A meta-analysis of effects and safety of Tripterygium wilfordii polyglycoside in the treatment of IgA nephropathy.

OBJECTIVE: To evaluate the effects and safety of Tripterygium wilfordii polyglycoside (TWP) in the treatment of immunoglobulin A (IgA) nephropathy. SUBJECTS AND METHODS: A computer-assisted study search of Chinese Biomedical Database (CBM), Chinese Journal Full-text Database (CNKI), Wanfang Database, Chinese Scientific Journal Database (VIP), PubMed, Medline, EMBASE and Cochrane Library was performed, with the time range of retrieval set between the establishment of the database to December 31, 2019. Articles of randomized controlled trials on the treatment of IgA nephropathy by Tripterygium wilfordii polyglycoside were collected, and then screened according to the inclusion and exclusion criteria. Next, the quality of the papers was assessed, effective data were extracted, and a meta-analysis of the included studies was conducted using the Review Manager 5.3 software provided by the Cochrane Collaboration. RESULTS: Thirty randomized controlled trials (RCT) were included ultimately, and the meta-analysis showed that 1) Single (Sgl) TWP group was superior to angiotensin-converting enzyme inhibitor/angiotension receptor blocker (ACEI/ARB) group in terms of complete remission [odds ratio (OR) = 4.74, p-value < 0.00001], total remission (OR = 3.90, p-value < 0.0001), 24-hour proteinuria [mean difference (MD) = 1.18, p-value < 0.00001], and serum albumin (MD = - 8.23, p-value < 0.00001), and no significant difference in serum creatinine (MD = 2.09, p-value = 0.08) was found between Sgl TWP and control groups; TWP + ACEI/ARB group was superior in complete remission (OR = 2.57, p-value < 0.00001), total remission (OR = 4.36, p-value < 0.00001), serum albumin [standardized mean difference (SMD) = -0.68, p-value = 0.0005], 24-hour proteinuria (SMD = 1.24, p-value < 0.00001) and serum creatinine (SMD = 0.48, p-value = 0.006); 2) TWP group was superior to glucocorticoid group in complete remission (OR = 1.93, p-value < 0.0010), total remission (OR = 3.71, p-value < 0.00001), serum albumin (MD = -3.50, p-value = 0.002), 24-hour proteinuria (SMD = 0.93, p-value < 0.0001) and serum creatinine (SMD = 0.88, p-value = 0.006); 3) TWP group was better than mycophenolate mofetil (MMF) group in complete remission (OR = 2.05, p = 0.005), total remission (OR = 3.30, p-value = 0.002), 24-hour proteinuria (MD = 2.61, p-value < 0.0001), and serum albumin (MD = -6.43, p-value < 0.00001), but the differences in serum creatinine (MD = 1.28, p-value = 0.89) between TWP and control groups were not significant. Besides, TWP + ACEI/ARB group had a higher adverse reaction rate than the control group (OR = 2.21, p-value = 0.04), but there was no significant difference in the adverse reaction rate between other control and experimental groups (p-value > 0.05). CONCLUSIONS: The present evidence shows that Tripterygium wilfordii polyglycoside can effectively improve the remission rate, reduce proteinuria, and protect kidney function of IgA nephropathy patients, and also has good safety. However, limited by the quality of the included studies, the effects and safety of Tripterygium wilfordii polyglycoside in the treatment of IgA nephropathy need to be verified by more high-quality, large-scale, multi-center RCTs.

Development of a high-rate submerged anaerobic membrane bioreactor.

Typically, anaerobic membrane bioreactors are operated at an organic loading rate (OLR) less than 10 kg chemical oxygen demand (COD)/m3 d. This paper discusses the development and performance of a high-rate submerged anaerobic membrane bioreactor (SAnMBR) for a high-strength synthetic industrial wastewater treatment. An OLR as high as 41 kg COD/m3 d was achieved with excellent COD removal efficiency (>99%). The membrane was operated at constant fluxes (9.4-9.9 ± 0.5 L/m2 h) and the change in trans-membrane pressure (TMP) was monitored to characterize the membrane performance. The results showed a low TMP (<5 kPa) under steady-state operation with only biogas sparging and relaxation as control strategy for over 300 days, implying no significant fouling was developed. Inorganic fouling was the dominant fouling mechanism occurred at the end of the study. The results suggest that the newly developed SAnMBR configuration can treat high-strength wastewater at lower capital expenditure while still providing superior effluent quality for water reuse or system closure.

Influence of COD:N ratio on sludge properties and their role in membrane fouling of a submerged membrane bioreactor.

The effect of COD:N ratio on sludge properties and their role in membrane fouling were examined using a well-controlled aerobic membrane bioreactor receiving a synthetic high strength wastewater containing glucose. Membrane performance was improved with an increase in the COD/N ratio (100:5-100:1.8) (i.e. reduced N dosage). Surface analysis of sludge by X-ray photoelectron spectroscopy (XPS) indicates significant differences in surface concentrations of elements C, O and N that were observed under different COD/N ratios, implying changes in the composition of extracellular polymeric substances (EPS). Fourier transform-infrared spectroscopy (FTIR) revealed a unique characteristic peak (CO bonds) at 1735 cm(-1) under nitrogen limitation conditions. Total EPS decreased with an increase in COD/N ratio, corresponding to a decrease in the proteins (PN) to carbohydrates (CH) ratio in EPS. There were no significant differences in the total soluble microbial products (SMPs) but the ratio of PN/CH in SMPs decreased with an increase in COD/N ratios. The results suggest that EPS and SMP composition and the presence of a small quantity of filamentous microorganisms played an important role in controlling membrane fouling.

Effect of organic matter to nitrogen ratio on membrane bioreactor performance.

Effect of chemical oxygen demand (COD) to nitrogen (COD:N) ratio in feed on the performance of aerobic membrane bioreactor (MBR) for treating a synthetic high-strength industrial waste water containing glucose was studied for over 370 days. The widely recommended nutrients ratio (COD:N:P = 100:5:1) is not necessary for aerobic biological industrial waste water treatment. An increased COD:N ratio from 100:5 to 100:2.5 and 100:1.8 had a limited impact on COD removal efficiency and further led to a significant improvement in membrane performance, a reduced sludge yield, and improved effluent quality in terms of residual nutrients. An increased COD:N ratio will benefit the industrial waste water treatment using MBRs by reducing membrane fouling and sludge yield, saving chemical costs, and reducing secondary pollution by nutrients addition. Optimization of nutrients usage should be conducted for specific industrial waste water streams.

A comparative study on thermomechanical pulping pressate treatment using thermophilic and mesophilic sequencing batch reactors.

A comparative study on the treatment of thermomechanical pulping (TMP) pressate was conducted under thermophilic (55 degrees C) and mesophilic (30 degrees C) temperatures to explore in-mill biological treatment, with the intention to operate under heat-efficient conditions. The experimental study involved sequencing batch reactors (SBRs) operated over 114 days. Receiving a total influent chemical oxygen demand (COD) of 3700-4100 mg L(-1), the COD removal efficiencies of 80-90% and 75-85% were achieved for the mesophilic and thermophilic SBRs, respectively, at a hydraulic retention time (HRT) of 12 and 24h. Excellent sludge settleability (sludge volume index < 100 mL g(-1) mixed liquor suspended solids) was obtained at both thermophilic and mesophilic SBRs. A higher level of effluent suspended solids was observed under thermophilic conditions. The results support the feasibility of applying thermophilic biological treatment of TMP pressate. The treated effluent has the potential for subsequent reuse as process water after polishing, thus addressing the long-standing desire to develop water system closure for the pulp and paper mill operation.

Characteristics of wastewater and mixed liquor and their role in membrane fouling.

Effects of wastewater and mixed liquor characteristics on membrane fouling in both a submerged anaerobic membrane bioreactor and a thermophilic submerged aerobic membrane bioreactor were studied with four types of industrial wastewaters. Significant differences in particle size distribution, colloidal content, the protein to polysaccharide ratio, and soluble compounds molecular weight distribution were observed among the four types of wastewaters and mixed liquors. Differences in wastewater and mixed liquor characteristics were correlated to the changes in membrane filtration behavior in both systems. The colloidal content in feed and mixed liquor plays a dominant role and is more important than the quantity of total suspended solids in controlling membrane fouling. The ratio of proteins to polysaccharides is more important than the total quantity of soluble organic substances in controlling membrane fouling. A full characterization of feed and mixed liquor may be used as a tool to predict membrane performance.

Integrated thermophilic submerged aerobic membrane bioreactor and electrochemical oxidation for pulp and paper effluent treatment--towards system closure.

A novel integrated thermophilic submerged aerobic membrane bioreactor (TSAMBR) and electrochemical oxidation (EO) technology was developed for thermomechanical pulping pressate treatment with the aim of system closure. The TSAMBR was able to achieve a chemical oxygen demand (COD) removal efficiency of 88.6 ± 1.9-92.3 ± 0.7% under the organic loading rate of 2.76 ± 0.13-3.98 ± 0.23 kg COD/(m(3) d). An optimal hydraulic retention time (HRT) of 1.1 ± 0.1d was identified for COD removal. Cake formation was identified as the dominant mechanism of membrane fouling. The EO of the TSAMBR permeate was performed using a Ti/SnO(2)-Sb(2)O(5)-IrO(2) electrode. After 6-h EO, a complete decolourization was achieved and the COD removal efficiency was increased to 96.2 ± 1.2-98.2 ± 0.3%. The high-quality effluent produced by the TSAMBR-EO system can be reused as process water for system closure in pulp and paper mill.

Effects of temperature and temperature shock on the performance and microbial community structure of a submerged anaerobic membrane bioreactor.

Effects of temperature and temperature shock on the performance and microbial community structure of a submerged anaerobic membrane bioreactor (SAnMBR) treating thermomechanical pulping pressate were studied for 416 days. The results showed that the SAnMBR system were highly resilient to temperature variations in terms of chemical oxygen demand (COD) removal. The residual COD in treated effluent was slightly higher at 55 °C than that at 37 and 45 °C. There were no significant changes in biogas production rate and biogas composition. However, temperature shocks resulted in an increase in biogas production temporarily. The SAnMBR could tolerate the 5 and 10 °C temperature shocks at 37 °C and the temperature variations from 37 to 45 °C. The temperature shock of 5 and 10 °C at 45 °C led to slight and significant disturbance of the performance, respectively. Temperature affected the richness and diversity of microbial populations.

Characteristics of different fractions of microbial flocs and their role in membrane fouling.

Characteristics of different fractions (small flocs vs. large flocs) of sludge flocs from a submerged anaerobic membrane bioreactor treating thermomechanical pulping (TMP) whitewater were determined using various analytic techniques, including extraction and chemical analysis of extracellular polymeric substances (EPS), particle size analyzer, and polymer chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that the fraction of smaller flocs contained a higher level of bound EPS and had a higher fractal dimension as compared to the fraction of larger flocs. PCR-DGGE analysis indicated that there were significant differences in microbial community between the fraction of smaller flocs and large flocs. The microbial community of the smaller flocs was similar to that of the sludge cake layers, indicating the pioneering role of the microbial community in smaller flocs in membrane fouling. These findings provide a new insight in the difference of membrane fouling potential between smaller flocs and larger flocs fraction.

Effects of temperature and dissolved oxygen on sludge properties and their role in bioflocculation and settling.

Effects of temperature (mesophilic (35 °C) vs. thermophilic (55 °C)) and dissolved oxygen (DO) concentration (under thermophilic conditions) on sludge properties and their role in bioflocculation and settling were studied using well-controlled sequencing batch reactors fed with a synthetic wastewater comprised of glucose and inorganic nutrients. Under a similar DO level, thermophilic sludge had a poorer bioflocculating ability and settleability than that of mesophilic sludge. Under a thermophilic condition, an increase in DO level led to a poorer settleability and a slightly improved bioflocculating ability. A poorer settleability was related to a higher level of filaments. Analysis of bound extracellular polymeric substances (EPS) indicates that thermophilic sludge had a higher level of total bound EPS content than that of mesophilic sludge under a similar DO level, and an increase in DO resulted in an increase in total bound EPS content in thermophilic sludge. Surface analysis of sludge by X-ray photoelectron spectroscopy (XPS) suggests that significant differences in the surface concentrations of elements N, C, O were observed between thermophilic and mesophilic sludge, implying significant differences in bound EPS composition. The results of gel permeation chromatography indicate that the weight-averaged molecular weight (M(w)) of bound EPS covered a range of 1159 Da to 13220 Da. The distribution of EPS "species" at floc surfaces was shown by transmission electron microscopy (TEM) to be uneven; different kinds of nanoscale materials were distributed in a patchy manner at the floc-water interface. The results suggest that it is the role of specific EPS molecules rather than the quantity of bound EPS that determine the difference in bioflocculation behavior between thermophilic and mesophilic sludge. The strategy of increasing the DO level could not solve the biomass separation problems associated with thermophilic sludge.

Treatment of thermomechanical pulping condensate using thermophilic and mesophilic sequencing batch reactors.

In-mill thermophilic treatment of individual wastewater streams to achieve water system closure has received much attention in pulp and paper mills. Aerobic biological treatment of thermomechanical pulping (TMP) condensate was conducted using thermophilic (55 °C) and mesophilic (35 °C) sequencing batch reactors (SBRs) for a period of 143 days at a cyclic time of 6, 8 and 12 h. A soluble chemical oxygen demand (SCOD) removal efficiency of 77 to 91% was achieved, given an organic loading rate of 0.7-1.3 kg/m³ d. The COD removal efficiency of the thermophilic SBR was slightly lower than that of the mesophilic SBR. Majority of the soluble COD was removed by biodegradation with a small portion (9-13%) of soluble COD stripped by aeration. The settleability (sludge volume index) and the flocculating ability (effluent suspended solids) of thermophilic sludge were comparable to or slightly poorer than that of the mesophilic sludge. The level of filaments in thermophilic sludge was usually higher than that in mesophilic sludge. The results of the study indicate that both thermophilic and mesophilic SBRs can be successfully operated for in-mill treatment of TMP condensate. The treated effluent has the potential for subsequent reuse in the mill.

Performance and fouling characteristics of a submerged anaerobic membrane bioreactor for kraft evaporator condensate treatment.

Submerged anaerobic membrane bioreactor (SAnMBR) technology was studied for kraft evaporator condensate treatment at 37 +/- 1 degrees C over a period of 9 months. Under tested organic loading rates of 1-24 kg COD/m3/day, a chemical oxygen demand (COD) removal efficiency of 93-99% was achieved with a methane production rate of 0.35 +/- 0.05 L methane/g COD removed and a methane content of 80-90% in produced biogas. Bubbling of recycled biogas was effective for in-situ membrane cleaning, depending on the biogas sparging rate used. The membrane critical flux increased and the membrane fouling rate decreased with an increase in the biogas sparging rate. The scanning electron microscopy images showed membrane pore clogging was not significant and sludge cake formation on the membrane surface was the dominant mechanism of membrane fouling. The results suggest that the SAnMBR is a promising technology for energy recovery from kraft evaporator condensate.

Treatment of kraft evaporator condensate using a thermophilic submerged anaerobic membrane bioreactor.

The feasibility of using a thermophilic submerged anaerobic membrane bioreactor (SAnMBR) for kraft evaporator condensate treatment was studied at 55+/-1 degrees C over 6.5 months. Under tested organic loading rate of 1-7 kg COD/m(3) day, a soluble COD removal efficiency of 85-97% was obtained. The methane production rate was 0.35+/-0.1 L methane/g COD and the produced biogas was of excellent fuel quality with 80-90% methane. A higher membrane fouling rate was related to the presence of a larger portion of fine colloidal particles (1-10 mum). The thermophilic SAnMBR was sensitive to the presence of toxic compounds in feed and unexpected pH probe failure (leading to a higher pH). Feed toxic shock caused sludge deflocculation and thus deteriorated membrane performance. Operating the reactor as a conventional anaerobic reactor to waste some of the fine flocs in treated effluent during the start-up process was an effective strategy to reduce membrane fouling. The experimental results from this study indicate that treatment of kraft evaporator condensate is feasible in terms of COD removal and biogas production using thermophilic SAnMBRs but pre-treatment may be needed to remove toxic sulfur compounds and membrane fouling caused by the large portion of fine particles may be a challenge.

Treatment of synthetic kraft evaporator condensate using thermophilic and mesophilic membrane aerated biofilm reactors.

A comparative study on the treatment of synthetic kraft evaporator condensate was conducted using thermophilic (55 degrees C) and mesophilic (30 degrees C) membrane aerated biofilm reactors (MABRs) and sequencing batch reactors (SBRs) for 8 months. Under tested conditions, a chemical oxygen demand (COD) removal efficiency of 80-95% was achieved with both thermophilic and mesophilic MABRs and SBRs. The COD removal efficiency of thermophilic MABR (80-90%) was slightly lower than that of the mesophilic MABR (85-95%) and the thermophilic SBR (90-95%). A significant amount (13-37%) of COD was stripped by conventional aeration in the SBRs, while stripping in MABRs was negligible. Simultaneous COD removal and denitrification were observed in the mesophilic MABR, while the thermophilic MABR contributed mainly for COD removal. Nitrification was not significant in both the thermophilic and mesophilic MABRs. The results suggest that treatment of kraft evaporator condensate is feasible with the use of both thermophilic and mesophilic MABRs in terms of COD removal with the advantages of negligible stripping.

Sludge properties and their effects on membrane fouling in submerged anaerobic membrane bioreactors (SAnMBRs).

Two submerged anaerobic membrane bioreactors (SAnMBRs) (thermophilic vs. mesophilic) were operated for a period of 3.5 months with kraft evaporator condensate at a feed chemical oxygen demand of 10,000 mg/L. The results show that the filtration behavior of the two systems was significantly different. The filtration resistance in the thermophilic SAnMBR was about 5-10 times higher than that of the mesophilic system when operated under similar hydrodynamic conditions. Comparison of sludge properties and cake layer structure from the two systems was made to elucidate major factors governing the different filtration characteristics. There were more soluble microbial products (SMP) and biopolymer clusters (BPC) produced and a larger portion of fine flocs (<15 microm) in the thermophilic SAnMBR. Analysis of bound extracellular polymeric substances (EPS) showed that the thermophilic sludge had a higher protein/polysaccharide ratio in EPS, as compared to that in the mesophilic sludge. A series of analyses, including Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and particle size analyzer showed that the cake layer formed in the thermophilic SAnMBR contained higher levels of both organic and inorganic foulants, smaller particle sizes, and especially, a denser and more compact sludge cake structure. These results indicate that floc size, SMP, BPC, bound EPS as well as cake layer structure are the major factors governing membrane fouling in SAnMBR systems.

Effect of solids retention time on structure and characteristics of sludge flocs in sequencing batch reactors.

The effect of solids retention time (SRT) (4-20 d) on sludge floc structure, size distribution and morphology in laboratory-scale sequencing batch reactors receiving a glucose-based synthetic wastewater was studied using image analysis in a long-term experiment over one year. Floc size distribution (>10 microm) could be characterized by a log-normal model for no bulking situations, but a bi-modal distribution of floc size was observed for modest bulking situations. In each operating cycle of the SBRs, the variation in food /microorganisms ratio (0.03-1.0) had no significant influence on floc size distribution and morphology. The results from a long-term study over one year showed that no clear relationship existed between SRT and median floc size based on frequency. However, sludge flocs at the lower SRTs (4-9 d) were much more irregular and more variable in size with time than those at higher SRTs (16 and 20 d). The level of effluent-suspended solids at lower SRTs was higher than that at higher SRTs.

A review of biofouling and its control in membrane separation bioreactors.

Membrane separation technology is increasingly becoming an important innovation in biological wastewater treatment. Biofouling of the membrane is a major factor affecting the efficient and economic operation of membrane separation bioreactors (MBRs). This review summarizes the state-of-the-art progress in understanding the mechanisms and factors affecting membrane biofouling and the strategies for biofouling control. Biofouling mechanisms include the adsorption of soluble and suspended extracellular polymers on membrane surfaces and in membrane pores, the clogging of membrane pore structure by fine colloidal particles and cell debris, and the adhesion and deposition of sludge cake on membrane surfaces. Design and operating conditions of membrane modules and materials, hydrodynamic conditions in MBRs, process and environmental conditions of activated sludge systems, and the physicochemical properties of the wastewater are the dominant factors determining membrane biofouling. Current strategies to control biofouling include periodic relaxation, backwashing, chemical cleaning, and possible manipulation of hydrodynamic conditions and sludge properties. Achieving full integration of MBRs in wastewater treatment technology requires further research and development. Fundamental information on the bacteria, colloid, and membrane interaction, developed through multimethod and multiscale approaches, is particularly needed.

Effect of solids retention time on floc structure.

Correlative microscopy was applied to study the influence of solids retention time on activated sludge floc structure. Conventional optical microscopy revealed flocs at lower SRTs (4 and 9 days) to be irregular in shape while flocs at higher SRTs (16 and 20 days) had a more spherical and compact structure. Flocs were examined by environmental scanning electron microscopy (ESEM) and by transmission electron microscopy (TEM) coupled with energy-dispersive spectroscopy (EDS). Distinctive differences in floc structure and the arrangement of EPS were revealed. Flocs from higher SRTs were less hydrated and were found to possess a dense EPS layer that covers much of the surface. Extracellular osmiophilic granules present in these flocs indicate that the cells at the higher SRT may produce more lipid-like material. This EPS layer appears to decrease the floc surface roughness and protects the interior cells from disruption by changes in the external environment. Sludge flocs at higher SRTs were found to be physically more stable than those at lower SRTs.

Interparticle interactions affecting the stability of sludge flocs.

Interparticle interactions affecting the stability of sludge flocs taken from laboratory-scale sequencing batch reactors at different solids retention times (SRTs) were investigated in batch experiments by varying the pH, ionic strength, cation valence, and urea and ethylenediaminetetraacetate concentrations of suspending solutions. The ultrastructure of sludge floc surfaces was observed by transmission electron microscopy. Changes in dissociation constants of sludge flocs under different conditions indicated that ionic interactions and hydrogen bonds held flocs together and compensated for the negative influence of electrostatic interactions on the stability of sludge flocs. Ionic interactions and hydrogen bonds were two dominant forces that maintained the stability of sludge flocs at lower SRTs; other mechanisms, such as physical enmeshment and van der Waals and/or hydrophobic interactions, were more important in controling the stability of sludge flocs at higher SRTs. Sludge flocs at higher SRTs (16 and 20 days) were physically more stable than those at lower SRTs (4 and 9 days). A conceptual model of floc structure, based on interparticle interactions, for describing the stability of sludge flocs is proposed. The floc matrix is proposed to consist of two physically distinct regions that are defined by the arrangement of extracellular polymeric substances (EPS). These are likely to be differentially affected by the agents applied to manipulate interparticle forces. Thus, the heterogeneity in the packing of and the type of EPS reflects the stability of the floc.

Surface properties of sludge and their role in bioflocculation and settleability.

The influence of sludge retention time (SRT) on the extracellular polymeric substances (EPS) and physicochemical properties (hydrophobicity and surface charge) of sludge was studied using laboratory-scale sequencing batch reactors (SBRs) fed a synthetic wastewater containing glucose and inorganic salts. Sludge surfaces were more hydrophobic (larger contact angle) and less negatively charged at higher SRTs (16 and 20 d) than at lower SRTs (4 and 9 d). The ratio of proteins to carbohydrates within the EPS of the sludges increased as the SRT increased from 4 to 12 d corresponding to the changes in the physicochemical properties of the sludge. The protein:carbohydrate ratio remained constant at SRTs of 16 and 20 d. A transition in sludge properties appeared to occur between the upper range of low- (9 d) and lower range of high-SRTs. The total EPS content, however, was independent of the SRT. A higher sludge volume index (SVI), an indication of poorer settleability or compression, was associated with a larger amount of total EPS but no significant correlation between SVI and the surface properties of sludge was observed. A more hydrophobic and less negatively charged surface corresponded to lower levels of ESS. These results indicate that it is the surface properties, hydrophobicity, surface charge and composition of EPS, of sludge, rather than the quantity of EPS, that govern bioflocculation. In contrast, the EPS content is more important in controlling the settleability of sludge.