, China. The quantity and quality of the EfOM were examined during the incubations to interpret changes in its lability and composition. The results showed that photodegradation facilitated and accelerated the EfOM biodegradation. After natural sunlight exposure, the EfOM degradation rate was significantly enhanced from 0.004 d−1 to 0.065 d−1 measured by dissolved organic carbon (DOC). Correspondingly, the DOC concentration of EfOM was reduced by 64.2% (26.6% by photodegradation and 37.5% by bio-photodegradation), while the concentration was only reduced by 5.3% in the direct biodegradation. Sunlight exposure of EfOM resulted in lower molecular weight, less aromatic, lower humified, more bleached photoproducts. These substances could be readily metabolized by the native microbial community in the receiving water, stimulating microbial respiration. Correspondingly, the oxygen consumption rate of EfOM increased from almost 0.11 mg L−1 d−1 in the direct biodegradation to 2.17 mg L−1 d−1 in the bio-photodegradation. This study highlights that after EfOM is discharged to the receiving water, its post-processing by sunlight can enhance biodegradability. The existence of the coupled photochemical and biological process is suggested to be considered when determining EfOM fate and managing effluent discharge in receiving waters.

Impact of pretreatment on RO membrane organic fouling: composition and adhesion of tertiary wastewater effluent organic matter

Organic fouling in RO desalination of tertiary wastewater is of major concern in the decline in membrane performance.

Characterization of wastewater effluent organic matter with different solid phase extraction sorbents

Effluent organic matter (EfOM) from municipal wastewater treatment plants (WWTPs) has received increasing attention due to its impacts on natural and engineered aquatic systems. A comprehensive understanding of molecular compositions of EfOM is crucial for controlling its negative effects and effective removal of it. Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS) is a powerful method to characterize molecular compositions of EfOM. However, application of this powerful technique is very depending on the sample preparation procedures (i.e. solid phase extraction, SPE) for enrichment and desalting. In this study, a systematic comparison of the difference in molecular compositions of the EfOM extracted using eighteen different SPE sorbents (Envicarb, PPL, ENV, HLB, C18, C18OH, C8, PH, CH, WAX, WCX, MAX, MCX, CBA, C2, CN-E, NH2, and SI) was investigated. Molecular characterization using FTICR MS showed that non-polar sorbents (Envicarb, PPL, ENV, HLB, C18, C18OH) and mixed mode sorbents (WAX, WCX, MAX, MCX) prefer to extract more aromatic and unsaturated molecules, while strongly-polar (SI), mid-polar (CBA, NH2), and weakly non-polar (C2, CN-E) sorbents prefer to extract more aliphatic components. In addition, it is found that combining extracts of CBA, ENV, and EnviCarb sorbents might be a practical way to provide a comprehensive information of molecular composition of EfOM. The results reported in this study provide valuable information on molecular compositions of EfOM and the selectivity of EfOM by different SPE sorbents.

Degradation and deactivation of a plasmid-encoded extracellular antibiotic resistance gene during separate and combined exposures to UV254 and radicals

This study investigated the degradation and deactivation of an extracellular ampicillin resistance gene (ampR) encoded in plasmid pUC19 during exposure to UV254, •OH (generated by UV>290/H2O2), and combined exposure to UV254 and •OH (and/or SO4•−) using UV254/H2O2 and UV254/S2O82−. The degradation rates of ampR measured by quantitative polymerase chain reaction increased with increasing target amplicon length (192–851 bps). The rate constants for the degradation of pUC19 (2686 bps) were calculated as 0.26 cm2/mJ for UV254 and 1.5 × 1011 M−1s−1 for •OH, based on the degradation rates of ampR amplicons and assuming an equal sensitivity of DNA damage across the entire plasmid. DNA repair-proficient Escherichia coli (E. coli) AB1157 strain (wild-type) and its repair-deficient mutants including AB1886 (uvrA−), AB2463 (recA−), AB2480 (uvrA−, recA−), and DH5α (recA−, endA−) were applied as recipient cells in gene transformation assays. Results suggested that the elimination efficiency of transforming activity during UV254 and •OH exposure was dependent on the type of DNA repair genes in recipient E. coli strains. Losses of transforming activity were slower than the degradation of pUC19 by a factor of up to ∼5 (for E. coli DH5α), highlighting the importance of DNA repair in recipient cells. The degradation rates of ampR amplicons were much larger (by a factor of ∼4) in UV254/H2O2 and UV254/S2O82− than UV254 direct photolysis, indicating the significant contribution of •OH and SO4•− to the gene degradation. Not only UV254 and SO4•−, but also •OH contributed to the degradation of ampR during UV254/S2O82−, which was attributed to the conversion of SO4•− to •OH and a 10-fold larger reactivity of •OH towards ampR as compared to SO4•−. However, the enhanced gene degradation by radicals did not lead to a faster elimination of gene transforming activity during UV254/H2O2 and UV254/S2O82−, suggesting that UV254- and radical-induced DNA damage were not additive in their contributions to losses of gene transforming activity. Wastewater effluent organic matter (EfOM) accelerated the degradation of ampR during UV254 irradiation by means of reactive species production through indirect photolysis reactions, whereas EfOM mainly acted as a radical scavenger during UV254/H2O2 and UV254/S2O82− treatments.

Methodology for selection of optical parameters as wastewater effluent organic matter surrogates

Absorbance- and fluorescence-based optical parameters are commonly used as surrogates in engineered systems, but there is no systematic approach for selecting robust parameters. This study develops a methodology that is applied to a case study of differentiating wastewater effluent organic matter from naturally-derived organic matter. The methodology defines criteria to identify optical parameters that could detect statistically significant compositional differences in organic matter, independent of organic matter concentration, and measure fluorescence-based parameters with low susceptibility to inner filter effects. The criteria were applied to 26 parameters that were measured for 11 pairs of source water and conventionally-treated wastewater samples collected from sites with varied spatial and temporal conditions. Only two parameters, apparent fluorescence quantum yield measured at excitation 370 nm and fluorescence peak ratio A:T, met the criteria across all sites. These results demonstrate and encourage an objective and robust process for selecting optical surrogates for organic matter characterization.

Characterization of fluorescence foulants on ultrafiltration membrane using front-face excitation-emission matrix (FF-EEM) spectroscopy: Fouling evolution and mechanism analysis

The understanding of fouling behavior and mechanism is critical for fouling control in membrane processes. This study adopted a novel fluorescence front-face excitation-emission matrix (FF-EEM) approach to characterize the fluorescence foulants deposited on membrane surface. Methods for quantifying protein and humic substances deposited on ultrafiltration (UF) membrane were established. Foulants deposited on the membrane surface during the UF of model foulants (bovine serum albumin (BSA) and humic acids (HA)) and wastewater effluent organic matter (EfOM) were quantified using the FF-EEM and liquid EEM coupled with mass balance calculation. The foulants mass data obtained by FF-EEM were further used to analyze fouling mechanism involved in UF. The FF-EEM based method was more accurate than the liquid EEM based method, as the problems associated with liquid EEM based method (such as the error propagation in the mass balance calculation and the ineffectiveness of inner filter correction) were avoided in FF-EEM based method. The fouling resistance did not correlate well with the amount of foulants, as the major fouling mechanism instead of the mass of foulants mainly determined the extent of fouling. This work demonstrated FF-EEM could be a powerful tool for investigating fouling evolution and fouling mechanism in UF process.

Influence of EfOM on simultaneous rejection and degradation of PhACs during a forward osmosis coupled with electrochemical oxidation process

In this study, a forward osmosis coupled with electrochemical oxidation (FO-EO) process was used to achieve simultaneous rejection and degradation of 15 pharmaceutically active compounds (PhACs) in wastewater. The influence of wastewater effluent organic matter (EfOM) on PhACs removal was investigated. Sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA) were used as model organics to represent major constituents of EfOM. Results demonstrated that a generally negative influence of SA on PhACs rejection was observed due to membrane fouling in FO processes. During FO-EO processes, high rejection (>95%) and degradation efficiencies (>94%) of 15 PhACs were achieved simultaneously. With the presence of model organics in feed, adverse impacts on PhACs degradation were observed in the order of HA > BSA > SA. Results of UV and EEM fluorescence spectroscopy detection verified the competition of EfOM with PhACs for electrochemical oxidation, further proving the role of natural organic matter (NOM) and proteins in impeding the PhACs removal in FO-EO processes. Moreover, degradation products of PhACs were identified. And the acute toxicity of the feed was decreased after treated by FO-EO processes although the mineralization of PhACs was partially achieved. Furthermore, PhACs in actual secondary effluent were well removed by FO-EO processes, exhibiting a desirable application performance.

Formation of iodinated THMs during chlorination of water and wastewater in the presence of different iodine sources

The formation potential of iodinated trihalomethanes (I-THMs) during chlorination of different organic precursors in the presence of various iodine sources was studied. Organic precursors included humic acid, natural organic matter from river water and wastewater effluent organic matter. Inorganic iodide and two iodinated X-ray contrast media compounds (iopamidol and diatrizoate) were used as iodine sources. The formation potential of I-THMs under different experimental conditions (chlorination contact time, iodide and bromide concentrations) was investigated. The formation of I-THM species upon chlorination of river water and humic acids rapidly increased up to 24h and then a decreasing trend was observed. Wastewater, showed a rapid formation of I-THMs within the first 6h, followed by a lower rate with extended time. Formation of I-THMs in the presence of iopamidol was more favorable regarding the other two iodine sources. CHBrClI was the dominant specie followed by CHCl2I and CHBr2I. Increasing iodide concentrations result in higher I-THMs formation. The presence of bromide enhanced the I-THMs yields and shifted towards bromine-containing species (CHBrClI and CHBr2I).

Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts

The reclamation and disinfection of waters impacted by human activities (e.g., wastewater effluent discharges) are of growing interest for various applications but has been associated with the formation of toxic nitrogenous disinfection byproducts (N-DBPs). Monochloramine used as an alternative disinfectant to chlorine can be an additional source of nitrogen in the formation of N-DBPs. Individual toxicity assays have been performed on many DBPs, but few studies have been conducted with complex mixtures such as wastewater effluents. In this work, we compared the cytotoxicity and genotoxicity of wastewater effluent organic matter (EfOM) before and after chloramination. The toxicity of chloraminated EfOM was significantly higher than the toxicity of raw EfOM, and the more hydrophobic fraction (HPO) isolated on XAD-8 resin was more toxic than the fraction isolated on XAD-4 resin. More DBPs were also isolated on the XAD-8 resin. N-DBPs (i.e., haloacetonitriles or haloacetamides) were responsible for the majority of the cytotoxicity estimated from DBP concentrations measured in the XAD-8 and XAD-4 fractions (99.4% and 78.5%, respectively). Measured DBPs accounted for minor proportions of total brominated and chlorinated products, which means that many unknown halogenated compounds were formed and can be responsible for a significant part of the toxicity. Other non-halogenated byproducts (e.g., nitrosamines) may contribute to the toxicity of chloraminated effluents as well.

Effect of coagulation conditions on ultrafiltration for wastewater effluent

Low-pressure membrane filtration is increasingly used for tertiary treatment of wastewater effluent organic matter (EfOM), mainly comprising organic base/neutral compounds. In-line coagulation with underdosing, charge neutralization, and sweep floc conditions prior to ultrafiltration (UF) was studied to determine removals of the EfOM components and consequent reduction of fouling using polyethersulfone membranes. Coagulation and UF substantially reduced fouling for all coagulation conditions while removing from 7 to 38% of EfOM organic acids. From 7 to 16% of EfOM organic base/neutrals were removed at neutral pH but there was no significant removal for slightly acid coagulation conditions even though fouling was substantially reduced. Sweep floc produced the lowest resistance to filtration but may be inappropriate for in-line use due to the large added volume of solids. Charge-neutralization resulted in poor recovery of the initial flux with hydraulic cleaning. Under-dosing paralleled sweep floc in reducing hydraulic resistance to filtration (for sub-critical flux) and the initial flux was also easily recovered with hydraulic cleaning. Hydrophobic and hydrophilic base/neutrals were identified on the fouled membranes but as previously reported the extent of fouling was not correlated with accumulation of organic base/neutrals.

Role of effluent organic matter in the photochemical degradation of compounds of wastewater origin

The photoreactivity of treated wastewater effluent organic matter differs from that of natural organic matter, and the indirect phototransformation rates of micropollutants originating in wastewater are expected to depend on the fractional contribution of wastewater to total stream flow. Photodegradation rates of four common compounds of wastewater origin (sulfamethoxazole, sulfadimethoxine, cimetidine and caffeine) were measured in river water, treated municipal wastewater effluent and mixtures of both to simulate various effluent-stream water mixing conditions that could occur in environmental systems. Compounds were chosen for their unique photodegradation pathways with the photochemically produced reactive intermediates, triplet-state excited organic matter (3OM*), singlet oxygen (1O2), and hydroxyl radicals (OH). For all compounds, higher rates of photodegradation were observed in effluent relative to upstream river water. Sulfamethoxazole degraded primarily via direct photolysis, with some contribution from OH and possibly from carbonate radicals and other unidentified reactive intermediates in effluent-containing samples. Sulfadimethoxine also degraded mainly by direct photolysis, and natural organic matter appeared to inhibit this process to a greater extent than predicted by light screening. In the presence of effluent organic matter, sulfadimethoxine showed additional reactions with OH and 1O2. In all water samples, cimetidine degraded by reaction with 1O2 (>95%) and caffeine by reaction with OH (>95%). In river water mixtures, photodegradation rate constants for all compounds increased with increasing fractions of effluent. A conservative mixing model was able to predict reaction rate constants in the case of hydroxyl radical reactions, but it overestimated rate constants in the case of 3OM* and 1O2 pathways. Finally, compound degradation rate constants normalized to the rate of light absorption by water correlated with E2/E3 ratios (sample absorbance at 254 nm divided by sample absorbance at 365 nm), suggesting that organic matter optical properties may hold promise to predict indirect compound photodegradation rates for various effluent mixing ratios.

Influence of activated carbon preloading by EfOM fractions from treated wastewater on adsorption of pharmaceutically active compounds

In this study, the preloading effects of different fractions of wastewater effluent organic matter (EfOM) on the adsorption of trace-level pharmaceutically active compounds (PhACs) onto granular activated carbon (GAC) were investigated. A nanofiltration (NF) membrane was employed to separate the EfOM by size, and two GACs with distinct pore structures were chosen for comparison. The results showed that preloading with EfOM substantially decreased PhAC uptake of the GACs; however, comparable PhAC adsorption capacities were achieved on GACs preloaded by feed EfOM and the NF-permeating EfOM. This indicates that: (1) the NF-rejected, larger EfOM molecules with an expectation to block the PhAC adsorption pores exerted little impact on the adsorbability of PhACs; (2) the smaller EfOM molecules present in the NF permeate contributed mainly to the decrease in PhAC uptake, mostly due to site competition. Of the two examined GACs, the wide pore-size-distributed GAC was found to be more susceptible to EfOM preloading than the microporous GAC. Furthermore, among the fourteen investigated PhACs, the negatively charged hydrophilic PhACs were generally subjected to a greater EfOM preloading impact.

Novel strategies for diagnosing the cause of short-term organic fouling in ultrafiltration

ABSTRACTThe main objective of this study was to demonstrate the usefulness of a multi-strategic approach for identifying the extent and mechanism of fouling in the ultrafiltration (UF) of wastewater effluent organic matter (EfOM). In this study, we combined EfOM fractionation with spectroscopic autopsies for clean and fouled UF membranes. The EfOM fractions were sequentially removed from the wastewater effluent using relatively gentle techniques (neutral pH and no extractions). The residual EfOM samples were then used in UF tests. This work showed that resistance to filtration was partially reduced with the removal of particles (>20 nm), but almost all of the short-term fouling was eliminated with the removal of organic acids, which constitute 22% of the total organic carbon. The membrane autopsies were conducted using attenuated reflectance infrared spectroscopy for the top and bottom fouled membranes, and comparison was made with the infrared spectra of a clean membrane. Hydrophilic base/neutrals were the dominant EfOM constituents at the top of the fouled membranes. Hydrophobic acids were adsorbed onto the pore walls deep inside the membranes, which coincided with the permeability recovery of fouled membranes. The fouling mechanisms were examined by measuring the resistance to filtration as a function of permeate flux using various operational conditions and by investigating the effectiveness of hydraulic and chemical cleaning on the restoration of membrane permeability.

Membrane distillation combined with an anaerobic moving bed biofilm reactor for treating municipal wastewater

A fermentative strategy with an anaerobic moving bed biofilm reactor (AMBBR) was used for the treatment of domestic wastewater. The feasibility of using a membrane separation technique for post-treatment of anaerobic bio-effluent was evaluated with emphasis on employing a membrane distillation (MD). Three different hydrophobic 0.2 μm membranes made of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polypropylene (PP) were examined in this study. The initial permeate flux of the membranes ranged from 2.5 to 6.3 L m−2 h−1 when treating AMBBR effluent at a temperature difference between the feed and permeate streams of 20 °C, with the permeate flux increasing in the order PP < PVDF < PTFE. The permeate flux of the PTFE membrane gradually decreased to 84% of the initial flux after the 45 h run for distillation, while a flux decline in MD with either the PVDF or PP membrane was not found under the identical distillation conditions. During long-term distillation with the PVDF membrane, total phosphorus was completely rejected and >98% rejection of dissolved organic carbon was also achieved. The characterization of wastewater effluent organic matter (EfOM) using an innovative suite of analytical tools verified that almost all of the EfOM was rejected via the PVDF MD treatment.

Ultrafiltration performance of EfOM and NOM under different MWCO membranes: Comparison with fluorescence spectroscopy and gel filtration chromatography

Ultrafiltration performance of wastewater effluent organic matter (EfOM) and background natural organic matter (NOM) under different molecular weight cutoff (MWCO) membranes was investigated. Permeates of EfOM and NOM from ultrafiltration were systematically compared by using fluorescence spectroscopy and gel filtration chromatography. The results revealed that anthropogenic polysaccharide- and protein-like substances including polysaccharides, proteins, and colloids in EfOM were mainly removed by ultrafiltration with the 100kDa membrane, which accounts for a large proportion of the total DOC in EfOM. With the decreasing of the membrane's MWCO, the humic substances in NOM were more easily removed compared with that in EfOM. The polysaccharides associated with the colloidal fraction, as well as the humic substances were speculated as the main potential foulants for UF membranes processing wastewater EfOM. As for NOM, humic substances were regarded as the main potential foulants. The fouling mechanism (cake filtrations or pore blocking) of EfOM or NOM in the ultrafiltration process was related with the MWCO of the membrane and the molecular size of the main foulants.