Adaptive regulation of activated sludge's core functional flora based on granular internal spatial microenvironment.

A great deal of efforts has been put into studying the influence of the external macroenvironment for activated sludge to survive on microbial community succession, while granular internal spatial microenvironment should be given equal attention, because it is more directly involved in the information exchange and material transfer among microorganisms. This study systematically investigated the effects of granular microenvironment on spatial colonization and composition of sludge's core functional flora, and the corresponding difference of biological treatment performance. High content of extracellular-proteins (67.53 mg/gVSS) or extracellular-polysaccharide (65.02 mg/gVSS) stimulated the microbial flocculation and aggregation of 0.5-1.5 mm granules (GS) or 1.5-3.0 mm granules (GM), respectively, which was resulted from excellent cell hydrophobicity (59.26%) or viscosity (3.47 mPa s), therefore, constituted relatively dense porous frame. More hollow space existed in 3.0-5.0 mm granules (GL), which formed loose skeleton with 0.213 mL/g of total pore volume and 17.21 nm of average pore size. Combining scanning electron microscope images and fluorescent in-situ hybridization based microbiological analysis, aerobic nitrifiers were observed to wrap or surround anaerobic bacteria, or facultative/anaerobic bacteria were self-encapsulated, which created granule's unique microenvironment with alternating aerobic and anaerobic zones. GS has the most rich organic matter degrading bacteria and anaerobic heterotrophic denitrifiers, while GM and GL presented the greatest relative abundance of facultative and aerobic denitrifiers, respectively. The activity of dehydrogenase and nitrogen invertase of GM showed be 1.32-3.09 times higher than those of GS and GL, contributing to its higher carbon and nitrogen removal. These findings highlight the importance of granular microenvironment to adaptive regulation of activated sludge's core functional flora and corresponding pollutant removal performance.

Artificially constructing mixed bacteria system for bioaugmentation of nitrogen removal from saline wastewater at low temperature.

To alleviate the inhibition effects of multi-stresses, a multi-bacterial bioaugmentation based on stimulating cell-to-cell interactions was applied to improve the stress potential of salt-tolerant aerobic granular sludge (AGS). Results showed that the consortium formed by a combination of salt-tolerant ammonia-nitrogen utilizing bacteria, salt-tolerant nitrite-nitrogen utilizing bacteria and salt-tolerant nitrate-nitrogen utilizing bacteria with a whole biomass ratio of 1:2:1 achieved maximum nitrogen consumption rate (µNH4+-N, µNO2--N and µNO3--N of 1.03, 0.57 and 11.62 mgN/L·h, respectively) at 35 gNaCl/L salinity and 15 °C. The flocculent consortium was aggregated by Aspergillus tubingensis mycelium pellet, which was made into a compound bacterial agent (CBA), and the comprehensive nitrogen consumption capability of CBA was further improved to 2.47-4.36-fold of single functional bacteria. 5% CBA (m/m) was introduced into the seafood processing wastewater in batches, in winter (12-16 °C), the removal efficiencies of NH4+-N and total nitrogen increased from 66.89% to 52.77% of native AGS system to 79.02% and 69.97% of nascent bioaugmentation system, respectively. The analysis of key enzyme activities demonstrated that the ammonia monooxygenase and nitrate reductase activities of the bioaugmentation system were increased to 2.73-folds and 1.94-folds those of the native system. Moreover, due to an increase of 6.18 mg/gVSS and 0.11 in the secreted exopolysaccharide and tightly-bound/total extracellular polymeric substances, respectively, bioaugmentation boosted the cell bioflocculation ability by 13.53%, which enhanced the robustness. This work provided a detailed and feasible technical proposal for enhancing the biological treatment performance of saline wastewater in cold regions.

Role of initial bacterial community in the aerobic sludge granulation and performance.

The structure of bacterial community was greatly varied from different seed sludge sources, which affected the sludge characteristics. To explore the role of different functional bacteria in AGS granulation and pollutant degradation, three different resources of seed sludge obtained from pharmaceutical wastewater (R1), livestock (R2), and municipal sludge (R3) were employed in this study. Results showed that the initial bacterial community had important significance for AGS formation and pollutants removal. Seed sludge taken from R3 granulated faster than those from R1 and R2. A large number of mature granules were formed after 20 days of operation in R3. In addition, the final mixed liquor suspended solids (MLSS) reached 6853 mg L-1, with 48 mL g-1 sludge volume index (SVI) in R3, indicating that it had better settling performance and granulation. In the stable stage of R3, the removal rates of COD, NH4+-N, and TN reached 99.2%, 98.5%, and 97.6%, respectively. The α-diversity analysis showed that the bacterial community of seed sludge greatly determined the microbial composition of AGS. Firmicutes, Gracilibacteria, and Spirochaetes were abundant in R3, which maintained the structures and functions of aerobic granules. This study might provide approaches and insights for AGS culture from different sludge sources.

Rapid colonization and biodegradation of untreated commercial polyethylene wrap by a new strain of Bacillus velezensis C5.

Biodegradation could be a potential alternative solution to polyethylene (PE) pollution. However, its hydrophobic surface and long carbon chains make extremely low biodegradation efficiency. In this study, we screened a novel potential bacterial strain C5 (CGMCC number: 1.18715) for low-density polyethylene (LDPE) biodegrading from landfills. The strain was identified as Bacillus velezensis according to its 16S rRNA sequence. The contact angle analysis indicated that C5 could rapidly form biofilm on untreated LDPE which resulted in contact angles decreasing from 100° to 54° over 7 d. After the LDPE film incubated with C5 for 90 d, the thickness and weight of LDPE film decreased by 26% and 8.01%, respectively. Besides, the biotreated PE film was found with increases in weight-averaged molecular weight by 29.8%, suggesting low molar mass chains were consumed. C24-C29 n-alkanes were detected in the biodegradation products, which proved the depolymerization of LDPE. Combined with the genome mining results, a possible biofilm-aided degrading mechanism was proposed and might involve key enzymes, such as laccase, cytochrome P450 and propionyl-CoA carboxylase, which could constitute a multienzyme system for the co-catalytic degradation of LDPE waste.

Detecting Pb2+by a 'turn-on' fluorescence sensor based on DNA functionalized magnetic nanocomposites.

Sensitive and selective detection of the lead ion (Pb2+) plays an important role in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. The highly stable fluorescence biosensor is composed of Fe3O4@TiO2core-shell nanocomposites, functionalized with a carboxyl fluorescein labeled DNA. The morphology, physical and chemical properties of the sensing nanomaterials were studied by transmission electron microscopy, FT-IR spectroscopy (FT-IR), x-ray powder diffraction and vibrating sample magnetometer. UV-visible and fluorescence spectroscopy were used to characterize the fluorescein functionalized magnetic nanoparticles. The performance of Pb2+detection displayed an excellent linearity (R2 = 0.995) in the range of 10-10to 5 × 10-9ppm with a detection limit of 10-10ppm, based on the optimization of the fabrication process and aptamers' specification. The fluorescence biosensor has an accurate response, excellent recoveries and high adsorbent capacities. It was successfully applied for the determination of Pb2+in contaminated water and serum samples; the detection of limit in both media were 10-10ppm. These features ensure the potential use of aptamer functionalized magnetic nanocomposites as a new class of non-toxic biocompatible sensors for biological and environmental applications.

Zirconia supported gold-palladium nanocatalyst for NAD(P)H regeneration via two-step mechanism.

The regeneration cycle of expensive cofactor, NAD(P)H, is of paramount importance for the bio-catalyzed redox reactions. Here a ZrO2supported bimetallic nanocatalyst of gold-palladium (Au-Pd/ZrO2) was prepared to catalyze the regeneration of NAD(P)H without using electron mediators and extra energy input. Over 98% of regeneration efficiency can be achieved catlyzed by Au-Pd/ZrO2using TEOA as the electron donor. Mechanism study showed that the regeneration of NAD(P)H took place through a two-step process: Au-Pd/ZrO2nanocatalyst first catalyzed the oxidation of triethanolamine (TEOA) to glycolaldehyde (GA), then the generated GA induced the non-catalytic reducing of NAD(P)+to NAD(P)H under an alkaline environment maintained by TEOA. This two-step mechanism enables the decoupling of the regeneration of NAD(P)H in space and time into a catalytic oxidation and non-catalytic reducing cascade process which has been further verified using a variety of electron donors. The application significance of this procedure is further demonstrated both by the favorable stability of Au-Pd/ZrO2nanocatalyst in 5 successive cycles preserving over 90% of its original activity, and by the excellent performance of the regenerated NADH as the cofactor in the catalytic hydrogenation of acetaldehyde using an ethanol dehydrogenase.

Enhanced resistance of Trichoderma harzianum LZDX-32-08 to hygromycin B induced by sea salt.

OBJECTIVES: To determine the effect of sea salt on the resistance of Trichoderma harzianum LZDX-32-08 to hygromycin B and speculate the possible mechanisms involved via transcriptome analysis. RESULTS: Sea salt addition in media to simulate marine environment significantly increased the tolerance of marine-derived fungus Trichoderma harzianum LZDX-32-08 to hygromycin B from 40 to 500 µg/ml. Meanwhile, sea salt addition also elicited the hygromycin B resistance of 5 other marine or terrestrial fungi. Transcriptomic analyses of T. harzianum cultivated on PDA, PDA supplemented with sea salt and PDA with both sea salt and hygromycin B revealed that genes coding for P-type ATPases, multidrug resistance related transporters and acetyltransferases were up-regulated, while genes coding for Ca2+/H+ antiporter and 1,3-glucosidase were down-regulated, indicating probable increased efflux and inactivation of hygromycin B as well as enhanced biofilm formation, which could jointly contribute to the drug resistance. CONCLUSIONS: Marine environment or high ion concentration in the environment could be an importance inducer for antifungal resistance. Possible mechanisms and related key genes were proposed for understanding the molecular basis and overcoming this resistance.

Enhancing robustness of activated sludge with Aspergillus tubingensis as a protective backbone structure under high-salinity stress.

High salt seriously destroys the stable interactions among key functional species of activated sludge, which in turn limits the performance of high-salinity wastewater biological treatment. In this study, pelletized Aspergillus tubingensis (AT) was used as a protective backbone structure for activated sludge under high-salinity stress, and a superior salt-tolerant AT-based aerobic granular sludge (AT-AGS) was developed. Results showed that the COD and NH4+-N removal efficiencies of salt-domesticated AT-AGS were 11.83% and 7.18% higher than those of salt-domesticated flocculent activated sludge (FAS) at 50 gNaCl/L salinity. Compared to the salt-domesticated FAS, salt-domesticated AT-AGS showed stronger biomass retention capacity (with a MLVSS concentration of 7.92 g/L) and higher metabolic activity (with a dehydrogenase activity of 48.06 mgTF/gVSS·h). AT modified the extracellular polymeric substances pattern of microbes, and the total extracellular polysaccharide content of AT-AGS (80.7 mg/gVSS) was nearly twice than that of FAS (46.3 mg/gVSS) after salt-domestication, which demonstrated that extracellular polysaccharide played a key role in keeping the system stable. The high-throughput sequencing analysis illustrated that AT contributed to maintain the microbial richness and diversity of AT-AGS in high-salt environment, and Marinobacterium (with a relative abundance of 32.04%) became the most predominant genus in salt-tolerant AT-AGS. This study provided a novel insight into enhancing the robustness of activated sludge under high-salinity stress.

A reusable chitosan/TiO2@g-C3N4 nanocomposite membrane for photocatalytic removal of multiple toxic water pollutants under visible light.

Photocatalysis has been proved to be a promising approach in wastewater purification. However, it is hard to recycle powdery photocatalysts from wastewater in industry, but immobilizing them using larger materials can overcome this drawback. For that reason, TiO2@g-C3N4 was embedded into chitosan to synthesize a highly reusable and visible-light-driven chitosan/TiO2@g-C3N4 nanocomposite membrane (CTGM). CTGM showed enhanced photoactivity and the photocatalytic efficiencies of the toxic water pollutants methyl orange (M.O.), rhodamine B (Rh.B), chromium (VI) (Cr (VI)), 2,4-dichlorophenol (2,4-DCP) and atrazine (ATZ) were more than 90% under visible light at ambient conditions. Significantly, CTGM was easy to recycle and showed excellent reusability: there was no decrease in the photocatalytic decolorization efficiency of Rh.B throughout 10 cycles. A continuous-flow photocatalysis system was set up and 90% of Rh.B was effectively decolorized. A simple approach was developed to prepare a novel, effective and visible-light-driven membrane that was easy to reuse, and a feasible photocatalysis continuous-flow system was designed to be a reference for wastewater treatment in industry.

Promotion and Inhibition of the Oxidase-Mimicking Activity of Nanoceria by Phosphate, Polyphosphate, and DNA.

Nanoceria (CeO2 nanoparticles) is an extensively studied nanozyme with interesting oxidase-mimicking activity. As they can work in the absence of toxic and unstable H2 O2 , CeO2 nanoparticles have been widely used in biosensing. CeO2 nanoparticles often encounter phosphate-containing molecules that can affect their catalytic activity, and various reports exist in the literature showing both promoted and inhibited activity. In this work, we systematically studied five types of phosphate: orthophosphate, pyrophosphate, triphosphate, trimetaphosphate, and a polyphosphate with 25 phosphate units (Pi25 ). In addition, DNA oligonucleotides of various length and sequence. DNA was included as they contain a phosphate backbone that can strongly adsorb on nanoceria. We observed that a high concentration of DNA in acetate buffer inhibited activity, whereas a low concentration of DNA in phosphate buffer increased activity. The change of activity was also related to the type of substrate and related to the aggregation of CeO2 . These discoveries provide an important understanding for the further use of CeO2 nanoparticles in biosensor development, materials science, and nanotechnology.

High-strength anaerobic digestion wastewater treatment by aerobic granular sludge in a step-by-step strategy.

To reduce the instability of aerobic granular sludge (AGS) caused by high-strength anaerobic digestion wastewater, a strategy of increasing proportion of anaerobic digestion wastewater step-by-step was adopted in this study. High-performance stable AGSs were successfully cultivated with sequencing batch reactors by this strategy, which could efficiently treat high-strength anaerobic digestion wastewater with an influent chemical oxygen demand (COD) up to 5090 mg⋅L-1. After six phases of stepwise increasing COD loads, the sludge sizes increased from 0.5 mm to 1.5 mm, with the final mixed liquor suspended solids increased to 13,814 mg⋅L-1, and the final sludge volume index decreased to 15 mL⋅g-1. The extracellular polymeric substance (EPS), which is crucial to keep the stability of AGS, increased continuously from 85.1 mg⋅g-1 SS to 307.8 mg⋅g-1 SS with the increase of COD loads. Moreover, the removal efficiency of COD and TN could reach 92% and 87% for real high-strength anaerobic digestion wastewater treatment. The bacterial community analysis revealed that the family Rhodocyclaceae, Flavobacteriaceae, and Xanthomonadaceae were the major microbes of AGS, and were responsible for COD and TN removal, as well as EPS secretion. These findings may provide novel information and enrich AGS treatment of high-strength real wastewater.

Enhancing robustness of aerobic granule sludge under low C/N ratios with addition of kitchen wastewater.

Aerobic granular sludge (AGS) is one of the most promising biotechnologies for wastewater treatment. However, the instability of AGS at low carbon to nitrogen (C/N) ratios limited its application. In this study, kitchen wastewater addition in the influent was found to improve the morphology, characteristics, and treatment performance of AGS at low C/N ratios of 10, 5 and 2, which strongly reduced the negative impact of low C/N ratios on the biomass concentration, settleability, EPS secretion, stability and performance of AGS. At C/N ratio of 2, sludge disintegration was observed in RA with synthetic wastewater as influent, while the sludge in RB was able to keep a compact microbial structure with particle size of 1.0-1.5 mm. When C/N ratio decreased from 20 to 2 (phase 1 to 4), the MLSS, SVI and EPS secretion in RB were negatively affected at the beginning of each phase, but recovered to 4800 mg L-1, 60 mL g-1, and 86 mg/g SS at the end of phase 4 (C/N ratio of 2), which were 1.3, 0.6 and 1.3 times of those in RA, respectively. Meanwhile, the removal efficiencies of COD, TN, TP and NH4+-N in RB were 90%, 73%, 53%, and 99% at the end of phase 4, which were 1.1, 1.2, 2.2 and 2.4 times of those in RA, respectively. Thus, high-performance AGS with enhanced robustness and high abundance of HN-AD functional bacteria Paracoccus was obtained. These findings provided a promising and cost-effective method to improve the long-term stability and performance of AGS dealing with wastewater of low C/N ratio.

Applications of DART-MS for food quality and safety assurance in food supply chain.

Direct analysis in real time (DART) represents a new generation of ion source which is used for rapid ionization of small molecules under ambient conditions. The combination of DART and various mass spectrometers allows analyzing multiple food samples with simple or no sample treatment, or in conjunction with prevailing protocolized sample preparation methods. Abundant applications by DART-MS have been reviewed in this paper. The DART-MS strategy applied to food supply chain (FSC), including production, processing, and storage and transportation, provides a comprehensive solution to various food components, contaminants, authenticity, and traceability. Additionally, typical applications available in food analysis by other ambient ionization mass spectrometers were summarized, and fundamentals mainly including mechanisms, devices, and parameters were discussed as well. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:161-187, 2017.

CD44-Targeted Facile Enzymatic Activatable Chitosan Nanoparticles for Efficient Antitumor Therapy and Reversal of Multidrug Resistance.

Nanoparticles are attractive platforms for the delivery of various anticancer therapeutics. Nevertheless, their applications are still limited by the relatively low drug loading capacity and the occurrence of multidrug resistance (MDR) against chemotherapeutics. In this study, we report that the integration of d-α-tocopherol succinate (VES) residue with both chitosan and paclitaxel (PTX) led to significant improvement of drug loading capacity and drug loading efficiency through the enhancement of drug/carrier interaction. After the incorporation of hyaluronic acid containing PEG side chains (HA-PEG), higher serum stability and more efficient cellular uptake were obtained. Due to HA coating, VES residues and the enzymatic responsive drug release property, such facile nanoparticles actively targeted cancer cells that overexpress CD44 receptor and efficiently reversed the MDR of treated cells, but caused no significant toxicity to mouse fibroblast (NIH-3T3). More importantly, with HA-PEG coating, longer blood circulation and more effective tumor accumulation were achieved for prodrug nanoparticles. Finally, superior anticancer activity and excellent safety profile was demonstrated by HA-PEG coated enzymatically activatable prodrug nanoparticles compared to commercially available Taxol formulation.

Self-assembled selenium nanoparticles and their application in the rapid diagnostic detection of small cell lung cancer biomarkers.

By coupling molecular imprinting, chitosan biosorption and TiO2 photocatalysis, selenium nanoparticles (Se NPs) were self-assembled in a controlled manner on the molecular imprinting sites of zeolite-chitosan-TiO2 microspheres. Se NPs with different sizes and areal densities were individually synthesized by controlling the rapid adsorption of molecular-imprinted nanocomposites and photocatalytic reaction of TiO2 nanoparticles. In order to improve the sensitivity and specificity of rapid diagnostic detection, Se NPs were self-assembled again into high-order and spherically stable structures with an average size of 80 nm by well-defined monomer units, after separation from zeolite-chitosan-TiO2 microspheres with a stabilizer of 0.3% (v/v) bovine serum albumin. Due to their biological activity, spherical-shaped Se NPs were used for dot-blot immunoassays with multiple native antigens for rapid serodiagnosis of human lung cancer. The sensitivity of the dot immunoassays for detecting progastrin-releasing peptide (ProGRP) was 75 pg mL-1. The detection time of colloidal Se dot immunoassays for ProGRP was only 5 min. No positive results were observed with other commonly potential interfering substances, including carcinoembryonic antigen, α-fetoprotein antigen and BSA. The research presents a simple and green method for the reuse of SeO32- and the controlled synthesis of Se NPs for biological and medical applications by bioaffinity adsorption and photoreduction.

Visible-light-driven activity and synergistic mechanism of TiO2@g-C3N4 heterostructured photocatalysts fabricated through a facile and green procedure for various toxic pollutants removal.

Heterostructured photocatalysts based on g-C3N4 and TiO2 represent a promising kind of photocatalyst in environmental fields, but the synthesis methods are always complex and not green. In the present paper, a facile and green one-step calcination procedure at lower temperature (450 °C) with the assistance of water is developed to synthesize a visible-light-active TiO2@g-C3N4 heterostructured photocatalyst, which shows higher visible-light-driven activity (k = 0.014 min-1) than pure g-C3N4 (k = 0.0036 min-1) and TiO2 (k = 0.0067 min-1) for methyl orange degradation. Excellent performance (over 90% conversion) was also observed for the removal of rhodamine B, phenol, and Cr(VI) under visible light. The heterostructured photocatalyst showed favorable reusability, preserving 86% of its activity after five successive cycles. A mechanism study demonstrates that the enhanced photocatalytic activity results from the efficient separation of the photo-generated charge carriers through the intimate interface between the two semiconductors based on their appropriate band structures and light-induced mechanism. The heterostructured photocatalyst will certainly find wide applications in the treatment of various toxic pollutants in wastewater using abundant solar energy. Furthermore, this facile and green procedure and the proposed synergistic mechanism will provide guidelines in designing other g-C3N4 based organic-inorganic composite photocatalysts for various applications.

Facile synthesis of dispersed Ag nanoparticles on chitosan-TiO2 composites as recyclable nanocatalysts for 4-nitrophenol reduction.

This paper presents a facile, rapid, and controllable procedure for the recovery of trace Ag+ ions and in situ assembly of well dispersed Ag nanoparticles on chitosan-TiO2 composites through bioaffinity adsorption followed by photocatalytic reduction. The prepared Ag nanoparticles are proven to be efficient and recyclable nanocatalysts for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. Well dispersed quasi-spherical Ag NPs are synthesized in 20 min in the designed inner-irradiated photocatalytic system under a wide range of Ag+ concentrations (50-200 mg l-1), temperatures (10 °C-25 °C) conditions, and UV or visible light irradiation. The synthesized Ag NPs can catalyze the reduction of 4-nitrophenol by NaBH4 at 100% conversion in 120 min and preserve the catalytic activity in five successive cycles. This procedure for trace Ag+ ions recovery and Ag NPs assembly has the potential to be scaled up for the mass production of recyclable Ag nanocatalysts. The present work provides a green and efficient procedure for the conversion of hazardous 4-nitrophenol to industrially important 4-aminophenol and also sheds a light on designing scaled-up procedures for treating high volumes of wastewater with dilute heavy metals to produce recyclable metallic nanocatalysts in aqueous systems.

Combining microwave irradiation with sodium citrate addition improves the pre-treatment on anaerobic digestion of excess sewage sludge.

This study investigated the synergistic effect of sodium citrate (SC; Na3C3H5O(COO)3) and microwave (MW) treatment on the efficiency of the anaerobic digestion of excess sewage sludge. In terms of the methane yield, an increase of the digestion's efficiency was observed. Taking into account the cost for the MW energy supplied to the system, the optimum treatment conditions were a MW energy input of 20 MJ/kg TS and a SC concentration of 0.11 g/g TS, obtaining a methane yield of 218.88 ml/g VS, i.e., an increase of 147.7% compared to the control. MW treatment was found to break the sludge structure, thereby improving the release of extracellular polymeric substances (EPS) and volatile fatty acids (VFAs). The treatment of sodium citrate further strengthened the breakage of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound extracellular polymeric substances (TB-EPS). The increased VFA content stressed the improved digestion by this pretreatment. Furthermore, the preliminary economic analysis showed that at this point in the research, only operational but no financial gains were achieved.

Analysis of aerobic granules under the toxic effect of ampicillin in sequencing batch reactors: Performance and microbial community.

To study the change of the aerobic granules' microbial community in the present of antibiotics, ampicillin (AMP) was selected as a model component. With acetate as carbon source, different concentrations of AMP (5, 10 and 15 mg L-1) were applied to the inflow intermittently and the results showed that the stability of the aerobic granules was maintained below 10 mg L-1 AMP. Simultaneously, under exposure to 5 and 10 mg L-1 AMP, the COD removal efficiency in the batch reactors remained at 86% and AMP was degraded almost completely with a removal efficiency of 97%. However, the EPS concentration and dehydrogenase activity decreased constantly with increasing AMP dosage. High-throughput sequencing analysis revealed that Proteobacteria was the most prominent phylum in the whole experiment and contributed to the degradation of AMP. The percentages of Azoarcus and Mycoplana increased at 10 mg L-1 AMP. In addition, Hydrogenophaga and Enterococcus played a key role in the microbial metabolism.

Role and influence of extracellular polymeric substances on the preparation of aerobic granular sludge.

Due to the important role of the extracellular polymeric substances in the formation of aerobic granular sludge, the variation of the EPS contents in the process of cultivation and that in the one running cycle time were studied in this work. Aerobic granules with diameters between 0.8 and 1.1 mm were obtained within 30-35 days. The results suggested that the increase of EPS contents significantly contributed to the formation of aerobic granules. A linear relationship between the EPS and SVI was also developed, and it revealed that the aerobic granules had good settling property when the EPS exceeded 200 mg/g MLVSS. Two mainly components of EPS, protein (PN) and polysaccharides (PS), could act as the endogenous food for the microbes during the starvation period. The survival of the microbial population was jeopardized when the F/M ration was below 0.5 g COD/g SS d.