• Membrane and Water Treatment
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• 제9권4호
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• pp.255-262
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• 2018

This study attempted to evaluate the process of self-forming dynamic membrane formation on mesh filter in membrane bioreactor with a two-stage method of batch (agitation) and continues (aeration) stage at different sludge concentrations. Four concentrations of activated sludge including $6{\pm}0.4$, $8{\pm}0.5$, $10{\pm}0.3$, $14{\pm}0.3g/L$ were used to demonstrate the optimal concentration of sludge for treating municipal wastewater and reducing fouling in dynamic membrane bioreactor. The formation time and effluent turbidity were decreased in the batch stage when increasing the activated sludge concentration. The minimum values of formation time and effluent turbidity were 14 min and 43 NTU for the optimum mixed liqueur suspended solids of $8{\pm}0.5g/L$, respectively. To improve operational condition and fouling reduction in the aeration stage, critical fluxes were measured for all concentrations by flux-step method. With increasing the sludge concentration, the relevant critical fluxes reduced. The optimum subcritical flux of $30L/m^2/h$ was applied as operating flux in the second stage. The maximum COD removal efficiency of 98% was achieved by the concentration of $8{\pm}0.5g/L$. Compressibility index of self-forming dynamic membrane and transmembrane pressure trend remained somewhat constant until the optimal concentration of $8{\pm}0.5g/L$ and thereafter they increased steeply.

• 한국환경과학회지
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• 제6권2호
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• pp.113-124
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• 1997

The basic mechanism of the granular sludge formation which is the most important factor in the start-up and stable operators is not confirmed yet. In this study, the effect of granular sludge formation was investigated with the different substrate concentrations and the various ratios of substrate supply/deficiency. The granular sludge formation in the UASB reactor was closely related to the substrate concentrations and the ratio of substrate supply/deficlency The granular sludge formation was not accelerated at low substrate concentration. It was convinced that granular sludge formation was accelerated when the substrate supply with high concentration was stopped at UASB reactor. From this experiment, it was estimated that granular sludge was formed by the combination of hydrogen utilizing bacteria that form hydrogen condition and acid forming bacteria at substrate deficit condition by mutual symbiosis. Though the removal efficiency of organic matter was decreased as the influent substrate concentration was Increased, the higher the influent substrate the better the granular sludge formation.

• Membrane and Water Treatment
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• 제9권4호
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• pp.245-253
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• 2018

The aim of this study is to investigate the membrane fouling in a thermophilic membrane bioreactor (TMBR) operated different sludge retention times (SRTs). For this purpose, TMBR was operated at four different SRTs (10, 30, 60 and 100 days). Specific cake resistance (${\alpha}$), cake resistance, gel resistance, total resistance, MFI (modified fouling index) and FDR (flux decrease ratio) were calculated for all SRTs. It was observed that flux in the membrane increases with rising SRT although the sludge concentrations in the TMBR increased. The steady state flux was found to be 31.78; 34.70; 39.60 and 43.70 LMH ($Liter/m^2/h$) for the SRTs of 10, 30, 60 and 100 days respectively. The concentrations of extracellular polymeric substance (EPS) and soluble microbial product (SMP) decreased with increasing SRT. The membrane fouling rate was higher at shorter SRT and the highest fouling rate appeared at an SRT of 10 d. Both the sludge cake layer and gel layer had contribution to the fouling resistance, but the gel layer resistance value was dominant in all SRTs.

• 대한환경공학회지
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• 제36권2호
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• pp.103-108
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• 2014

하수슬러지의 해양투기 규제에 따른 처리대안으로 석탄화력발전소 보조연료로서의 활용이 제안되고 있다. 슬러지를 석탄과 혼합하여 사용한다면 연료의 조성변화로 인하여 산성가스의 배출특성이 달라질 것으로 예상된다. 본 연구에서는 국내 하수처리장 7곳에서 발생한 하수슬러지를 수거하여 석탄과 혼합한 뒤 실험실 규모의 연소로에서 연소시킨 후 배출되는 질소산화물($NO_x$), 이산화황($SO_2$), 염화수소(HCl), 염소($Cl_2$) 가스를 분석하였다. $NO_x$는 슬러지 혼합에 따른 배출농도 변화가 가장 작았고, $SO_2$는 슬러지를 혼합하여 연소하였을 때 석탄 연소가스와 비교하여 높은 배출농도 증가를 보였다. HCl + $Cl_2$는 슬러지의 염소함량에 따라 서로 다른 배출농도를 보였다.

• 한국물환경학회지
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• 제21권1호
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• pp.29-33
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• 2005

In order to recycle the waste material and to develop the thickening unit of waste activated sludge from wastewater treatment facilities, the filtration bio-reactor equipped with a shadow mask filter module was employed for this work from which the operating properties and parameters were drawn. The sludge thickening and filtration unit is made of cylindrical acryl tank(12cm i.d. ${\times}$ 58cm height: working volume of 6L), where the flat-sheet type of shadow mask filter module(pore size: 220~250um, opening area: 34.8~39.6%) was installed and the effluent was withdrawn from the effluent port at the lowest point of the reactor, and the filtration was performed only by the hydraulic pressure. For evaluating the operating performance of this reactor, some parameters such as the solid-liquid separation of different biomass concentrations, the water quality of filtrate, the aeration cleaning time and the cleaning effect were investigated. Depending on the MLSS concentrations, the different time to withdraw 3L of filtrate was required in which the longer filtration time was necessary for the higher MLSS concentrations caused by the thicker formation of cake layer: 40 minutes for 5,000 mg/L, 70 minutes for 10,000 mg/L and 100 minutes for 15,000 mg/L, where the concentrations of SS were 8.9, 6.7 and 6.5 mg/L, respectively. Under the same operating conditions (the intensity of aeration cleaning: 80 L/min, MLSS: 10,000 mg/L), the proper aeration cleaning time was revealed 30 seconds, and the stable formation of cake layer was in the range of 10 to 15 minutes. Therefore, the shadow mask considered as a waste material can be of use as a filter material for the sludge thickening system.

• Environmental Engineering Research
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• 제20권1호
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• pp.105-109
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• 2015

Triclosan is a synthetic antimicrobial agent used in numerous industrial and personal care products. Triclosan collected in wastewater treatment plants can be biodegraded up to 80%. However, little is studied about the abundances of known triclosan-degrading bacteria in activated sludge systems. A previous study reported that Sphingopyxis strain KCY1 isolated from activate sludge can cometabolically degrade triclosan. Recently, a quantitative PCR (qPCR) assay specific to strain KCY1 has been developed. Thus, this study investigated the abundance of strain KCY1 in three different activated sludge wastewater treatments using a qPCR assay. Additionally, ammonia-oxidizing bacteria (AOB), known as triclosan-degraders, and amoA gene were quantified. Strain KCY1 were detected in activated sludge samples from three different wastewater treatment plants. The concentrations of strain KCY1 and AOB were on the order of $10^5-10^6$ gene copies/mL, while amoA gene concentration was on the order of $10^4$ gene copies/mL.

• Journal of Korean Society for Atmospheric Environment
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• 제21권E2호
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• pp.41-48
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• 2005

A novel hybrid system composed of a biotrickling filter and an activated sludge reactor was investigated under the conditions of four different SRTs (sludge retention times). The performance of the hybrid reactor was found to be directly comparable among the four different sludge ages. Discernible differences in the removal performance were observed among four different SRTs of 2, 4, 6, and 8 days. High removal efficiency was achieved by continuous circulation of activated sludge over the immobilized mixture culture, which allowed on pH control, addition of nutrients, and removal of paint VOCs (volatile organic compounds). The results also showed that the removal efficiency for a given pollutant depends on the activity of microorganisms based on the SRT. As the SRT increased gradually from 2 to 8 days, the average removal performance decreased. The highest removal rate was achieved at the SRT of 2 days at which the highest OUR (oxygen uptake rate), $6.1mg-O_2/liter-min$ was measured. Biological activity in the recycle microbes decreased to a much lower level, $3.6mg-O_2/liter-min$ at a SRT of 8 days. It is thus believed that young microorganisms were more active and more efficient for the VOCs removal of low concentrations and high flow rates. The apparent correlation of $R^2=0.996$ between the average removal efficiency and the average OUR at each SRTs suggests that VOCs degradation by young cells significantly affected the overall removal efficiency for the tested SRTs.

• 유기물자원화
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• 제12권4호
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• pp.130-138
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• 2004

서로 다른 지역에서 발생한 음식물 쓰레기에 제지슬러지, 인분케익을 혼합하여 부숙시킨 후, 부숙기간에 따른 음식물 쓰레기의 이화학적 성상 및 줄지렁이의 섭식반응 및 생체량 변화를 조사하였다. 발생지역에 따른 음식물 쓰레기의 이화학적 성상은 큰 차이가 없는 것으로 나타났으며, 지렁이가 섭식하기에는 음식물 쓰레기내의 염분 농도가 전반적으로 높게 나타났다. 음식물 쓰레기에 인분케?을 혼합하여 부숙시켰을 때보다 제지슬러지를 혼합, 부숙시켰을 경우 염류농도 저하효과가 높게 나타났으나, 지렁이의 섭식효율과 생장률을 크게 개선시킬만큼 효율적이지는 않은 것으로 나타났다. 따라서 음식물 쓰레기에 대해서 지렁이 처리법을 적용시키기 위해서는 음식물 쓰레기내의 염류농도를 저하시키는 방법의 개발이 선행되어야 할 것으로 판단된다.

• Environmental Engineering Research
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• 제19권1호
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• pp.91-99
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• 2014

Ordinary heterotrophic organism (OHO) active biomass plays key roles in biological wastewater treatment processes. However, due to the lack of measurement techniques, the OHO active biomass exists hypothetically within the design and simulation of biological wastewater treatment processes. This research was purposed to develop a quick and easy quantifying technique for the OHO active biomass applying a modified batch aerobic growth test. Two nitrification-denitrification activated sludge systems, with 10- and 20-day sludge ages, were operated to provide well-cultured mixed liquor to the batch tests. A steady state design model was firstly applied to quantify the "theoretical" OHO active biomass concentration of the two parent systems. The mixed liquor from the parent systems was then inoculated to a batch growth test and a batch digestion test to estimate the "measured" OHO active biomass concentration in the mixed liquor. The measured OHO active biomass concentrations with the batch growth test and the batch digestion test were compared to the theoretical concentrations of the parent system. The measured concentrations with the batch growth test were generally smaller than the theoretical concentrations. However, the measured concentrations with the batch aerobic digestion tests showed a good correlation to the theoretical concentrations. Thus, a different microbial growth condition (i.e., a higher food/biomass ratio) in the batch growth test, compared to the parent system or the batch digestion test, was found to cause underestimation of the OHO active biomass concentrations.

• Membrane and Water Treatment
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• 제6권6호
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• pp.501-512
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• 2015

A laboratory-scale submerged membrane bioreactor (MBR) was continuously operated for 100 d at an infinite sludge retention time (SRT) with the aim of identifying possible relation between the filterability of mixed liquor and sludge properties, such as extracellular polymeric substances (EPS), soluble microbial products (SMP), viscosity of mixed liquor, zeta potential of flocs and particle size distributions (PSD). Research results confirmed that MBR can operate with a complete sludge retention ensuring good treatment performances for COD and $NH_3-N$. However, the long term operation (about 40 d) of MBR with no sludge discharge had a negative influence on sludge filterability, and an increase in membrane fouling rates with the time was observed. There as a strong correlation between the sludge filterability and the fouling rate. Among the different sludge properties parameters, the concentration SMP and EPS had a more closely correlation with the sludge filterability. The concentrations of SMP, especially SMP with MW above 10 kDa, had a strong direct correlation to the filterability of mixed sludge. The protein fractions in EPS were biodegradable and available for microorganism metabolism after about 60 days, and the carbohydrates in EPS had a significantly negative effect on sludge filterability in MBR at an infinite SRT.