[Nitrogen Removal in Low-C/N Rural Sewage Treatment by Anoxic/Oxic Biofilter Packed with New Types of Fillers].

When low-concentration rural sewage is treated biologically, the effluent total nitrogen (TN) concentration often does not meet the discharge limit because of its low carbon-to-nitrogen ratio (C/N). To solve this problem, a laboratory-scale anoxic/oxic (A/O) biofilter packed with Arundo donax and activated carbon as the anoxic and aerobic column fillers (No. 2) was operated for treatment of simulated rural sewage and advanced nitrogen removal, while an ordinary gravel-packing A/O biofilter (No. 1) was set up as the control group. The results were as follows. When the influent chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and TN concentrations were (79.47±14.21), (34.49±2.08), and (34.73±3.87) mg·L-1, respectively, the No. 1 and No. 2 reactors achieved removal efficiencies of (88.00±7.00)% and (89.00±10.00)%, (90.00±2.00)% and (97.00±7.00)%, and (37±15)% and (68±7)%, respectively. The results revealed that using Arundo donax and activated carbon new fillers could significantly enhance NH4+-N and TN removal. High-throughput sequencing results indicated that the microorganisms involved in the nitrification process in the No. 1 reactor mainly belong to Proteobacteria, whereas those in the No. 2 reactor belong to Proteobacteria and Nitrospirae. In addition, the main denitrification bacterial phyla in the anoxic column of the No. 1 reactor were Chloroflexi, Proteobacteria, Bacteroidetes, and Planctomycetes, whereas those in the anoxic column of the No. 2 reactor were primarily Bacteroidetes, Proteobacteria, Firmicutes, and Patescibacteria. Quantitative real time polymerase chain reaction (qPCR) results showed that the microbial nitrification (amoA and Nitrospira 16S rDNA), denitrification (narG, nosZ, nirS, and nirK), and anaerobic ammonium oxidation functional genes (ANAMMOX) in the No. 2 reactor were significantly higher than those in the No. 1 reactor. All the genes, except for the narG and nosZ genes, had one to two orders of magnitude of improvement in the No. 2 reactor compared to those in the No. 1 reactor.

[Distribution Characteristics and Ecological Risk Assessment of Phthalate Esters in Surface Sediments of the Songhua River].

This study assesses the spatial distribution characteristics and ecological risk of phthalate esters (PAEs) in the surface sediments of the mainstream and tributaries of the Songhua River, China, using concentrations and composition of six PAEs, which were analyzed using gas chromatography-mass spectrometery (GC-MS). We assess the ∑6PAEs ecological risk using the hazard quotient (HQ) method and environmental risk levels (ERL). The results were as follows. ① It was found that the total concentrations of ∑6PAEs ranged from 6832.5 to 36298.9 ng·g-1 dry weight (average 18388.6 ng·g-1), with the main contributions coming from di-(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP). The difference between the main stream ∑6PAEs (6832.5-36298.9 ng·g-1, average 18616.9 ng·g-1) and the tributary ∑6PAEs (10367.6-26593.3 ng·g-1, average 18264.1 ng·g-1) was not significant (P >0.05). The mean concentrations of individual PAEs in the tributary stream differed little from that of the main stream. The ∑6PAEs concentration of the Songhua River decreased initially but then increased from the upstream to the downstream. The average ∑6PAEs concentration in natural agricultural areas (18677.5 ng·g-1) was similar to that found in urban industrial areas (18063.7 ng·g-1), and DBP and DEHP contributed 98% of ∑6PAEs. ② The main sources of ∑6PAEs were domestic, agricultural production, and industrial production using plasticizers. ③ The ecological risk assessment indicated that DMP and BBP in the surface sediments of the Songhua River did not pose an ecological risk for aquatic organisms, and that DEP was associated with a low ecological risk, whereas DEHP and DBP posed a high ecological risk for aquatic organisms.

[Effect of On-line NaClO Backwashing on Microbial Communities in an Inverted A2O-MBR System].

To study the effect of on-line NaClO backwashing on the microbial community structure of membrane bioreactor (MBR) systems, a reversed A2O-MBR reactor was used to monitor system performance, membrane fouling, and microbial community structure. Measurements were made during the stabilization stage, the on-line pure water backwashing stage, and the on-line NaClO backwashing stage. The results showed that key system performance indicators during NaClO backwashing stage, such as COD, ammonia nitrogen, and TN treatment efficiency, were similar to previous stages. The average membrane fouling rate during the on-line pure water backwashing period was lower than that of the stable stage, while the membrane fouling rate increased during the on-line NaClO backwashing stage, and EPS concentration was the highest and membrane fouling was aggravated. The results of the Chao index, Simpson index, and Shannon index showed that the microbial diversity in the aerobic tank sludge remained almost stable after on-line NaClO backwashing, while the abundance of cake layer sludge increased slightly, but the microbial diversity decreased significantly. Proteobacteria was the main microbial phylum in both the aerobic tank and cake layer sludge, followed by Bacteroidetes. After on-line NaClO backwashing, the relative abundance of Proteobacteria and Bacteroides in the aerobic tank sludge did not change notably, but the composition of filter cake sludge changed significantly. Proteobacteria that possess resistance to chlorine disinfectant increased from 53.4% to 77.8%, while Bacteroides decreased from 33.44% to 14.5%. After on-line NaClO backwashing, the composition of the microbial community in aerobic tank and cake layer was similar. Azospira and Comamonadaceaea also increased significantly after NaClO backwashing. Microbial species that can tolerate NaClO treatment may be the main cause of membrane fouling.

[Effect of Nitrogen on Magnesium Modified Biochar Adsorption to Phosphorus].

The effect of ammonia-nitrogen in water on phosphorus removal by magnesium modified biochar (MBC) was developed to increase the utilization of wetland plants. The crystal structures were measured by X-ray powder diffraction (XRD). MBC was prepared using reed as the biomass feedstock, which was modified with magnesium chloride. The raw biochar (BC) was prepared as a control. The removal of phosphate from solution using four different methods, i.e. MBC, BC, BC, and MgCl2 solutions (BC+Mg2+) and MgCl2 solutions (Mg2+), under different nitrogen to phosphorus molar ratios and initial phosphorus concentrations was investigated in batch experiments. The results demonstrated that the phosphorus removal efficiency of the four treatment methods, which followed the order of MBC>>BC+Mg2+≈Mg2+>BC. NH4+ in the solution, promoted phosphorus removal by MBC. In addition, the larger the ratio of nitrogen to phosphorus and the higher the initial phosphorus concentration, the stronger the phosphorus removal capacity of MBC was. In the three treatments with MBC, BC+Mg2+, and Mg2+, the XRD analysis showed that NH4+ reacted with Mg2+ and PO43- in the solution to form MgNH4PO4·6H2O at N:P=5 or 10, promoting the removal of phosphorus. For recycling purposes, waste biomass from constructed wetlands could be used to produce MBC and treat polluted water rich in ammonium and phosphate. Moreover, the ammonium-nitrogen promotes the phosphate removal by MBC. The results from this study provide a new theoretical basis and data support for the treatment of water eutrophication.

Structural and functional brain abnormalities in drug-naive, first-episode, and chronic patients with schizophrenia: a multimodal MRI study.

BACKGROUND: Structural and functional brain abnormalities in schizophrenia (SZ) have been widely reported. However, a few studies have investigated both structural and functional characteristics in SZ patients at different stages to understand the neuropathology of SZ. METHODS: In this study, we recruited 44 first-episode drug-naive SZ (FESZ) patients, 44 medicated chronic SZ (CSZ) patients, and 56 normal controls (NCs) and acquired their structural and resting-state functional magnetic resonance imaging (MRI). We then made group comparisons on structural and functional characteristics, including regional gray matter volume (GMV), regional homogeneity, amplitude of low-frequency fluctuation, and degree centrality. A linear support vector machine (SVM) combined with a recursive feature elimination (RFE) algorithm was implemented to discriminate three groups. RESULTS: Our results indicated that the regional GMV was significantly decreased in patients compared with that in NCs; CSZ patients have more diffused GMV decreases primarily involved in the frontal and temporal lobes when compared with FESZ patients. Both FESZ and CSZ patients showed significant functional alterations compared with NCs; when compared with FESZ patients, CSZ patients showed significant reductions in functional characteristics in several brain regions associated with auditory, visual processing, and sensorimotor functions. Moreover, a linear SVM combined with a RFE algorithm was implemented to discriminate three groups. The accuracies of the three classifiers were 79.80%, 83.16%, and 81.71%, respectively. The performance of classifiers in this study with multimodal MRI was better than that of previous discriminative analyses of SZ patients with single-modal MRI. CONCLUSION: Our findings bring new insights into the understanding of the neuropathology of SZ and contribute to stage-specific biomarkers in diagnosis and interventions of SZ.

Alterations of regional homogeneity in freezing of gait in Parkinson's disease.

INTRODUCTION: Freezing of gait (FOG) is a serious complication in patients with Parkinson's disease (PD), and is more common in the late state of the disease. The high risk of falling in patients with FOG impacts their quality of life. OBJECTIVE: To explore altered neuroactivity related to cognitive and executive function of PD patients with FOG. METHODS: Fourteen PD patients with FOG (FOG+), 20 PD patients without FOG (FOG-), and 18 normal controls (NC) were enrolled. Functional MRI data of all PD patients were collected during OFF medication state. Data were analyzed using software of DPARSF and REST. Resting brain activity was measured by regional homogeneity (ReHo). ANOVA test was performed for ReHo among FOG, PD, and NC groups. RESULTS: ReHo alterations of left supplementary motor area (SMA) (Brodmann 6), left superior frontal region (Brodmann 9), and the right putamen (Brodmann 48) were significantly different among the three groups. The ReHo values within left SMA (Brodmann 6) and left superior frontal region (Brodmann 9) were significantly decreased in FOG+ patients compared with FOG- patients. CONCLUSION: Changes in neural hypoactivity within the frontal region and SMA appear to be associated with FOG in PD patients, which suggests that the mechanism underlying FOG may relate to disruption of execution and cognition.

[Automatic classification of first-episode, drug-naive schizophrenia with multi-modal magnetic resonance imaging].

A great number of studies have demonstrated the structural and functional abnormalities in chronic schizophrenia (SZ) patients. However, few studies analyzed the differences between first-episode, drug-naive SZ (FESZ) patients and normal controls (NCs). In this study, we recruited 44 FESZ patients and 56 NCs, and acquired their multi-modal magnetic resonance imaging (MRI) data, including structural and resting-state functional MRI data. We calculated gray matter volume (GMV), regional homogeneity (ReHo), amplitude of low frequency fluctuation (ALFF), and degree centrality (DC) of 90 brain regions, basing on an automated anatomical labeling (AAL) atlas. We then applied these features into support vector machine (SVM) combined with recursive feature elimination (RFE) to discriminate FESZ patients from NCs. Our results showed that the classifier using the combination of ReHo and ALFF as input features achieved the best performance (an accuracy of 96.97%). Moreover, the most discriminative features for classification were predominantly located in the frontal lobe. Our findings may provide potential information for understanding the neuropathological mechanism of SZ and facilitate the development of biomarkers for computer-aided diagnosis of SZ patients.

Discriminative analysis of schizophrenia using support vector machine and recursive feature elimination on structural MRI images.

Structural abnormalities in schizophrenia (SZ) patients have been well documented with structural magnetic resonance imaging (MRI) data using voxel-based morphometry (VBM) and region of interest (ROI) analyses. However, these analyses can only detect group-wise differences and thus, have a poor predictive value for individuals. In the present study, we applied a machine learning method that combined support vector machine (SVM) with recursive feature elimination (RFE) to discriminate SZ patients from normal controls (NCs) using their structural MRI data. We first employed both VBM and ROI analyses to compare gray matter volume (GMV) and white matter volume (WMV) between 41 SZ patients and 42 age- and sex-matched NCs. The method of SVM combined with RFE was used to discriminate SZ patients from NCs using significant between-group differences in both GMV and WMV as input features. We found that SZ patients showed GM and WM abnormalities in several brain structures primarily involved in the emotion, memory, and visual systems. An SVM with a RFE classifier using the significant structural abnormalities identified by the VBM analysis as input features achieved the best performance (an accuracy of 88.4%, a sensitivity of 91.9%, and a specificity of 84.4%) in the discriminative analyses of SZ patients. These results suggested that distinct neuroanatomical profiles associated with SZ patients might provide a potential biomarker for disease diagnosis, and machine-learning methods can reveal neurobiological mechanisms in psychiatric diseases.

[A Maternal Health Care System Based on Mobile Health Care].

Wearable devices are used in the new design of the maternal health care system to detect electrocardiogram and oxygen saturation signal while smart terminals are used to achieve assessments and input maternal clinical information. All the results combined with biochemical analysis from hospital are uploaded to cloud server by mobile Internet. Machine learning algorithms are used for data mining of all information of subjects. This system can achieve the assessment and care of maternal physical health as well as mental health. Moreover, the system can send the results and health guidance to smart terminals.

Key issues to consider when using alum sludge as substrate in constructed wetland.

Globally, alum sludge is an easily, locally and largely available by-product from water treatment plants where aluminium sulphate is used as the coagulant for raw water purification. Owing to the high content of Al ions (29.7±13.3% dry weight) in alum sludge and the strong affinity of Al ions to adsorb various pollutants especially phosphorus (P), alum sludge (in the form of dewatered cakes) has been investigated in recent years as a low-cost alternative substrate in constructed wetland (CW) systems to enhance the treatment efficiency especially for high strength P-containing wastewater. Long-term trials in different scales have demonstrated that the alum sludge-based CW is a promising technique with a two-pronged feature of using 'waste' for wastewater treatment. Alum sludge cakes in CW can serve as a medium for wetland plant growth, as a carrier for biofilm development and as a porous material for wastewater infiltration. After the intensive studies of the alum sludge-based CW system, this paper aims to address the key issues and concerns pertaining to this kind of CW system. These include: (1) Is alum sludge suitable for reuse in CWs? (2) Is Al released from the sludge a concern? (3) What is the lifespan of the alum sludge in CWs? (4) How can P be recovered from the used alum sludge? (5) Does clogging happen in alum sludge-based CW systems and what is the solution?

Enhancement and Mitigation Mechanisms of Protein Fouling of Ultrafiltration Membranes under Different Ionic Strengths.

To determine further the enhancement and mitigation mechanisms of protein fouling, filtration experiments were carried out with polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes and bovine serum albumin (BSA) over a range of ionic strengths. The interaction forces, the adsorption behavior of BSA on the membrane surface, and the structure of the BSA adsorbed layers at corresponding ionic strengths were investigated. Results indicate that when the ionic strength increased from 0 to 1 mM, there was a decrease in the PVDF-BSA and BSA-BSA electrostatic repulsion forces, resulting in a higher deposition rate of BSA onto the membrane surface, and the formation of a denser BSA layer; consequently, membrane fouling was enhanced. However, at ionic strengths of 10 and 100 mM, membrane fouling and the BSA removal rate decreased significantly. This was mainly due to the increased hydration repulsion forces, which caused a decrease in the PVDF-BSA and BSA-BSA interaction forces accompanied by a decreased hydrodynamic radius and increased diffusion coefficient of BSA. Consequently, BSA passed more easily through the membrane and into permeate. There was less accumulation of BSA on the membrane surface. A more nonrigid and open structure BSA layer was formed on the membrane surface.

Identifying polyvinylidene fluoride ultrafiltration membrane fouling behavior of different effluent organic matter fractions using colloidal probes.

The interaction forces between effluent organic matter (EfOM) fractions and membrane were measured by atomic force microscopy in conjunction with self-made membrane material colloidal probes. The inter-EfOM-fraction and intra-EfOM-fraction interactions were investigated using corresponding EfOM-fraction-coated colloidal probe. We combined this analysis with corresponding fouling experiments to identify the EfOM fractions responsible for polyvinylidene fluoride (PVDF) ultrafiltration membrane fouling. Results show that hydrophilic and hydrophobic fractions were the dominant fractions responsible for membrane fouling and flux decline in the initial and later filtration stages, respectively, which was mainly attributed to the stronger PVDF-hydrophilic fraction and intra-hydrophobic-fraction interaction forces. This phenomenon, in conjunction with the fact that each interaction force of PVDF-EfOM fraction was stronger than corresponding intra-EfOM-fraction force, suggests that the elimination of the PVDF-hydrophilic fraction interaction force is the best strategy for controlling EfOM fouling. Moreover, the inter-EfOM-fraction interaction force was mainly controlled by the corresponding intra-EfOM-fraction interaction forces. And, while the membrane-EfOM fraction and intra-EfOM-fraction interactions for each type of EfOM fraction are equivalent, the EfOM fractions with the molecular weight smaller than the molecular weight cutoff of the membranes used were mainly responsible for membrane fouling rather than the relatively high-molecular-weight fractions.

Fouling behavior of typical organic foulants in polyvinylidene fluoride ultrafiltration membranes: characterization from microforces.

To further unravel the organic fouling behavior of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes, the adhesion forces of membrane-foulant and foulant-foulant were investigated by atomic force microscopy (AFM) in conjunction with self-made PVDF colloidal probe and foulant-coated colloidal probe, respectively. Fouling experiments with bovine serum albumin, sodium alginate, humic acid, and secondary wastewater effluent organic matter (EfOM) were carried out with PVDF UF membrane. Results showed a positive correlation between the membrane-foulant adhesion force and the flux decline rate and extent in the initial filtration stage, whereas the foulant-foulant interaction force was closely related to the pseudostable flux and the cake layer structure in the later filtration stage. For each type of foulant used, the membrane-foulant adhesion force was much stronger than the foulant-foulant interaction force, and membrane flux decline mainly occurred in the earlier filtration stage indicating that elimination of the membrane-foulant interaction force is important for the control of membrane fouling. Upon considering the foulant-foulant interaction force and the membrane flux recovery rate of fouled membranes, it was evident that the main contributor to physically irreversible fouling is the foulant-foulant interaction force.

Effects of the substrate depth on purification performance of a hybrid constructed wetland treating domestic sewage.

The depth of substrate in constructed wetlands (CWs) has a significant effect on the construction investment and the purification performance of CWs. In this study, a pilot scale CW system was operated in a domestic sewage treatment plant in Xi'an, China. The experimental systems included three-series CWs systems with substrate depths of 0.1m, 0.3 m and 0.6 m, respectively. Each series was composed of a hydroponic ditch, a horizontal subsurface flow CW and a vertical flow CW. The effluent from the primary clarifier in the sewage treatment plant was intermittently conducted to the wetlands at a flow rate of 0.3 m(3)/d. The hydraulic loading rate of each CWs system was regulated at 0.1 m(3)/m(2).d and the hydraulic retention time was 3 days. Canna indica L. was planted both in the hydroponic ditches and the CWs systems. Results showed that the highest removal efficiency of NH(+)(4)-N and TP was obtained in the hybrid CW with 0.1 m substrate depth. The average removal efficiency for NH(+)(4)-N and TP were 90.6 % and 80.0 %, respectively. The highest average removal efficiency of COD was obtained in hybrid CWs system with 0.6 m substrate depth. Therefore, a simultaneous removal of COD and nutrients can be achieved through the combination of different wetlands using different substrate depths. In addition, the substrate depth presents significant effects on the concentration of DO and root growth characteristics of canna in the system. As a result, the highest concentration of DO (>2 mg/L) and the highest amount of roots production were achieved in the 0.1 m substrate depth horizontal and vertical flow CWs.

Macroscale and microscale analysis of Anammox in anaerobic rotating biological contactor.

Inoculated with conventional anaerobic activated sludge, the Anammox process was successfully developed in an anaerobic rotating biological contactor (AnRBC) fed with a low ratio of C/N synthetic wastewater. Operated in a single point feed mode, the AnRBC removed 92.1% (n = 126) of the influent N at the highest surface load of 12 g/(m2 x day). The biomass increased by 25% and 17.1 g/(m2 x day) of maximum N removal surface load was achieved by elevating flow rate with another feed point. Fluorescence in situ hybridization and polymerase chain reaction analysis indicated that the Anammox genus Candidatus Kuenenia stuttgartiensis dominated the community. Both Anammox and denitrifying activity were detected in biofilm by the application of microelectrodes. In the outer layer of the biofilm (0-2500 microm), nitrite and ammonium consumed simultaneously in a ratio of 1.12/1, revealing the occurrence of Anammox. In the inner layer (> 2500 microm), a decrease of nitrate was caused by denitrification in the absence of nitrite and ammonium.

Autotrophic nitrogen removal discovered in suspended nitritation system.

A lab-scale sequencing batch reactor was operated in batch mode to treat ammonium-rich synthetic wastewater, and minor N loss (about 9%) was observed without seeding anaerobic ammonium oxidation bacteria (AnAOB). Around 4 wk after the dissolved oxygen concentration was decreased (from 0.9+/-0.1 to 0.4+/-0.1 mg L(-1)) and the hydraulic retention time was elevated (from 11.0 to 14.7 h), 80% of total nitrogen removal efficiency and 0.49 kg N m(-3) d(-1) of maximum nitrogen removal capacity were obtained. During a single cycle, a peak of NO2(-) concentration was observed at 60 min, and the pH first increased from 8.02 to 8.17 and then returned to 8.04. Fluorescence in situ hybridization analysis revealed that the aerobic ammonium-oxidizing genus Nitrosomonas dominated the community, while AnAOB and very small amounts of Nitrospira spp. were also detected. The ratio of nitrate produced to ammonia consumed (0.10+/-0.02) was lower than that achieved with the completely autotrophic nitrogen removal over nitrite process. This study revealed that nitritation, Anammox and autotrophic denitrification were responsible for the nitrogen removal. The nitrate production was caused by the co-action of nitrite-oxidizing bacteria and AnAOB.

[Experiment of simultaneous denitrifying phosphorus accumulation].

Denitrifying phosphorus accumulation (DNPA) and the factors affecting it were studied in a SBR with synthetic wastewater. The results showed that the sludge acclimatized under anaerobic/aerobic operation with good phosphorus removal ability, showed DNPA soon when fed nitrate instead of aeration following the anaerobic stage. Anaerobic stage was a vital premise to DNPA. If DNPA sludge was fed with nitrate prior to anaerobic stage, the DNPA would weaken even disappear. When acetate was used as sole carbon resource in the influent and nitrate did not exist in anaerobic, 1 hour of anaerobic time was optimal. NO3- -concentration in the anoxic was one of the factors affecting DNPA. When nitrate concentration was advanced from 5mg/L to 20mg/L, the percentage of DNPA increased from 11.9% to 48.7% under the condition of anaerobic(2h)-anoxic(1h)-aerobic(2h). But when the NO3- -concentration was enhanced upwards of 20mg/L, the efficiency cannot be improved. Induced DNPA did not disappear even though there was aerobic stage following anoxic stage, but the shorter the aerobic stage lasted the higher proportions of phosphorus removal via DNPA to total removal.

The largest Lyapunov exponent of chaotic dynamical system in scale space and its application.

The largest Lyapunov exponent is an important invariant of detecting and characterizing chaos produced from a dynamical system. We have found analytically that the largest Lyapunov exponent of the small-scale wavelet transform modulus of a dynamical system is the same as the system's largest Lyapunov exponent, both discrete map and continuous chaotic attractor with one or two positive Lyapunov exponents. This property has been used to estimate the largest Lyapunov exponent of chaotic time series with several kinds of strong additive noise.