Mechanisms of denitrifying granular sludge disintegration and calcium ion-enhanced re-granulation in acidic wastewater treatment.

Granular sludge is an alternative technology for the direct treatment of acidic nitrate-containing wastewater. Rapid remediation of disintegrated granules is essential to achieve efficient nitrogen removal. In this study, denitrifying granules were inactivated and disintegrated when the influent nitrate-nitrogen concentration was elevated from 240 to 360 mg L-1 in acidic wastewater (pH = 4.1) in a sequencing batch reactor. Tightly bound extracellular polymeric substances (TB-EPS) decreased by 60%, and extracellular protein (PN) was the main component of the reduced EPS. The three-dimensional excitation emission matrices (3D-EEM) results confirmed that the PNs that decreased were mainly tryptophan-like, tyrosine-like, and aromatic. This study further confirmed that the decrease in PN was mainly from the destruction of C=O (amide I) and N-H functional groups. Overloading of nitrogen-inhibited denitrifying activity and the destruction and dissolution of TB-EPS by acidic pH were responsible for granule disintegration, with PNs playing a major role in maintaining granule stability. Based on this, new granules with an average particle size of 454.4 µm were formed after calcium chloride addition; EPS nearly doubled during granule formation with PN as the dominant component, accounting for 64.7-78.4% of the EPS. Atomic force microscopy (AFM) revealed that PN-PN adhesion increased by 1.6-4.9 times in the presence of calcium ions, accelerating the re-granulation of disintegrated particles. This study provides new insights into the disintegration and remediation of granular sludge under acidic conditions.

In situ acid production by organic matter induced with trace homogeneous Fenton reagent for membrane fouling control.

The homogeneous Fenton process involves both coagulation and oxidation, but it requires added acidity, so it is rarely used to control membrane fouling. This work found that the pH of neutral simulated wastewater sharply declined to 4.1 after pre-treatment with 0.1 mM Fenton reagent (Fe2+:H2O2=1:1) without added acidity. This occurred mainly because the trace homogeneous Fenton reagent induced in situ acid production by organic matter in the wastewater, which supplied the acidic conditions required for the Fenton reaction and ensured that the reaction could proceed continuously. Then, oxidation during the pre-Fenton process enhanced the electrostatic repulsion forces and effectively weakened the hydrogen bonds of organic matter at the membrane surface by altering the net charge and hydroxyl content of organic matter, while coagulation caused the foulants to gather and form large aggregates. These changes diminished the deposition of foulants onto the membrane surface and resulted in a looser fouling layer, which eventually caused the membrane fouling rate to decline from 83 % to 24 % and the flux recovery rate to increase from 44 % to 98 % during 2 h of filtration. This membrane fouling mitigation ability is much superior to that of pre-H2O2, pre-Fe2+ or pre-Fe3+ processes with equivalent doses.

Achievement of waste sludge deep dehydration under acidic conditions with polydimethyldiallylammonium chloride and ferric chloride: performance and mechanism.

The biological treatment of wastewater generates a substantial amount of waste sludge that requires dewatering before final disposal. Efficient sludge dewatering is essential to minimize storage and transportation costs. In this study, the sludge conditioners polydimethyldiallylammonium chloride (PDMDAAC) and ferric chloride (FeCl3) were sequentially dosed, and the pH was adjusted to 3. As a result, the sludge moisture content (MC) was reduced to 59.4%, achieving deep dewatering. After conditioning, the tightly bound extracellular polymeric substances (TB-EPS) were reduced from 34.5 to 10.2 mg g-1 VSS, with the majority of the reduced fractions being composed of protein (PN). In contrast, soluble EPS increased more than 8 times. Subsequent studies revealed that the decrease in PN from TB-EPS primarily involved tryptophan and tyrosine proteins, accompanied by a significant reduction in the N-H and C[double bond, length as m-dash]C absorption peaks. These results highlight the critical role of TB-EPS dissolution in achieving deep dehydration, with the N-H in PN was identified as the key group influencing sludge dewatering. Combined with the changes in sludge particle size and morphology, the dewatering mechanism can be summarized as follows: PDMDAAC dissolves TB-EPS, simultaneously disrupting the floc structure and refining the sludge. Subsequently, FeCl3 reconstructs these elements, forming larger particle sizes. Finally, hydrochloric acid reduces TB-EPS once again, releasing bound water. This study offers alternative methods and new insights for achieving deep dewatering of waste sludge.

Trends of hospitalisation for patients with liver cirrhosis in Ningxia, China: a cross-sectional study.

OBJECTIVE: To evaluate the changing trends of hospitalisation for patients with liver cirrhosis between 2015 and 2019 by using hospitalisation summary records in Ningxia Hui Autonomous Region (NHAR), China. DESIGN: A cross-sectional study. SETTING: Hospitalisation summary records between 1 January 2015 and 31 December 2019 from 28 top-ranking hospitals in NHAR were extracted and rigorously analysed. PARTICIPANTS: During the study period, hospitalisation records referring to liver cirrhosis were included. Records with missing data were excluded. A total of 16 566 patients with liver cirrhosis were included in this study. OUTCOME MEASURES: International Classification of Diseases codes, tenth version (ICD-10) and text-diagnoses were used to identify hospitalisation records referring to liver cirrhosis. RESULTS: Between 2015 and 2019, hospitalisation rates for liver cirrhosis declined from 8.38% to 5.57%. Chronic viral hepatitis accounted for almost 70% of all liver cirrhosis admissions; the remaining 30% of patients were admitted due to non-viral hepatitis cirrhosis (28.06%) and alcoholic cirrhosis (2.05%). The male-to-female hospitalisation rate ratio for liver cirrhosis was 2.57. The hospitalisation rate for workers with hepatitis cirrhosis was significantly higher than farmers (hospitalisation rate ratio (RR)=1.06, 95% CI 1.01 to 1.15, p<0.001); this was also the case for alcoholic cirrhosis (RR=5.23, 95% CI 3.34 to 8.20). However, the hospitalisation rate for workers with non-viral hepatitis cirrhosis was significantly lower than for farmers (RR=5.23, 95% CI 3.34 to 8.20, p<0.001). The hospitalisation rate increased in patients over the age of 30 years and reached a peak at the age of 45-50 years. CONCLUSIONS: The hospitalisation rate for liver cirrhosis has declined over recent years and chronic viral hepatitis remains the major cause of liver cirrhosis in NHAR. Hospitalisation summary records can efficiently reflect the local changing trends of hospitalisation for liver cirrhosis and represent an efficient strategy for the surveillance of chronic disease.

Enhanced degradation of reactive black 5 via persulfate activation by natural bornite: influencing parameters, mechanism and degradation pathway.

Reactive black 5 (RBk5) is a refractory azo dye that constitutes a serious threat to the environment and humans. Herein, natural bornite (Nbo) was utilized to activate persulfate (PDS) for the RBk5 removal. The particle size of the Nbo catalyst was optimized and the RBk5 degradation rate constant that responded positively to the particle size of the Nbo catalyst was exhibited. Then, the operational factors affecting RBk5 removal were comprehensively investigated. With the addition of 1.5 g L-1 Nbo and 1.5 mM PDS, 99.05% of the RBk5 (20 mg L-1) was removed in 150 min compared with 0.46% removal with PDS only, which was caused by the additional reactive oxygen species (ROS) produced by the synergistic action of Fe-Cu bimetallic metal and reductive sulfur species. The Nbo catalyst presented high stability and reusability toward RBk5 removal. Identification of reactive oxygen species revealed that SO4⋅-, ·OH, O2⋅- and 1O2 collectively participated in RBk5 removal. Additionally, a possible degradation pathway for RBk5 was proposed, including cleavage of the azo, C-S and S-O bonds, hydroxylation, hydrolyzation, direct oxidation and other pathways. This work developed a highly effective and low-cost natural mineral-based bimetallic sulfide material for PDS activation for the degradation of contaminants and environmental remediation.

Recent advances in thin film nanocomposite membranes containing an interlayer (TFNi): fabrication, applications, characterization and perspectives.

Polyamide (PA) reverse osmosis and nanofiltration membranes have been applied widely for desalination and wastewater reuse in the last 5-10 years. A novel thin-film nanocomposite (TFN) membrane featuring a nanomaterial interlayer (TFNi) has emerged in recent years and attracted the attention of researchers. The novel TFNi membranes are prepared from different nanomaterials and with different loading methods. The choices of intercalated nanomaterials, substrate layers and loading methods are based on the object to be treated. The introduction of nanostructured interlayers improves the formation of the PA separation layer and provides ultrafast water molecule transport channels. In this manner, the TFNi membrane mitigates the trade-off between permeability and selectivity reported for polyamide composite membranes. In addition, TFNi membranes enhance the removal of metal ions and organics and the recovery of organic solvents during nanofiltration and reverse osmosis, which is critical for environmental ecology and industrial applications. This review provides statistics and analyzes the developments in TFNi membranes over the last 5-10 years. The latest research results are reviewed, including the selection of the substrate and interlayer materials, preparation methods, specific application areas and more advanced characterization methods. Mechanistic aspects are analyzed to encourage future research, and potential mechanisms for industrialization are discussed.

Denitrification for acidic wastewater treatment: Long-term performance, microbial communities, and nitrous oxide emissions.

Acidic nitrogenous wastewater often requires alkali pretreatment before biological treatment, which results in increased system complexity and operating costs. The demonstration of denitrification under acidic conditions would provide a theoretical basis for the direct treatment of such wastewater. In this study, the denitrification performance, microbial community, and nitrous oxide (N2O) emissions under acidic conditions were investigated using a sequencing batch reactor. When the influent pH decreased from 5.5 to 4.5, the sequencing batch reactor removed 99.8 ± 0.2% of the nitrate and 92.5 ± 1.6% (n = 171) of the chemical oxygen demand, and the production efficiency of N2O increased significantly to 11.45%. This was 2.6-fold higher than that observed at pH 5.5. The long-term denitrification treatment of acidic wastewater (pH 4.5) led to the formation of granular sludge, and Thauera, Allorhizobium-Neorhizobium-Parararhizobium-Rhizobium, and Diaphorobacter became the dominant microbes with a collective abundance of 81.3%. More importantly, only 0.25% of the nitrate was denitrified as N2O, and the batch test revealed that the emissions of N2O decreased with the increase in sludge size. These results indicate that denitrifying granular sludge formed under acidic conditions and denitrifying bacteria capable of N2O reduction proliferated, which both resulted in a significant reduction in the release of N2O.

Drug and therapeutics committee interventions in managing irrational drug use and antimicrobial stewardship in China.

Aim: This study aimed to investigate the key points in the transformation of the functions of the Drug and Therapeutics Committee (DTC) of the Shandong Provincial Third Hospital and how to provide full authority to its role in the control of rational drug use, especially in the management of antibiotic use. Method: A prescription review management group, antimicrobial stewardship group, and rational drug use service group were established under the DTC. From January 2016 to December 2021, each group played a role in promoting rational drug use and antimicrobial stewardship. In addition, we performed statistics on typical management cases, irrational drug use, bacterial resistance rate, and drug costs from 2015 to 2021 to evaluate the effect of management by the DTC. Results: Intervention by the DTC led to a significant reduction in prescribing errors (71.43%, p < 0.05), the intervention acceptance rate increased by 16.03%, and the problem solved rate increased by 32.41% (p < 0.05). Resistance rates of general spectrum antibiotics were reduced remarkably after the intervention. The quality of drug treatment was improved and patient drug expenses was continuously reduced. Conclusion: Giving full play to the functions of the DTC can significantly improve the level of drug treatment and reduce unreasonable drug use to save unnecessary drug expenses and slow the development of drug resistance.

Evaluating the effectiveness of drug and therapeutics committees (DTCs) in controlling irrational drug use: A retrospective analysis.

WHAT IS KNOWN AND OBJECTIVE: This study aimed to explore methods to optimize the function of Drug and Therapeutics Committees (DTCs) in controlling irrational drug use. Clinical pharmacologists contribute their specific knowledge and skills to DTCs and help guide rational therapeutics. The DTC is the highest organization of hospital pharmacy management. METHODS: From January 2016 to August 2021, the DTC promoted the optimization of clinical drug treatment schemes and reduced unreasonable drug use by improving the organizational framework, clarifying the division of functions, regularly monitoring drug use, organizing expert comments, scientific decision-making and functional intervention. During this time, we statistically analysed typical management cases, irrational drug use and drug cost to evaluate the effectiveness of the DTC's management. RESULTS AND DISCUSSION: The DTC's intervention led to a significant reduction in prescribing errors (65.98%, p < 0.05); the intervention acceptance rate increased by 16.37%; and the rate of problem resolution increased by 45.84% (p < 0.05). The level of drug treatment was improved, and the proportion of patients' drug expenses was reduced. WHAT IS NEW AND CONCLUSION: The DTC carried out a series of continuous improvement work that played a significant normative role in clinical drug use. Giving more power to the DTCs can significantly improve the level of drug treatment and reduce unreasonable drug use, which reduces unnecessary drug expenses.

Efficient degradation of minocycline by natural bornite-activated hydrogen peroxide and persulfate: kinetics and mechanisms.

Natural bornite (NBo), a sulfide mineral of copper and iron, is one of the main mineral raw materials for copper extraction. In this study, NBo-activated hydrogen peroxide (H2O2) and persulfate processes (PS) for the degradation of minocycline (MNC) in aqueous solution were systemically investigated and compared. The MNC removal rates with the NBo/PS and NBo/H2O2 processes were 86.40% and 87.50%, respectively. The mineralization rate of NBo/PS (33.96%) was higher than that of NBo/H2O2 (29.94%) after reaction for 180 min. The effects of oxidant and activator dosage, pH, common inorganic anions (i.e., Cl-, NO3-, and HCO3-), and water composition on MNC degradation were systematically evaluated. In addition, the degradation of MNC in natural water matrix and toxicity evaluation was also studied to better evaluate the feasibility of practical application of those two processes. The results of free radical quenching experiments and electron paramagnetic resonance spectroscopy (EPR) showed that HO· was the main activated species in the NBo/H2O2 system, while SO4·- and HO· were the main activated species in the NBo/PS system. The degradation of MNC in the NBo/PS system was achieved through electron transfer, while the degradation of MNC in the NBo/H2O2 system was mainly achieved through free radical addition. The degradation pathway mainly included deamidation reactions, C-C bond breakage and hydroxylation. Reusability of NBo showed that NBo was considerably stable in activating PS and H2O2 for degradation of MNC, which was cost-effective activator. This work provides a new perspective on the degradation mechanism of pollutants by Fe-Cu bimetallic sulfide activation of PS and H2O2.

Identifying the fouling behavior of forward osmosis membranes exposed to different inorganic components with high ionic strength.

Functionalized multiwalled carbon nanotube (f-MWCNT) mixed matrix forward osmosis (FO) membranes were fabricated by phase inversion, and the mechanism of sodium alginate (SA) membrane fouling in the presence of various inorganic components with high ionic strength was thoroughly investigated. The membrane incorporated with 0.5% f-MWCNTs (M-0.5) exhibited enhanced performance, which was attributed to the hydrophilicity of the modified nanoparticles and their good compatibility with the cellulose acetate (CA) substrate. Moreover, it was found that the initial permeate flux decline rate for all FO membranes investigated followed the order Na+ + Ca2+ + Mg2+ > Na+ + Ca2+ > Na+ + Mg2+ > Na+, which was attributed to the particle size of SA macromolecules in the corresponding solutions. However, the gradual change in attenuation was consistent with adhesion force observations made for the SA-fouled FO membrane in the later steady-state stage, and there was little difference among M-0 (without f-MWCNTs), M-0.5, and M-1 (with 1% f-MWCNTs). Furthermore, the SA adsorption layer was most compact in the presence of Ca2+, and the flux recovery rate (FRR) was the lowest after simple hydraulic cleaning, but the overall FRRs for FO membranes were greater than 85%. This implies that although a decrease in electrostatic repulsion leads to the formation of a compact fouling layer, an increase in hydration repulsion of hydrated salt ions plays a major role in membrane fouling under high ionic strength conditions.

Upregulated microRNA-126 induces apoptosis of dental pulp stem cell via mediating PTEN-regulated Akt activation.

INTRODUCTION: Human dental pulp stem cells (DPSCs) have potential applications in regenerative medicine. The molecular mechanisms underlying DPSCs viability and apoptosis are not completely understood. Here, we investigated the role of miR-126 in DPSCs viability and apoptosis. MATERIAL AND METHODS: Senescent DPSCs were compared with early passage DPSCs. real-time PCR and microARRAY were performed to identify the differential expression of miR-126, and western blot was performed to detect the expression of PTEN. MTT assay was utilized to reveal the proliferative rate of both senescent and early passage DPSCs. Flow cytometry was used to examine the apoptotic rate of DPSCs. Dual-luciferase reporter assay was carried out to detect the interaction of miR-126 and PTEN. RESULTS: Senescent DPSCs showed a high level of apoptosis. Further study showed that miR-126 is upregulated in senescent DPSCs and its overexpression in early passaged DPSCs induced apoptosis. Phosphatase and tensin homolog gene (PTEN) was identified as a target of miR-126. PTEN was downregulated in senescent DPSCs, whereas miR-126 inhibition upregulated PTEN level, and subsequently activated Akt pathway and suppressed the apoptotic phenotype of senescent DPSCs. In addition, PTEN overexpression rescued apoptosis of DPSCs at later stage. CONCLUSION: Our results demonstrate that the miR-126-PTEN-Akt axis plays a key role in the regulation of DPSCs apoptosis and provide a candidate target to improve the functional and therapeutic potential of DPSCs.

Stable Forward Osmosis Nanocomposite Membrane Doped with Sulfonated Graphene Oxide@Metal-Organic Frameworks for Heavy Metal Removal.

A sulfonated graphene oxide@metal-organic framework-modified forward osmosis nanocomposite (SGO@UiO-66-TFN) membrane was developed to improve stability and heavy metal removal performance. An in situ growth method was applied to uniformly distribute UiO-66 nanomaterial with a frame structure on SGO nanosheets to form SGO@UiO-66 composite nanomaterial. This nanomaterial was then added to a polyamide layer using interfacial polymerization. The cross-linking between SGO@UiO-66 and m-phenylenediamine improved the stability of the nanomaterial in the membrane. Additionally, the water permeability was improved because of additional water channels introduced by SGO@UiO-66. SGO, with its lamellar structure, and UiO-66, with its frame structure, made the diffusion path of the solute more circuitous, which improved the heavy metal removal and salt rejection performances. Moreover, the hydrophilic layer of the SGO@UiO-66-TFN membrane could block contaminants and loosen the structure of the pollution layer, ensuring that the membrane maintained a high removal rate. The water flux and reverse solute flux of the SGO@UiO-66-TFN membrane reached 14.77 LMH and 2.95 gMH, and compared with the thin-film composite membrane, these values were increased by 41 and 64%, respectively. The membrane also demonstrated a good heavy metal ion removal performance. In 2 h, the heavy metal ion removal rate (2000 ppm Cu2+ and Pb2+) was greater than 99.4%, and in 10 h the removal rate was greater than 97.5%.

Effect of Polydatin on Neurological Function and the Nrf2 Pathway during Intracerebral Hemorrhage.

This study investigates the effect of polydatin on the neurological function of cerebral hemorrhage rats and on the Nrf2 pathway of the endogenous antioxidant system in tissues around cerebral hematoma. Further, the study also aims to provide solid insights for clinical diagnosis and treatment. A total of 54 SPF grade male Wistar rats were divided into three groups: the sham group, model group, and polydatin group. Various parameters such as neurological deficit score, brain water content, pathological morphology, oxidative stress index content, Nrf2, NQO1, HO-1 mRNA expression, and the expression of HO-1, Nrf2, and kelch-like epichlorohydrin-1 (Keap1) protein were observed. Compared with the sham group, the mNSS score and brain water content of rats in the model group increased significantly after dosing (P < 0.05). When compared with the model group, the mNSS score and brain water content of rats in the polydatin group decreased significantly after dosing (P < 0.05). Compared with the other group, the serum NSE content of rats in the polydatin group decreased (P < 0.05). An increase was observed in the contents of NO, SOD, MDA, GSSG, and GSH in the brain tissue of rats in the model group when compared with the sham group. Compared with the model group, the contents of NO and MDA in the brain tissue of rats in the polydatin group decreased, while the contents of SOD, GSSG, and GSH increased (P < 0.05). The relative expressions of Nrf2, NQO1, and HO-1mRNA in the brain tissue of rats in the polydatin group was relatively high compared with both groups (P < 0.05). Polydatin can improve the neurological function of ICH rats and reduce the oxidative stress response by regulating the Nrf2-ARE pathway and downstream gene expression. This study preliminarily discussed the relevant mechanism of polydatin in the treatment of ICH rats, thus providing a theoretical reference to ICH treatment.

Electro-membrane extraction of cadmium(II) by bis(2-ethylhexyl) phosphate/kerosene/polyvinyl chloride polymer inclusion membrane.

The development of the electroplating and battery industries has increased the environmental problems and the needs for resource recovery of Cd(II). In this study, the Electro-membrane extraction (EME) behaviour of Cd(II) was investigated by using polymer inclusion membrane with bis(2-ethylhexyl) phosphate as carrier and polyvinyl chloride as base polymer(PD-PIM) at 0-80 V. Results showed that the EME of Cd(II) by PD-PIM can be obtained in the feed phase with pH 3-8 and stripping phase of dilute acid. Voltage is the main factor to increase the mass transfer rate of Cd(II). The applied electric field reduced the mass transfer activation energy of Cd(II) by PD-PIM and weakened the mass transfer interference of Cd(II) on the background material of the feed phase. After using kerosene-stabilised PD-PIM for operation at pH5, 60 V for 120 h, Cd(II) in the 1 L solution reduced from 15 mg/L to 0.08 mg/L, and the enrichment factor was 9.79.

Study on stable mass transfer and enrichment of phenol by 1-octanol/kerosene/polyvinyl chloride polymer inclusion membrane.

A polymer inclusion membrane (PIM) that contains a polyvinyl chloride (PVC) polymer matrix and 1-octanol (OCT) as specific carrier (PO-PIM) was prepared to investigate the mass transfer behaviour of phenol in aqueous solutions. Results showed that the mass transfer behaviour of the PO-PIM for phenol conformed to the first-order kinetics. In addition, the mass transfer efficiency for phenol reached the maximum when the OCT content was 82.8 wt%. The mass transfer activation energy (Ea) was 14.46 kJ mol-1, which indicated that intramembranous diffusion was the main controlling factor in the mass transfer process. The introduction of hydrophobic additives, such as kerosene, liquid paraffin and vegetable oil, into the PO-PIM could remarkably improve its stability. In an aqueous solutions of phenol ranging from 0 mg L-1 to 9000 mg L-1, the initial flux (J0) of kerosene/PVC/OCT-PIM (KPO-PIM) was positively correlated with the initial concentration of phenol. For a stripping solution with a feed solution pH of 2.0 and a sodium hydroxide concentration of 0.1 mol L-1, the maximum permeability coefficient during stable mass transfer reached 12.55 µm s-1. At a mass transfer area of 3.14 cm2, an enrichment factor (EF) of 3.5 for 200 mg L-1 of phenolic aqueous solution was achieved within 48 h through KPO-PIM.

New insights into the humic acid fouling mechanism of ultrafiltration membranes for different Ca2+ dosage ranges: results from micro- and macro-level analyses.

To reveal the mechanisms of the influence of Ca2+ on membrane fouling with humic acid (HA), the adhesion forces of HA with both other HA molecules and the membrane, the HA fouling layer structure, HA fouling experiments, and the HA rejections at a wide range of Ca2+ dosages were investigated. The results indicated that the effect of Ca2+ on HA fouling can be divided into three stages. At lower ionic strength (IS) of CaCl2, the change in electrostatic forces is the main factor in controlling HA fouling behavior; i.e., increasing Ca2+ dosages resulted in more serious membrane fouling. When the IS of CaCl2 reached 10 mM, HA aggregates became the dominant factor in the fouling process, which could result in a porous fouling layer accompanied by less membrane fouling. Interestingly, much weaker membrane fouling was observed when the IS increased to 100 mM and the HA rejection began to decline. This was because a stronger hydration repulsion force was generated, which could weaken the compactness of the fouling layer and the adhesion forces of HA with both the membrane and HA, while enabling smaller-sized HA to pass more easily into the permeate, which led to less membrane fouling and a lower HA rejection.

Effect of Hydration Forces on Protein Fouling of Ultrafiltration Membranes: The Role of Protein Charge, Hydrated Ion Species, and Membrane Hydrophilicity.

To investigate the influence of hydration forces on the protein fouling of membranes and the major influence factors of hydration forces during the ultrafiltration process, bovine serum albumin (BSA) was chosen as model foulant. For various pH levels and hydrated ion and membrane species, the membrane-BSA and BSA-BSA interaction forces, and fouling experiments with BSA, as a function of ionic strength, were measured. Results showed that hydration forces were a universal phenomenon during the membrane filtration process, when the levels of pH, ion species, and membrane performances were appropriate. First, for the BSA negatively charged or neutral, hydration forces caused a decrease in the membrane fouling. Conversely, for the BSA positively charged, the hydration forces were absent because the counterions were not hydrated, and membrane fouling was enhanced. For different hydrated ions, the smaller the radii of the ions were, the stronger the hydration forces that were produced, and the membrane fouling observed was less, indicating that hydration forces are closely correlated with the size of the hydrated ions. Moreover, in comparison with a hydrophobic membrane, it is more difficult to observe hydrophilic membrane-BSA hydration forces because the hydrophilic membrane surface adsorbs water molecules, which weakens its binding efficiency to hydrated ions.

Enhanced gypsum scaling by organic fouling layer on nanofiltration membrane: Characteristics and mechanisms.

To investigate how the characteristics of pregenerated organic fouling layers on nanofiltration (NF) membranes influence the subsequent gypsum scaling behavior, filtration experiments with gypsum were carried out with organic-fouled poly(piperazineamide) NF membranes. Organic fouling layer on membrane was induced by bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), respectively. The morphology and components of the scalants, the role of Ca(2+) adsorption on the organic fouling layer during gypsum crystallization, and the interaction forces of gypsum on the membrane surface were investigated. The results indicated that SA- and HA-fouled membranes had higher surface crystallization tendency along with more severe flux decline during gypsum scaling than BSA-fouled and virgin membranes because HA and SA macromolecules acted as nuclei for crystallization. Based on the analyses of Ca(2+) adsorption onto organic adlayers and adhesion forces, it was found that the flux decline rate and extent in the gypsum scaling experiment was positively related to the Ca(2+)-binding capacity of the organic matter. Although the dominant gypsum scaling mechanism was affected by coupling physicochemical effects, the controlling factors varied among foulants. Nevertheless, the carboxyl density of organic matter played an important role in determining surface crystallization on organic-fouled membrane.

In situ probing of microbial activity within anammox granular biomass with microelectrodes.

An anaerobic rotating biological contactor was fed with inorganic synthetic wastewater for anammox. Besides biofilm, granular biomass with average diameter of approximately 5 mm formed. NH4(+), NO2(-), NO3(-) and pH microelectrodes were used to probe microbial activity in situ within the granules. At a sufficient substrate concentration, the anammox reaction was observed in the upper layer of granules, and the most active zone was found to be in the surface of 200-400 µm. The in situ anammox activity increased with increasing substrate concentration, and a maximum ammonium consumption rate of 83.3 µmol cm(-3) h(-1) was obtained at an ammonium concentration of 1000 µmol L(-1). Under an ammonium-limited condition, denitrification activity was observed in the inner layer, and the most active zone was limited to 700-1000 µm. This study revealed that denitrification bacteria coexisted with anammox bacteria within inorganic anammox granules.