• Journal of Environmental Science International
• /
• v.21 no.12
• /
• pp.1495-1501
• /
• 2012

In this study, an experiment was conducted on influent water with low concentrations of organic matter, such as river water or secondary treatment water of a sewage treatment plant, according to HRT changes by using aerobic biofilm. In the biofilm process, as the biofilm increases in thickness, the inner membrane can be low in oxygen transfer rate and become anaerobic conditions, while the detachment of biomass from biofilm occurs. To overcome these limitations in the detachment of microorganisms in biofilm, the yarn, which was made from poly propylene(PP), was weaved and manufactured into a tube. Then, a test was carried out by injecting air so that the interior of the biofilm could create aerobic conditions. The results of the experiment showed that the removal efficiency of $TCOD_{cr}$ reached 66.1~81.2% by HRT 2hr, and 50.9 ~61.8% after HRT 1 hr. The removal efficiency of $SCOD_{cr}$ was 45.9 to 55.1% by HRT 1hr, and 26.1% in HRT 0.5hr, showing the highest removal efficiency in HRT 1hr. The SS removal efficiency was at 81.8 to 94.6%, and the effluent SS concentration was very low, indicating less than 2.2 mg/L in all HRT's. As a result, the $SCOD_{cr}$ and $NH_4{^+}$-N that were removed per specific surface area and attached to microbial biofilm showed the highest efficiency in HRT 1hr with 8.37 $gSCOD_{cr}/m^2{\cdot}d$, 2.93 $gNH_4{^+}-N/m^2{\cdot}d$. From the result of reviewing the characteristics of biofilm growth, microorganisms were found to be attached, and increased by 36 days. Later, they decreased in number through detachment, but showed a tendency to increase again 41 days later due to microbial reproduction.

• Journal of Wetlands Research
• /
• v.9 no.1
• /
• pp.115-121
• /
• 2007

A novel hydrogen fermentation technique by using polyvinyl alcohol (PVA) gel beads as a biomass carrier was investigated. The hydrogen gas was stably produced throughout the experimental period in a continuous reactor. Even though the hydrogen productivity was suddenly decrease by experimental troubles, the bacteria attached to the PVA gel beads played as an inoculum, it was promptly recovered. The hydrogen yield per glucose was not very high ($1.0-1.2mol-H_2/mol-glucose$), thus the optimization of the experimental conditions such as ORP and HRT should be considered to improve the hydrogen productivity. Bacterial community was stable during experimental period after the PVA gel beads applying, which indicated that applying of biomass carrier was specific to keep not only the biomass but also the bacteria commonly. Clostridium species were phylogenetically detected, which suggested that these bacteria contributed to the hydrogen production in the biofilm attached to the PVA gel beads.

• KSBB Journal
• /
• v.6 no.4
• /
• pp.345-350
• /
• 1991

The purpose of this study is to investigate biomass characteristics and organic removal efficiency by changing superficial upflow velocity and organic loading rate in treating alcoholic distillery wastewater. Since the biomass concentration and the thickness of biofilm are very sensitive to superficial upflow velocity, a high concentration of biomass could be achieved by decreasing superficial upflow velocity that lowered the organic removal efficiency. Therefore, superficial upflow velocity should be controlled as to give optimum conditions and removal efficiency. Generally, activated sludge system shows 70% COD removal efficiency at$1.5kgCOD/m^3{\cdot}day$, but the fluidized-bed biofllm reactor shows 80% COD removal efficiency even at 6kgCOD/$m^2{\cdot}day$.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.6
• /
• pp.1221-1228
• /
• 2005

Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

• Food Science of Animal Resources
• /
• v.40 no.6
• /
• pp.1001-1013
• /
• 2020

The formation of biofilms on the enamel surface of teeth by Streptococcus mutans is an important step in dental plaque formation, demineralization, and early caries because the biofilm is where other bacteria involved in dental caries attach, grow, and proliferate. The objectives of this study were to determine the effect of phosvitin (PSV) on the biofilm formation, exopolysaccharides (EPS) production, adherence activity of S. mutans, and the expression of genes related to the compounds essential for biofilm formation (quorum-sensing inducers and components of biofilm matrix) by S. mutans. PSV significantly reduced the biofilm-forming activity of S. mutans and increased the degradation of preformed biofilms by S. mutans. PSV inhibited the adherence activity of S. mutans by 31.9%-33.6%, and the production of EPS by 62%-65% depending upon the strains and the amount of PSV added. The expressions of genes regulating the production of EPS and the quorum-sensing-inducers (gtfA, gtfD, ftf, relA, vicR, brpA, and comDE) in all S. mutans strains were down-regulated by PSV, but gtfB was down-regulated only in S. mutans KCTC 5316. Therefore, the anti-biofilm-forming activity of PSV was accomplished through the inhibition of biofilm formation, adherence activity, and the production of quorum-sensing inducers and EPS by S. mutans.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.6
• /
• pp.1121-1129
• /
• 2008

A series of steady-state and short-term experiments on a three-phase circulating-bed biofilm reactor (CBBR) for removing toluene from gas streams were conducted to investigate the effect of macroporous-carrier size (1-mm cubes versus 4-mm cubes, which have the same total surface area) on CBBR performance. Experimental conditions were identical, except for the carrier size. The CBBR with 1-mm carriers (the 1-mm CBBR) overcame the performance limitation observed with the CBBR with 4-mm carriers (the 4-mm CBBR): oxygen depletion inside the biofilm. The 1-mm CBBR consistently had the superior removal efficiencies of toluene and COD, higher than 93% for all, and the advantage was greatest for the highest toluene loading, $0.12\;M/m^2-day$. The 1-mm carriers achieved superior performance by minimizing the negative effects of oxygen depletion, because they had 4.7 to 6.8 times thinner biofilm depths. The 1-mm carriers continued to provide protection from excess biomass detachment and inhibition from toluene. Finally, the 1-mm CBBR achieved volumetric removal capacities up to 300 times greater than demonstrated by other biofilters treating toluene and related volatile hydrocarbons.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.4 no.1
• /
• pp.51-58
• /
• 1999

A mathematical model for a three phase fluidized bed bioreactor (TFBBR) was proposed to describe oxygen utilization rate, biomass concentration and the removal efficiency of Chemical Oxygen Demand (COD) in wastewater treatment. The model consisted of the biofilm model to describe the oxygen uptake rate and the hydraulic model to describe flow characteristics to cause the oxygen distribution in the reactor. The biofilm model represented the oxygen uptake rate by individual bioparticle and the hydrodynamics of fluids presented an axial dispersion flow with back mixing in the liquid phase and a plug flow in the gas phase. The difference of setting velocity along the column height due to the distributions of size and number of bioparticle was considered. The proposed model was able to predict the biomass concentration and the dissolved oxygen concentration along the column height. The removal efficiency of COD was calculated based on the oxygen consumption amounts that were obtained from the dissolved oxygen concentration. The predicted oxygen concentration by the proposed model agreed reasonably well with experimental measurement in a TFBBR. The effects of various operating parameters on the oxygen concentration were simulated based on the proposed model. The media size and media density affected the performance of a TFBBR. The dissolved oxygen concentration was significantly affected by the superficial liquid velocity but the removal efficiency of COD was significantly affected by the superficial gas velocity.

• Journal of Life Science
• /
• v.33 no.11
• /
• pp.936-943
• /
• 2023

This study was conducted to investigate the potential of Stewartia koreana as anti-microbial materials. The branches, stems and leaves of S. koreana were extracted into 70% ethanol and their antibacterial activity against P. aeruginosa was confirmed. The leaf, branch and stems extracts (1 mg/disc) showed the antibacterial activity against P. aeruginosa and leaf extracts showed higher antibacterial activities than those from branch extracts. The MIC against P. aeruginosa was 0.8 mg/ml and showed bacteriostatic action. The inhibitory effects of extract on biofilm formation and gene expression related to biofilm formation of P. aeruginosa was determined by biofilm biomass staining, SEM and qRT-PCR analysis. The biofilm biomass and cell growth of P. aeruginosa in the cultures treated with 0.2~2.0 mg/ml of S. koreana leaf extracts were significantly decreased in a concentration-dependent manner. We observed that the extract had an inhibitory effect on the formation of P. aeruginosa biofilms at concentrations of 0.8 mg/ml by SEM. qRT-PCR analysis showed that the lasI and rh1I gene expression associated to quorum sensing (QS) in the cultures treated with 0.2~2.0 mg/ml of S. koreana leaf extracts were suppressed in a concentration-dependent manner. Based on the above results, it can be concluded that S. koreana leaf extracts can be used as anti-microbial material derived from natural materials, as demonstrated by the antibacterial action and inhibition of biofilm formation of P. aeruginosa by QS inhibition.

• Journal of Industrial Technology
• /
• v.16
• /
• pp.51-60
• /
• 1996

This research was performed for the fundamental data using a advanced treatment process of piggery wastewater. Characteristics of influent wastewater was divided with various methods in fixed biofilm batch reasctor. Fractons of organic were divided into readily biodegradable soluble COD(Ss), slowly biodegradable COD(Xs), nonbiodegradable soluble COD($S_I$), and nonbiodegradable suspended COD($X_I$). Experimental results were summerized as following : i) biodegradable organics fraction in piggery wastewater was about 88.1 percent, and fraction of readily biodegradable soluble COD was about 66.1 percent. ii) Fractions of nonbiodegradable soluble COD was 11~12 percent, and soluble inert COD by metabolism was producted about 6~8 percent. iii) Active biomass fraction of attached biofilm was about 54.7 percent, and substrate utilization rate and maximum specific growth rate of heterotrophs were $8.315d^{-1}$ and $3.823d^{-1}$, respectively.

• Journal of Korean Society of Water and Wastewater
• /
• v.7 no.1
• /
• pp.37-45
• /
• 1993

This research was performed to examined the applicability of a fixed-biofilm process for the wastewater treatment of military installations. Utilizing plastic net media, synthetic wastewater-average $BOD_5$ cocentration was $192mg/l$ treated in the three sets of reactors that have 8 hours, 6 hours, and 4 hours of hydraulic retention time. The results of this experiment showed that the biofilm was not detached easily, and the reactor was not closed by excess biomass. The average soluble $BOD_5$ concentrations of effluent were $6.0mg/l$ with 8 hours of retention time, $11.3mg/l$ with 6 hours of retention time, and $19.4mg/l$ with 4 hours of retention time. Especially it was reduced to $5.7mg/l$ in the second stage reactor with 4 hours of retention time. These resulted that the fixed-biofilm process could be adapted for the treatment of military installation wastewater.