EPS Content Research Articles

Triple action of FeCl3-assisted hydrothermal treatment of digested sludge for deep dewatering

In this study, a FeCl3-assisted hydrothermal treatment (HTT) process under mild conditions (90 °C–130 °C) was developed for deep dewatering of anaerobically digested sludge. HTT of sludge at 90 °C–130 °C with 4%–6% Fe3+ ions loading based on total sludge solids followed by mechanical dewatering reduced sludge water content from 82% to 38%–53% and sludge weight by 62%–72%. The treatment increased the flowability of sludge through reduction of apparent viscosity and disintegration of colloidal forces between sludge particles. This study unveiled that FeCl3-assisted HTT process had three mechanisms for improving sludge dewaterability and flowability. The treatment hydrolysed sludge flocs in the presence of Lewis acid FeCl3 and high temperature (90–130 °C). Fe3+ ions also improved dewaterability through the formation of double electric layers and neutralisation of surface negative charges, leading to flocculation of sludge flocs. More importantly, the hydrolysed sludge components produced during HTT process acted as reducing agents and led to in-situ generation of iron oxyhydroxide nanoparticles through reduction-oxidation reactions, further enhancing flocculation/co-precipitation of sludge flocs. The treatment reduced EPS content and changed conformational structures of EPS proteins by breaking down hydrogen bond-maintaining α-helix which led to a loose EPS protein structure and enhanced hydrophobicity and flocculability. Furthermore, the FeCl3-assisted treatment promoted immobilisation of the majority of heavy metals in the sludge matrix through co-precipitation/complexation reactions with iron species and organic/inorganic matters. This indicates that the FeCl3-assisted treatment reduced direct toxicity/bioavailability of the majority of heavy metals and the treated sludge may be suitable for land application. Overall, this study provides new insights into mechanism of FeCl3-assisted HTT process for dewaterability of anaerobically digested sludge and immobilisation of heavy metals.

Extracellular polymeric substance profiling and biophysical analysis reveal influence factors of spontaneous flocculation in rich lipid alga Heveochlorella sp. Yu

Microalgae harvest and lipid accumulation were important factors influencing commercialized development of microalgae biodiesel. Spontaneous flocculation was an ideal method in microalgae harvest, but few rich lipid microalgae could be harvested by spontaneous flocculation. Rich lipid alga Heveochlorella sp. Yu has a characteristic of spontaneous flocculation to be harvested. Heveochlorella sp. Yu has high lipid productivity (105.24 mg L−1 d−1) and fine spontaneous flocculation efficiency (82.93 %, 2 h) on early stationary phase (day 9). The polysaccharides consisting of glucose, mannose, galactose, rhamnose and fructose (8.67:4.90:3.27:2.16:1) in loose-bound extracellular polymeric substance (LB-EPS) might make great contribution in microalgae flocculation. Meanwhile, the zeta potential close to zero was also beneficial to microalgae flocculation. Besides, the adhesion free energy related with cells adhesion was detected by thermomechanical analysis. Afterward, Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was utilized to quantitatively evaluate short-range interactions involved in the spontaneous aggregation among cells. Collectively, biophysical analyses indicated that content and composition of EPS, Zeta potential, thermodynamic parameter and total interaction based on XDLVO theory were closely connected with spontaneous flocculation in microalga Yu. Our study provided a harvest-simplified process of rich microalgae, which proposes a new idea for commercial development of microalgae biodiesel.

Layer-by-layer self-assembly of sodium alginate and zinc ions on the surface of graphene oxide to improve the fire protection ability of intumescent waterborne epoxy coatings

In this study, polyethyleneimine (PEI) was first adsorbed on the GO surface, resulting in a positively charged GO/PEI composite. Afterwards, SA and Zn2+ were loaded on the surface of GO/PEI through a facile route to obtain an organic-inorganic hybrids (GPS@Zn). Among them, the gas phase products of SA delayed the progress of the combustion reaction, while the catalytic carbonization of zinc oxide and the high barrier effect of GO effectively improved the thermal insulation efficiency of the char layer. The fire performance test results showed that the backside temperature of GPS@Zn/EP decreased to 161.2 °C after burning for 60 min. The swelling height and swelling ratio of GPS@Zn based EP remained at the highest value compared to the other samples. In addition, the residual char content of EP loaded GPS@Zn was as high as 31.2 %, which lays the foundation for its high thermal insulation performance. The PHRR, THR, SPR and TSP values of GPS@Zn/EP were 420.2 ± 13 kW/m2, 13.2 ± 0.6 MJ/m2,0.078 ± 0.05 m2/s and 1.87 ± 0.05 m2, respectively, which were significantly lower than the other samples, thus proving its best flame retardant and smoke suppressing properties. The carbon residue analysis confirmed that zinc oxide remained in the char layer, which was beneficial to the improvement of its thermal insulation performance and strength.

Biological characteristics of the gluten-free sourdough system fermented by Lactobacillus plantarum ST-III and its effect on dough quality and nutritional value during freezing.

In this study, the biological characteristics of wheat, tartary buckwheat, and wheat-tartary buckwheat sourdough systems fermented by Lactobacillus plantarum ST-III at different times were explored, and the quality and nutritional characteristics of sourdough frozen dough bread products with different fermentation substrates were investigated. Comparing the metabolic properties of sourdough during fermentation, it was found that the density of colony growth in TBS was the best, when fermented for 12h, the protein degradation effect was the best, and the content of EPS (3.109g/kg) and free amino acid was the highest. Although the quality of fresh TBS bread was worse than that of WS, after 13weeks of frozen storage, the quality deterioration of TBS frozen dough bread was the smallest, the water migration rate was slower, and the protein digestibility was higher. Therefore, tartary buckwheat sourdough system can delay the degradation of bread quality and nutrition.

Coupling of sponge fillers and two-zone clarifiers for granular sludge in an integrated oxidation ditch

Considering that aerobic granular sludge (AGS) exhibits a long granulation time in continuous flow and that the poor removal effects on N and P have severely restricted its large-scale application, a novel strategy was developed involving sponge fillers to construct an anoxic zone coupling two-zone clarifiers to promote granulation in an integrated oxidation ditch. The different pores in the sponge fillers were used to accelerate the accumulation and formation of aggregates under the impetus of water flow, meanwhile, the A/O operation mode and the formation of AGS were also improved the denitrification and phosphorus removal capacity of the reactor. The experimental results indicated that AGS was shaped in the anoxic and aerobic zones on day 30 and on day 43, respectively. When running for 90 days, the mixed liquor suspended solids (MLSS), sludge volume index (SVI5) and average particle size in the anoxic zone and aerobic zone were 5848 mg/L and 4812 mg/L, 31.2 mL/g and 35.8 mL/g, and 329.2μm and 362.3μm, respectively. During the granulation process, the EPS content in the anoxic zone was significantly higher than that in the aerobic zone, indicating that the sponge fillers played a dominant role in granulation. After the reactor reached steady conditions, the removal efficiencies of COD and N were 87.29%±2.61% and 60.11%±4.68%, respectively. The TP removal efficiency gradually increased from 26.90% on day 1 to 77.54% on day 90. Moreover, the microbial community transformed conspicuously throughout granulation, including an enrichment of microorganisms exhibiting EPS secretion and pollutants degradation.

Transition of fouling characteristics after development of membrane wetting in membrane-aerated biofilm reactors (MABRs)

The practical applications of water treatment techniques based on hydrophobic aeration membrane are limited due to membrane pores blocking. Various studies have revealed that both biofilm and microbial secretion can exacerbate membrane fouling. Recently, we constructed a membrane-aerated biofilm reactor (MABR) system for treating micro-polluted surface water in order to identify the primary cause for oxygen transfer rate (OTR) decline. It was found that microbial secretion had a more prominent negative effect than that caused by biofilm, as manifested by the fact the effect of microbial secretion (66.49%) was greater than the resistance of biofilm (38.83%). Fouling decreased the total pore volume of all membrane. The peak location of adsorption capacity was more likely to occur at smaller pore sizes with longer running time. Notably, continuous fluorescence distribution between the separating layer and pores like finger in MABR system exhibited an increasing trend with the operation time, indicating a gradual increase of microbial viability. Core protein structure was revealed by different bond peaks (0–90 d). Specifically, for different organic components of EPS, the hydrophilic HIS was the main content, while the mass transfer resistance caused by the gel increased, which reduced the contact angle and increased the bubble point pressure. Therefore, effects of EPS content and composition should be considered during the application of water treatment techniques based on MABR.

Metagenomics uncovers the effect of nitrogen-doped graphene on anammox consortia and microbial function

The effect of 50 mg/L nitrogen-doped graphene (N-G) on anammox microbial guild was studied by metagenomics in this paper. The continuous experiment results showed the average NRE improved by 17.57% with N-G addition. The metagenomic analysis revealed N-G significantly increased the relative abundance of dominant AnAOB (Candidatus Kuenenia) from 18.10% to 28.30%. And the FISH assay further manifested N-G promoted the growth of AnAOB biomass. Meanwhile, metagenomics indicated that N-G enriched the abundance of genes (Hzs, Hdh, NosZ, NorB, NirK, NirS and NrfA) involved in nitrogen metabolism to varying degrees. Furthermore, N-G not only improved the microbial functionality in terms of “Metabolism”, but markedly upregulated the abundance of c-di-GMP synthesized genes and genes related to quinolone signal molecule, which contributed to more EPS content and better sludge settleability. In brief, this study provided a novel perspective for anammox biomass enrichment, which may be valuable for practical engineering applications of anammox.

Modification of mechanical properties of Shanghai clayey soil with expanded polystyrene

Abstract In the present study, the resistance characteristics of Shanghai clayey soil-expanded polystyrene (EPS) mixture have been explored, using unconfined compressive and consolidation and rebound tests. EPS beads were mixed homogenously with clay soil in accordance with different mass ratios of beads to soil, that is, 0, 0.02, and 0.03%. Four particle sizes of EPS were used in the mixtures, that is, 0.5, 1, 3, and 7 mm, to reconstruct the samples. The experimental results indicated that (1) under the condition of unconfined compressive test, with the increase of EPS particle size, the compressive strength of reinforced soil increases significantly, but the compressive strength of reinforced soil decreases compared with the control sample, and it also decreases with high content compared to low EPS content; (2) under the consolidation and rebound test, compression index and rebound index of reinforced soil increased obviously compared with the control sample, but the compression modulus of reinforced soil decreases significantly; (3) in addition, the ductility of reinforced soil decreases with the increase of EPS particle size but increases compared with the control sample. At the same time, the stiffness of reinforced soil is much decreased compared with the control sample. Finally, the cause of deformation characteristics of reinforced soil was explained based on the feature of EPS material and the interaction between soil particles and particles of EPS beads.

Mechanism and regulation of filamentous algal-bacterial symbiosis based on microbiological quorum sensing.

In algae-bacteria symbiotic systems, algae and bacteria work cooperatively to reduce aeration demand and carbon emissions during wastewater treatment. However, controlling and stabilizing microbial communities in the conventional algae-bacteria symbiotic systems are complicated and unstable. We, therefore, developed a novel sewage treatment system based on a filamentous algae-bacterial symbiotic granule system (AB) in a photo-sequencing batch reactor (PSBR). The exogenous signal molecules (i.e., N-acyl-homoserine lactones [AHLs]) were applied to promote the algae-bacteria consortia formation. The characteristics and performance of the mature algae-bacterial granular consortia were investigated and then compared with that of the activated sludge (AS) system under identical operating conditions. The chemical oxidation demand (COD) removal efficiencies were greater than 90% in the dynamic synergistic investigation, even without aeration. However, the addition of AHLs (5, 50, and 200 nmol/L) had a negligible effect on treatment performance. In static conditions, 10-9nmol/L of AHLs can significantly regulate the algae-bacteria symbiotic system, and AHLs (<50 nmol/L) improved COD and NH4 + removal efficiencies by up to 90%. Moreover, the addition of AHLs augmented polysaccharide secretion but had little effect on protein secretion. In comparison to the AS system, the AB system demonstrated promise in terms of pollution removal efficiency and microbial diversity enhancement. PRACTITIONER POINTS: Oscillatoria can serve as an excellent biological carrier for immobilizing bacteria. AHLs (10-9mol/L) regulated the operation state of algae-bacteria symbiotic system. AHLs altered the composition and content of EPS in the algae-bacteria system.

Improvement of sludge characteristics and mitigation of membrane fouling in the treatment of pesticide wastewater by electrochemical anaerobic membrane bioreactor

Electrochemical anaerobic membrane bioreactor attracted attention due to stable treatment quality with low footprint, and draw solute has significant effect on the sludge characteristics and membrane fouling performance. In this pilot-scale study, an electrochemical anaerobic membrane bioreactor (E-AnMBR) was proposed for treating pesticide wastewater at different hydraulic retention times (HRTs), demonstrating that E-AnMBR was superior on improvement of sludge characteristics and mitigation of membrane fouling, compared with the conventional anaerobic membrane bioreactor (C-AnMBR). E-AnMBR reduced sludge yield by 41.2 ± 6.7% and the SVI was significantly decreased by 32.5±13.8%. The accumulation of VFA in E-AnMBR was slighter than that of C-AnMBR, and the minimum average VFA was 255±6 mg/L. The methane yield of E-AnMBR (0.22–0.29 L CH4/g CODremoved) was 1.2–1.4 times than that of C-AnMBR. The EPS contents in suspended and attached sludge of E-AnMBR were significantly reduced by 41.8 ± 3.3% and 77.4 ± 14.5% than that of C-AnMBR, respectively. These results suggested that E-AnMBR has lower sludge disposal pressure, higher stability and methane recovery potential. Not only that, E-AnMBR successfully reduced membrane resistance, delaying the fouling rate by 31.0–38.5%. Finally, the linear relationship between EPS characteristics and membrane pollution was determined.

Influence of N ∶P ratio on the phosphorus accumulation and distribution of &lt;i&gt;Microcystis&lt;/i&gt; and &lt;i&gt;Scenedesmus&lt;/i&gt;

太湖水体氮浓度及氮磷比的改变可能影响藻类对磷元素的赋存及分配，进而影响水体总磷浓度. 为此，本研究选取常见蓝藻(群体微囊藻和单细胞微囊藻)和绿藻(斜生栅藻)，设置低氮磷比(N ∶P=2)和高氮磷比(N ∶P=20)培养实验，分析藻体胞内磷(INT-P)和胞外磷(EPS-P)含量、形态及分布，探究氮磷比对藻体磷元素赋存及分配的影响. 结果表明：低氮磷比组斜生栅藻和群体微囊藻的藻体磷(CTP，即INT-P与EPS-P之和)显著增加，分别为高氮磷比组的2.7和1.4倍. 斜生栅藻和群体微囊藻EPS-P含量(约占CTP的80%)分别增加了3.1和0.48倍，而INT-P含量对氮磷比无明显响应. 低氮磷比组的斜生栅藻和群体微囊藻EPS含量分别增加了51.7% 和63.5%. 此外，微囊藻的CTP与EPS-P主要以可交换态活性磷存在，而INT-P主要以铁铝结合态磷存在. 本研究发现低氮磷比促进了藻类EPS分泌，导致EPS-P升高，显著增加了藻体颗粒态磷的含量. 这或许是近年来太湖水体总磷波动的原因之一.;Variations of nitrogen (N) concentration and the ratio of N to phosphorus (P) in Lake Taihu may impact P accumulation and allocation of algal cells, and even influence total P concentration in water. In this study, common cyanobacteria (colonial and unicellular Microcystis strains) and a green alga (Scenedesmus obliquus) were cultured in different N ∶P groups (N ∶P=2 and N ∶P=20). Changes in their P forms, content, and distribution (intracellular P (INT-P) and extracellular P (EPS-P)) were explored. Results showed that the total cellular P contents (CTP, including INT-P and EPS-P) of S. obliquus and colonial Microcystis in the low N ∶P group were 2.7 and 1.4 times higher than those in the high N ∶P group, respectively. In the low N ∶P group, EPS-P occupied about 80% of the CTP. Particularly, EPS-P contents of the low-N ∶P treated S. obliquus and colonial Microcystis increased by 3.1 and 0.48 times higher than those of the high N ∶P group. In the low N ∶P groups, EPS content of S. obliquus and colonial Microcystis increased by 51.7% and 63.5%, respectively. However, changes of INT-P were not significant in both species. Moreover, CTP and EPS-P mainly existed as NH₄Cl-P, while INT-P was mainly found as Fe/Al-P. These findings revealed that low N ∶P ratio affects the P accumulation and distribution patterns of algal cells, by promoting EPS secretion and EPS-P accumulation. It may be a potential reason for total P fluctuation in the water of Lake Taihu.

Robustness of the partial nitrification-anammox system exposing to triclosan wastewater: Stress relieved by extracellular polymeric substances and resistance genes

The partial nitrification-anammox (PN/A) process is a promising method for the treatment of municipal wastewater. It is necessary to clarify the responses of PN/A system to antimicrobial agent triclosan (TCS) widely existed in the influent of wastewater treatment plants. In this study, it was found that PN/A system was robust to cope with 0.5 mg/L TCS. Specifically, the control reactor reached 80% total nitrogen removal efficiency (TNRE) on day 107, while the reactor feeding with 0.5 mg/L TCS reached the same TNRE on day 84. The results of the activity test, high-throughput sequencing and DNA-based stable isotope probing showed that 0.5 mg/L TCS did not impede the performance of ammonia oxidizing archaea, ammonia oxidizing bacteria (Nitrosomonas) and anammox bacteria (Candidatus Brocadia and Ca. Kuenenia), but significant inhibited the nitrite oxidizing bacteria (Nitrospira and Ca. Nitrotoga) and denitrifying bacteria. The influent TCS led to the increase of EPS content and enrichment of four resistance genes (RGs) (intI1, sul1, mexB, and tnpA), which might be two principal mechanisms by which PN/A can resist TCS. In addition, functional bacteria carrying multiple RGs also contributed to the maintenance of PN/A system function. These findings improved the understandings of antimicrobial effects on the PN/A system.

A dynamically controlled anaerobic/aerobic granular sludge reactor efficiently treats brewery/bottling wastewater.

This study investigated the application of a dynamic control strategy in an aerobic granular sludge (AGS) reactor treating real variable brewery/bottling wastewater. For 482 days, the anaerobic and aerobic reaction steps in a lab-scale AGS system were controlled dynamically. A pH-based control was used for the anaerobic step, and an oxygen uptake rate (OUR) based control for the aerobic step. Additionally, the effect of an elongated aerobic step, and the effect of the removal of the suspended solids from the influent, on AGS formation were also investigated. In comparison to a static operation, the dynamic operation resulted in similar reactor performance, related to effluent quality and the anaerobic dissolved organic carbon (DOC) uptake efficiency, while the organic loading rate was significantly higher. The removal of suspended solids from the influent by chemical coagulation with FeCl3 turned hybrid floccular-granular sludge into fully granular sludge. The granulation coincided with a significant increase in the abundance of the glycogen-accumulating Candidatus Competibacter and an increase in the content of gel-forming EPS to respectively around 14% and 30%. In conclusion, this study showed the successful application of a dynamic control strategy based on common and low-cost sensors for AGS treatment of industrial wastewater.

Exploration of mechanisms for calcium phosphate precipitation and accumulation in nitrifying granules by investigating the size effects of granules

Calcium phosphate could be accumulated in aerobic granules, which attracts attention recently for phosphorus removal and recovery from wastewater. In this study, partial nitrifying granules with high calcium precipitate content were sorted into different size groups for characterization and evaluation to reveal the dynamic balance of granules at stead state and relevant calcium phosphate precipitation and accumulation mechanism. It was found that light yellow small granules without calcium precipitates but high microbial activity co-existed with deep brown granules with calcium precipitate of around 91% and low microbial activity. Characterization with specific oxygen uptake rates, specific ammonium oxidation rates, calcium and phosphate removal rates from solution, EPS contents, elemental compositions by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for different size groups of granules enabled a proposal of a new hypothesized mechanism for calcium precipitation and accumulation. With this proposed mechanism, it is believed that sufficient granule retention time in reactors was critical for the accumulation of calcium precipitates followed by a slow microbial growth rate of biomass due to mass transfer resistance. The co-precipitation of calcium carbonate and calcium phosphate mainly occurred in granules with a size less than 710 µm while calcium phosphate dominant minerals were accumulated in granules larger than 710 µm. The results and conclusions in this study shed light on the mechanisms of calcium phosphate accumulation in granules, which could be used to better operate and control aerobic granular sludge with calcium phosphates for phosphorus removal and recovery.

Screening and identification of Euphorbiae pekinensis Rupr. anti-angiogenic multi-components with UPLC-QTOF-MS in zebrafish

Euphorbia pekinensis Rupr. (EP) (Euphorbiaceae), as Traditional Chinese Medicine (TCM), exhibits therapeutic effects on tumors in clinical practice. Anti-angiogenesis may be an underlying molecular mechanism of EP’s actions. However, the anti-angiogenic active ingredients of EP remain unclear. The screening and analysis of anti-angiogenic agents were essential for the sufficient utilization and development of EP. Thus, we established a UPLC-QTOF-MS method based on a transgenic zebrafish model to screen anti-angiogenesis activity components in EP. UPLC-QTOF-MS was used to characterize compounds from EP and in vivo compounds in Tg (flk1: mCherry) zebrafish larvae treated with EP. Based on the identification results, five components were selected, and their anti-angiogenesis activity were investigated via assessment of intersegmental blood vessels during the development of the transgenic zebrafish. Three of these components (3,3′-O-dimethoxy ellagic acid, quercetin, and ingenol) are active components of EP with anti-angiogenic effects. Among them, 3, 3′-O-dimethoxy ellagic acid and ingenol were first demonstrated with anti-angiogenesis effects. UPLC-PDA analysis was performed on EP water extracts to determine anti-angiogenesis active ingredients quantitatively. In the concentration range of 100–200 μg/mL, EP and the active ingredient compositions, mixed according to the content of EP, had equivalent anti-angiogenesis activities. These experimental results indicate that the UPLC-QTOF-MS method, combined with a transgenic zebrafish model, is rapid, sensitive and reliable. The combination in TCM offers the potential to achieve certain effect levels with lower concentrations of the individual compound.

Shortening SRT of Intermittent Gradient Aeration to Realize Nitrogen and Phosphorus Removal in Short-range SNEDPR System

This study explored the effect of sludge retention time (SRT) on ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) under intermittent gradient aeration, as well as the effect of the short-range nitrification endogenous denitrification phosphorus removal system on the treatment of low C/N ratio domestic sewage. In this study, an SBR reactor was used to cultivate aerobic granular sludge, using actual domestic sewage as the influent substrate. As the SRT decreased from 50 d to 30 d, the specific ammonia oxidation rate increased from 3.16 mg·(g·h)-1to 4.38 mg·(g·h)-1, and the specific nitrite oxidation rate decreased from 3.4 mg·(g·h)-1to 1.8 mg·(g·h)-1. The activity of NOB decreased by about 44%, resulting in short-range nitrification within the system. With an SRT of 30 d, the maximum nitrite accumulation was 6.93 mg·L-1. Because the reduced SRT led to a slight decrease in sludge concentration within the system, an aeration reduction strategy was adopted after 40 d, according to the DO curve. When the final SRT was 30 d, the effluent COD concentration was 40.76 mg·L-1, the TN concentration was 12.4 mg·L-1, the TP concentration was 0.31 mg·L-1, and the simultaneous removal of C, N and P was realized. Thus, a stable short-range nitrification endogenous denitrification phosphorus removal system was finally obtained. At the same time, the EPS content of aerobic granular sludge was negatively correlated with SRT, the protein content increased from 66.7 mg·g-1 to 95.1 mg·g-1, and the polysaccharide content remained in the range of 12.1-17.2 mg·g-1, indicating that the decreased SRT had a great effect on the protein content. With an SRT of 30 d, the PN/PS value was maintained at approximately 6.2, and the structural stability of aerobic granular sludge can be maintained under such conditions.

The feasibility of aerobic granular sludge formation without inoculated sludge

In this study, the feasibility of aerobic granular sludge formation without inoculated sludge was detected. After 10 days operation, AGSs were discovered in reactor and the MLSS and settling ability of AGS enhanced gradually. After 21 days operation, the effluent NH4 +-N and COD keep low than 10 and 100 mg/L, respectively. During the formation of AGS, the content of EPS gradually increased and remained stable. Microbial community showed that EPS secretion genera (such as Paracoccus, Flavobacterium and Thauera) were main genera in AGS.

Effects of 5-hydroxymethylfurfural on removal performance and microbial community structure of aerobic activated sludge treating digested swine wastewater

5-Hydroxymethylfurfural (HMF) is a high value-added chemical, the starting material for the production of a large number of platform chemicals, and an inhibitor of anaerobic digestion. The selection of microorganisms that can metabolize HMF or have high tolerance to HMF is rapidly arousing scientific interest. For selecting suitable microorganisms from aerobic sludge and exploring the effects of HMF on aerobic digestion, the removal capability, activated sludge characteristics, and microbial community structure of activated sludge treating digested swine wastewater in the presence of HMF were studied. Results showed that HMF deteriorated the removal performance of activated sludge. Removal rates of chemical oxygen demand (COD), total phosphorus (TP) and ammonium (NH4+-N) were reduced from 95.7%, 84.6% and 80.0% to 46.5%, 77.6% and 21.0%, respectively. Besides, HMF also increased EPS content which reduced the settleability and dewatering capacity of activated sludge. Moreover, HMF inhibited dehydrogenase (DHA) activity in activated sludge and increased superoxide dismutase (SOD) activity. Meanwhile, the functions of microorganisms had changed, extracellular structure increased, carbohydrates and lipids transport and metabolism decreased, and energy production and conversion were inhibited. Microbial community analysis illustrated HMF adversely affects Enterobacteriaceae and streptococcaceae, while Bacillaceae, Rhodocyclaceae and Nitrospira better tolerate HMF.

Assessment of the compression characteristics and coefficient of lateral earth pressure of aggregate-expanded polystyrene beads composite fill-backfill using large oedometer experiments

We examined the compression behaviour of aggregate-expanded polystyrene (EPS) granular composites using large-size oedometer tests measuring directly the coefficient of lateral earth pressure at rest (K0). The results showed that increasing the aggregate particles size led to a decrease of K0 and the coefficient of volume compressibility, in pure aggregates and aggregate-EPS composites with rigid particles of d50<2mm. Increased angularity and coefficient of uniformity were observed to display competitive mechanisms in controlling K0. The increase of EPS content led to a transition from a behaviour dominated by aggregate contacts to aggregate-EPS and EPS-EPS major contributions in the load transfer mechanism.

Enhanced dimensional stability and mechanical properties of SBR/EVA foam by a scaffold structure constructed in the bubble cavity-wall

The poor dimensional stability of rubber foam directly restricts its industrialization. Hence, a scaffold structure was constructed by controlling zinc oxide (ZnO) particles with a small amount of bisphenol-A epoxy resin (EP), which effectively improved the dimensional stability and made it have a promising application prospect. The scaffold structure has controlled ZnO particles densely and evenly distributed in the bubble cavity-wall of styrene butadiene rubber/ethylene vinyl acetate (SBR/EVA) foam. The construction of the scaffold structure was ascribed to EP with high N2-affinity and strong infiltration to ZnO particle based on cell nucleation in the cavity at the melt−nucleator interface. The construction mechanism and the effect of the scaffold structure on dimensional stability and mechanical property of SBR/EVA foams were investigated by scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction. Compared with SBR/EVA foam, the shrinkage of SBR/EVA foam with the scaffold structure was reduced by 19.4%. The rigidity increased by 59.8% and decreased the toughness by only 3.87% at 3 phr EP content. And its compressive stress (60%) was about 8 times that of SBR/EVA foam. Meanwhile, the ZnO particles were densely and evenly distributed in the bubble cavity-wall that can reinforce the flame retardant of SBR/EVA foams.