Experimentation and Mathematical Models for Partial Nitrification in Aerobic Granular Sludge Process

Fenghao Cui,박세용,모경,이원배,이해승,김문일 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

In this study, the characteristics partial nitrifying biomass in the Sequencing Batch Reactor (SBR) for aerobic granulation was investigated based on experiments and simulation modeling. The reactor operation was carried out at high concentration of ammonium (200~850 mg N/L) which favored Ammonia-Oxidizing Bacteria (AOB) growth over Nitrite-Oxidizing Bacteria (NOB) growth. In partial nitrifying granulation, both Free Ammonia (FA) and Free Nitrous Acid (FNA) simultaneously influenced the activity of NOB much more than that of AOB. According to the simulation results, thE Dissolved Oxygen (DO) concentration and oxygen affinity affect the growth competition and can influence the species that are predominant in the reactor. Both AOB and NOB can have growth potential under toxicants (FA and FNA) inhibition and limited oxygen condition. The AOB growth forms inner part of granule’s biofilm, but the NOB growth does not engage in the formation of granules.

Application of Principal Component Analysis to Anaerobic Digestion Process

Fenghao Cui,Minkyung Kim,Chul Park,Kyung Mo,Moonil Kim 대한토목학회 2021 대한토목학회 학술대회 Vol.2021 No.10

Comparative Study on SBNR, GSBR and Anammox for Combined Treatment of Anaerobic Digester Effluent

Fenghao Cui,모경,박세용,김문일 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

In this study Shortcut Biological Nitrogen Removal (SBNR), Granular Sequencing Batch Reactor (GSBR), and anaerobic ammonium oxidation (Anammox) were comparatively discussed for combined treatment of anaerobic digester effluent. The experiments were carried out through operating pilot and lab scale reactors. These processes have common ground that biologically removes high strength ammonium and they are cost effective and energy efficient. The SBNR process could remove significant nitrogen from anaerobic digestion effluent without supplementation with additional carbon and alkalinity at a low C/N ratio. The aerobic granular sludge which was generated by the GSBR process demonstrated an effective simultaneous organic and ammonium removal. The Anammox process was successfully started using UASB and SBR. After 100 days, the ammonium removal exponentially increased and finally approached to around 75% in both reactors. However, the high active biomass and the long period, which are needed to start up Anammox process, limited the application of this process.

Use of Steady-State Biofilm Model to Characterize Aerobic Granular Sludge

Cui, Fenghao,Kim, Moonil American Chemical Society 2013 Environmental science & technology Vol.47 No.21

<P>In this study, a steady-state biofilm model was utilized to elucidate the aerobic granular sludge process. In order to describe the experiment data using the model, two different sizes of stabilized aerobic granules (with mean diameters of 0.6 mm and 3 mm, respectively) were investigated through the laboratory operations of sequencing batch reactors (SBRs). On the basis of the estimated parameters from experiments, the model was established to describe the biofilm functions in aerobic granules, such as substrate transfer and substrate concentration variations within the granules. In the modeling at different chemical oxygen demand (COD) concentrations (100–1000 mg/L), the biofilm functions were affected by the characteristics of aerobic granules, such as diameter and density. The larger granules modeled higher substrate fluxes (1.8–14 mg/cm<SUP>2</SUP>-d) and deeper effective film thicknesses (0.18–1.3 cm). The multi-aspect simulation results demonstrated that the substrate either approaches zero in the film (at low concentration) or penetrates the granules (at high concentration). The sum of aerobic granules in the SBRs can be considered as a mass of biofilm, where the substrate approaches zero at sufficient depth. The steady-state biofilm model could be an effective prediction method for optimizing the aerobic granular sludge process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-21/es4025639/production/images/medium/es-2013-025639_0009.gif'></P>

Characteristics of aerobic granulation at different organic and ammonium compositions

Cui, Fenghao,Kim, Bohyun,Mo, Kyung,Kim, Moonil Taylor Francis 2015 Desalination and Water Treatment Vol. No.

An innovative U-shaped sludge bed anammox process for nitrogen removal

Cui, Fenghao,Kim, Minkyung,Kim, Moonil Elsevier 2018 Journal of environmental management Vol.226 No.-

<P><B>Abstract</B></P> <P>In this study, we proposed an innovative U-shaped sludge bed reactor which could be a cost effective and simplified approach for the operation of an anammox reactor. The performance for nitrogen removal and the composition of bacterial communities were investigated for about 500 days of operation. The nitrogen removal rate could be approximately 85% when the total nitrogen loading rate was about 0.54 kg N/m<SUP>3</SUP>/d. The 16S rRNA gene pyrosequencing analysis of the bacterial community determined that <I>Betaproteobacteria</I> (class level) of the ammonia-oxidizing bacteria (AOB) community, <I>Nitrospira</I> (genus level) of the nitrite-oxidizing bacteria (NOB) community, and <I>Brocadia</I> (genus level) of the anammox bacteria community simultaneously coexisted in the reactor sludge. These results demonstrated that simultaneous growth and coexistence of AOB, NOB, and anammox were capable within the reactor. Furthermore, a mathematical modeling system was developed to simulate the nitrification and anammox processes. The model simulation showed that the oxygen was rapidly depleted and that led to a drop in the activity of AOB and NOB, then the growth of anammox bacteria started under anaerobic conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new operating type of bioreactor cultivated anammox bacteria in settled sludge. </LI> <LI> Effective nitrogen removal was demonstrated using cost effective reactor operation. </LI> <LI> The simultaneous presence of AOB, NOB, and anammox communities was determined. </LI> <LI> The Monod kinetic model showed interaction between anammox and nitrification. </LI> <LI> A simplified and effective anammox reactor operating strategy was advised. </LI> </UL> </P>

Use of Nonsteady-state Biofilm Model to Characterize Heterotrophic and Autotrophic Biomass within Aerobic Granules

김문일,Fenghao Cui 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7

A pseudo-analytical solution for a Nonsteady-state Biofilm Model (NSBM) was used to describe heterotrophic and autotrophic biofilms within aerobic granules. This model was validated with the experimental results obtained from a granule-based SBR process that removes organics and ammonia simultaneously. The calibrated model (with boundary conditions including involved species, operating conditions, granular characteristics and biological reactions) predicted effluent COD and NH4 values that were in good agreement with the measured values. The model simulation showed that the increase of the substrate concentration did not dramatically influence the flux trends if the biomass concentration in the reactor is insufficient (less than 1000 mg VSS/L). The heterotrophic and autotrophic biofilms develop layer by layer on the outside of the aerobic granules. These can form simultaneously in independent patterns for substrate utilization and biomass growth. The NSBM could be an effective prediction method for the understanding of aerobic granulation.

Experimental investigation and evaluation of the performance of air-source heat pumps for indoor thermal comfort control

Zhihua Wang,Fenghao Wang,Zhenjun Ma,Mengmeng Bai,Shuai Liu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.3

Air-source heat pumps (ASHPs) have been widely used in domestic buildings. However, the regulation performance of ASHPs for indoor thermal comfort control is influenced by the factors such as cold draft and slow response to the variation in room temperature. In this paper, a range of experiments was carried out for 14 ASHPs in an indoor environmental chamber under both cooling and heating conditions. A multi-index comprehensive evaluation model including the questionnaire survey method, the weighted scoring method and the quartile algorithm method was then adopted to analyze the tested data in order to give some intuitive indices to evaluate the regulation performance of ASHPs for indoor thermal comfort control. The results showed that unsatisfied factor of the overall thermal comfort under the cooling conditions was reached to 71 %. Besides, the precision of the temperature control was poor in both cooling and heating conditions, which manifesting ASHPs need a novel matched adjust mode and more intelligent control system to meet thermal comfort requirement. This study provided a reference basis for evaluating ASHP’s regulation performance on indoor thermal comfort.

Microbial Evaluation for Biodegradability of Recalcitrant Organic in Textile Wastewater using an Immobilized-cell Activated Sludge Process

배우근,한덕규,Fenghao Cui,김문일 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4

Textile wastewater is difficult to be treated because it contains recalcitrant matters. This study evaluated the performance of an immobilized-cell process using polyethylene glycol media and microbial properties of the immobilized-cells for biodegradation of recalcitrant organics. The immobilized-cell process could remove hardly-biodegradable soluble COD more than 50% at various Hydraulic Retention Times (HRTs) over 8~24 hours. Active microbial distribution was fluctuated at the start-up operation, but became stable at both lower and upper part of the reactor after 92 days of operation. Cell mass in the media at the bottom was higher than at the middle or top parts of the reactor. The microbial decay in the media was more dependent on oxygen than organics. Stentrophomonas sp. and Pseudomonas putida, known as aromatic and aliphatic compound degraders, were identified in the media, confirming spontaneous selection and growth of cells that could oxidize the hardly biodegradable contaminants in the textile wastewater.

Effect of heat treatment on microstructure and tensile strength of KD-II SiC fibers in argon and oxidation atmosphere

Huan Yin,Fenghao Yang,Guangmin Hu,Maozhong Yi 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.4

The polycarbosilane derived KD-II SiC fibers were heat treated in argon atmosphere at temperatures from 1000 °C to 1800°C and in oxidation atmosphere at temperatures from 1000 °C to 1500 °C for 1 hour, respectively. The effect of heat treatmenton microstructure of all fibers were characterized by X-ray diffraction, scanning electron microscopy, transmission electronmicroscopy, X-ray photoelectron spectroscopy and Atomic Force Microscopeand, and the tensile strength of fibers wereevaluated by monofilament tensile test and Weibull model. The results reveal that the fibers of heat treatment in argonatmosphere can maintain their original tensile strength (~2.5 GPa) up to the temperature at 1200 °C. After that, their tensilestrength starts to decline, especially when the temperature exceeds 1400 °C a sharp strength degradation is observed. Throughdetailed characterization, we find that the reasons for the strength degradation of fibers heat treatment in argon atmosphereinclude the appearance of surface defects, growth of β-SiC grains and decomposition of SiCxOy amorphous phase. Correspondingly, the fibers heat treated in oxidation atmosphere have lower tensile strength compared with those fibers heattreatment in argon atmosphere at the same temperature. Furthermore, their tensile strength starts to degenerate at 1000 °C,and only 30% of original strength is retained when the temperature reached 1500 °C. Obviously, for fibers heat treatment inoxidation atmosphere, their tensile strength degradation starting temperature is lower and degradation speed is faster thanthose fibers heat treatment in argon atmosphere. This can be attributed to the interface stress existed between silica layer withinternal fibers, the surface cracks caused by the thermal stress and the growth of β-SiC grains.