Effects of operational factors on soluble microbial products in a carrier anaerobic baffled reactor treating dilute wastewater

The effects of feed strength, hydraulic residence time （HRT）, and operational temperatures on soluble microbial product （SMP） production were investigated, to gain insights into the production mechanism. A carrier anaerobic baffled reactor （CABR） treating dilute wastewater was operated under a wide range of operational conditions, namely, feed strengths of 300-600 mg/L, HRTs of 9- 18 h, and temperatures of 10-28℃. Generally, SMP production increased with increasing feed strength and decreasing temperature. At high temperature （28℃）, SMP production increased with decreasing HRT. As the temperature was decreased to 18 and 10℃, the SMP production was at its peak for 12 h HRT. Therefore, temperature could be an important determinant of SMP production along with HRT. A higher SMP to soluble chemical oxygen demand （SCOD） ratio was found at high temperature and long HRT because of complete volatile fatty acid degradation. SMP accounted for 50%-75% of the SCOD in the last chamber of the CABR. As a secondary metabolite, some SMP could be consumed at lower feed strength.

Modeling the formation of soluble microbial products(SMP) in drinking water biofiltration

Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.

Correlation between soluble receptor for advanced glycation end products levels and coronary artery disease in postmenopausal nondiabetic women

BACKGROUND The established cardiovascular risk factors cannot explain the overall risk of coronary artery disease(CAD),especially in women.Therefore,there is a growing need for the assessment of novel biomarkers to identify women at risk.The receptor for advanced glycation end products(RAGE)and its interaction with the advanced glycation end product(AGE)ligand have been associated with atherogenesis.The soluble fraction of RAGE(sRAGE)antagonizes RAGE signaling and exerts an antiatherogenic effect.AIM The study aim was to explore the association between plasma levels of sRAGE and CAD in nondiabetic postmenopausal women.METHODS This case-control study included 110 nondiabetic postmenopausal women who were enrolled in two groups.Group I included 55 angiographically proven CAD subjects with>50%stenosis in at least one of the major coronary arteries and Group II included 55 healthy control women who did not have CAD or had<50%stenosis of the coronary arteries.Stenosis was confirmed by invasive angiography.Plasma sRAGE was determined by an enzyme-linked immunosorbent assay.RESULTS We observed significantly lower plasma sRAGE concentrations in subjects with CAD vs healthy controls(P<0.05).Univariate and multivariate logistic regression analysis also revealed a significant correlation between plasma sRAGE levels and CAD(P=0.01).Multivariate odds ratios for CAD revealed that subjects with sRAGE concentrations below 225 pg/mL(lowest quartile)had a 6-fold increase in CAD prevalence independent of other risk factors.CONCLUSION Our findings indicated that low sRAGE levels were independently associated with CAD in nondiabetic postmenopausal women.Risk assessment of CAD in postmenopausal women can be improved by including sRAGE along with other risk factors.

Study on Solubility of Cerium(Ⅳ) Phosphate

The solubility product constant of cerium(Ⅳ) phosphate according to the concentration of phosphate detected by spectrophotometer at pH=0.4 and 20 ℃ were determined. The solubility product constant of cerium(Ⅳ) phosphate is 2.915×10 -34. The reliability of determination data is proved by s=0.004 and CV=1.30%. The result indicate that solubility product constant of cerium(Ⅳ) phosphate is effected by temperature and acidity significantly. Therefore, temperature and acidity increase over a particular range could result in an increase of solubility of cerium(Ⅳ) phosphate.

The Applicaton of IAF Theory to the Study of Dissociation Equilibrium (Ⅱ) --The Calculation of Solubility Product Constant in Nonaqueous Solvents

This article reports a theoretical calculation of solubility product constant of several slightly soluble silver salts in a number of nonaqueous solvents according to the IAF (interaction force) theory based on the interaction free energy of electrostatic, orientation, induction and dispersion. The calculated values of pKsp are in good accordance with those from literature.

Numerical Modelling of Dissolving and Driving Exploitation of Potash Salt in the Qarhan Playa——A Coupled Model of Reactive Solute Transport and Chemical Equilibrium in a Multi-component Underground Brine System

Firstly, the macroscopic chemical equilibrium state of a series of chemical reactions between intercrystal brine and its media salt layer （salt deposit） in Qarhan Salt Lake was studied by using the Pitzer theory. The concept of macroscopic solubility product and its relation with accumulated ore dissolving ratio were presented, which are used in the numerical model of dissolving and driving exploitation of potassium salt in Qarhan Salt Lake. And secondly, with a model forming idea of transport model for reacting solutes in the multi-component fresh groundwater system in porous media being a reference, a two-dimensional transport model coupled with a series of chemical reactions in a multi-component brine porous system （salt deposits） was developed by using the Pitzer theory. Meanwhile, the model was applied to model potassium/magnesium transport in Qarhan Salt Lake in order to study the transfer law of solid and liquid phases in the dissolving and driving process and to design the optimal injection/abstraction strategy for dissolving and capturing maximum Potassium/ Magnesium in the mining of salt deposits in Qarhan Salt Lake.

Effect of components in activated sludge liquor on membranefouling in a submerged membrane bioreactor

By a membrane bioreactor with a settle tank in long-term operation and batch experiments, the effects of floes, soluble microorganism products （SMPs） and metal ions in activated sludge liquor on membrane fouling were investigated. The results showed that foulants absorbed each other and formed a fouling layer as a ＂second membrane＂ influencing the permeability of the membrane. The ＂gel layer＂ caused by SMPs and ＂cake layer＂ by floes showed great differences in morphology by analysis of scanning electron microscope and atomic force microscope. The ＂gel layer＂ was more compact and of poor permeability. When the membrane flux was 40 L/（m^2·h）, the rate of membrane fouling caused by supernatant （0.011 MPa/h） was greater than that by sludgc liquor （0.0063 MPa/h）. SMPs played very important roles on membrane fouling. In the bulking sludge, with SMPs increasing, the rate of membrane fouling （0.0132 MPa/h） was faster. While after flocculation of the SMPs, the rate of fouling decreased to 0.0034 M Pa/h. Floes could keep holes in their overlaps. They could alleviate membrane fouling by preventing the SMPs directly attaching on membrane surface.

Intrafollicular Soluble RAGE Benefits Embryo Development and Predicts Clinical Pregnancy in Infertile Patients of Advanced Maternal Age Undergoing In Vitro Fertilization

Soluble receptor for advanced glycation end products（s RAGE） can decoy the toxic AGEs and is considered to be a protective factor.This study aimed to evaluate the correlation between intrafollicular s RAGE levels and clinical outcomes in infertile women of young or advanced maternal age（AMA） undergoing in vitro fertilization（IVF）.A total of 62 young women and 62 AMA women who would undergo IVF were included in this prospective study.The intrafollicular s RAGE concentration was measured to determine its association with the number of retrieved oocytes,fertilized oocytes,high-quality embryos or achievement of clinical pregnancy in young and AMA women,respectively.Besides,correlations between sR AGE and age or follicle-stimulating hormone（FSH） were examined.We found that the intrafollicular s RAGE levels were higher in young patients than those in AMA patients,suggesting that the s RAGE levels were inversely correlated with age.In young patients,sR AGE showed no correlation with the number of retrieved oocytes,fertilized oocytes,high-quality embryos or achievement of clinical pregnancy.But it was found that AMA patients with more retrieved oocytes,fertilized oocytes and high-quality embryos demonstrated higher sR AGE levels,which were a prognostic factor for getting clinical pregnancy independent of age or FSH level.In conclusion,the s RAGE levels decrease with age.Elevated intrafollicular s RAGE levels indicate good follicular growth,fertilization and embryonic development,and successful clinical pregnancy in AMA women,while in young women,the role of s RAGE may not be so predominant.

Insight into the interaction between trimethoprim and soluble microbial products produced from biological wastewater treatment processes

Soluble microbial products(SMPs),dissolved organic matter excreted by activated sludge,can interact with antibiotics in wastewater and natural water bodies.Interactions between SMPs and antibiotics can influence antibiotic migration,transformation,and toxicity but the mechanisms involved in such interactions are not fully understood.In this study,integrated spectroscopy approaches were used to investigate the mechanisms involved in interactions between SMPs and a representative antibiotic,trimethoprim(TMP),which has a low biodegradation rate and has been detected in wastewater.The results of liquid chromatography-organic carbon detection-organic nitrogen detection indicated that the SMPs used in the study contained 15% biopolymers and 28% humic-like substances(based on the total dissolved organic carbon concentration)so would have contained sites that could interact with TMP.A linear relationship of fluorescent intensities of tryptophan protein-like substances in SMP was observed(R^(2)>0.99),indicating that the fluorescence enhancement between SMP and TMP occurred.Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that carboxyl,carbonyl,and hydroxyl groups were the main functional groups involved in the interactions.The electrostatic andπ-πinteractions were discovered by the UV-vis spectra and 1H nuclear magnetic resonance spectra.Structural representations of the interactions between representative SMP subcomponents and TMP were calculated using density functional theory,and the results confirmed the conclusions drawn from the 1H nuclear magnetic resonance spectra.The results help characterize SMP–TMP complexes and will help understand antibiotic transformations in wastewater treatment plants and aquatic environments.

Solubility Product for CuS and Cu_2S in Iron

The solubility product formulae of CuS and Cu2S in ferrite and in austenite have been obtained via thermodynamic method,according to the formation energy of CuS and Cu2S and the solubility formulae of elements Cu and S in ferrite and in austenite.By comparing the solubility products for CuS and Cu2S in iron,it is found that Cu2S instead of CuS should be precipitated in iron due to competitative precipitation,in the view of thermodynamics.The formulae of CuS and Cu2S deduced from thermodynamic method would play an important role in related theoretical research and practical production.

Removal of anaerobic soluble microbial products in a biological activated carbon reactor

The soluble microbial products （SMP） in the biological treatment effluent are generally of great amount and are poorly biodegradable. Focusing on the biodegradation of anaerobic SMP, the biological activated carbon （BAC） was introduced into the anaerobic system. The experiments were conducted in two identical lab-scale up-flow anaerobic sludge blanket （UASB） reactors. The high strength organics were degraded in the first UASB reactor （UASB1） and the second UASB （UASB2, i.e., BAC） functioned as a polishing step to remove SMP produced in UASB1. The results showed that 90% of the SMP could be removed before granular activated carbon was saturated. After the saturation, the SMP removal decreased to 60% on the average. Analysis of granular activated carbon adsorption revealed that the main role of SMP removal in BAC reactor was biodegradation. A strain of SMP-degrading bacteria, which was found highly similar to Klebsiella sp., was isolated, enriched and inoculated back to the BAC reactor. When the influent chemical oxygen demand （COD） was 10,000 mg/L and the organic loading rate achieved 10 kg COD/（m 3 ·day）, the effluent from the BAC reactor could meet the discharge standard without further treatment. Anaerobic BAC reactor inoculated with the isolated Klebsiella was proved to be an effective, cheap and easy technical treatment approach for the removal of SMP in the treatment of easily-degradable wastewater with COD lower than 10,000 mg/L.

Potential acute effects of suspended aluminum nitride (AlN) nanoparticles on soluble microbial products (SMP) of activated sludge

The study aims to identify the potential acute effects of suspended aluminum nitride（Al N）nanoparticles（NPs） on soluble microbial products（SMP） of activated sludge.Cultured activated sludge loaded with 1,10,50,100,150 and 200 mg/L of Al N NPs were carried out in this study.As results showed,Al N NPs had a highly inverse proportionality to bacterial dehydrogenase and OUR,indicating its direct toxicity to the activated sludge viability.The toxicity of Al N NPs was mainly due to the nano-scale of Al N NPs.In SMP,Al N NPs led to the decrease of polysaccharide and humic compounds,but had slight effects on protein.The decrease of tryptophan-like substances in SMP indicated the inhibition of Al N NPs on the bacterial metabolism.Additionally,Al N NPs reduced obviously the molecular weight of SMP,which might be due to the nano-scale of Al N.

Formation of disinfection byproducts from accumulated soluble products of oleaginous microalga after chlorination

When microalgae are simultaneously applied for wastewater treatment and lipid production, soluble algal products （SAP） should be paid much attention, as they are important precursors for formation of disinfection byproducts （DBPs）, which have potential risks for human health. Chlorella sp. HQ is an oleaginous microalga that can generate SAP during growth, especially in the exponential phase. This study investigated the contribution of SAP from Chlorella sp. HQ to DBP formation after chlorination.The predominant DBP precursors from SAP were identified with the 3D excitation-emission matrix fluorescence. After chlorination, a significant reduction was observed in the fluorescence intensity of five specific fluorescence regions, particularly aromatic proteins and soluble microbial by-product-like regions, accompanied with slight shifting of the peak. The produced DBPs were demonstrated to include trihalomethanes and haloacetic acids. As the algal cultivation time was extended in wastewater, the accumulated SAP strengthened the formation of DBPs. The trend for DBP formation was as follows： chloroform〉dichloroacetic acid〉trichloroacetic acid.

Molecular behavior and interactions with microbes during anaerobic degradation of bio-derived DOM in waste leachate

It is the key to control bio-derived dissolved organic matters (DOM) in order to reduce the effluent concentration of wastewater treatment, especially for waste leachate with high organic contaminants. In the present study, the anaerobic degradation of aerobically stabilized DOM was investigated with DOM substrate isolated through electrodialysis. The degradation of bio-derived DOM was confirmed by reduction of 15%of total organic carbon in 100 days.We characterized the molecular behavior of bio-derived DOM by coupling molecular and biological information analysis. Venn based Sankey diagram of mass features showed the transformation of bio-derived DOM mass features. Occurrence frequency analysis divided mass features into six categories so as to distinguish the fates of intermediate metabolites and persistent compounds. Reactivity continuum model and machine learning technologies realized the semi-quantitative determination on the kinetics of DOM mass features in the form of pseudo-first order, and confirmed the reduction of inert mass features. Furthermore, network analysis statistically establish relationship between DOM mass features and microbes to identify the active microbes that are able to utilize bio-derived DOM. This work confirmed the biological technology is still effective in controlling recalcitrant bio-derived DOM during wastewater treatment.

Characterization of dissolved organic matter as N-nitrosamine precursors based on hydrophobicity, molecular weight and fluorescence

It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter （DOM） from two source waters was fractionated with XAD resins and ultra- filtration membranes. The N-nitrosamine formation potential （FP） （ng of N-nitrosamines formed per mg of dissolved organic carbon （DOC）） from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix （EEM）, molecular weight （MW） and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products （SMPs） and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA254 values.

Transformation mechanism and fate of dissolved organic nitrogen(DON) in a full-scale drinking water treatment

Dissolved organic nitrogen(DON) has attracted much attention in drinking water treatment due to its potential to produce nitrogenous disinfection by-products(N-DBPs). This work was designed to explore the transformation and fate of DON and dissolved inorganic nitrogen(DIN) in drinking water treatment. The changes of DON and formation of N-DBPs were evaluated along the water treatment route(i.e., pre-ozonation and biologicalcontact oxidation, delivery pipes’ transportation, coagulation-sedimentation, sand filtration, post-ozonation, biological activated carbon, ultrafiltration and disinfection) of drinking water treatment plant(DWTP). The transformation mechanism of DON was comprehensively investigated by molecular weight fractionation, three-dimensional fluorescence, LCOCD(Liquid Chromatography-Organic Carbon Detection), total free amino acids. A detailed comparison was made between concentrations and variations of DON and DIN affected by seasons in the drinking water treatment. Regardless of seasonal variation in raw water concentration, the DON removal trends between different treatment processes remain constant in the present study. Compared to other treatment processes, pre-ozonation and coagulation-sedimentation exhibited the dominant DON removal in different seasons, i.e.,11.13%-14.45% and 14.98%-22.49%, respectively. Contrary, biological-contact oxidation and biological activated carbon negatively impacted the DON removal, in which DON increased by 1.76%-6.49% in biological activated carbon. This may be due to the release of soluble microbial products(SMPs) from bacterial metabolism, which was further validated by the rise of biopolymers in LC-OCD.

The effect of continuous Ni(Ⅱ) exposure on the organic degradation and soluble microbial product(SMP) formation in two-phase anaerobic reactor

A two-phase anaerobic reactor fed with glucose substrate（3 g chemical oxygen demand（COD）/L） was used to investigate the effects of toxic metals on the degradation of organics and the soluble microbial product（SMP） formation. Low concentrations of Ni（II）（5 and10 mg/L） promoted the acid phase, whereas high concentrations（15, 20, and 25 mg/L）exhibited an inhibitory effect on, but did not alter the fermentative method, which mainly involved the fermentation of propionic acid. The methanogenic microorganism exhibited a strong capability adapting constantly increased Ni（II） levels. The acid phase was an accumulation stage of SMP. In the absence of Ni（II）, the high-molecular-weight material in the effluent SMP mainly contained polysaccharide, tryptophan, and casein. Methanogens metabolized most of the polysaccharide, the whole tryptophan content, and part of the casein, leading to the presence of humic acid and protein in effluent. After Ni（II） dosage, the protein and polysaccharide of the acid phase increased, and tryptophan changed, while casein remained stable. More protein than polysaccharide was produced, suggesting the prominent function of protein when addressing the negative effect of toxic metals. The analysis of DNA confirmed the change of bacterial activity.

Evaluation of factors influencing soluble microbial product in submerged MBR through hybrid ASM model

In this study,a mathematical model was established to predict the formation of the soluble microbial product(SMP)in a submerged membrane bioreactor.The developed model was calibrated under the reference condition.Simulation results were in good agreement with the measured results under the reference condition.The calibrated model was then used in the scenario studies to evaluate the effect of three chosen operating parameters:hydraulic retention time(HRT),dissolved oxygen concentration,and sludge retention time(SRT).Simulation results revealed that the SMP dominated the soluble organic substances in the supernatant.The scenario studies also revealed that the HRT can be decreased to 1 h without deteriorating the effluent quality;dissolved oxygen concentration in the reactor can be kept at 2–3 mg/L to maintain the effluent quality,reduce the content of SMP,and minimize operating costs;the optimal SRT can be controlled to 10–15 d to achieve complete nitrification process,less membrane fouling potential,and acceptable organic removal efficiency.

Investigation on removal pathways of Di 2-ethyl hexyl phthalate from synthetic municipal wastewater using a submerged membrane bioreactor

Highly hydrophobic Di 2-ethyl hexyl phthalate（DEHP） is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25 days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand（COD）and ammonia concentration were detected below 10 and 1.0 mg/L, respectively for operating conditions of hydraulic retention time（HRT） = 4 and 6 hr, sludge retention time（SRT） = 140 day and sludge concentration between 11.5 and 15.8 g volatile solid（VS）/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor,which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.

Purification and molecular weight distribution of a key exopolysaccharide component of Bacillus megaterium TF10

Extracellular polymeric substances（EPS） are organic metabolic compounds excreted by microorganisms. They largely impact microbial aggregate structures and functions.Extracellular polysaccharides（EP） in EPS are responsible for the formation of microbial aggregates. In this work, we successfully separated and characterized EP from EPS of the bacterium Bacillus megaterium TF10. Extraction of EP from EPS was optimized using Sevag＇s reagent. Chemical characteristics, functional groups, and molecular weight（MW） distribution of EP were compared with the harvested EPS and soluble microbial products（SMP）. We found that the polymers of lower MW and free proteins were successfully removed by Sevag＇s reagent. The higher MW components of EPS were predominantly polysaccharides,while the polymers of lower MW tended to secrete to the supernatant and were described as SMP. A part of the proteins in the EP was polysaccharide-bonded. Our results can be further used in elucidating the complex flocculation mechanisms in which EP play a major role.