Characteristics Of Effluent Organic Matter Research Articles

Introducing a prediction method for the photodegradation of p-cresol, a phenolic contaminant of emerging concern, in wastewater effluent

Despite extensive efforts to understand the photodegradation of phenolic contaminants of emerging concern (PhCECs) in aquatic systems, prediction methods, especially in waters containing effluent organic matter (EfOM), remain underdeveloped. This study introduces a prediction method for p-cresol, a representative PhCECs, based on correlations between EfOM optical parameters and p-cresol kinetic parameters. We examined p-cresol photodegradation in various EfOM samples, characterized by their optical properties, and used the reaction rate coefficient between EfOM and p-cresol, α3EfOM⁎, to quantify and predict p-cresol degradation in different wastewater effluent samples. Results showed significant correlations between p-cresol's photodegradation rate constant (0.144 to 0.441 h−1) and EfOM characteristics, with α3EfOM⁎ values ranging from 4 × 1011 to 10 × 1011 M−1 s−1. The method was validated with p-cresol at concentrations ranging from 25 to 100 μM and multiple EfOM samples. The method's applicability was further evaluated using propranolol, a pharmaceutical contaminant of emerging concern, demonstrating its versatility for predicting the degradation behavior of other contaminants in different wastewater samples. The method accurately predicted p-cresol and propranolol degradation across diverse wastewater samples, suggesting its potential for expansion to other classes of contaminants, aiding in water quality management, improving wastewater treatment processes, and enhancing environmental risk assessments.

Effects of alternative disinfection methods on the characteristics of effluent organic matter and the formation of disinfection byproducts

The characteristics of effluent organic matter (EfOM) and the type of disinfection methods are closely related to the formation of disinfection byproducts (DBPs) in reclaimed water. In this study, five disinfection methods, i.e., chlorination, ultraviolet (UV) followed by chlorination (UV + Cl), UV/chlorine (UV/Cl), chloramination, and chlorine dioxide (ClO2), were applied to investigate the changes in the properties of EfOM, the formation of DBPs, and the relationship between EfOM properties and DBP formation during the disinfection of four secondary biological effluents. The results showed that EfOM with medium molecular weight (MW) (0.5–6 kDa) was the dominant fraction for all WWTPs. From a fluorescence perspective, the EfOM of the AAO process was rich in humic matter, while the EfOM of the oxidation ditch (OD) process was rich in protein matter. Disinfectants tended to transfer EfOM with high molecular weight (MW) (>6 kDa) to those with low MW (<0.5 kDa). Chlorination, UV + Cl and UV/Cl were more reactive to humic matter, while chloramination and chlorine dioxide were more reactive to protein matter. The formation of known DBPs was mainly dependent on humic matter, while protein matter was more likely to generate unknown DBPs. N-DBPs only accounted for 5.7%–17.7% of the total DBPs, but contributed more than 70% of the calculated toxicity, among which bromochloroacetonitrile (BCAN), dichloroacetonitrile (DCAN), and monobromoacetamide (MBAcAm) were the most important contributors to the calculated cytotoxicity. Monobromoacetic acid (MBAA) and MBAcAm were the primary drivers of the calculated genotoxicity. Overall, UV + Cl was the suggested optimal disinfection method for WWTPs.

Changes in the structural characteristics of EfOM during coagulation by aluminum chloride and the effect on the formation of disinfection byproducts

The effects of coagulation on the removal efficiency of different fractions of effluent organic matter (EfOM) from wastewater treatment plants were investigated to identify changes in their structural characteristics and the influences on trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP). The results indicated that coagulation performed better for the removal of hydrophobic base (HOB) and hydrophobic neutral (HON) fractions than hydrophilic (HI) and hydrophobic acid (HOA) fractions. The removal efficiency was higher under neutral than under acidic conditions for all fractions. As a result, lower levels of THMFP and HAAFP were detected at pH7. The excitation-emission matrix spectra indicated that the HI fraction contained humic acid-like substances that reacted with chlorine to form THMs. The HON fraction contained soluble microbial byproduct-like substances with a higher potential to create HAAs. The results of Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-pressure size exclusion chromatography (HP-SEC) of the raw and coagulated water indicated that a higher molecular weight, α-carbon, COOH, aromatic structures, and polysaccharides were associated with a higher production of disinfection byproducts (DBP). These results elucidate the coagulation efficiencies of EfOM fractions associated with different mechanisms and facilitate the prediction of DBP formation by each fraction based on specific structural characteristics.

Advanced technique of catalytic ozonation-enhanced coagulation for the efficient removal of low coagulability refractory organics from secondary effluent

The novel cascaded catalytic ozonation-enhanced coagulation process (FeCeAC/O3-PAC) was developed with much success towards second effluent organic matter (EfOM) in chemical industrial wastewater. Compared with the conventional techniques, FeCeAC/O3-PAC exhibited remarkable performances in the advanced removal of EfOM. The characteristics of EfOM and interactivities of reaction process played the crucial roles. Especially, the removal rate constant of soluble microbial products (SMPs) with FeCeAC/O3-PAC exceeded 55.38% versus FeCeAC/O3. The outstanding synergistic effect was contributed to the enhanced generation of active oxygen species by FeCeAC and PAC, which increased the content of oxygen-containing functional groups of EfOM and thus facilitated the interaction between PAC and EfOM. As the result, the larger-sized flocs could be formed and separated easily. Herein, this work found a far more effective way to remove EfOM especially low-coagulability refractory organics (LCRO) in chemical sewage plant.

Effect of chlorination on the characteristics of effluent organic matter and the phototransformation of sulfamethoxazole in secondary wastewater

Chlorination is the most common disinfection technology used to treat wastewater effluent discharged into receiving aquatic environments. Effluent organic matter (EfOM) abundant in wastewater is a well-known photosensitizer and it greatly affects phototransformation of antibiotics in water. However, effects of chlorination on the characteristics and photochemical properties of EfOM have not been studied in sufficient detail. This paper investigated effects of chlorination on the characteristics of EfOM, and its impact on the phototransformation of sulfamethoxazole (SMX). Correlations between the EfOM characteristics and steady-state concentrations of reactive intermediates (RI) formed in the system were established. Chlorination was shown to preferentially remove the aromatic protein-like substances in EfOM, and the incorporation of chlorine into followed by the cleavage of the aromatic rings in EfOM molecules led to the formation of low molecular aliphatic organic matter. Both unaltered and chlorinated EfOM promoted the photodegradation of SMX whose rate constant in the wastewater was 1.32–1.65 times higher than that in pH 8 phosphate buffer. However, the rate of SMX photodegradation decreased at higher chlorination concentrations. The photodegradation of SMX was found to proceed through direct photolysis and oxidation by the RIs generated from EfOM and the self-sensitization of SMX. The steady-state concentrations of ·OH, 1O2 and 3EfOM* were 2.15–5.50 × 10−16, 0.42–1.51 × 10−13, and 2.54–5.82 × 10−14 M in unaltered and chlorinated wastewater. The steady-state concentrations of ·OH were well correlated with the removal of the fluorescence regional integration (ΔFRI) for humic-like and soluble microbial products (SMPs), while the photodegradation rate constant of SMX and the steady-state concentration of 1O2 and 3EfOM* showed good correlations with ΔFRI for tryptophan and fulvic-like substances. Six transformation products (TPs) of SMX were identified. These findings provide new insights into the photochemical properties of chlorinated EfOM in the aquatic environments and its roles in the degradation of antibiotics and other trace-level pharmaceuticals.

The combination effect of preozonation and CNTs layer modification on low-pressure membrane fouling control in treating NOM and EfOM

In this study, the combination effect of preozonation and carbon nanotubes (CNTs) layer modification on low-pressure membrane (LPM) fouling control was systematically investigated. To understand the alleviation mechanism of the hybrid process, natural organic matter (NOM) from IHSS and effluent organic matter (EfOM) from actual sewage effluent were both selected as the typical organic foulants presented in actual surface water and wastewater. A dead-end continuous flow model combined with programmable logic control system was used to operate four membrane filtration units and their backwash processes. With a constant permeates flux, the fouling resistant of CNT modified LPM after preozonation could be evaluated according to the increase in transmembrane pressure (TMP). The results revealed that the hybrid approach of preozonation and CNTs modification could significantly improve the anti-fouling ability of LPM, reduce the backwash frequency, and improve the reversibility of membrane fouling. During the filtration of EfOM and NOM, preozonation improved the water treatment capacity of the CNTs modified membranes. The experiment of mass balance revealed that preozonation enhanced the recoverability of CNTs modified membrane and greatly increased its operation time in treating EfOM and NOM. The molecular weight distribution as well as EEM analysis demonstrated the dissimilar characteristics of EfOM and NOM, which caused the different treatment efficiency by preozonation and CNT modification. The mechanism of EfOM/NOM fouling on LPM was summarized as the primary blocking by medium-MW EfOM/NOM. CNTs modification had a better effect on the control of LPM fouling when treating EfOM, as it removed the medium-MW EfOM by adsorption and prevented the pores blockage of the original PVDF membrane. Preozonation had a better effect on the control of LPM fouling when treating NOM, as it greatly changed the MWD of NOM by removing medium-MW NOM. The combination effect of the hybrid preozonation and CNTs modification resulted in the most effective fouling control of LPM by both decreasing the medium-MW and large-MW EfOM/NOM. At the same time, it decreased irreversible fouling related with membrane pore blocking. The hybrid approach demonstrated its promising application for LPM fouling control in actual sewage water and surface water treatment process.

Pre-chlorination effects on fouling during microfiltration of secondary municipal wastewater effluent

Chlorination-induced changes in the physicochemical characteristics of effluent organic matter (EfOM) and their role in fouling of hollow fiber polyvinylidene fluoride (PVDF) microfiltration membranes during wastewater reclamation was mechanistically investigated. Pre-chlorination strongly influenced pressure rise during constant flux forward filtration as well as hydraulically irreversible fouling by backwashing with low doses exacerbating it and high doses alleviating it. Dose-dependent fouling trends originated from alterations in EfOM size and polarity and consequently its interactions with the membrane based on whether applied chlorine concentrations were above or below a threshold value. Variations in macroscopic phenomena such as sorption tendency, streaming potential, and initial fouling upon exposure to pre-chlorinated EfOM were consistent with favorable adhesion energies calculated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Progressive fouling even though XDLVO theory predicted unfavorable EfOM-EfOM cohesive energies under all chlorination conditions demonstrated that hydrodynamics (permeation drag) dominated later stages of fouling. EfOM in the raw wastewater was largely deposited on the membrane surface resulting in compressible cake filtration. In contrast, pre-chlorination fragmented EfOM leading to intrapore fouling (standard blocking) at the beginning stages of filtration later transitioning to surface fouling (intermediate blocking).

Membrane fouling control by UV/persulfate in tertiary wastewater treatment with ultrafiltration: A comparison with UV/hydroperoxide and role of free radicals

The membrane fouling caused by effluent organic matter (EfOM) is a bottleneck for application of ultrafiltration (UF) in tertiary wastewater treatment. In this study, two ultraviolet-based oxidation pretreatments, i.e., ultraviolet/persulfate (UV/PS) and ultraviolet/hydrogen peroxide (UV/H2O2), were used to alleviate EfOM fouling at a low UV dose of 2.36 × 103 mJ cm−2, in consideration of the widely use of UV radiation for disinfection in wastewater treatment plants. Effects of the pretreatments on characteristics of EfOM were investigated in terms of fluorescence spectrum, molecular weight distribution, and hydrophobicity. Moreover, filtration tests were performed to assess impacts of the oxidation pretreatments on flux decline, fouling reversibility, and fouling mechanisms. The results showed that the UV/PS pretreatment substantially reduced flux decline and improved fouling reversibility during filtration of the secondary effluent, attributed to efficient degradation (~67%, in terms of UV254) and partial mineralization (~39%, in terms of DOC) of EfOM. In particular, the irreversible resistance was decreased by nearly one order of magnitude at the PS dose of 1.0 mM. UV/H2O2 was not effective in EfOM fouling control under the conditions investigated. The UV/PS pretreatment resulted in a shift of mechanisms for EfOM fouling from successive pore blocking and cake filtration to single standard blocking, attributing to preferential degradation of macromolecular components in EfOM and a weakened role of cake interception. The radical quenching experiment showed that the sulfate radicals played a dominant role in EfOM fouling control by UV/PS, and that transformation of sulfate radicals into hydroxyl radicals negatively affected EfOM fouling control.

Removal Characteristics of Effluent Organic Matter (EfOM) in Pharmaceutical Tailwater by a Combined Coagulation and UV/O3 Process

A novel coagulation combined with UV/O3 process was employed to remove the effluent organic matter (EfOM) from a biotreated pharmaceutical wastewater for harmlessness. The removal behavior of EfOM by UV/O3 process was characterized by synchronous fluorescence spectroscopy (SFS) integrating two-dimensional correlation (2D-COS) and principal component analysis (PCA) technology. The highest dissolved organic carbon (DOC) and ratio of UV254 and DOC (SUVA) removal efficiency reached 55.8% and 68.7% by coagulation-UV/O3 process after 60 min oxidation, respectively. Five main components of pharmaceutical tail wastewater (PTW) were identified by SFS. Spectral analysis revealed that UV/O3 was selective for the removal of different fluorescent components, especially fulvic acid-like fluorescent (FLF) component and humus-like fluorescent (HLF) component. Synchronous fluorescence/UV-visible two-dimensional correlation spectra analysis showed that the degradation of organic matter occurred sequentially in the order of HLF, FLF, microbial humus-like fluorescence component (MHLF), tryptophan-like fluorescent component (TRLF), tyrosine-like fluorescent component (TYLF). The UV/O3 process removed 95.6% of HLF, 80.0% of FLF, 56.0% of TRLF, 50.8% of MHLF and 44.4% of TYLF. Therefore, the coagulation-UV/O3 process was proven to be an attractive way to reduce the environmental risks of PTW.

Evaluation of a hybrid process of magnetic ion-exchange resin treatment followed by ozonation in secondary effluent organic matter removal

The presence of effluent organic matter (EfOM) and organic micro-pollutants (OMPs) in secondary effluent is receiving increasing concern due to their potential impacts on the aquatic environment and human health. In this study, the removal characteristics of EfOM by magnetic ion-exchange resin (MIEX), ozonation, and the hybrid process of MIEX followed by ozonation (M + O) were compared by measuring the bulk organic indicators (BOIs), OMPs, bio-toxicity, and fluorescence. Furthermore, the desorption characteristics of MIEX were comprehensively studied. Ozonation could reduce the OMPs, total fluorescence (TF), genotoxicity, and oestrogenic activity more effectively than MIEX, with reductions of 80.3%, 97.8%, 98.9%, and 94.6%, respectively. The M + O process was capable of removing more EfOM than the individual MIEX or ozonation processes and could reduce the genotoxicity and oestrogenic activity to the detection limit. By implementing MIEX as a pre-treatment, the generation of ammonia–nitrogen and nitrate–nitrogen was effectively reduced in the subsequent ozonation process as MIEX adsorbed organic nitrogen and nitrite-nitrogen. The different regenerants influenced the OMP desorption performance of MIEX by changing the desorption mechanisms, and NaCl + NaOH was the best regenerant due to its high total OMP desorption efficiency. Parallel factor analysis coupled with self-organising maps further explained the differences in fluorescence desorption due to the addition of NaOH to the regenerated solution. Pearson correlation analysis indicated the potential of using spectroscopic indicators, such as ultraviolet absorbance and TF, to assess the evolution of OMPs and bio-toxicity during the M + O and MIEX desorption processes.

Tracking the reactivity of ozonation towards effluent organic matters from WWTP using two-dimensional correlation spectra.

The characteristics of effluent organic matter (EfOM) from a wastewater treatment plant (WWTP) during ozonation were investigated using excitation and emission matrix (EEM) spectra, Fourier transform infrared spectroscopy (FT-IR) and high-performance size exclusion chromatography (HPSEC) at different ozone dosages. The selectivity of ozonation towards different constituents and functional groups was analysed using two-dimensional correlation spectra (2D-COS) probed by FT-IR, synchronous fluorescence spectra and HPSEC. The results indicated that ozonation can destroy aromatic structures of EfOM and change its molecular weight distribution (MWD). According to 2D-COS analysis, microbial humic-like substances were preferentially removed, and then the protein-like fractions. Terrestrial humic-like components exhibited inactivity towards ozonation compared with the above two fractions. Protein-like substances with small molecular weight were preferentially reacted during ozonation based on 2D-COS probed by HPSEC. In addition, the selectivity of ozone towards different functional groups of EfOM exhibited the following sequence: phenolic and alcoholic CO groups > aromatic structures containing CC double bonds > aliphatic CH. X-ray photoelectron spectroscopy (XPS) further elucidated the preferential reaction of aromatic structures in EfOM during ozonation.

Forward osmosis membrane performance during simulated wastewater reclamation: Fouling mechanisms and fouling layer properties

A thin-film composite (TFC) FO membrane was used to study the fouling characteristics of effluent organic matter (EfOM) fractions in treated wastewater effluent represented by alginate, bovine serum albumin, humic acid and octanoic acid. These model foulants were chosen to represent carbohydrates, proteins, humic substances and fatty acids. Inter foulant interactions and their influence on membrane flux loss was established by running series of fouling tests with feed solutions containing mixtures of model foulants. The obtained results demonstrated that under our experimental conditions humic acid (HA) and octanoic acid (OA) had no significant role on permeate flux loss during wastewater treatment over short periods. However, alginate and bovine serum albumin (BSA) and their mixtures caused significant total flux loss, through alginate-calcium complexation that led to the formation of a resistant gel layer on the membrane surface. Protein fouling was mainly attributed to multiple layer adsorption onto the polyamide membrane surface. Mixing alginate with BSA saw a further decline in permeate flux, worse than that caused individually by either of the foulants, and gives an indication of the synergistic effect between the two foulants. There were favourable inter-foulant interactions between the carbohydrates and the proteins that promoted the formation of hybrid aggregates that were deposited on the membrane surface and enhanced flux loss. The additional presence of humic acid to the mixture of BSA and alginate further aggravated membrane fouling. Polysaccharides and proteins were found to be the most dominant foulants during wastewater reclamation. The extent of interactions between the organic foulants had an effect on the fouling layer structure and its role in permeate flux loss.

The role of a combined coagulation and disk filtration process as a pre-treatment to microfiltration and reverse osmosis membranes in a municipal wastewater pilot plant

A pilot study was conducted to assess the performance of a municipal wastewater reclamation plant consisting of a combined coagulation–disk filtration (CC–DF) process, microfiltration (MF) and reverse osmosis (RO) membranes, in terms of the removal of water contaminants and changes in characteristics of effluent organic matter (EfOM). The CC–DF and MF membranes were not effective for the removal of dissolved water contaminants. However, they could partially reduce the turbidity associated with the cake layer formation by particulate materials on the membrane surfaces. Furthermore, most of water contaminants were completely removed by the RO membranes. Although the CC–DF process could remove approximately 20% of turbidity, the aluminium concentrations considerably increased after the CC–DF process due to the residual coagulants complexed with both carboxylic acid and alcohol functional groups of EfOM. Those aluminium–EfOM complexes had a lower negative charge and higher molecular weight (>0.1μm pore size of the MF membranes) compared to non-complexed EfOM. These results indicate that the control of the formation of the aluminium–EfOM complexes should be considered as a key step to use the CC–DF process as a pre-treatment of the MF and RO membranes for mitigation of membrane fouling in the tested pilot plant.

Effects of ozonation and coagulation on effluent organic matter characteristics and ultrafiltration membrane fouling

Effluent organic matter (EfOM) is the major cause of fouling in the low pressure membranes process for wastewater reuse. Coagulation and oxidation of biological wastewater treatment effluent have been applied for the fouling control of microfiltration membranes. However, the change in EfOM structure by pre-treatments has not been clearly identified. The changes of EfOM characteristics induced by coagulation and ozonation were investigated through size exclusion chromatography, UV/Vis spectrophotometry, fluorescence spectrophotometry and titrimetric analysis to identify the mechanisms in the reduction of ultrafiltration (UF) membrane fouling. The results indicated that reduction of flux decline by coagulation was due to modified characteristics of dissolved organic carbon (DOC) content. Total concentration of DOC was not reduced by ozonation. However, the mass fraction of the molecules with molecular weight larger than 5 kDa, fluorescence intensity, aromaticity, highly condensed chromophores, average molecular weight and soluble microbial byproducts decreased greatly after ozonation. These results indicated that EfOM was partially oxidized by ozonation to low molecular weight, highly charged compounds with abundant electron-withdrawing functional groups, which are favourable for alleviating UF membrane flux decline.

하수처리장 방류수의 UV 처리시 유기물질, 잔류염소 및 소독부산물 생성 거동

Study on effluent organic matter (EfOM) characteristic and removal efficiency is required, because EfOM is impor­tant in regard to the stability of effluents reuse, quality issues of artificial recharge and water conservation of aqueous system. UV technology is widely used in wastewater treatment. Many reports have been conducted on microbial disinfection and micro pollutant reduction with UV treatment. However, the study on EfOM with UV has limited because low/medium pressure UV lamp is not sufficient to affect refractory organics. The high intensity of pulsed UV would mineralize EfOM itself as well as change the characteristics of EfOM. Chlorine demand and DBPs formation is affected on the changed amounts and properties of EfOM. The objective of this study is to investigate the effect on EfOM, chlorine residual, and chlorinated DBPs formation with low pressure and pulsed UV treatment. The removal of organic matter through low pressure UV treatment is insignificant effect. Pulsed UV treatment effectively removes/transforms EfOM. As a result, the chlorine consumption is changed and chlorine DBPs formation is decreased. However, excessive UV treatment caused problems of increasing chlorine consumption and generating unknown by-products.

Toxicity assessment of chlorinated wastewater effluents by using transcriptome-based bioassays and Fourier transform mass spectrometry (FT-MS) analysis

Effects of chlorination on the toxicity of wastewater effluents treated by activated sludge (AS) and submerged membrane bioreactor (S-MBRB) systems to HepG2 human hepatoblastoma cells were investigated. In addition to the cytotoxicity and genotoxicity assays, the DNA microarray-based transcriptome analysis was performed to evaluate the change in types of biological impacts on HepG2 cells of the effluents by chlorination. Effluent organic matter (EfOM) and disinfection by-products (DBPs) were also characterized by using Fourier transform mass spectrometry (FT-MS). Although no significant induction of genotoxicity was observed by chlorination for both effluents, the chlorination elevated the cytotoxicity of AS effluent but reduced that of S-MBRB effluent. The FT-MS analyses revealed that more DBPs including nitrogenated DBPs (N-DBPs) were formed in the AS effluent than in the S-MBRB effluent by chlorination, supporting the increased cytotoxicity of AS effluent. The lower O/C ratio of S-MBRB EfOM suggests that a large number of organic molecules were detoxified by chlorination, which consequently decreased the cytotoxicity of S-MBRB effluent. Integration of all the results highlights that both cytotoxicity and biological impacts of chlorinated wastewater effluents were clearly dependent on the EfOM characteristics such as DBPs and O/C ratio, namely, on types of treatment systems.

Fouling characteristics of a membrane bioreactor and nanofiltration hybrid system for municipal wastewater reclamation

A laboratory-scale membrane bioreactor (MBR) and nanofiltration (NF) hybrid system has been built to investigate effects of changes in characteristics of effluent organic matter by the MBR on fouling characteristics of the NF membranes. Large amounts of polysaccharide-like substances with small molecular weight and strong fluorescence intensity at the excitation wavelength of 230nm and the emission wavelength of 420nm were produced by microbial growth in the MBR. These substances had a great influence on fouling formation of the NF membranes. Fouling characteristics of the MBR were governed by both hydrophobic and hydrophilic fractions while hydrophilic fractions were found as major constituents of the desorbed NF membrane foulants. Flux decline rates of the NF membranes were closely associated with differences in their fouling layer compositions, meaning that performances of the NF membranes (i.e., flux decline) could be influenced by the membrane characteristics (i.e., surface zeta potential and contact angle).

Membrane fouling due to alginate, SMP, EfOM, humic acid, and NOM

Several commercially available organic materials have frequently been used as surrogates for surface water natural organic matter (NOM) and for wastewater effluent organic matter (EfOM), e.g., for identifying the extent and mechanism of membrane fouling. However there is a lack of experimental evidence that the surrogate organic materials are representative of EfOM and surface water NOM. Therefore the main objectives were to compare the organic composition (by empirical fractionation methods), the molecular size distributions, and fouling and the mechanisms of fouling of ultrafiltration (UF) membranes for the surrogate materials sodium alginate, soluble microbial products (SMP), and commercial humic acid (HA) with the characteristics of EfOM and Suwannee River NOM (SRNOM). The fouling mechanisms were probed by measuring resistance to filtration as a function of permeate flux using several filtration modes, by determining the effects of Ca2+ on fouling, and by investigating the effectiveness of hydraulic and chemical cleaning on restoration of membrane permeability. Results showed that SMP was most similar to EfOM, Aldrich HA (AHA) was most similar to SRNOM, and alginate was a poor surrogate for either EfOM or SRNOM. Alginate was also unique among the five organic materials in that fouling was decreased when 0.8mM Ca2+ was added, consistent with the formation of a gel that formed a porous cake on top of the membrane. Fouling increased with addition of Ca2+ for the other materials. Addition of Ca2+ increased the colloidal fraction and the concentration of molecules >100kDa for all of the materials but the increases were particularly dramatic for alginate and were also large for AHA. Differences in fouling mechanisms and cake compressibility as a function of the applied trans-membrane pressure (TMP) between surrogate and natural organic materials were also observed.

Correlation between effluent organic matter characteristics and membrane fouling in a membrane bioreactor using advanced organic matter characterization tools

Three identical bench-scale membrane bioreactors (MBRs) were operated to investigate the formation of effluent organic matter (EfOM) via biodegradation at different solid retention times (8, 20 and 80days). The characteristics of organic matter in supernatants, bound extracellular polymeric substances (EPS), soluble microbial products (SMP) and effluents changed at different solid retention times (SRTs). EfOM characteristics affecting membrane fouling with respect to total hydraulic resistances and specific cake resistances were investigated using advanced organic characterization tools. EfOM characteristics determined by size exclusion chromatography with organic carbon detection, fluorescence excitation–emission matrix spectroscopy and polarity rapid assessment method were compared with the membrane fouling. In this study, a database collected from three identical bench-scale MBRs operated at different SRTs for 12months is analyzed to investigate the intercorrelations (either positive or negative) between EfOM characteristics and membrane fouling using principal component analysis (PCA). Principal component-1 embodied the characteristics of EfOM (i.e., aliphatic biopolymers vs. aromatic humic substances), and explained 59% of the data variability. This study provides useful data on EfOM characteristics with membrane fouling, and a multivariate statistical analysis (PCA) can be used to depict the intercorrelations between EfOM characteristics and SRTs in MBRs.

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

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