Sulfur autotrophic denitrification filter and heterotrophic denitrification filter: Comparison on denitrification performance, hydrodynamic characteristics and operating cost

Sulfur autotrophic denitrification (SAD) process, as an alternative to heterotrophic denitrification (HD) filter, receives growing interest in polishing the effluent from secondary sewage treatment. Although individual studies have indicated several advantages of SAD over HD, rare study has compared these two systems under identical condition and by using real secondary effluent. In this study, two small pilot scale filters (SAD and HD) were designed with identical configuration and operated parallelly by feeding the real secondary effluent from a WWTP. The results showed SAD filter can be started up without the addition of soluble electron donor, although the time (14 days) was about 3 times longer than that of HD filter. The nitrate removal rate of SAD filter at HRT of 1.4 h was measured as 0.268 ± 0.047 kg N/(m³∙d). Similar value was observed in HD filter with supplementing 90 mg/L COD. The COD concentration of effluent always kept lower than that of influent in SAD filter but not in HD filter. In addition, SAD filter could maintain a stable denitrification performance without backwash for 15 days, while decline of nitrate removal rate was observed in HD filter just 2 days after stopping the backwash. This different behavior was further confirmed as the SAD filter had a better hydraulic flow pattern. Analysis according to high-throughput 16S rRNA gene-based Illumina MiSeq sequencing clearly showed the microbial community evolution and differentiation among the samples of seed sludge, SAD and HD filters. Finally, the economic assessment was carried out, showing the operation cost of SAD filter was over 50% lower than that of HD filter.

Next-Generation AUC Adds a Spectral Dimension: Development of Multiwavelength Detectors for the Analytical Ultracentrifuge

We describe important advances in analytical ultracentrifugation (AUC) hardware, which add new information to the hydrodynamic information observed in traditional AUC instruments. In contrast to the Beckman-Coulter XLA UV/visible detector, multiwavelength (MWL) detection is able to collect sedimentation data not just for one wavelength, but for a large wavelength range in a single experiment. The additional dimension increases the data density by orders of magnitude, significantly improving the statistics of the measurement and adding important information to the experiment since an additional dimension of spectral characterization is now available to complement the hydrodynamic information. The new detector avoids tedious repeats of experiments at different wavelengths and opens up new avenues for the solution-based investigation of complex mixtures. In this chapter, we describe the capabilities, characteristics, and applications of the new detector design with biopolymers as the focus of study. We show data from two different MWL detectors and discuss strengths and weaknesses of differences in the hardware and different data acquisition modes. Also, difficulties with fiber optic applications in the UV are discussed. Data quality is compared across platforms.

Next-Generation AUC: Analysis of Multiwavelength Analytical Ultracentrifugation Data

We describe important advances in methodologies for the analysis of multiwavelength data. In contrast to the Beckman-Coulter XL-A/I ultraviolet-visible light detector, multiwavelength detection is able to simultaneously collect sedimentation data for a large wavelength range in a single experiment. The additional dimension increases the data density by orders of magnitude, posing new challenges for data analysis and management. The additional data not only improve the statistics of the measurement but also provide new information for spectral characterization, which complements the hydrodynamic information. New data analysis and management approaches were integrated into the UltraScan software to address these challenges. In this chapter, we describe the enhancements and benefits realized by multiwavelength analysis and compare the results to those obtained from the traditional single-wavelength detector. We illustrate the advances offered by the new instruments by comparing results from mixtures that contain different ratios of protein and DNA samples, representing analytes with distinct spectral and hydrodynamic properties. For the first time, we demonstrate that the spectral dimension not only adds valuable detail, but when spectral properties are known, individual components with distinct spectral properties measured in a mixture by the multiwavelength system can be clearly separated and decomposed into traditional datasets for each of the spectrally distinct components, even when their sedimentation coefficients are virtually identical.

Periodic-peristole agitation for process enhancement of butanol fermentation

BACKGROUND

Mass transfer plays an important role in determining the efficiency of the biofuel conversion. However, adverse effect of shear stress from traditional agitation inhibits the cell growth and production of biofuels. How to enhance the mass transfer with less adverse effect is considered as one of the important bioengineering issues.

RESULTS

In this study, a novel agitation type, named periodic-peristole was applied to butanol fermentation with Clostridium acetobutylicum ATCC 824. Meanwhile, the enhancement mechanism was studied. Initially, the fermentation performance of periodic-peristole agitation was compared with the traditional Rushton impeller and stationary cultivation. Result showed that the biomass, butanol and total solvent in periodic-peristole group (PPG) was enhanced to 1.92-, 2.06-, and 2.4-fold of those in the traditional Rushton impeller group (TIG), as well as 1.64-, 1.19- and 1.41-fold of those in the stationary group (SG). Subsequently, to get in-depth insight into enhancement mechanism, hydromechanics analysis and metabolic flux analysis (MFA) were carried out. The periodic-peristole agitation exhibits significant difference on velocity distribution, shear force, and mixing efficiency from the traditional Rushton impeller agitation. And the shear force in PPG is only 74 % of that in TIG. According to MFA result, fructose 6-phosphate, pyruvate, acetyl-CoA, oxaloacetate and α-ketoglutarate were determined the key nodes of cells in response to hydrodynamic mechanical stress. Based on such key information, rational enhancement strategies were proposed and butanol production was further improved.

CONCLUSION

The agitation associated with three issues which resulted in significant changes in cell metabolic behaviors: first, a rebalanced redox status; second, the energy (ATP) acquirement and consumption; third, the tolerance mechanism of the cell for survival of solvent. Periodic-peristole agitation provides an answer to address a long-standing problem of biofuel engineering. Key information derived from current study deepens the understanding of agitation, which can guide the designment of new bioreactors and development of enhancement strategies for biofuel refinery.

Upflow fixed bed bioelectrochemical reactor for wastewater treatment applications

A cylindrical Upflow Fixed Bed Reactor (UFB-BER) with granular activated carbon, steel mesh electrodes and anaerobic microorganisms, was constructed for analyzing how hydrodynamic parameters affect the reactions involved during wastewater treatment processes for azo dye degradation. Dye removal percentage was not compromised by decreasing HRTm (99-90% upon changing HRTm from 4 to 1h in single pass mode). Using the residence time distribution method for hydrodynamic characterization, it was found that a higher dispersion in the reactor occurs for HRTm=1h, than for HRTm=4h. A kinetic analysis suggests that this dispersion effect could be associated to a higher specific reaction rate dependent on the azo dye concentration.

Deep learning enables super-resolution hydrodynamic flooding process modeling under spatiotemporally varying rainstorms

Real-time information on flooding extent, severity, and duration is necessary for effective metropolitan flood emergency management. Existing pluvial flood analysis methods are unable to simulate real-time regional flooding processes under spatiotemporally varying rainstorms. This paper presents a deep learning-enabled super-resolution hydrodynamic flood analysis method to simulate the real-time pluvial flooding process over a large area under spatiotemporally varying rainstorms. Compared with existing flood downscaling techniques, which are limited to flow depth, the proposed method produces high-resolution flow depth and velocity predictions, providing more comprehensive information for flood emergency management. The proposed method adopts a coarse-grid hydrodynamic model to generate a low-resolution flood map time series, which is subsequently converted to high-resolution flood maps by a deep learning model. The deep learning model can be trained using a limited number of assumed rainfall scenarios, which greatly reduces data preparation effort. The proposed method is applied to a complex terrain of 352 km² in Hong Kong that covers both mountainous and urban areas. Results show that the proposed method simulates the spatiotemporal variations of flood depth and velocity with root mean square errors as low as 0.082 m and 0.088 m/s, respectively, and correlation coefficients of 0.962 and 0.921, respectively. The computation time for a 48-h rainfall event in the study area is less than 30 s, which is 2690 times faster than the direct fine-grid hydrodynamic analysis. The deep learning-enabled super-resolution hydrodynamic flood analysis method provides a promising computational tool for emergency flood risk management.

Hydrodynamic analysis and manipulation control on a streamlined I-AUV

Hydrodynamics analysis and control are very significant for the seabed operations, particularly for the intelligent manipulation process of streamlined intervention autonomous underwater vehicles (I-AUVs). The computation fluid dynamics simulations and verification were conducted in the consideration with water channel domain, mesh insensitivity, support straight bar connector, free surface and other boundary conditions. The variation trend of hydrodynamic coefficients in the process of manipulation is obtained, by simulations of streamlined I-AUV manipulation under dynamic manipulation state. To further realize underwater floating manipulation, a novel controller with an integral termed nonlinear sliding mode surface and disturbance observer has been developed. The disturbance observer can make quantity analysis on the interaction forces between I-AUV and the environment from hydrodynamic analysis. Simulations and experiments have verified the controller performance.

Optimum design of the entrance of a fishpond laterally to the main stream of an open channel

In this study, the optimum design of the entrance of a fishpond laterally to the main flow of an open channel was investigated numerically and experimentally. The flow characteristic measurements were realized with the PIV (particle image velocimetry) method. The mathematical simulations were based on the development of a two dimensional -mean in depthhydrodynamic model and a quasi three dimensional sediment transport model which includes processes of advection, diffusion, and settling of conservative suspended matter. The study was completed with the comparison of the final results of the mathematical models with the findings of the physical model revealing the hydrodynamic interaction and coupling between the main flow of the channel and the lateral reservoir-fishpond and leading to the optimum technical design of the system.