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Allomyrina dichotoma has a natural ultra-high flying ability and maneuverability. Especially its ability to fly flexibly in the air, makes it more adaptable to the harsh ecological environment. In this study, a bionic flapping-wing micro air vehicle (FMAV) is designed and fabricated by mimicking the flight mode of A. dichotoma. Parametric design was employed for combining the airframe structure and flight characteristics analysis. To improve the transmission efficiency and compactness of the FMAV mechanisms, this study first analyses the body structure of A. dichotoma, and then proposes a novel mechanism of FMAV based on its biological motion characteristics, the flight motion characteristics, and its musculoskeletal system. By optimizing the flapping-wing mechanism and mimicking the flying mechanism of A. dichotoma, the large angle amplitude and the high-frequency flapping motion can be achieved to generate more aerodynamic force. Meanwhile, to improve the bionic effect and the wing performance of FMAV, the flexible deformation of A. dichotoma wings for each flapping period was observed by a high-speed camera. Furthermore, the bionic design of wings the prototype was carried out, therefore the wings can generate a high lift force in the flapping process. The experiment demonstrated that the aircraft can achieve a flapping angle of 160 degrees and 30 Hz flapping frequency. The attitude change of FMAV is realized by mimicking the movement for the change of attitude of the A. dichotoma, by changing the angle of attack of the wing, and executing the flight action of multiple degrees of freedom including pitch, roll and yaw. Finally, the aerodynamic experiment demonstrated that the prototype can offer 27.8 g lift and enough torque for altitude adjustment.

The transport and concentration distribution of sludge in a high performance anaerobic bioreactor, termed spiral symmetry stream anaerobic bioreactor (SSSAB), was directly related to its effective retention of the biomass, as well as its stable operation under high loading rate. Therefore, the transport and concentration distribution of sludge in a lab-scale SSSAB were modelled and investigated in comparison with a same-sized upflow anaerobic sludge blanket reactor (UASBR), and two larger scale SSSABs were used for validating and expanding the application field of the model. The results showed that the model established can effectively describe the sludge transport and concentration distribution in the SSSAB. The SSSAB performed relatively low sludge transport factor compared with the UASBR, proving the favorable sludge retention ability of the SSSAB. The sludge transport factor remained constant with the scale-up of the SSSAB. The model could predict the sludge concentration distribution of a 130 L SSSAB treating traditional Chinese pharmaceutical wastewater. Also, the model can be applied to the SSSAB treating other types of wastewater with biogas production fractions in zone 1 and 2 (f1 and f2) at the ranges of 0.19–0.41 and 0.18–0.41, respectively.

Abundant organic compounds in textile dyeing sludge (TDS) provide possibility for its anaerobic digestion (AD) treatment. However, preliminary test showed little biogas generation in direct AD of the TDS during 20 days. In order to improve the AD availability of TDS, alkaline, acid, thermal and thermal alkaline pretreatments were performed. Color and aromatic amines were specifically measured as extra characteristics for the AD of TDS. The rate-limiting steps of AD of TDS were slow hydrolysis rate and inhibited acidogenesis, which were somewhat overcome by pretreatments. Thermal alkaline pretreated TDS performed best enhancement on solubilisation. The biochemical methane potential tests revealed that thermal pretreated TDS showed highest total methane production of 55.9 mL/g VS fed compared to the control with little methane generation. However, thermal alkaline pretreated TDS did not perform well in BMP test as expected. Moreover, the hydrophilicity of reactive dyes in TDS could seriously affect dewaterability of TDS.

Inhibitory effect of azo dyes on anaerobic methanogenic wastewater treatment (AMWT) has been studied mainly focusing on biological toxicity in the batch test with simulated sole co-substrate. Detailed information on inhibitory effect and mechanism of azo dyes during the long-term operation with real complex co-substrate is limited. Moreover, whether redox mediator (RM) could remediate the inhibition is still unclear in previous studies, especially under the complex scenario. In this study, the real textile wastewater with alternative concentrations of azo dyes (0-600 mg/L) were used to operate a lab-scale high-rate anaerobic methanogenic bioreactor for 127 days, and 50 μM anthraquinone-2-sulfonate (AQS) as RM was added at the last period of operation. Azo dyes with concentration of 600 mg/L could cause significant inhibition on overall (decolorizing and methanogenic) performance of AMWT. Specific methanogenic activity assays showed that acetoclastic methanogens was more susceptible to high concentration azo dyes than hydrogenotrophic methanogens. The spatial distribution of extracellular polymeric substance in the anaerobic granular sludge (AGS) showed that the high biological toxicity of azo dyes was mainly attributed to enrichment effect in tightly bound-EPS (TB-EPS). The channels of AGS was clogged by azo dyes, which was evidenced by the hard release of aromatic amines in EPSs as well as decreased porosity of AGS and scanning electron microscope images. Meanwhile, the settling ability, particle size and strength of AGS all deteriorated after azo dyes concentration exceeded 450 mg/L. The dosing of AQS could mostly remediate overall performance of the bioreactor even if the recovery of acetoclastic methanogens was slow. However, except for the porosity with a part of recovery, physical characteristics of AGS hardly recovered, and washout of sludge from the bioreactor was still happening. It suggested that additional attention should be paid to prevent sludge from washout if RM was practically used to remediate the anaerobic reactor inhibited by azo dyes.

The soluble redox mediator had been employed for catalyzing anaerobic bio-reduction of recalcitrant contaminants such as azo compounds (mainly azo dyes), nitroaromatics, halogenated pollutants and high valence heavy metal, etc. However, the continuous dosing of soluble redox mediators would not only be economically unreasonable, but also have a risk of causing secondary pollution. Therefore the insoluble/immobilized redox mediators were widely studied in last decades trying to overcome above drawbacks. This paper reviewed insoluble redox mediators including carbonaceous (activated carbon, emerging activated carbon fiber, carbon nanotubes, graphene oxide and biochar) and natural materials (humin and henna plant), as well as immobilized redox mediators such as immobilizing model quinones or humic acid on calcium alginate, polyurethane foam, Poly(ethylene terephthalate) fiber, anion exchange resin, etc. The catalyzing performance, characteristics, disadvantages (if any) and lab-scale applications of those insoluble/immobilized RMs were critically discussed, in order to provide reference for the evolvement and promoting further utilizations of novel insoluble/immobilized redox mediators. In addition, future research needed was suggested towards the engineering application of insoluble/immobilized redox mediators.

An anaerobic process, termed the spiral symmetry stream anaerobic bioreactor (SSSAB), had been developed by setting inner components of elliptic plates and gas collection pipes. And our previous study had demonstrated that a SSSAB was more efficient and stable than a same-sized up-flow anaerobic sludge bed (UASB) reactor. This study investigated the optimum treatment efficiency and super-high-rate mechanisms for the SSSAB. The performance with super-high-rate organic loading rate (OLR), volumetric removal rate (VRR) and improved volumetric methane production (VMP) of 361.5 kg COD/(m 3 d), 268.3 kg COD/(m 3 d) and 73.0 m 3 /(m 3 d), respectively, were revealed for a lab-scale SSSAB. The elliptic plates set in the SSSAB could form spiral flow which increased along with the shortening of hydraulic retention time (HRT). The super-high-rate mechanisms were analyzed in terms of biomass, transfer condition around granules and sludge activity. The sludge retention ability in the SSSAB was achieved by the gas entrapment role of elliptic plates and gas collection pipes. The transfer condition around the granular sludge was changed to adapt to the variation of OLR. The rich channels of granules provided a favorable environment for substrate in and product out. The difference of methane productions between the batch test and the reactor operation illustrated that high substrate concentration and especially dramatic mixing condition in the SSSAB were significantly responsible for the super-high efficiency of SSSAB.

The dispersion characteristics of an anaerobic reactor affect its flow patterns and consequently impact its removal efficiency η (assumed). The dispersion characteristics of a spiral symmetry stream anaerobic bio-reactor (SSSAB) were investigated under overall and local dispersion conditions, which were well described by the axial dispersion model and increasing-sized CSTRs model, respectively. The flow patterns of the SSSAB under super-high (hydraulic loading rate L = 18.45 L L −1 d −1 , biogas production rate G = 80.24 L L −1 d −1 ) and high loadings ( L = 9.23 L L −1 d −1 , G = 40.12 L L −1 d −1 ) tended to the completely mixed flow, while under middle ( L = 4.61 L L −1 d −1 , G = 20.06 L L −1 d −1 ) and low loadings ( L = 2.31 L L −1 d −1 , G = 10.03 L L −1 d −1 ) tended to the plug-flow. The axial dispersion decreases along the height of the SSSAB. The fluid in the reactor mixed completely after the actual completely mixed time θ acm , which decreases from 1.54 to 0.44 with the loading rate increases. The maximum and minimum values of the mean increasing rate v m are 14.00 and 0.72 at super-high and loading rate, respectively. And η positively correlates to the number of tanks N and negatively to v m . Reducing v m and enlarging N are the favorable method to further improve the treatment efficiency for the reactor operated under low or medium loading and high or super-high loading conditions, respectively.

The rheological behaviors of the anaerobic granular sludge (AGS) in a spiral symmetry stream anaerobic bioreactor (SSSAB) were investigated. Shear-thinning behavior, thixotropic behavior, concentration–viscosity behavior and temperature–viscosity behavior were evaluated based on the constitutive equation of the AGS. The results indicated that the Herschel–Bulkley model was able to adequately describe the constitutive relation of AGS in the SSSAB. The AGS also showed shear-thinning behavior as well as thixotropic behavior. The critical shear rate and network strength of the AGS were 61.8 s−1 and 497.0 W m−3, respectively. The relationship between the apparent viscosity and the sludge concentration was illustrated and explained by the Woodcock formula. The relationship between apparent viscosity of the AGS and temperature could be modeled using the Arrhenius equation. The AGS was significantly thermo-sensitive and its mean energy of activation was 14.640 kJ mol−1. Notably, it was necessary to consider such behaviors in the hydrodynamic modeling of SSSAB in which shear condition, sludge concentration and temperature were in non-uniform distribution.

Artificial redox mediators (ARM) have been proven to accelerate the azo dye anaerobic bio-reduction (ADAB) but the mechanisms involved are still unclear. Previous studies do seldom focus on the production of methane during the ADAB, particularly if supplemented with ARM. Our studies revealed that the supplement of ARM could significantly accelerate the decolorization rate, recover the inhibited methanogenesis and decrease extracellular polymeric substance secretion in an ADAB system. Supplement of an ARM only enhanced the pre-existing metabolic pathway of the ADAB system. Significant differences in metabolic pathway and microbial community were found between traditional methanogenic system and ADAB system by high-throughput sequencing technique. The ADAB system performed an “over-requirement for electron donor” phenomenon and the requirement amount can be altered by regulating ARM dosage. Response surface methodology was then successfully employed to optimize the dosage of ARM and possible additional electron donor required for ADAB under different conditions.

Since the inocula for the start-up of the anaerobic reactors (ABs) is still limited in many places, the expansion of the source of feeding anaerobic granular sludge is critical for the appl...

The minimization and methane production of textile dyeing sludge (TDS) can be simultaneously attained via anaerobic digestion (AD). However, the possible toxicity and complex recalcitrant organic matters involved in limited the hydrolysis of TDS. Therefore, the low-temperature of thermal pretreatment (LTTP) lasting for 1h at temperatures from 60 to 100°C was employed to accelerate the hydrolysis and subsequent methane generation of TDS. The results showed that LTTP with temperatures higher than 70°C obviously improve the AD performance of TDS. Highest accumulative methane production was achieved for 100°C pretreated TDS and from thermal analysis point of view it was due to the disintegration of some recalcitrant macromolecules in TDS. Nevertheless, 90°C pretreated TDS did not perform favorable methane yield as expected, attributing to the inhibited acetogenesis as well as the hindered methanogenesis which was simultaneously competed by dye reducer for electrons.

BACKGROUND The models presented for bed optimum fluidization velocity (uopt), which was worthwhile for treatment efficiency and operation stability of anaerobic fluidized-bed bioreactors (AFB), were developed for AFB, and the anaerobic granular sludge diameter (dp) and shape were analyzed by a dynamic image analyzer. RESULTS The results showed that the granular size from 0.05 to 0.30 cm sludge dominated the total biomass (accounted for 92.34%) in an expanded granular sludge bed reactor, the mean sphericity 0.835 and mean granular diameter 0.1606 cm were achieved. The uopt range was 0.000949–0.2851 cm s-1 when dp was 0.05–0.30 cm, and the fluidization number was 8.43–38.77. The maximum value of 0.2851 cm s-1 was the basic parameter for pump power matching. From parametric sensitivity analyses, uopt was significantly influenced by liquid holdup, granular diameter, granular density and liquid viscosity. CONCLUSION According to the models of uopt, a better operating scheme for AFB can be provided; from parametric sensitivity analysis, further optimizing designs of such bioreactors can be achieved. © 2013 Society of Chemical Industry

The shock resistance characteristic (SRC) of an anaerobic bioreactor characterizes the ability of the anaerobic community in the reactor to withstand violent change in the living environment. In comparison with an upflow anaerobic sludge blanket reactor (UASBR), the SRC of a spiral symmetry stream anaerobic bio-reactor (SSSAB) was systematically investigated in terms of removal efficiency, adsorption property, settling ability, flocculability and fluctuations in these parameters. A quantitative assessment method for SRC was also developed. The results indicated that the SSSAB showed better SRC than the UASBR. The average value ( m value) of chemical oxygen demand removal rates of the SSSAB was 86.0%. The contact angle of granules in the SSSAB present gradient distribution, that is the m value of contact angle increasing from bottom (84.5°) to top (93.9°). The m value of the density at the upper and lower sections of the SSSAB were 1.0611 g·cm−3 and 1.0423 g·cm−3, respectively. The surface mean diameter of granules in the SSSAB increased from 1.164 to 1.292 mm during operation. The absolute m value of zeta potential of granular sludge at the upper and lower sections of the SSSAB were 40.4 mV and 44.9 mV, respectively. The weighted mean coefficient variance (![Graphic][1] ) value indicated SSSAB was more stable than the UASBR. [1]: /embed/inline-graphic-1.gif