• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.365-369
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• 2004

Submerged membrane bio-reactor equipped with a hollow fiber microfiltration was applied to reuse weaving wastewater of water jet loom, where two parameters such as the concentration of MLSS and the flux were controlled. While the flux at the concentration of MLSS around 900mg/L was constantly kept over 0.4m/d and 0.8m/d in a short time, the stable flux at around 300mg/L of MLSS was shown at the 8 days later. Regardless of MLSS and flux, BOD, CODcr and Turbidity of the permeate were 1~2mg/L, 7~10mg/L and below 1 NTU, which were 85~90%, 87~90% and 98% of removal efficiency, respectively. The stable operation without fouling was achieved because the contents of ECP were smaller than those of common MBR processes and the composition(saccharide/protein) was kept constantly. In this study, 0.5~1.0m/d of flux and 400~900mg/L of MLSS were considered as the most recommendable operating condition for the reuse of weaving wastewater.

• Membrane and Water Treatment
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• v.7 no.1
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• pp.11-22
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• 2016

The characterization of treatment performance with respect to mixed liquor suspended solids (MLSS) concentration enables greater control over system performance and contaminant removal efficiency. Hybrid membrane bioreactors (HMBRs) have yet to be well characterized in this regard, particularly in the context of greywater treatment. The aim of this study, therefore, was to determine the optimal MLSS concentration for a decentralized HMBR greywater reclamation system under typical loading conditions. Treatment performance was measured at MLSS concentrations ranging from 1000 to 4000 mg/L. The treated effluent was characterized in terms of biochemical oxygen demand ($BOD_5$), chemical oxygen demand (COD), turbidity, ammonia ($NH_3$), total phosphorus (TP), total kjeldahl nitrogen (TKN), and total nitrogen (TN). An MLSS concentration ranging from 3000 to 4000 mg/L yielded optimal results, with $BOD_5$, COD, turbidity, $NH_3$, TP, TKN, and TN removals reaching 99.2%, 97.8%, 99.8%, 99.9%, 97.9%, 95.1%, and 44.8%, respectively. The corresponding food-to-microorganism ratio during these trials was approximately 0.23 to 0.28. Operation at an MLSS concentration of 1000 mg/L resulted in an irrecoverable loss of floc, and contaminant residuals exceeded typical guideline values for reuse in non-potable water applications. Therefore, it is suggested that operation at or below this threshold be avoided.

• Journal of Environmental Health Sciences
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• v.32 no.1 s.88
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• pp.27-35
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• 2006

This study was carried out to investigate the removal of nitrogen and phosphorus in municipal sewage depending on existence of biological coated media in BCM reactor. The reactor with biological coated media is the process combining $A_2/O$ process. The removal efficiencies for $COD_{Mn},\; BOD_5,\;SS$, T-N and T-P were $78\%,\;90.5\%,\;92.3\%,\;61.9\%,\;60.2\%$, respectively. The specific nitrification rate$(mgNO_3-N/gMLSS{\cdot}d)$ of Contact aeration basin was 52.2 and the specific denitrification rate$(mgNO_3N/gMLSS{\cdot}d)$ in anoxic basin was 95.1. Also, phosphorus release$(mgPO_4-P/gMLSS{\cdot}d)$ in Anaerobic basin was 71.8 and Phosphorus uptake$(mgPO_4-P/gMLSS{\cdot}d)$ in contact aeration was 27.1.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.101-112
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• 1984

The mechanisms and the models of the contact stabilization process were briefly reviewed. The researchers proposed the more practical and rational models and the procedure for the design of the contact stabilization process. These models were derived from the material balances of the system based on the increase of Mixed Liquor Suspended Solids (MLSS) in. the contact tank and the decrease of MLSS in the stabilization tank. The proposed models were also discussed with the experimental data.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.222-228
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• 2010

Biological degradation of nitrogen-containing aromatic compounds was investigated in activated sludge previously adapted to mineralize low concentrations of nitrogen-containing aromatic compounds. Normally, the time required for 95% degradation of 10 mg/l dinitrophenol (DNP) under aerobic conditions was less than 4 hours without any lag, and with mixed liquor suspended solid (MLSS) levels from 600 to 1,000 mg/l. However, when the initial DNP concentration was increased to 75 mg/l, lags and even complete inhibition of DNP degradation were observed. The length of the lag was found to increase proportionally with decreasing MLSS levels. When dilute activated sludge was incubated for extended periods (192 hours), degradation of 75 mg/l DNP did eventually occur after lag periods of 37 to 144 hours, depending on the MLSS concentration. DNP was degradable in high concentrations if MLSS concentrations were sufficiently high to allow growth of bacteria resistant to the toxic effects of DNP.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.772-779
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• 2005

Ammonia-oxidizing bacteria (AOB) were enriched by repeating fed-batch cultivations in an AOB-selective medium of activated sludges from a domestic wastewater treatment plant. Enriched culture showed strong capabilities of ammonia oxidation [0.810 mg $NH_4^+$-N/mg mixed liquor suspended solids (MLSS)$\cdot$day] as well as $NO_x^-$-N production (0.617 mg $NO_x^-$-N/ mg MLSS$\cdot$day). Degree of enrichment was examined through fluorescent in situ hybridization (FISH) analyses using an AOB-specific Cy3-labeled oligonucleotide probe (NSOl90) and terminal-restriction fragment length polymorphism (T-RFLP) analyses. FISH analyses confirmed that the fraction of AOB among 4',6-diamidino-2-phenylindole (DAPI)-stained cells increased from about less than $0.001\%$ to approximately $42\%$ after enrichment of AOB, and T-RFLP analyses showed that bacterial community became simpler as enrichment was continued. When the enriched culture of AOB was added (150 mg/l as dry suspended solid) to the normal activated sludge (3,000 mg/l as dry suspended solid), nitrification efficiencies were improved from 0.020 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.041 mg $NO_x^-$-N/mg MLSS$\cdot$day in a synthetic wastewater and also from 0.0007 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.0918 mg $NO_x^-$-N/mg MLSS$\cdot$day in a real domestic wastewater. Therefore, it is expected that this enrichment method could be used for improving efficiency of nitrification in wastewater treatment plants.

• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.42-47
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• 2004

This study was accomplished to develope an advanced wastewater treatment process using high MLSS in anoxic tank aimed to improve nutrient removal and to reduce wasting sludge. It was operated with 4 Modes with varing solid concentration and internal recycle ratios. Mode I, II, III was operated 1.0~1.5% MLSS concentration at anoxic tank with 50% sludge recycle rate, however, each internal recycle rate were 100%, 200%, 300% and Mode IV was operated 1.5~2.0% MLSS concentration at anoxic tank with 50% sludge recycle rate and 100% internal recycle rate. The COD removal efficiency didn't show any big difference from Mode I to IV. The average COD removal rate was over than 90%. The T-N removal rate was 73%, the highest rate in all mode. The 36% of SCOD is used for the denitrification and phosphorus release in the anoxic tank. Specific denitrification rate was 3.5mg $NO_3{^-}-N/g$ Mv/hr and denitrification time was 0.7hr. As MLSS concentration is higher in anoxic tank as denitrification time would be shorter. The T-P removal rate was average 70%. The phosphorus release accomplished from the anoxic tank because the anaerobic condition was prevalent in the anoxic due to the prompt completion of denitrification. Sludge production was 0.28 kgVSS/kg $BOD_{removed}$ under the 1.5% MLSS and 17 day SRT. It is prominent result which has 40% sludge reduce comparing with traditional activate sludge system.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.508-514
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• 2017

Water-bloom and red tide due to eutrophication have been overgrown and have caused various environmental problems. Recently, however, research on bid-diesel that can utilize algae as an energy source has been actively carried out. In particular, many studies variously have been conducted to utilize algal photosynthesis oxygen as a supply method for reducing the energy by an air blower in MWTP. In this study, a lab scale algae-nitrification reactor was operated to replace the oxygen required for nitrogen removal and the operation period was largely divided into three sections. In the first section, ammonia nitrogen removal efficiency was 24 ~ 38% according to the MLSS (Mixed Liquer Suspended Solid) concentration. In the second section, ammonia nitrogen removal efficiency was 38 ~ 50% according to the micro-algae concentration and in the last section ammonia nitrogen removal efficiency was 61 ~ 80% according to HRT (Hydraulic Retention Time). As a result, as the MLSS decreased and algae biomass increased, the ammonia nitrogen removal efficiency tended to increase, but the effect of Algae biomass was greater than that of MLSS.

• Membrane and Water Treatment
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• v.10 no.4
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• pp.307-311
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• 2019

The ejector type microbubble generator, which is the method to supply air to water by using cavitation in the nozzle, does not require any air supplier so it is an effective and economical. Also, the distribution of the size of bubbles is diverse. Especially, the size of bubbles is smaller than the bubbles from a conventional air diffuser and bigger than the bubbles from a pressurized dissolution type microbubble generator so it could be applied to the aeration tank for wastewater treatment. However, the performance of the ejector type microbubble generator was affected by hydraulic pressure and MLSS(Mixed Liquor Suspended Solid) concentration so many factors should be considered to apply the generator to aeration tank. Therefore, this study was performed to verify effects of hydraulic pressure and MLSS concentration on oxygen transfer of the ejector type microbubble generator. In the tests, the quantity of sucked air in the nozzle, dissolved oxygen(DO) concentration, oxygen uptake rate(OUR), oxygen transfer coefficient were measured and calculated by using experimental results. In case of the MLSS, the experiments were performed in the condition of MLSS concentration of 0, 2,000, 4,000, 8,000 mg/L. The hydraulic pressure was considered up to $2.0mH_2O$. In the results of experiments, oxygen transfer coefficient was decreased with the increase of MLSS concentration and hydraulic pressure due to the increased viscosity and density of wastewater and decreased air flow rate. Also, by using statistical analysis, when the ejector type microbubble generator was used to supply air to wasterwater, the model equation of DO concentration was suggested to predict DO concentration in wastewater.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.371-380
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• 2013

Though MBR process has many advantages, the greatest risk factors in operating MBR process are occurrence of membrane fouling and decrease of flux. It is very difficult to find exact mechanism due to complex influence by many effects, although there have been recently many studies of membrane fouling. The purposes of this study are firstly evaluating bioreactor of lab-scale and micro-filtration hollow fiber membrane, secondly investigating correlation between foulants affecting membrane performance and membrane fouling, and lastly evaluating various parameters affecting fouling and applicability of membrane fouling reducer. This study found that TMP was increasing rapidly and showed 0.32 bar and the average of flux was 88 LMH. EPS concentration tends not to change much above MLSS concentration (6,000 mg/L). However, EPS concentration variation is wide below MLSS concentration (6,000 mg/L). Also, from results of membrane surface condition and element analysis using SEM/EDX, carbon and fluorine were founded to be the highest percentage in membrane because of characteristics of membrane material. In operating continuously, inorganic fouling was generated by increase of these inorganic substances such as $Al^{3+}$ and $Mg^{2+}$. Lastly, the best filtration performance was obtained for 0.03 mg MFR/mg MLSS by results of particle size, zeta potential, $SCOD_{cr}$, EPS and MLSS concentration.