High Molecular Weight Organic Compounds Research Articles

Sustainable approach for landfill leachate treatment through dielectric barrier discharge/ferrate (DBD/Fe(VI)) enhanced nanofiltration

Landfill leachate, with its high concentrations of persistent organic pollutants, salts, heavy metals, and emerging contaminants, presents significant environmental challenges. This study investigated the combination of dielectric barrier discharge (DBD) and ferrate (Fe(VI)) pretreatment technology in landfill leachate treatment, focusing on its effectiveness in enhancing oxidation performance and mitigating membrane fouling. The results indicated that after DBD/Fe(VI) treatment, TOC and UV254 removal efficiencies increased by 44 % and 67 %, respectively. Additionally, the DBD/Fe(VI) system excelled in removing fluorescent substances and high molecular weight organic compounds, thereby reducing the formation of the cake layer on the nanofiltration membrane. This system enhanced oxidation performance through the synergistic production of reactive intermediates, with Fe(V)/Fe(IV) and •OH being the main active species, O2•-, and 1O2 also contributing significantly. The degradation pathway of perfluorooctanoic acid was investigated by utilizing it as the representative pollutant. Compared to the raw landfill leachate system, the DBD/Fe(VI) increased membrane flux by 104 %, while reducing reversible and irreversible fouling resistances by 67 % and 75 %, respectively. Furthermore, the advantages and practical application potential of the DBD/Fe(VI) system were evaluated from energy consumption, economic cost, and carbon dioxide emissions. The study offers an innovative method for landfill leachate treatment and fouling mitigation.

Evolution of nucleophilic high molecular-weight organic compounds in ambient aerosols: a case study

Abstract. Nucleophilic high molecular-weight organic compounds (HMWOCs) are sensitive to protons (H+) in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. A comprehensive evaluation of the diurnal evolution of nucleophilic HMWOCs was performed. HMWOCs aged significantly in daily cycles, accompanied by functionality shifts, particularly oxygenated and reduced nitrogen (CHON and CHN) as well as oxygenated organics. The intensities of high molecular-weight (HMW) oxygenated compounds increased during both daytime and nighttime. The daytime evolution produced more nitrogen-containing compounds with carboxylic group (–COOH) homologues with molecular weights greater than 300, while the nighttime evolution produced mostly small CHON compounds (molecular weights < 300). During evolution, nighttime CHON removals were observed; meanwhile, carboxylation was also identified in CHON groups. The daytime evolution produced significantly more reduced-nitrogen-containing compounds; a day- and nighttime increase in CHN compounds with five members was also observed. This study can provide insights into the aging of less polar organic aerosols.

Soluble carbon source recovery using preconditioning coagulants for applicable short-term fermentation of waste activated sludge in WWTPs

A huge production of waste activated sludge (WAS) has been a burden for wastewater treatment plants (WWTPs) with high disposal cost and little benefit back to wastewater purification. The short-chain fatty acids (SCFAs) produced by a short-term acidogenic fermentation of WAS before methane production have been proven to be a high-quality carbon source available for microbial denitrification process. The dual purpose of full recovery of fermentation liquid products and facilitating disposal of residual solid waste necessitate an efficient solid-liquid separation process of short-term fermentation liquid. The transformation and loss of various soluble carbon sources between solid and liquid are very important issues for carbon recovery efficiency when combining short-term fermentation and sludge dewatering in WWTPs. Here we testified the three conventional preconditioning coagulants, Polyferric Sulfate (PFS), Poly Aluminum Chloride (PAC) and Polyacrylamide (PAM), to improve the efficiency of subsequent solid-liquid separation. The results show that conversion yield of SCFAs in the liquid phase of sludge after short-term fermentation was 195 mg COD/g VSS, when using the coagulants PFS, PAC, and PAM for recovery, the recovery ratio was 79.5%, 82.0%, and 85.9%, respectively, while the dewaterability could be improved after preconditioning short-term fermentation sludge. The complexation of Al3+/Fe3+ in metal coagulants with carboxyl groups of SCFA demonstrated by Density Functional Theory calculation led to small part of soluble carbons co-migration to the solid phase, mainly a loss of high molecular weight organic compounds (carbohydrate, proteins, humic acids), while the application of PAM had little impact on carbon recovery. Economic calculations further showed PAM preconditioning short-term fermentation liquid of WAS could achieve higher recovery benefits.

Modeling the Migration Behavior of Extractables from Mono- and Multilayer Polyolefin Films to Mathematically Predict the Concentration of Leachable Impurities in Pharmaceutical Drug Products. Part 1: Experimental Details and Modeling Experimental Results.

An important step in the development of a pharmaceutical drug product is to demonstrate acceptable levels of leachable impurities during the shelf-life and therapeutic use of the drug product. If the diffusion and partition coefficients are known, the concentration profile of a leachable impurity in the drug product can be predicted theoretically at a given temperature and time. With this objective in mind, kinetic experiments were performed to study the migration of low- to high-molecular-weight organic compounds from mono- and multilayer polyolefin films. Migration curves at different temperatures were generated for each compound when these films were brought in contact with aqueous solutions with varying pH or with another plastic film made from a different polyolefin material. "Best fit" migration curves and the corresponding diffusion and partition coefficients (about 300 pieces) were obtained by using numerical software developed by FABES. The results obtained show that, in general, the correlation between the calculated diffusion and partition coefficients and temperature, between 30°C and 85°C, obeys the Arrhenius and Van't Hoff equations. In this temperature range, the diffusion and partition coefficients can be used to model and predict migration of the investigated compounds from the same pharmaceutical packaging materials. A comparison of these coefficient values with other polyolefin films also provides insights into the chemistry of the mono- and multilayers and the impact it has on the migration behavior of the compounds. In a consecutive paper, an approach to overestimate the diffusion and partition coefficients to account for the variability in experimental data is explained and finally, the use of these overestimated parameters to predict the concentrations for other compounds leaching from the multilayer films into aqueous drug product formulations is discussed.

Modeling the Migration Behavior of Extractables from Mono- and Multilayer Polyolefin Films to Mathematically Predict the Concentration of Leachable Impurities in Pharmaceutical Drug Products. Part 2: Conservative Diffusion and Partition Coefficient Determinations.

In the development of a pharmaceutical drug product packaging, an important step is to demonstrate acceptable levels of leachable impurities migrating from the packaging material into the drug product during its shelf life and therapeutic use. Such migration processes can be quantified either by analytical methods (which is often challenging and labor intensive) or (in many cases) through theoretical modeling, which is a reliable, quick, and cost-effective method to forecast the level of leachable impurities in the packaged drug when the diffusion and partition coefficients are known. In the previous part, it was shown how these parameters can be determined experimentally, and subsequent theoretical fitting of the results for a series of low- and high-molecular-weight organic compounds (known leachables) in a series of polyolefin materials was performed. One of the interpretations of these results is that a theoretical calculation can be made only for organic compounds and materials whose diffusion/partition/solubility coefficients were determined experimentally and theoretical fitting was achieved. However, in practice, there will be situations in which other leachable compounds may have to be investigated. In such cases, strictly speaking, it would be necessary to perform the whole experimental and fitting procedure for the new compound before a proper theoretical modeling is possible. But this would make the theoretical calculation of a leaching process from a pharmaceutical packaging material a cumbersome and cost intensive procedure. To address this problem, the pools of diffusion and partition coefficients were used to develop an approach that allows the estimation, without any additional experimentation, of so-called "conservative" diffusion and partition coefficients for a much wider range of potential leachables in the polyolefin pharmaceutical packaging materials and aqueous solutions investigated previously.

Photochemical processes in surface water bodies and their potential impacts on the chemical composition of water: A review

AbstractThe present study is a review of photochemical processes that occur in surface water bodies and which can affect the chemical composition of water. It is expected that water bodies with a slow rate of water exchange, including lakes, reservoirs, estuaries and ponds with significant areas of shallow water will be most vulnerable to the impacts of these processes. It involves natural organic compounds and xenobiotics of organic origin that enter water bodies from anthropogenic sources or are formed in water bodies because of the development of cyanobacteria and other algae species. Photodegradation of dissolved organic matter (DOM) occurs as a result of both direct photolysis and photosensitized cleavage involving inorganic and organic compounds, which are characterized by chromophore properties, such as humic substances. Photolysis is accompanied by the transformation of high molecular weight organic compounds into lower molecular weight compounds that can become bioavailable to, and promote the development of, microorganisms. Photodegradation results in bioavailable forms of nitrogen and phosphorus being released into the water column. Accordingly, the present study presents the results of analysis of the photochemical destruction of humic substances, such as the most widespread group of the surface water body DOM under the influence of artificial UV irradiation and solar radiation. The results provide data on the products of humic substances photolysis, as well as the influence of the latter on the destruction of a number of organic substances, including xenobiotics (herbicides, pesticides, etc.). Photolysis of algotoxins, which are mainly concentrated in the water of highly trophic reservoirs and lakes during the period of water “blooming,” is among the main concerns being addressed, noting photochemical destruction of these dangerous toxicants can be considered an important means of removing them from drinking water. Also emphasized is that photochemical processes in surface water will likely intensify in the future amid the recent climate changes, also affecting the chemical composition of water.

Novel insight into iodine enrichment in alluvial-lacustrine aquifers: Evidence from stable carbon and iron isotopes

Reductive dissolution of Fe (oxyhydr)oxides triggered by biodegradation of organic matter (OM) are considered to be key processes controlling iodine (I) release in groundwater systems. However, the precise mechanisms involved in release from organic matter degradation and from Fe (oxyhydr)oxides are unclear. In this study, dual stable isotope analysis (δ13C and δ56Fe) was combined with ultraviolet–visible spectral characterization of dissolved organic matter to elucidate the mechanisms of iodine enrichment in groundwater of the central Yangtze River basin, China, which represents Quaternary alluvial-lacustrine floodplains. High iodine groundwater mainly occurs along the Yangtze River (YR) and Han River (HR), with a maximum concentration of 1220 μg/L. The results suggest that methanogenesis driven by the biodegradation of high molecular weight organic compounds can promote the reductive dissolution of amorphous Fe (oxyhydr)oxides, which is the predominant process controlling iodine enrichment in the YR groundwater system. In addition, fermentation accompanied by sulfate reduction can also trigger the release of iodine into groundwater. The reductive dissolution of crystallized Fe (oxyhydr)oxides driven by the fermentation of small-molecule organic compounds is the dominant process responsible for iodine enrichment in the HR groundwater system. This study provides novel insight into the mechanisms of iodine enrichment in Quaternary alluvial-lacustrine aquifers.

Distinct diurnal chemical compositions and formation processes of individual organic-containing particles in Beijing winter

Organic aerosols (OA) are major components of fine particulate matter, yet their formation mechanism remains unclear, especially in polluted environments. In this study, we investigated the diurnal chemical compositions and formation processes of OA in carbonaceous particles during winter in Beijing using aerosol time-of-flight mass spectrometry. We found that 84.5% of the measured carbonaceous particles underwent aging processes, characterized by larger diameter and more secondary species compared to fresh carbonaceous particles, and presented different chemical compositions of OA in the daytime and nighttime. During the day, under high O3 concentrations, organosulfates and oligomers existed in the aged carbonaceous particles, which were mixed with a higher signal of nitrate compared with sulfate. At night, under high relative humidity, distinct spectral signatures of hydroxymethanesulfonate and organic nitrogen compounds, and minor signals of other hydroxyalkylsulfonates and high molecular weight organic compounds were present in the aged carbonaceous particles, which were mixed with a higher signal of sulfate compared with nitrate. Our results indicated that photochemistry contributed to OA formation in the daytime, while aqueous chemistry played an important role in OA formation in the nighttime. The findings can help improve the performance of air quality and climate models on OA simulation.

ANALISIS ASAP DAN EMISI GAS BUANG BUS BAGI KESEHATAN PETUGAS TICKETING HALTE

Motor vehicles emit a wide variety of gases and particles including a variety of high molecular weight organic and inorganic compounds that can be inhaled directly through the nose. Several components of air pollutants as primary pollutants include most of the other air pollutants that can affect air quality and can be grouped into CO, NO2, SO2, HC, and others. Initial observations made at the ticketing bus stop officers found that the officers did not wear perfect personal protective equipment when doing their work. The terminal is a transit point for public transportation modes such as buses. Stop ticketing officers are workers who work in an environment that is prone to smoke pollution and motor vehicle gas emissions. The purpose of this study is to create a work environment, especially ticketing station attendants that are safe, comfortable and able to improve the health and productivity of ticketing bus stop officers and analyze CO and SO2 exposure to ticketing bus stop workers' diseases. The study took data from 20 respondents, all of whom were ticketing bus stop officers at the Sumberlawang terminal, Sragen. The method used in this study is multiple linear regression which functions to measure the relationship between variables and test the research hypothesis. Then the results showed that the effect of SO2 exposure on pain had no significant effect on the disease of ticketing bus stop officers, because the condition of the bus had no significant effect. Buses that stop briefly at the bus stop are the average new bus. has zero emissions and emits less SO2.

Stratospheric Chemical Lifetime of Aviation Fuel Incomplete Combustion Products

The stratosphere contains haze rich in sulfuric acid, which plays a significant role in stratospheric chemistry and in global climate. Commercial aircraft deposit significant amounts of incomplete combustion products into the lower stratosphere. We have studied the stability of these incomplete combustion products to reaction with sulfuric acid, using a predictive model based on experimental reaction kinetics. We demonstrate that sulfuric acid chemistry is likely to be a significant component of the chemistry of organics in the stratosphere. We find that at least 25 of the 40 known incomplete combustion products from aviation fuel have lifetimes to reaction with aerosol sulfuric acid of at least months. We estimate that ~109 kg of long-lived products could be deposited per year in the lower stratosphere. We suggest that the high molecular weight organic compounds formed as incomplete combustion products of commercial long-haul aviation could play a significant role in the stratosphere.

Study of the Behavior of Alkalinities Predicted by the AM2 Model

Anaerobic digestion (AD) is an efficient wastewater bioprocess, suitable for treating agroindustrial residues with high organic loads and characterized by both a low environmental impact and energy generation. This process is conformed by several chemical and biological reactions in an oxygen free atmosphere, that degrades high molecular weight organic compounds into carbon dioxide and methane mainly but also into traces of hydrogen and ammonia. This process is potentially unstable to volatile fatty acids (VFA), and the alkalinity. variations and is satisfactorily described by the non-linear AM2 model. In this contribution, the AM2 model is modified to include a more general expression for the pH, a cheap and continuous measurement, and also to add more detail in the interactions of the VFA, bicarbonates, and the alkalinity, key factors in the process stability. The stability of the AM2 modified model is explored through a rigorous bifurcation analysis that identifies unstable operation zones and viability of operation trajectories as a function of the dilution rate. Finally, an experimental validation is carried out to show the feasibility and accuracy of the proposed modifications.

Unraveling the impact of iron oxides-organic matter complexes on iodine mobilization in alluvial-lacustrine aquifers from central Yangtze River Basin

The biodegradation of organic matter triggers the reductive dissolution of iron oxides with the transformation among iodine species has been mostly accepted as the key iodine mobilization process in groundwater system. However, molecular characteristics of natural organic matter (NOM) and their interaction with iron oxides on geogenic iodine enrichment remain unclear. We used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to characterize the molecular composition of both dissolved organic matter (DOM) in groundwater and water-soluble organic matter (WSOM) in aquifer sediments being depth-matched with groundwater from monitoring wells in typical iodine-affected aquifers within the central Yangtze River Basin. The results show that WSOM in high-iodine sediments contains more high molecular weight (HMW) organic compounds with higher aromaticity and nominal oxidation state of carbon (NOSC), including polycyclic aromatics, polyphenols and highly unsaturated compounds. These compounds are mostly positively associated with amorphous iron oxides (Feox1) in aquifer sediments. The association between iodine and WSOM is highly consistent with that between amorphous Feox1 and WSOM, but is contrary to that between crystalline iron oxides (Feox2) and WSOM. DOM in groundwater with higher iodine concentration contains more aliphatic compounds and less polyphenols. The complexation of HMW organic compounds of WSOM to iodine-bearing amorphous Feox1 plays an important role in iodine mobilization, which could inhibit the amorphous Feox1 transformation to crystalline Feox2. These observations indicate the biodegradation of HMW organic matter (polycyclic aromatics, polyphenols and highly unsaturated compounds) in WSOM fueling the reductive dissolution of amorphous Feox1 predominantly promotes the release of iodine from aquifer sediments into groundwater. This research provides new insights into the mobilization mechanisms of iodine in alluvial-lacustrine groundwater system controlled by the Fe-OM complexation at the molecular level.

Transformation of high molecular weight organic compounds in Arctic peatlands under climate change

The molecular structure of humic substances in the European Arctic permafrost hummocky peatlands has been characterized for three geographical subzones of the tundra biotope. The data obtained make it possible to assume the main trends in the transformation of peat HAs under various environmental conditions of their formation. The key focus of HA transformation in Arctic hummocky peatland is associated with decreased share of carbon in paraffin structures with their subsequent cyclization and aromatization and lower content of oligopolypeptide fragments that are included in the structure of the non-hydrolysable part of the molecules. The results of this process are most pronounced in the layers formed during the Holocene climatic optimum. The climatic conditions of this period determined the specific composition of vegetation dominated by sedge and woody communities, and consequently – of HA precursors with higher content of lignin components. Modern peat deposits formed in the middle and late Holocene period out of bryophyte residues contain HAs with long-chain carbon and paraffin structures in their composition.

Nonspecific organic compounds in permafrost hummocky peatland

Regularities of vertical distribution of nonspecific organic compounds (NOC) in the tundra peatland and boggy soil of the European Arctic zone have been identified. The content of NOC of the soils under study is mainly predetermined by the botanic composition of plant residues and their decomposition degree. Local maxima of NOC have been found in permafrost layers formed through transformation of high molecular-weight organic compounds following decomposition of woody and grassy vegetation that used to dominate during the Holocene climatic optimum.

Water-soluble brown carbon in atmospheric aerosols along the transport pathway of Asian dust: Optical properties, chemical compositions, and potential sources

As an important type of light-absorbing aerosol, brown carbon (BrC) has the potential to affect the atmospheric photochemistry and Earth's energy budget. A comprehensive field campaign was carried out along the transport pathway of Asian dust during the spring of 2016, including a desert site (Erenhot), a rural site (Zhangbei), and an urban site (Jinan), in northern China. Optical properties, bulk chemical compositions, and potential sources of water-soluble brown carbon (WS-BrC) were investigated in atmospheric total suspended particulate (TSP) samples. Samples from Zhangbei had higher mass absorption efficiency at 365 nm (MAE365, 1.32 ± 0.34 m2 g−1) than those from Jinan (1.00 ± 0.23 m2 g−1) and Erenhot (0.84 ± 0.30 m2 g−1). Compere to the non-dust samples, elevated water-soluble organic carbon (WSOC) concentrations and MAE365 values of dust samples from Erenhot are related to the input of high molecular weight organic compounds and biogenic matter from the Gobi Desert, while lower values from Zhangbei and Jinan are attributed to the dilution effect caused by strong northwesterly winds. Based on fluorescence excitation–emission matrix spectra and parallel factor analysis, two humic-like (C1 and C2) and two protein-like (C3 and C4) substances were identified. Together, C1 and C2 accounted for ~64% of total fluorescence intensity at the highly polluted urban Jinan site; C3 represented ~45% at the rural Zhangbei site where local biomass burning affects; and C4 contributed ~24% in the desert region (Erenhot) due to dust-sourced biogenic substances. The relative absorptive forcing of WS-BrC compared to black carbon at 300–400 nm was about 31.3%, 13.9%, and 9.2% during non-dust periods at Erenhot, Zhangbei, and Jinan, respectively, highlighting that WS-BrC may significantly affect the radiative balance of Earth's climate system and should be included in radiative forcing models.

Characterizing the gaseous and particulate SVOC emissions of a commercial light-duty compression ignition engine via GCxGC-ToF-MS

Semi-volatile organic compounds (SVOCs) in gaseous and particulate states from a commercial light-duty compression ignition (CI) engine burning diesel fuel have been investigated by adopting two dimensional Gas-Chromatography Time-of-Flight Mass-Spectrometry (GC × GC-ToF-MS) coupled with a thermal desorption technique. Owing to the enhanced separation capability of the multidimensional gas chromatography, the SVOCs including 21n-alkanes (C12-C32), 16n-alkylcyclohexanes (C11-C25 and C33) and 13 polycyclic aromatic hydrocarbons (PAHs) (2–5 rings) have been identified and quantified under different steady engine loads. The experimental results demonstrated that at high engine load (8 bar BMEP @ 1800 rpm), SVOC emissions were higher than those at low engine load (2 bar BMEP @ 1800 rpm) by factors of 2.74 and 2.02 for gaseous and particulate states respectively. The impact of the diesel oxidation catalyst (DOC) on engine-out SVOCs was also analyzed. The results demonstrated that SVOCs did not reduce significantly (less than 16% for different compounds) at low engine load but decrease more dramatically at high engine load (by 37%–55%) when the DOC was above its light-off temperature. At high engine load, it turned out to be that the DOC mitigating effect was more remarkably on the gaseous SVOCs (38%–62%) than on the particulate SVOCs (26%–46%). Limited SVOC reductive capability of the DOC spurs the need of catalyst improvement, especially for capturing high molecular weight (HMW) organic compounds. Therefore, it would be desirable to further investigate the relationship between SVOC emissions and different types of aftertreatment techniques (i.e. DPF) in a more specific way.

Effect of High-Molecular Weight Organic Compounds on Improvement of Pore Structure of Cement Materials

Effect of High-Molecular Weight Organic Compounds on Improvement of Pore Structure of Cement Materials

Seasonal variation of amine-containing particles in urban Guangzhou, China

Amines are ubiquitous in the environment and pose potential impacts on atmospheric chemistry; however, their seasonal variations and atmospheric processes remain unclear. In this study, a single-particle aerosol mass spectrometer is employed to investigate the seasonal variations of amine-containing particles as well as the oxidation of trimethylamine (TMA) in the urban region of Guangzhou, China. Number fractions of the amine-containing particles exhibit distinct seasonal variations, with higher fractions in spring and summer. Four amines, namely, TMA, diethylamine (DEA), dipropylamine, and tripropylamine are observed over all the seasons. DEA and TMA are the most dominant and account for approximately 90% of all these amine-containing particles. They are mainly clustered into eight types, comprised of internally mixed organics and elemental carbon (OCEC), OC–K, EC, Metal–rich, Dust, NaK–EC, Amine–rich, and high molecular weight organic compounds. DEA and TMA distribute differently over particle types and exhibit a distinct mixing state because of their different physicochemical properties. Compared with TMA, DEA is associated with more sulfate. The possible oxidation of TMA is also investigated, and the results indicate the potential contribution of aqueous oxidation or NO3 radical oxidation to the formation of TMA oxide. Overall, the results improve the comprehension of the formation and evolution processes of amines in atmospheric environment.

Enhancing biological stability of disinfectant-free drinking water by reducing high molecular weight organic compounds with ultrafiltration posttreatment

The production of biologically stable drinking water is challenging in conventional surface water treatment plants. However, attainment of biological stability is essential to avoid regrowth in disinfectant-free distribution systems. A novel application of ultrafiltration as a posttreatment step to enhance biological stability of drinking water produced in an existing conventional surface water treatment plant was investigated. The conventional full-scale plant comprised coagulation/sedimentation/filtration, UV-disinfection, biological activated carbon filtration and chlorine dioxide post-disinfection. The produced water exhibited substantial regrowth of Aeromonads, invertebrates and colony counts in the distribution network. Recent literature attributes this phenomenon to the specific presence of slowly biodegradable, high molecular weight (MW) biopolymeric organic compounds. Hence, the aim of this study is to enhance the biological stability of conventionally treated surface water by reducing the concentration of high-MW organic compounds. For this purpose, biological active carbon filtrate was subjected to ultrafiltration with membrane pore sizes of 10 kDa, 150 kDa and 0.12 μm respectively, operating in parallel. The UF performance was evaluated in terms of the achieved reduction in particulate and high-MW organic carbon (PHMOC); the biopolymer fraction in Liquid Chromatography-Organic Carbon Detection; biomass (cells, ATP); Assimilable Organic Carbon (AOC) by the AOC-P17/NOX method for easily biodegradable, low-MW compounds and by the AOC-A3 method for slowly biodegradable, high-MW compounds; and overall microbial growth potential (MGP) as assessed by Biomass Production Potential (BPP) and Bacterial Growth Potential (BGP) bio-assays. Results showed increasing removal of high-MW organic carbon with decreasing UF pore size, i.e., 30%, 60% and 70% removal was observed for the 0.12 μm, 150 kDa and 10 kDa membranes, respectively. Biomass and particulates retention was more than 95% for all UF membranes. AOC-A3, BPP and BGP were substantially reduced by 90%, 70% and 50%, respectively. These respective reductions were similar for all three UF membranes despite their difference in pore size. Easily biodegradable organic compounds (as AOC-P17/NOX) were not reduced by any of the membranes, which was in accordance with expectations considering the low MW of the compounds involved. Based on the obtained results, growth potential appears to be largely attributable to high-MW organic compounds which are retained by a 0.12 μm UF membrane. Furthermore, the quality of all three UF permeates was equal to or better than in reference cases (literature data) which exhibit little regrowth in their disinfectant-free distribution networks. The results demonstrate that ultrafiltration posttreatment in conventional surface water treatment plants is a potentially promising approach to enhance the biological stability of drinking water.

Modelling the hygroscopic growth factors of aerosol material containing a large water-soluble organic fraction, collected at the Storm Peak Laboratory

The compositions of six aggregated aerosol samples from the Storm Peak Laboratory site have been comprehensively analysed (Hallar et al., 2013), focusing particularly on the large water-extractable organic fraction which consists of both high molecular weight organic compounds and a range of acids and sugar-alcohols. The contribution of the soluble organic fraction of atmospheric aerosols to their hygroscopicity is hard to quantify, largely because of the lack of a detailed knowledge of both composition and the thermodynamic properties of the functionally complex compounds and structures the fraction contains. In this work we: (i) develop a means of predicting the relative solubility of the compounds in the water-extractable organic material from the Storm Peak site, based upon what is known about their chemical composition; (ii) derive the probable soluble organic fraction from comparisons of model predictions with the measured hygroscopicity; (iii) test a model of the water uptake of the total aerosol (inorganic plus total water-extractable organic compounds). Using a novel UNIFAC-based method, different assignments of functional groups to the high molecular weight water soluble organic compounds (WSOC) were explored, together with their effects on calculated hygroscopic growth factors, constrained by the known molecular formulae and the double bond equivalents associated with each molecule. The possible group compositions were compared with the results of ultrahigh resolution mass spectrometry measurements of the organic material, which suggest large numbers of alcohol (–OH) and acid (–COOH) groups. A hygroscopicity index (HI) was developed. The measured hygroscopic growth is found to be consistent with a dissolution of the WSOC material that varies approximately linearly with RH, such that the dissolved fraction is about 0.45–0.85 at 90% relative humidity when ordering by HI, depending on the assumptions made. This relationship, if it also applies to other types of organic aerosol material, provides a simple approach to calculating both water uptake and CCN activity (and the κ parameter for hygroscopic growth). The hygroscopicity of the total aerosol was modelled using a modified Zdanovskii-Stokes-Robinson approach as the sum of that of the three analysed fractions: inorganic ions (predicted), individual organic acids and “sugar alcohols” (predicted), and the high molecular weight WSOC fraction (measured). The calculated growth factors broadly agree with the measurements, and validate the approach taken. The insights into the dissolution of the organic material seem likely to apply to other largely biogenic secondary organic aerosols from similar remote locations.