• Journal of Environmental Science International
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• v.19 no.3
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• pp.371-377
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• 2010

The purpose of this study is to investigate treatment efficiency in dyeing wastewater treatment by the high rate aeration system(HRA) and a combination of the HRA with magnetized wastewater treatment system(MWS). At the hydraulic retention time of 16hr, 24hr, 30hr, BOD removal efficiencies of HRA system were 93%, 96% and 98%, combination of the HRA with MWS system were 94%, 96.8% and 98.2%, respectively. In ease of COD, at the hydraulic retention time of 16hr, 24hr, 30hr, COD removal efficiencies of HRA system were 66%, 77.1% and 83.1%, combination of the HRA with MWS system were 70.2%, 80.1% and 86.6%, respectively. The comparison of the HRA and combination of the HRA with MWS, effluent BOD of the former was 22.7mg/${\ell}$ and the latter was 19.4mg/${\ell}$, theretore biological treatment efficiency identified to increase by the MWS.

• Microbiology and Biotechnology Letters
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• v.25 no.4
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• pp.427-433
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• 1997

Sludge Returned CMAS process was applied to treat the wastewater from electric accessory manufacturing company while this type of wastewater was usually treated by chemical process. This result show that the removal rate of TCOD was about 70-80% regardless of hydraulic retention time, On the contrary, the removal rate of BOD was abtained in a range of 77-92% depending on hydraulic retention time. In order to remove more than 80% of organic materials with the proposed process, the F/M ratio should be maintained below 0.17. In this case, the calculated value of organic removal rate, Km, was calculated to be 1.26 hr$^{-1}$, and the ratio of cell synthesis/total energy was 0.32 and 0.26 for COD and BOD base, respectively. The yield coefficient was calculated to be 0.242 and the half velocity coefficient was 0.3 hr$^{-1}$. The value of endogenous respiration coefficient was 0.02 hr$^{-1}$. The measured effluent BOD concentration, MLSS concentration in aeration tank, oxygen uptake rate, and sludge production were matched relatively well with the calculated values using above coefficients, In order to optimize the dewatering of sludge, the hydraulic retention time was recommended to be 15. 6 hrs. These results indicate that the wastewater from an eletric accessory manufacturing company can be treated safely with a biological process.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.134-139
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• 2006

Partial nitirification and denitrification process has been reported to be technically feasible and economically favorable, especially for wastewater treatment with high ammonium concentration or low Carbon/Nitrogen ratio. This research was performed to survey nitrite accumulation by nitritation in treating ADEPT effluent of piggery wastewater, which contains highly concentrated ammonia. To estimate the possibility of nitrite accumulation, DO concentration and SRT were investigated as key operational parameters. This result proved that nitritation to nitrite was steadily obtained under short sludge retention time. Oxygen limitation was proved to be just a subsidiary parameter. Energy efficiency of nitritation-denitritation process was higher than complete nitrification-denitrification because external carbon requirement for denitritation could be saved. Though the influent contained significant nonbiodegradable organic substrate, total nitrogen removal efficiency was more than 51% in nitritation-denitritation system.

• Membrane and Water Treatment
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• v.8 no.6
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• pp.517-528
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• 2017

This study evaluates the performance of membrane bioreactor (MBR) coupled with a modified walnut shell granular activated carbon (WSGAC) for tannery wastewater treatment. For this purpose, a pilot with overall volume of 80L and 12 hours hydraulic retention time (HRT) is operated in three scenarios. Here, the chemical oxidation demand (COD) of wastewater is reduced more than 98% in both C:N ratios of 13 (S1) and 6.5 (S2). This performance also remains intact when alkalinity depletes and pH reduces below 6 (S3). The ammonium removal ranges between 99% (S2) and 70% (S3). The reliability of system in different operating conditions is due to high solids retention time and larger flocs formation in MBR. The average breakthrough periods of WSGAC are determined between 15 minutes (S2) and 25 minutes (S1). In this period, the overall nitrate removal of MBR-WSGAC exceeds 95%. It is also realized that adding no chemicals for alkalinity stabilization and consequently pH reduction of MBR effluent (S3) can slightly lengthen the breakthrough from 15 to 20 minutes. Consequently, MBR can successfully remove the organic content of tannery wastewater even in adverse operational conditions and provide proper influent for WSGAC.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.107-116
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• 1993

This study is conducted to investigate treatability by activated sludge process for wastewater from acetaldehyde manufacturing plant. The optimum hydraulic retention time in aeration tank for removal of high strength substrate were measured. The removal efficiency were checked out by hydraulic retention time : 35hr., 40hr. and 45hr., respectively. $COD_{Cr}$, like substances were removed in all hydraulic retention time zone directed for efficiency, but non-biodegradable substances were remained. $COD_{Cr}$ biomass loading was 0.81kg $COD_{Cr}/kgMLVSS$ . day at 35hr. of retention time, 0.34 kg$COD_{Cr}$/kg MLVSS . day at 40hr., and O.l9kg$COD_Cr$/kgMLVSS . day at 45hr. And the mean $COD_{Cr}$, removal efficiency was 65.5%, 81.6% and 83.0%, respectively. And also $COD_{Cr}$, volume loading was 1.01kg$COD_{Cr}/m^3$ day, 0.87kg$COD_{Cr}/m^3$ - day, and 0.79kg$COD_{Cr}/m^3{\cdot }$day, respectively. The basic design parameter obtained is as fallows. The value of Specific substrate removal rate coefficient (k), Yield coefficient(Y) and Decay coefficient($k_d$) was $0.0013day^{-1}$, $0.505kgMLVSS/kgCOD_{Cr}$ and $0.040day^{-1}$, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.815-824
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• 2011

In this study, a non-thermal plasma system was employed to simultaneously remove odorous compounds and organic sludge. The system consisted of two reactors; the first one was the non-thermal plasma reactor where ozone was produced by the plasma reaction and the ozone oxidized hydrogen sulfide, the model odorous compound, and then the ozone-laden gas stream was introduced to the second reactor where wasted sludge was disintegrated and solubilized by ozone oxidation. In this study, the gas retention time (GRT) and the hydraulic retention time (HRT) were changed in the two-reactor system, and the effects of GRT and HRT on reduction efficiencies of odor and sludge were determined. As the GRT increased, the ozone concentration increased resulting in an increasing efficiency of hydrogen sulfide removal. However, the overall ozone loading rate to the second sludge reactor was the same at any GRT, which resulted in an insignificant change in sludge reduction rate. When HRTs in the sludge reactor were 1, 2, 4 hours, the sludge reduction rates were approximately 30% during the four-hour operation, while the rate increased to 70% at the HRT of 6 hours. Nevertheless, at HRTs greater than 4 hours, the solubilization efficiency was not proportionally increased with increasing specific input energy, indicating that an appropriate sludge retention time needs to be applied to achieve effective solubilization efficiencies at a minimal power consumption for the non-thermal plasma reaction.

• KSBB Journal
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• v.19 no.3
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• pp.236-240
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• 2004

Korean wastewaters have higher nitrogen concentrations than typical wastewaters of other countries. Most treatment processes such as activated sludge processes will need to supplement extra carbon sources for a complete removal of remaining nitrogen after the initial wastewater treatment, Because of these difficult matters, we have searched wastewater treatment methods that require no additional carbon sources. Wastewater treatment by microalgae in photobioreactors, using a green eukaryotic microalgae, Chlorella kessleri, showed a promising results and thus was selected to study further. This system is not intended to replace the conventional system but is to assist the existing biological treatment systems as a supplemental nitrogen removal process. Thus the secondary treated livestock wastewater was tested. Column type photobioreactors developed in our laboratory were used. When aerated with 5% CO$_2$ balanced with air at 1 vvm and illuminated at 100 ${\mu}$mol/㎡/s under 25$^{\circ}C$ and PH 7-8 by CO$_2$ buffering effect, the maximum nitrogen removal rate was 2.6 mg/L/hr. The results confirmed a possibility of microalgal wastewater treatment system as a secondary system to remove extra nitrogen sources. Based on these experimental results, the size of the optimal microalgal wastewater system was calculated. For the wastewater whose initial nitrogen concentration of 150 mg/L, the optimal batch system was found to be a 2 stage system with a combined retention time of 4.6 day. From the continuous experiments, nitrogen removal rates were examined under different dilution rates and 2 stage system was also found to be the optimal system. The combined retention time for the continuous system was 3.5 days. It is expected that conventional biological wastewater treatment systems followed by microalgal systems would reliably decrease the nitrogen concentration below the government criteria even for the livestock wastewater with low C/N ratio.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.523-532
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• 2000

The purpose of this study was to investigate the effects of the hydraulic retention time (HRT) and organic loading rate (OLR) on microbial characteristics and treatment efficiency in sewage treatment using aerated submerged biological filter (ASBF) reactor. This reactor combines biodegradation of organic substrates by fixed biomass with a physical separation of biomass by filtration in a single reactor. Both simulated wastewater and domestic wastewater were used as feed solutions. The experimental conditions were a temperature of 17 to $27^{\circ}C$, a hydraulic retention time of 1 to 9hr, an organic loading rate of 0.47 to $3.84kg\;BOD/m^3{\cdot}day$ in ASBF reactor. This equipment could obtain a stable effluent quality in spite of high variation of influent loading rate. Total biomass concentration. biofilm thickness and biofilm mass increased an exponential function according to the increasing OLR. The relationships between water content and biofilm density were in inverse proportion. The percentage of backwash water to influent flow was almost 9%. The separation efficiency of biomass was the percentage of 91 to 92 in ASBF reactor. The sludge production rates in feed solutions of simulated wastewater and domestic wastewater were 0.14~0.26 kg VSS/kg BODrem, 0.43~0.48 kg VSS/kg BODrem, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.141-148
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• 2008

This study was conducted to evaluate the effect of PAC(Powder Activated Carbon) retention time on stable operation of high concentration powered activated carbon(HCPAC-MBR) in the treatment of secondary domestic wastewater. The pilot scale HCPAC-MBR system was operated at two different SRTs, 25 days and 100 days. The main drawback of HCPAC-MBR system was the rapid increase of trans-membrane pressure. The increase rate of trans-membrane pressure was proportional to SRT value at constant flux. This result seemed to be caused by reduced amount of EPS adsorbed on the PAC in the reactor by decreasing the SRT of the PAC. The particle size of the PAC was also influenced by SRT. The PAC size was decreased as SRT was increased. The change of particle size could be one reason for the change of trans-membrane pressure. The pore volume in the cake-layer formed on the membrane surface became to be increased by reducing SRT, because the cake-layer was highly composed of the PAC. Therefore, increased pore volume might play a role to reduce the trans-membrane pressure. The removal rate of E260 and TOC was also inversely proportional to SRT value.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.120-124
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• 2009

This study was performed to investigate the application of submerged membrane bioreactor (MBR) system for biological nutrient removal of municipal wastewater. MBR bioreactor consists of four reactors such as anaerobic, stabilization, anoxic and submerged membrane aerobic reactors with two internal recycles. The hydraulic retention time (HRT), sludge retention time (SRT) and flux were 6.2 hr, 34.1 days and $19.6L/m^2/hr$ (LMH), respectively. As a result of operation, the removal efficiency of $COD_{Cr}$, SS, TN and TP were 94.3%, 99.9%, 69.4%, and 74.6%, respectively. There was no significant effect of microbial activity after the maintenance cleaning using 200 mg/L of NaOCl. Membrane filtration for the treatment of municipal wastewater was performed for longer than 9 months without chemical recovery cleaning.