Mechanistic exploration of COVlD-19 antiviral drug ritonavir on anaerobic digestion through experimental validation coupled with metagenomics analysis.

Aggregation of antiviral drugs (ATVs) in waste activated sludge (WAS) poses considerable environmental risk, so it is crucial to understand the behavior of these agents during WAS treatment. This study investigated the effects of ritonavir (RIT), an ATV used to treat human immunodeficiency virus infection and coronavirus disease 2019, on anaerobic digestion (AD) of WAS to reveal the mechanisms by which it interferes with anaerobic flora. The dosage influence results showed that methane production in AD of WAS decreased by 46.56 % when RIT concentration was increased to 1000 µg/kg total suspended solids (TSS). The AD staging test revealed that RIT mainly stimulated microbial synthesis of the extracellular polymeric substance (EPS), limiting organic matter solubilization. At 500 µg/kg TSS, RIT decreased CHO and CHON levels in dissolved organic matter by 23.12 % and 56.68 %, respectively, significantly reducing substrate availability to microorganisms. Metagenomic analysis of microbial functional gene sets revealed that RIT had greater inhibitory effects on protein and amino acid metabolism than on carbohydrate metabolism. Under RIT stress, methanogens switched from hydrogenotrophic and acetotrophic methanogenesis to methylotrophic and acetotrophic methanogenesis.

Investigating removal mechanisms of long- and short-chain per- and polyfluoroalkyl substances using specialty adsorbents in a field-scale surface water filtration system.

This study assessed the application of two specialty adsorbents, also known as green sorption media (GSM), including clay-perlite and sand sorption media (CPS) and zero-valent iron and perlite green environmental media (ZIPGEM) to remove long- and short-chain per- and polyfluoroalkyl substances (PFAS) at field scale. The field-scale demonstration employed four GSM filter cells installed near the C-23 Canal (St. Lucie County, FL), which discharges water to the ecologically sensitive St. Lucie River estuary and to the Atlantic Ocean finally. Although prior lab-scale experiments had demonstrated the effectiveness of CPS and ZIPGEM in treating long-chain PFAS, their performance in field-scale application warranted further investigation. The study reveals the critical roles of divalent cations such as Ca2+ and monovalent cations such as ammonium and hydronium ions, as well as other water quality parameters, on PFAS removal efficacy. Ammonia, most likely resulting from photo- and bacterial ammonification, gives rise to elevated ammonium ion formation in the wet season due to the decrease in pH, which ultimately worsens PFAS adsorption. Moreover, there is a strong negative correlation between pH and PFAS removal efficiency in the presence of ammonia, as evidenced by the reduced removal of PFAS during events associated with low pH.

Fractionation of biomass-burning smoke-derived dissolved organic matters on the surface of clay minerals: Variations of molecular properties and components.

Biomass burning (e.g., wildfire) frequently occurs globally, inevitably produces abundant biomass-burning smoke-derived dissolved organic matters (BBS-DOMs) which eventually deposits on the surface environment. The adsorption and fractionation of BBS-DOMs on clays inevitably alter their biogeochemical process and environmental behaviors in the surface environment. It is therefore important to clarify the adsorption and fractionation of BBS-DOM on clay surfaces. This study found that the fractionation of BBS-DOMs on clays (montmorillonite and kaolinite) were controlled by their functional groups, aromaticity, molecular size and organic components. The spectral indexes (SUVA254 and S275-295) of BBS-DOMs in solution after clays adsorption suggested that with the increasing DOC concentration, the primary interaction between BBS-DOMs and clays changed from hydrogen bond to hydrophobic/pore filling effects, and the adsorption ratio of the large molecules increased, which were very different from natural fulvic acid. Furthermore, various BBS-DOMs and fulvic acid had different component fractionation behaviors during clay adsorption, because they had different abundances of protein-like matters (hydrogen bond donors), pyridine-N/pyrimidine-N (positive charge doners of electrostatic interaction), and fulvic-like matters (hydrophobic interaction and pore filling effect). Additionally, the increasing pH weakened the adsorption of bulk BBS-DOMs and enhanced the adsorption ratio of aromatic matters and smaller BBS-DOM molecules. Meanwhile, at a higher pH, the adsorption ratio of protein-like matters increased, while the adsorption ratio of humic- and fulvic-like matters decreased. The result was ascribed to the enhanced hydrogen bond between protein-like matters and clays as well as the enhanced electrostatic repulsion between humic-/fulvic-like matters and clays. This study is helpful for deeply understanding the multimedia-crossing environmental behavior of BBS-DOMs in the surface environment.

Influence of suspended particles and dissolved organic matters on virus enrichment in reclaimed water by two-step tangential flow ultrafiltration: Phenomena and mechanisms.

Enteric virus concentration in large-volume water samples is crucial for detection and essential for assessing water safety. Certain dissolution and suspension components can affect the enrichment process. In this study, tangential flow ultrafiltration (TFUF) was used as an enrichment method for recovering enteric virus in water samples. Interestingly, the bacteriophage MS2 recovery in reclaimed water and the reclaimed water without particles were higher than that in ultrapure water. The simulated reclaimed water experiments showed that humic acid (HA) (92.16% ± 4.32%) and tryptophan (Try) (81.50 ± 7.71%) enhanced MS2 recovery, while the presence of kaolin (Kaolin) inhibited MS2 recovery with an efficiency of 63.13% ± 11.17%. Furthermore, Atomic force microscopy (AFM) revealed that the MS2-HA cluster and the MS2-Try cluster had larger roughness values on the membrane surface, making it difficult to be eluted, whereas MS2-Kaolin cluster had compact surfaces making it difficult to be eluted. Additionally, the MS2-HA cluster is bound to the membrane by single hydrogen bond with SO, whereas both the MS2-Try cluster and the MS2-Kaolin cluster are bound to the membrane by two hydrogen bonds, making eluting MS2 challenging. These findings have potential implications for validating standardized methods for virus enrichment in water samples.

Effect of interaction between dissolved organic matter and iron/manganese (hydrogen) oxides on the degradation of organic pollutants by in-situ advanced oxidation techniques.

Iron and manganese (hydrogen) oxides (IMHOs) exhibit excellent redox capabilities for environmental pollutants and are commonly used in situ chemical oxidation (ISCO) technologies for the degradation of organic pollutants. However, the coexisting dissolved organic matter (DOMs) in surface environments would influence the degradation behavior and fate of organic pollutants in IMHOs-based ISCO. This review has summarized the interactions and mechanisms between DOMs and IMHOs, as well as the properties of DOM-IMHOs complexes. Importantly, the promotion or inhibition impact of DOM was discussed from three perspectives. First, the presence of DOMs may hinder the accessibility of active sites on IMHOs, thus reducing their efficiency in degrading organic pollutants. The formation of compounds between DOMs and IMHOs alters their stability and activity in the degradation process. Second, the presence of DOMs may also affect the generation and transport of active species, thereby influencing the oxidative degradation process of organic pollutants. Third, specific components within DOMs also participate and affect the degradation pathways and rates. A comprehensive understanding of the interaction between DOMs and IMHOs helps to better understand and predict the degradation process of organic pollutants mediated by IMHOs in real environmental conditions and contributes to the further development and application of IMHO-mediated ISCO technology.

Dissolved organic matter promoted hydroxyl radical formation and phenanthrene attenuation during oxygenation of iron-pillared montmorillonites.

The oxygenation of Fe(II)-bearing minerals for hydroxyl radicals (HO•) formation and contaminant attenuation receives increasing attentions. However, information on dissolved organic matter (DOM) with different types, concentrations, and molecular weights (MWs) in manipulating HO• formation and contaminant attenuation during mineral oxygenation remain unclear. In this study, four iron-pillared montmorillonites (IPMs) and two DOM samples [e.g., humic acids (HA) and fulvic acids (FA)] were prepared to explore the HO• formation and phenanthrene attenuation during the oxygenation of IPMs in the presence or absence of DOMs. Results showed that iron-pillared and high-temperature calcination procedures extended the interlayer domain of IPMs, which provided favorable conditions for a high HO• production from 1293 to 14537 µmol kg-1. The surface-absorbed/low crystalline Fe(Ⅱ) was the predominant Fe(Ⅱ) fractionations for HO• production, and presence of DOMs significantly enhanced the HO• production and phenanthrene attenuation. Moreover, regardless of the types and concentrations, the low MW (LMW, <1 kDa) fraction within DOM pool contributed highest to HO• production and phenanthrene attenuation, followed by the bulk and high MW (HMW-, 1 kDa∼0.45 µm) fractions, and FA exhibited more efficient effects in promoting HO• production and phenanthrene attenuation than HA. The fluorescent spectral analysis further revealed that phenolic-like fluorophores in LMW-fraction were the main substances responsible for the enhanced HO• production and phenanthrene attenuation. The results deepen our understandings toward the behaviors and fate of aquatic HO• and contaminants, and also provide technical guidance for the remediation of contaminated environments.

Coagulation pretreatment coupled with indigenous microalgal-bacterial consortium system for on-site treatment of rural black wastewater.

Improper treatment of rural black wastewater (RBW) presents substantial challenges, including the wastage of resource, environmental contamination, and economic consequences. This study proposed an integrated process for RBW treatment, consisting of coagulation/flocculation (C/F) pretreatment and subsequent inoculation of indigenous microalgal-bacterial consortium (IMBC) for nitrogen recovery, namely C/F-IMBC process. Specifically, the optimal C/F conditions (polyaluminium chloride of 4 g/l, polyacrylamide of 50 mg/l, and pH of 6) were determined through a series of single-factor experiments, considering CN, turbidity, and dissolved organic matter (DOM) removal, economic cost, and potential influence on the water environment. Compared to the sole IMBC system for RBW treatment, the proposed C/F-IMBC process exhibited a remarkable 1.23-fold increase in microalgal growth and a substantial 17.6-22.6 % boost in nitrogen recovery. The altered RBW characteristic induced by C/F pretreatment was supposed to be responsible for the improved system performance. In particular, the abundance of DOM was decreased and its composition was simplified after C/F pretreatment, based on the analysis for excitation-emission matrices with parallel factor and gas chromatography-mass spectrometry, thus eliminating the potential impacts of toxic DOM components (e.g., Bis(2-ethylhexyl) phthalate) on IMBC activity. It should also be noted that C/F pretreatment modified microbial community structure as well, thereby regulating the expression of nitrogen-related genes and enhancing the system nitrogen recovery capacity. For instance, the functional Cyanobacteria responsible for nutrient recovery was enriched by 1.95-fold and genes involved in the assimilatory nitrate reduction to ammonia pathway were increased by 1.52-fold. These fundamental findings are expected to offer insights into the improvement of DOM removal and nitrogen recovery for IMBC-based wastewater treatment system, and provide valuable guidance for the development of sustainable on-site RBW treatment technologies.

Coagulation/co-catalytic membrane integrated system for fouling-resistant and efficient water purification.

Low-pressure catalytic membranes allow efficient rejection of particulates and simultaneously removing organics pollutant in water, but the accumulation of dissolved organic matters (DOM) on membrane surface, which cover the catalytic sites and cause membrane fouling, challenges their stable operation in practical wastewater treatment. Here we propose a ferric salt-based coagulation/co-catalytic membrane integrated system that can effectively mitigate the detrimental effects of DOM. Ferric salt (Fe3+) serving both as a DOM coagulant to lower the membrane fouling and as a co-catalyst with the membrane-embedded MoS2 nanosheets to drive perxymonosulfate (PMS) activation and pollutant degradation. The membrane functionalized with 2H-phased MoS2 nanosheets showed improved hydrophilicity and fouling resistance relative to the blank polysulfone membrane. Attributed to the DOM coagulation and co-catalytic generation of surface-bound radicals for decontamination at membrane surface, the catalytic membrane/PMS/ Fe3+ system showed much less membrane fouling and 2.6 times higher pollutant degradation rate in wastewater treatment than the catalytic membrane alone. Our work imply a great potential of coagulation/co-catalytic membrane integrated system for water purification application.

Iron-Nitrogen Amendment Reduced Perfluoroalkyl Acids' Phyto-Uptake in the Wheat-Soil Ecosystem: Contributions of Dissolved Organic Matters in Soil Solution and Root Extracellular Polymeric Substances.

Understanding the mechanisms underlying perfluoroalkyl acids (PFAAs) translocation, distribution, and accumulation in wheat-soil ecosystems is essential for agricultural soil pollution control and crop ecological risk assessment. This study systematically investigated the translocation of 13 PFAAs under different iron and nitrogen fertilization conditions in a wheat-soil ecosystem. Short-chain PFAAs including PFBA, PFPeA, PFHxA, and PFBS mostly accumulated in soil solution (10.43-55.33%) and soluble extracellular polymeric substances (S-EPS) (11.39-14.77%) by the adsorption to amino- (-NH2) and hydroxyl (-OH) groups in dissolved organic matter (DOM). Other PFAAs with longer carbon chain lengths were mostly distributed on the soil particle surface by hydrophobic actions (74.63-94.24%). Iron-nitrogen amendments triggered (p < 0.05) soil iron-nitrogen cycling, rhizospheric reactive oxygen species fluctuations, and the concentration increases of -NH2 and -OH in the DOM structure. Thus, the accumulation capacity of PFAAs in soil solution and root EPS was increased. In sum, PFAAs' translocation from soil particles to wheat root was synergistically reduced by iron and nitrogen fertilization through increased adsorption of soil particles (p < 0.05) and the retention of soil solution and root EPSs. This study highlights the potential of iron-nitrogen amendments in decreasing the crop ecological risks to PFAAs' pollution.

Copper regulates degradation of typical antibiotics by microalgal-fungal consortium in simulated swine wastewater: insights into metabolic routes and dissolved organic matters.

Microalgae-based biotechnology for antibiotics biodegradation in swine wastewater has been receiving an increasing attention. In this study, microalgae and fungi co-cultivation system, regulated by copper (Cu(II)), was investigated in terms of nutrients and sulfonamides degradation in simulated swine wastewater. Results showed that the removal of ammonium nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) by microalgal-fungal consortium increased under 0.1-0.5 mg/L Cu(II) with the highest removal efficiency of 79.19%, 76.18%, 93.93% and 93.46%, respectively. The addition of Cu(II) (0-0.5 mg/L) enhanced the removal of sulfamonomethoxine (SMM), sulfamethoxazole (SMX) and sulfamethazine (SMZ) from 49.05% to 58.76%, from 59.31% to 63.51%, and from 37.51% to 63.9%, respectively, and the main removal mechanism was found to be biodegradation. Biodegradation followed a pseudo-first-order model with variable half-lives (10.12 to 15.51 days for SMM, 9.01 to 10.88 days for SMX, and 8.74 to 12.85 days for SMZ). Through mass spectrometry analysis, metabolites and intermediates of sulfonamides were accordingly identified, suggesting that the degradation routes were involved with hydroxylation, deamination, oxidation, de-sulfonation and bond cleavage. Dissolved organic matters released by microalgal-fungal consortium were induced by Cu(II). Fulvic acid-like and protein-like substances were bound to Cu(II), reducing its concentration and thus mitigating the organismal damage to microorganisms. These findings drew an insightful understanding of microalgal-fungal consortium for sulfonamides remediation by Cu(II) regulation in simulated swine wastewater.

Tracking the transformation pathway of dissolved organic matters (DOMs) in biochars under sludge pyrolysis via reactomics and molecular network analysis.

This work examined the transformation pathways of sludge biochar-derived dissolved organic matters (SBC-derived DOMs) under sludge pyrolysis via FT-ICR-MS-based reactomics and molecular network analysis. Lignin/carboxylic-rich alicyclic molecules, proteins/aliphatic, and lipids of SBC-derived DOMs did not contribute equally to the overall pyrolytic reactions. Reactomics suggested that the pyrolysis reactions of SBC-derived DOMs consist of multiple cascade reactions involving the elimination of assemblages of reactive fragments during each pyrolysis reaction region, and the overall pyrolysis process was divided into three stages according to cascade reaction variations. Especially, cascade reactions at 400-500 °C produced potential environmental risk substances of N-containing, carbonyl-containing, and phenolic compounds. Besides, network analysis unraveled the complexity and number of molecular reaction pairs of SBC-derived DOMs decreased with the increase in pyrolytic temperatures. Keystone molecules and pathways results indicated that the pyrolytic temperature of the sludge pyrolysis process should be controlled at temperatures above 500 °C according to the harmful substances generation pattern in reaction products. Overall, the possible transformation pathways of SBC-derived DOMs during sludge pyrolysis treatment were proposed. This study elucidated the underlying mechanisms in generating SBC-derived DOMs and provided theoretical support for process optimization and harmful substances control of sludge pyrolysis.

Conversion and impact of dissolved organic matters in a heterogeneous catalytic peroxymonosulfate system for pollutant degradation.

Dissolved organic matters (DOM) are widely present in different water sources, causing significant effects on water treatment processes. Herein, the molecular transformation behavior of DOM during peroxymonosulfate (PMS) activation by biochar for organic degradation in a secondary effluent were comprehensively analyzed. Evolution of DOM was identified and inhibition mechanisms to organic degradation were elucidated. DOM underwent oxidative decarbonization (e.g., -C2H2O, -C2H6, -CH2 and -CO2), dehydrogenation (-2H) and dehydration reactions by ·OH and SO4·-. N and S containing compounds witnessed deheteroatomisation (e.g., -NH, -NO2+H, -SO2, -SO3, -SH2), hydration (+H2O) and N/S oxidation reactions. Among DOM, CHO-, CHON-, CHOS-, CHOP- and CHONP-containing molecules showed moderate inhibition while condensed aromatic compounds and aminosugars exhibited strong and moderate inhibition effects on contaminant degradation. The fundamental information could provide references for the rational regulation of ROS composition and DOM conversion process in a PMS system. This in turn offered theoretical guidance to minimize the interference of DOM conversion intermediates on PMS activation and degradation of target pollutants.

Transport of dissolved organic matters derived from biomass-pyrogenic smoke (SDOMs) and their effects on mobility of heavy metal ions in saturated porous media.

Biomass-pyrogenic smoke-derived dissolved organic matter (SDOMs) percolating into the underground environment profoundly impacts the transport and fate of environmental pollutants in groundwater systems. Herein, SDOMs were produced by pyrolyzing wheat straw at 300-900 °C to explore their transport properties and effects on Cu2+ mobility in quartz sand porous media. The results indicated that SDOMs exhibited high mobility in saturated sand. Meanwhile, the mobility of SDOMs was enhanced at a higher pyrolysis temperature due to the decrease in their molecular sizes and the declined H-bonding interactions between SDOM molecules and sand grains. Furthermore, the transport of SDOMs was elevated as pH values were raised from 5.0 to 9.0, which resulted from the strengthened electrostatic repulsion between SDOMs and quartz sand particles. More importantly, SDOMs could facilitate Cu2+ transport in the quartz sand, which stemmed from forming soluble Cu-SDOM complexes. Intriguingly, the promotional function of SDOMs for the mobility of Cu2+ was strongly dependent on the pyrolysis temperature. Generally, SDOMs generated at higher temperatures exhibited superior effects. The phenomenon was mainly due to the differences in the Cu-binding capacities of various SDOMs (e.g., cation-π attractive interactions). Our findings highlight that the high-mobility SDOM can considerably affect heavy metal ions' environmental fate and transport.

An extensive assessment of seasonal rainfall on intracellular and extracellular antibiotic resistance genes in Urban River systems.

Rainfall events are responsible for the accelerated transfer of antibiotic-resistant contaminants to receiving environments. However, the specific profiles of various ARG types, including intra- and extracellular ARGs (iARGs and eARGs) responding to season rainfall needed more comprehensive assessments. Particularly, the key factors driving the distribution and transport of iARGs and eARGs have not been well characterized. Results revealed that the absolute abundance of eARGs was observed to be more than one order of magnitude greater than that of iARGs during the dry season in the reservoir. However, the absolute abundance of iARGs significantly increased after rainfall (p < 0.01). Meanwhile, seasonal rainfall significantly decreased the diversity of eARGs and the number of shared genes between iARGs and eARGs (p < 0.01). Results of structural equation models (SEM) and network analysis showed the rank and co-occurrence of influencing factors (e.g., microbial community, MGEs, environmental variables, and dissolved organic matter (DOM)) concerning the changes in iARGs and eARGs. DOM contributed majorly to eARGs in the reservoir and pathogens was responsible for eARGs in the river during the wet season. Network analysis revealed that the tnp-04 and IS613 genes-related MGEs co-occurred with eARGs in the dry and wet seasons, which were regarded as potential molecular indicators to shape eARGs profiles in urban rivers. Besides, the results demonstrated close relationships between DOM fluorescence signatures and two-typed ARGs. Specifically, humic acid was significantly and positively correlated with the eARGs in the reservoir during the wet season, while fulvic acid-like substances exhibited strong correlations of iARGs and eARGs in the river during the dry season (p < 0.01). This work provides extensive insights into the potential effect of seasonal rainfall on the dynamic distribution of iARGs and eARGs and the dominance of DOM in driving the fate of two-typed ARGs in urban river systems.

Autochthonous DOM had solar disinfection effect but nitrate counteracted with them.

Pathogens in natural water can pose great threat to public health and challenge water quality. In sunlit surface water, dissolved organic matters (DOMs) can inactivate pathogens due to their photochemical activity. However, the photoreactivity of autochthonous DOM derived from different source and their interaction with nitrate on photo-inactivation remained limited understood. In this study, the composition and photoreactivity of DOM extracted from Microcystis (ADOM), submerged aquatic plant (PDOM) and river water (RDOM) were studied. Results revealed that lignin and tannin-like polyphenols and polymeric aromatic compounds negatively correlated with quantum yield of 3DOM*, whilst lignin like molecules positively correlated with •OH generation. ADOM had highest photoinactivation efficiency of E. coli, followed by RDOM and PDOM. Both the photogenerated •OH and low energy 3DOM* could inactivate bacteria damaging cell membrane and causing increase of intracellular reactive species. PDOM with more phenolic or polyphenols compounds not only weaken its photoreactivity, also increase regrowth potential of bacteria after photodisinfection. The presence of nitrate counteracted with autochthonous DOMs on photogeneration of •OH and photodisinfection activity, as well as increased the reactivation rate of PDOM and ADOM, which might be attributed to the increase of survival bacteria and more bioavailable fractions provided in systems.

Biostimulants in dissolved organic matters recovered from anaerobic digestion sludge with alkali-hydrothermal treatment: Nontarget identification by ultrahigh-resolution mass spectrometry.

Recovering high-value biomaterials from anaerobic digestion sludge (ADS) has attracted considerable attention. However, the molecular features and biological effects of abundant dissolved organic matters (DOMs) in ADS are still unclear, which limits the efficient recycling and application of these bioproducts. This study investigated the molecular composition and transformation of DOMs recovered from ADS through a mild-temperature alkali-hydrothermal treatment (AHT) with ultrahigh-resolution mass spectrometry and energy spectroscopy, and the fertilizing effects of DOMs were evaluated by rice hydroponics. The results indicated that AHT processes significantly promoted the solubilization and release of DOMs from ADS, where most of DOMs molecules remained unchanged and mainly consisted of N-containing compounds with 1-3 N atoms, featuring aromatic or N-heterocyclic rings. Furthermore, AHT processes at pH of 9-10 induced the hydrolysis of partial protein-like substances in DOMs, which was accompanied by formation of heterocyclic-N compounds. Under AHT at pH of 11-12, protein-like and heterocyclic-N substances were increasingly decomposed into amino-N compounds containing 1 or 5 N atoms, while numerous oxygenated aromatic substances with phytotoxicity were degraded and removed from DOMs. Rice hydroponic test verified that ADS-derived DOMs recovered by AHT process at pH of 12 exhibited the highest bioactivity for rice growth, which was attributed to the abundance of amino compounds and humic substances. This study proposed a novel process for the recovery of high-quality liquid organic fertilizer from ADS through AHT process, which can further enrich the technical options available for the safe utilization of sludge resources.

Impacts of properties of dissolved organic matters on indirect photodegradation of genistein.

Excited triplet states of dissolved organic matters (3DOM*) are one of the most important photochemically-produced reactive intermediates leading to transformation of organic contaminants. However, relationships of photodegradation kinetics of different dissociation states of phenolic organic contaminants with chemical components or properties of 3DOM* are largely unknown. In this study, roles of 3DOM* in photodegradation of polyhydroxy phenolic genistein (Gs) at pH 5, 8 and 12 were investigated taking five kinds of DOM from different sources as examples. Relationships between photodegradation kinetics constants and DOM properties were built. Results showed that the contributions of direct 3DOM*-induced reactions to the total indirect photodegradation of Gs and second-order reaction rate constants (kDOM,Gs) of Gs with 3DOM* increased with pH increases. This was mainly attributed to decreases in vertical ionization energy of Gs at higher pH, endowing Gs with stronger electron donating capacities. kDOM,Gs was found to positively correlate with the specific ultraviolet absorbance at 254 nm, reflecting aromaticity of DOM, and negatively correlate with the absorbance ratio at 254 and 365 nm and contents of dissociated acidic functional groups of DOM, representing molecular weights of DOM, antioxidants and the repulsive forces between 3DOM* and Gs. This study provided a new insight into relationship between DOM properties and indirect photodegradation kinetics of phenolic contaminants in aquatic environments.

The characters of dissolved organic matters from litter-mimic with the different humification states and their effects on drinking water treatment processes.

Dissolved organic matter (DOM) is one kind of the main pollutant in surface water that will cause many problems during drinking water treatment processes. In this study, a simulated humification process of forest litter-mimic was investigated for eight weeks continuously to study the variations in chemical properties such as DOM composition, polysaccharide/protein ratio, average molecular weight, oxidation degree, hydrophilicity, etc., as well as the impact of these variations on the coagulation, ultra-/nanofiltration (UF/NF). Results showed that the removal rate of coagulation (from 67.5 % to 37.0 %) and UF (from 14.4 % to 5.8 %) decreased significantly during the humification process as a function of time, while the removal rate of NF increased from 40.0 % to 72.9 % at first, and then decreased to 47.4 %. This study gave a deep insight into the effect of DOM with different humification ages on the drinking water treatment process with the influence of seasons and vegetation around the water source, which finally aimed to improve drinking water treatment.

Enhancing two-phase anaerobic digestion of mixture of primary and secondary sludge by adding granular activated carbon (GAC): Evaluating acidogenic and methanogenic efficiency.

Although the granular activated carbon (GAC) has been proved to enhance conventional single-phase anaerobic digestion (AD), how it impacts on acidogenic and methanogenic fermentation is still unknown. In this study, GAC was introduced to elevate the efficiency of two-phase AD, with mixture of primary and secondary sludge as substrate. Five dosages: 0, 0.1, 0.3, 0.5 and 0.7 g GAC/g TSS (Total Suspended Solids) were investigated to determine influences of GAC. The variations of biogas (hydrogen and methane), volatile fatty acids (VFAs), organics degradation and transformation in extracellular polymeric substances (EPS) and dissolved organic matters (DOM) were analyzed. Modified Gompertz model and first-order reaction equation was applied to analyze the kinetics of biogas yield and VFAs utilization, respectively. Sludge reduction, electrical conductance and pH were also quantified to evaluate the system performance. The results showed that GAC could improve two-phase AD performance by enhancing methane production and organics conversion.

Dissolved organic matters-enhanced Pb releases from nano- or submicron Pb sulfides and oxides.

Diverse lead (Pb) particles possess different ecological risks not only due to their own toxicity differences but also because of different abilities to release toxic dissolved Pb. Dissolved organic matter (DOM) was a key factor influencing dissolution processes of metal particles. However, impacts of DOM on dissolution of different Pb nano- or submicron particles were not known yet. Herein, impacts of DOM on dissolution kinetics of lead sulfide (PbS), lead sulfate (PbSO4), lead monoxide (PbO), lead tetroxide (Pb3O4) and lead dioxide (PbO2) nano- or submicron particles were firstly investigated taking Pahokee Peat humic acid (PPHA) as an example. Results indicated PPHA improved the suspending stability of Pb particles through electrostatic repulsion, and enhanced releases of dissolved Pb. Final concentration of dissolved Pb was raised by 1.22-8.82 times with PPHA. This was attributed to ligand exchange interactions between PPHA and Pb particles. Theoretical computations indicated that not only sorption or ligand exchange energy, but also numbers of ligands on the surface of particles were key factors governing impacts of PPHA on dissolved Pb. This study provided a new mechanism insight into dissolution behavior of various Pb particles and will be beneficial to their ecological risk assessment.