Mechanistic insight into the aggregation ability of anammox microorganisms: Roles of polarity, composition and molecular structure of extracellular polymeric substances.

The chemical characteristics of extracellular polymeric substances (EPS) of anammox bacteria (AnAOB) play a crucial role in the rapid enrichment of AnAOB and the stable operation of wastewater anammox processes. To clarify the influential mechanisms of sludge EPS on AnAOB aggregation, multiple parameters, including the polarity distribution, composition, and molecular structure of EPS, were selected, and their quantitative relationship with AnAOB aggregation was analyzed. Compared to typical anaerobic sludge (anaerobic floc and granular sludge), the anammox sludge EPS exhibited higher levels of tryptophan-like substances (44.82-56.52 % vs. 2.57-39.81 %), polysaccharides (40.02-53.49 mg/g VSS vs. 30.22-41.69 mg/g VSS), and protein structural units including α-helices (20.70-23.98 % vs. 16.48-19.32 %), ß-sheets (37.43-42.98 % vs. 25.78-36.72 %), and protonated nitrogen (Npr) (0.065-0.122 vs. 0.017-0.061). In contrast, it had lower contents of ß-turns (20.95-27.39 % vs. 28.17-39.04 %). These biopolymers were found to originate from different genera of AnAOB. Specifically, the α-helix-rich proteins were mainly derived from Candidatus Kuenenia, whereas the extracellular proteins related to tryptophan and Npr were closely associated with Candidatus Brocadia. Critically, these EPS components could drive anammox aggregation through interactions. Substantial amounts of tryptophan-like substances facilitated the formation of ß-sheet structures and the exposure of internal hydrophobic clusters, which benefited the anammox aggregation. Meanwhile, extracellular proteins with high Npr content played a pivotal role in the formation of mixed protein-polysaccharide gel networks with the electronegative regions of polysaccharides, which could be regarded as the key component in the maintenance of anammox sludge stability. These findings provide a comprehensive understanding of the multifaceted roles of EPS in driving anammox aggregation and offer valuable insights into the development of EPS regulation strategies aimed at optimizing the anammox process.

Effect and potential mechanisms of sludge-derived chromium, nickel, and lead on soil nitrification: Implications for sustainable land utilization of digested sludge.

Increasing occurrence of heavy metals (HMs) in sewage sludge threatens its widespread land utilization in China due to its potential impact on nutrient cycling in soil, requiring a better understanding of HM-induced impacts on nitrification. Herein, lab-scale experiments were conducted over 185-day, evaluating the effect of sludge-derived chromium (Cr3+), nickel (Ni2+), and lead (Pb2+) on soil nitrification at different concentrations. Quantitative polymerase chain reaction and linear regression results revealed an inhibitory sequence of gene abundance by HMs' labile fraction: ammonia-oxidizing bacteria (AOB)-ammonia monooxygenase (amoA)> nitrite oxidoreductase subunit alpha (nxrA)> nitrite oxidoreductase subunit beta (nxrB). The toxicity of HMs' incremental labile fraction decreased in the order of Ni2+>Cr3+>Pb2+, with respective threshold values of 5.01, 24.03 and 38.42 mg·kg-1. Furthermore, extending incubation time reduced HMs inhibition on ammonia oxidation, mainly related to their fraction bound to carbonate minerals. Random Forest analysis, variation partitioning analysis, and Mantel test indicated that soil physicochemical properties primarily affected nitrification genes, especially in the test of Cr3+ on AOB-amoA, nxrA, nxrB, Ni2+ for complete ammonia-oxidizing bacteria-amoA, and Pb2+ for nxrA and nxrB. These findings underline the importance of labile HMs fractions and soil physicochemical properties to nitrification, guiding the establishment of HM control standards for sludge utilization.

Ionic regulation whey protein composition on membrane fouling during ultrafiltration process analyzed by HPLC.

In order to meet the market demand and avoid the increase of operation amount and cleaning cost in the process of ultrafiltration, it is particularly important to find more practical and efficient methods to control and improve membrane fouling. In this study, the ions in the ultrafiltration process were regulated to affect membrane surface proteins composition (lactoferrin, α-lactalbumin, ß-lactoglobulin A and ß-lactoglobulin B) and delay membrane fouling. It was found that Na+ (21 mmol/L), Zn2+ (0.25 mmol/L) and K+ (44 mmol/L) was added at 4 min, 8 min and 12 min, respectively during ultrafiltration process. The continuous regulation slowed down the decline rate of membrane flux and reduced the content of α-lactalbumin, ß-lactoglobulin A and ß-lactoglobulin B on the membrane surface analyzed by HPLC. This could reduce the irreversible membrane fouling of proteins cake resistance. Furthermore, the ions concentration was also investigated after filtration. The concentration of K+ was increased significantly and other ions concentration was not significantly changed after continuous regulation such Na+, Mg2+, Zn2+ and Ca2+ compared to control. Therefore, dynamic ionic regulation of whey protein ultrafiltration process is a simple and effective method, which provides technical theoretical basis for optimizing and improving membrane technology.

Extracellular polymeric substances-antibiotics interaction in activated sludge: A review.

Antibiotics, the most frequently prescribed drugs, have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems, a hotspot where the occurrence and transformation of antibiotic resistance take place. Extracellular polymeric substances (EPS), biopolymers secreted via microbial activity, play an important role in cell adhesion, nutrient retention, and toxicity resistance. However, the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear. This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS, highlights the critical role of EPS in antibiotics removal, evaluates their defense performances under different antibiotics exposures, and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics. Next, interactions between microbial EPS and antibiotic resistance genes are analyzed. Future perspectives, especially the engineering application of microbial EPS for antibiotics toxicity detection and defense, are also emphatically stressed.

Calcium peroxide and freezing co-pretreatment enhancing short-chain fatty acids production from waste activated sludge towards carbon-neutral sludge treatment.

Short-chain fatty acids (SCFAs) recovery through anaerobic fermentation is a promising technology to achieve carbon-neutral in waste activated sludge (WAS) management. After 0.15 g CaO2/g volatile suspended solids (VSS) addition and three-cycle freezing co-pretreatments, the maximal SCFAs production of 438.5 mg COD/g VSS was achieved within 4 days fermentation, and more than 70 % of SCFAs was composed of acetate and propionate, which achieved a higher level than reported in previous studies. Mechanism explorations elucidated that co-pretreatment triggered sludge solubilization, promoting the release of biodegradable organics, providing more biodegradable substrates for SCFAs generation. Further microbial community analysis indicated that the abundances of hydrolytic microorganisms and acidogens were enriched, whereas methanogens were inhibited. Besides, environmental analysis suggested that co-pretreatment could achieve carbon reduction benefits of 0.116-0.291 ton CO2/ton WAS, demonstrating its huge carbon-neutral potential benefits.

The effect of ion environment changes on retention protein behavior during whey ultrafiltration process.

The factors affecting membrane fouling are very complex. In this study, the membrane fouling process was revealed from the perspective of ion environment changes, which affected the whey protein structure during ultrafiltration. It was found that the concentrations of Ca2+ and Na+ were overall increased and the concentrations of K+, Mg2+ and Zn2+ were decreased at an ultrafiltration time of 11 min, which made more hydrophilic groups buried inside and increased the content of α-helix, leading to more protein aggregation. The relatively higher K+ ratio in retention could lead to an antiparallel ß-sheet configuration, aspartic acid, glutamic acid and tryptophan increased, which resulted in more protein aggregation and deposition on the membrane surface at 17 min. When the ion concentration and ratio restored the balance and were close to the initial state in retention, the protein surface tension decreased, and the hydrophilic ability increased at 21-24 min.

Sources, fates and treatment strategies of typical viruses in urban sewage collection/treatment systems: A review.

The ongoing coronavirus pandemic (COVID-19) throughout the world has severely threatened the global economy and public health. Due to receiving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a wide variety of sources (e.g., households, hospitals, slaughterhouses), urban sewage treatment systems are regarded as an important path for the transmission of waterborne viruses. This review presents a quantitative profile of the concentration distribution of typical viruses within wastewater collection systems and evaluates the influence of different characteristics of sewer systems on virus species and concentration. Then, the efficiencies and mechanisms of virus removal in the units of wastewater treatment plants (WWTPs) are summarized and compared, among which the inactivation efficiencies of typical viruses by typical disinfection approaches under varied operational conditions are elucidated. Subsequently, the occurrence and removal of viruses in treated effluent reuse and desalination, as well as that in sewage sludge treatment, are discussed. Potential dissemination of viruses is emphasized by occurrence via aerosolization from toilets, the collection system and WWTP aeration, which might have a vital role in the transmission and spread of viruses. Finally, the frequency and concentration of viruses in reclaimed water, the probability of infection are also reviewed for discussing the potential health risks.

Effect of pig manure-derived sulfadiazine on species distribution and bioactivities of soil ammonia-oxidizing microorganisms after fertilization.

To evaluate the effect of pig manure-derived sulfadiazine (SDZ) on the species distribution and bioactivities of ammonia-oxidizing microorganisms (AOMs), ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and complete ammonia oxidizer (comammox) within the soil were investigated pre- and post-fertilization. Kinetic modeling and linear regression results demonstrated that the DT50 value of different SDZ fractions under initial SDZ concentrations of 50 and 100 mg·kg-1 exhibited the following trend: total SDZ>CaCl2-extractable SDZ>MeOH-extractable SDZ, whereas their inhibiting effect on AOMs showed an opposite trend. qPCR analysis suggested that comammox was the predominant ammonia oxidizer in soils regardless of SDZ addition, accounting for as much as 77.2-94.7% of the total amoA, followed by AOA (5.3-22.5%), whereas AOB (<0.5%) was the lowest. The SDZ exhibited a significant effect on the AOM abundance. Specifically, SDZ exerted the highest inhibitory effect on comammox growth, followed by AOA, whereas negligible for AOB. The community diversity of AOMs within the pig manure-fertilized soils was affected by SDZ, and AOA Nitrososphaera cluster 3 played a key role in potential ammonia oxidation capacity (PAO) maintenance. This study provides new insights into the inhibition mechanisms of pig manure-derived antibiotics on AOMs within the fertilized soil.

Removal trend of amoxicillin and tetracycline during groundwater recharging reusing: Redox sensitivity and microbial community response.

The abundant existence of antibiotics within the effluent of wastewater treatment plant seriously threatened their safety recharging. To investigate the fate and biodegradation of those toxic antibiotics within the soil aquifer system, typical antibiotics of amoxicillin (AMX) and tetracycline (TC) were selected and their removal mechanisms were investigated. Experimental results revealed that totally 93.4% and 87.2% of the AMX and TC recharged (10 µg/L) were, respectively, removed within 1 m depth column operation. Specifically, the aerobic biodegradation, abiotic processes and anoxic/anaerobic microorganism contributed as higher as 37.5%, 33.7% and 28.8% of the AMX reduction, via the controlling tests of NaN3 inhibition and soil sterilisations. By contrast, the percentage contribution of the TC was aerobic (54.3%) ˃abiotic processes (32.7%) ˃anoxic/anaerobic (13.0%), a higher aerobic degradation whereas weaker anoxic/anaerobic microorganism. Column systems (CSs) were constructed to study the effect of redox conditions (methanogenic, sulfate-reducing, nitrate-reducing, aerobic) on antibiotics degradation, and microbial community results revealed that Verrucomicrobia, Actinobacteria, Deinococcus-Thermus and Armatimonadetes contributed to the aerobic biodegradation of TC. For comparison, AMX could be efficiently degraded under nitrate reduction (19.95%) > sulfate reduction (16.64%) > methanogenic (9.53%), and Actinobacteria, Bacteroidetes and Verrucomicrobia were the dominant bacteria for AMX degradation. This study provided optimal directions for antibiotics removal within the groundwater recharging systems and is conducive to obtain highly value-added reclaimed water.

A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms.

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h+ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

A Review Study on Sulfate-Radical-Based Advanced Oxidation Processes for Domestic/Industrial Wastewater Treatment: Degradation, Efficiency, and Mechanism.

High levels of toxic organic pollutants commonly detected during domestic/industrial wastewater treatment have been attracting research attention globally because they seriously threaten human health. Sulfate-radical-based advanced oxidation processes (SR-AOPs) have been successfully used in wastewater treatment, such as that containing antibiotics, pesticides, and persistent organic pollutants, for refractory contaminant degradation. This review summarizes activation methods, including physical, chemical, and other coupling approaches, for efficient generation of sulfate radicals and evaluates their applications and economic feasibility. The degradation behavior as well as the efficiency of the generated sulfate radicals of typical domestic and industrial wastewater treatment is investigated. The categories and characteristics of the intermediates are also evaluated. The role of sulfate radicals, their kinetic characteristics, and possible mechanisms for organic elimination are assessed. In the last section, current difficulties and future perspectives of SR-AOPs for wastewater treatment are summarized.

Dewatering efficiency of sewage sludge during Fe2+-activated persulfate oxidation: Effect of hydrophobic/hydrophilic properties of sludge EPS.

To clarify the effect of the hydrophobic/hydrophilic polarity of extracellular polymeric substances (EPS) on sludge filterability improvement during S2O82-/Fe2+ oxidation, waste activated sludge (WAS), glucose-fed hydrophilic sludge (HPI-WAS), and sodium acetate-fed hydrophobic sludge (HPO-WAS) samples were cultivated, and their dewatering behaviors were individually explored. Experimental results showed that S2O82- oxidation effectively disintegrated the polymeric EPS and led to a more significant reduction in the water content for HPO-WAS than for HPI-WAS (12.87-15.23% vs 9.31-12.12%), especially regarding the bound water (Wb) content. After oxidation, as high as 38.88-42.61% of the Wb within HPO-WAS samples were declined, much higher than the HPI-WAS samples (19.27-29.20%). Specifically, carbohydrates within sludge EPS negatively influenced the dewatering process of S2O82-/Fe2+ oxidation. By contrast, abundant existence of humic acids and polymeric proteinaceous components (especially those hydrophilic proteins and transitional humic acids) within the sludge EPS exhibited a converse trend. FT-IR and EEM spectral, as well as particle sizes variation for the sludge samples before and after S2O82-/Fe2+ oxidation was also evaluated. This study provides new insight into the enhancement of S2O82-/Fe2+ oxidation for sludge dewatering based on polarity analysis of EPS.

Seasonal concentration distribution of PM1.0 and PM2.5 and a risk assessment of bound trace metals in Harbin, China: Effect of the species distribution of heavy metals and heat supply.

To clarify the potential carcinogenic/noncarcinogenic risk posed by particulate matter (PM) in Harbin, a city in China with the typical heat supply, the concentrations of PM1.0 and PM2.5 were analyzed from Nov. 2014 to Nov. 2015, and the compositions of heavy metals and water-soluble ions (WSIs) were determined. The continuous heat supply from October to April led to serious air pollution in Harbin, thus leading to a significant increase in particle numbers (especially for PM1.0). Specifically, coal combustion under heat supply conditions led to significant emissions of PM1.0 and PM2.5, especially heavy metals and secondary atmospheric pollutants, including SO42-, NO3-, and NH4+. Natural occurrences such as dust storms in April and May, as well as straw combustion in October, also contributed to the increase in WSIs and heavy metals. The exposure risk assessment results demonstrated that Zn was the main contributor to the average daily dose through ingestion and inhalation, ADDIng and ADDinh, respectively, among the 8 heavy metals, accounting for 51.7-52.5% of the ADDIng values and 52.5% of the ADDinh values. The contribution of Zn was followed by those of Pb, Cr, Cu and Mn, while those of Ni, Cd, and Co were quite low (<2.2%).

Enhanced visible light photocatalytic performance with metal-doped Bi2WO6 for typical fluoroquinolones degradation: Efficiencies, pathways and mechanisms.

To clarify the photocatalytic mechanisms of metal-doped Bi2WO6 for fluoroquinolones (FQs) degradation, the effects of the chemical characteristics of four metals, molar ratios of the doped metals, morphology of the catalysts, and electrostatic interactions on the degradation of norfloxacin (NOR) and ciprofloxacin (CIP) were evaluated under visible light irradiation. Experimental results implied that the doping of Mg2+, Fe3+, Zn2+ and Cu2+ dramatically improved the photodegradation of Bi2WO6 for NOR and CIP removal, in which 1% Mg/Bi2WO6 exhibited the highest degradation rate of 89.44% for NOR and 99.11% for CIP. Photodegradation of NOR fitted to the pseudo-first-order model (k1 value of 0.02576 min-1), whereas that of CIP be better described by pseudo-second-order model. Moreover, the two FQs photodegradation pathways and the possible intermediates were summarized. The mechanisms of the metal dopants for the enhancement of photocatalytic activity were attributed to its enhanced specific surface area, electrostatic absorption, as well as the significant photogeneration of ·O2- and h+. Also, the photocatalyst exhibited a high stability with 78.5% photocatalytic performance after four cycles of repeated usage.

Adsorption behaviors of Cu2+, Zn2+ and Cd2+ onto proteins, humic acid, and polysaccharides extracted from sludge EPS: Sorption properties and mechanisms.

To clarify the adsorption behaviors of typical heavy metals onto sludge extracellular polymeric substances (EPS), the adsorption capacities and mechanisms, as well as the contributions of the different EPS components (proteins, humic acids and polysaccharides), to the adsorption of Zn2+, Cu2+ and Cd2+ were separately explored. Overall, proteins exhibited a relatively high adsorption capacity for the three metals ions, followed by humic acid, whereas least for polysaccharides. The adsorption of Cu2+ and Cd2+ onto proteins, humic acid and polysaccharides fit well to the Freundlich isotherm, whereas Langmuir model was the best fit for Zn2+ bindings onto polysaccharides/humic acid. The binding of Cu2+, Zn2+ and Cd2+ onto the three EPS components was exothermically favorable, and significant electrostatic interactions were observed for the heavy metals sorption onto humic acid and proteins. In addition, the effect of metal ions sorption on the spectrum of the proteins, polysaccharides and humic acid was also explored.

Across-sectional study on anxiety and stress in pregnant women with chronic HBV infection in the People's Republic of China.

PURPOSE: To investigate the anxiety and pregnancy-associated stress of pregnant women with chronic hepatitis B virus (HBV) infection in the People's Republic of China and analyze the relationship between anxiety and pregnancy-associated stress in the hope of finding ways to reduce the stress or improve the coping skills for these mothers-to-be during pregnancy. METHODS: A cross-sectional study was conducted. One hundred and sixty chronic HBV-infected pregnant women (HBV group) and 160 healthy pregnant women (control group) selected from three Peking University-affiliated hospitals participated in the study, and completed the State-Trait Anxiety Inventory (STAI) and Pregnancy Stress Rating Scale (PSRS) survey. RESULTS: The mean scores of STAI and PSRS for the HBV group were higher than for the control group. Factor 2 of PSRS (stress caused by worrying about mother and child's health and safety) was the highest, and was significantly higher in the HBV group than in the control group. Correlation analysis showed STAI scores were significantly correlated with economic status and diagnosis, as well as the total score, factor 1 (stress about identifying with the role of mother), and factor 2 of PSRS, but not significantly correlated with factor 3 of PSRS (stress caused by the changes of body shape and physical activity). CONCLUSION: Pregnant women with chronic HBV infection experienced higher levels of anxiety and stress than healthy pregnant women. Their major stress came from concerns for the health and safety of the mother and the child.