• Membrane Journal
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• v.28 no.1
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• pp.62-66
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• 2018

In this study the cleaning spherical beads with same density as water were fabricated. Bead moving velocity was measured with respect to the aeration rate and bead concentration in water reservoir. The permeation experiments for FR (filtration and relaxation) and SFCO (sinusoidal filtration continuous operation) modes were simultaneously carried out under the condition of 1 to 3% cleaning spherical bead concentration, 20 LMH and 500 mL/min aeration rate in the MLSS 8,000 mg/L activated sludge solution. The used membrane was the $90cm^2$ effective area and $0.4{\mu}m$ nominal pore size flat membrane. The TMP (transmembrane pressure) decreased as the bead concentration increased, and was shown most effective in FR mode with 2% bead concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.970-976
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• 2013

An evaluation of the organic matter removal efficiency showed high removal efficiencies of 91.1~96.3% and 91.4~97.5% for TCODcr and TBOD5, respectively, for 9hr or longer of HRT. However, the removal efficiencies decreased to 86.9~90.5% and 88.0~90.9%, respectively for 6hr of HRT. $NH_3$-N showed a high removal efficiency of 95% or higher for 9hr or longer of HRT. The total nitrogen removal efficiency was 67.6~76.7% for 9~12hr of HRT, and it decreased to 50% for 6hr of HRT, which seems to be due to the insufficient carbon source required for denitrification. The T-P removal efficiency was 32% on average. To comply with the legal standards, a chemical phosphorus removal process is needed after the reactor.

• Journal of Korea Soil Environment Society
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• v.5 no.1
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• pp.97-108
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• 2000

A Gram-type negative bacteria that can utilize crude oil as the sole source of carbon and energy was isolated from an activated sludge of a local sewage treatment plant and identified tentatively as belonging to the genus Acinetobacter. The isolate could degrade n-alkanes and unidentified hydrocarbons in crude oil and utilize n-alkanes, hydrophobic substrates, as sole carbon and energy sources. n-Alkanes from tridecane (Cl3) to triacontane (C30) in crude oil were degraded simultaneously with no difference in degradation characteristics between the two close odd and even numbered alkanes in carbon numbers. The linear growth of the isolate and the degradation characteristics of Pr-alkanes suggested that the transport of substrates from the oil phase to the site where the substrates undergo the initial oxidation in microorganism might be the rate limiting in the biodegradation process of crude oil constituents. The remainder fraction of substrates after cultivation was considered to reflect the hydrocarbon inclusions in the cell mass, characteristics in Acinetobacter species, and to control the transport of substrates from crude oil phase. On the basis of the results, the isolate was considered to play an important role in the degradation study of hydrophobic environmental pollutants.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1908-1919
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• 2015

This work investigated the potential of curcumin (CCM) and (-)-epigallocatechin gallate (EGCG) to inhibit N-acyl homoserine lactone (AHL)-mediated biofilm formation in gram-negative bacteria from membrane bioreactor (MBR) activated sludge. The minimum inhibitory concentrations (MICs) of CCM alone against all the tested bacteria were 200-350 μg/ml, whereas those for EGCG were 300-600 μg/ml. Biofilm formation at one-half MICs indicated that CCM and EGCG alone respectively inhibited 52-68% and 59-78% of biofilm formation among all the tested bacteria. However, their combination resulted in 95-99% of biofilm reduction. Quorum sensing inhibition (QSI) assay with known biosensor strains demonstrated that CCM inhibited the expression of C4 and C6 homoserine lactones (HSLs)-mediated phenotypes, whereas EGCG inhibited C4, C6, and C10 HSLs-based phenotypes. The Center for Disease Control biofilm reactor containing a multispecies culture of nine bacteria with one-half MIC of CCM (150 μg/ml) and EGCG (275 μg/ml) showed 17 and 14 μg/cm² of extracellular polymeric substances (EPS) on polyvinylidene fluoride membrane surface, whereas their combination (100 μg/ml of each) exhibited much lower EPS content (3 μg/cm²). Confocal laser scanning microscopy observations also illustrated that the combination of compounds tremendously reduced the biofilm thickness. The combined effect of CCM with EGCG clearly reveals for the first time the enhanced inhibition of AHL-mediated biofilm formation in bacteria from activated sludge. Thus, such combined natural QSI approach could be used for the inhibition of membrane biofouling in MBRs treating wastewaters.

• Journal of Microbiology and Biotechnology
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• v.27 no.3
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• pp.573-583
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• 2017

Biofilm formation on the membrane surface results in the loss of permeability in membrane bioreactors (MBRs) for wastewater treatment. Studies have revealed that cellulose is not only produced by a number of bacterial species but also plays a key role during formation of their biofilm. Hence, in this study, cellulase was introduced to a MBR as a cellulose-induced biofilm control strategy. For practical application of cellulase to MBR, a cellulolytic (i.e., cellulase-producing) bacterium, Undibacterium sp. DM-1, was isolated from a lab-scale MBR for wastewater treatment. Prior to its application to MBR, it was confirmed that the cell-free supernatant of DM-1 was capable of inhibiting biofilm formation and of detaching the mature biofilm of activated sludge and cellulose-producing bacteria. This suggested that cellulase could be an effective anti-biofouling agent for MBRs used in wastewater treatment. Undibacterium sp. DM-1-entrapping beads (i.e., cellulolytic-beads) were applied to a continuous MBR to mitigate membrane biofouling 2.2-fold, compared with an MBR with vacant-beads as a control. Subsequent analysis of the cellulose content in the biofilm formed on the membrane surface revealed that this mitigation was associated with an approximately 30% reduction in cellulose by cellulolytic-beads in MBR.

• Environmental Engineering Research
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• v.21 no.3
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• pp.276-283
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• 2016

The goal of this study was to evaluate the effect of effluents from conventional activated sludge (CAS) and biological nutrient removal (BNR) processes on algal bloom in receiving waters. We made multiple effluent sampling from one CAS and two BNR facilities, characterized their effluents, and conducted bioassay using river and ocean water. The bioassay results showed that CAS effluents brought similar productivity in both river and ocean water, while BNR effluents were more reactive and productive in ocean water. Unexpectedly, nitrogen-based biomass yields in ocean water were up to six times larger for BNR effluents than CAS effluent. These results indicated that nitrogen in BNR effluents, although its total concentration is lower than that of CAS effluent, is more reactive and productive in ocean water. The ocean water bioassay further revealed that effluents of BNR and CAS led to considerably different phytoplankton community, indicating that different characteristics of effluents could also result in different types of algal bloom in receiving waters. The present study suggests that effects of upgrading CAS to BNR processes on algal bloom in receiving waters, especially in estuary and ocean, should be further examined.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.267-276
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• 2010

Many plants have been improved to adapt the target of the biological treatment processes changed from organics to nutrients since the water quality criteria of effluent was reinforced and included T-N and T-P for the municipal wastewater treatment plant. To meet the criteria of T-N and T-P, the conventional biological reactor such as aeration tank in activated sludge system is changed to the BNR (biological nutrient removal) processes, which are typically divided into three units as anaerobic, anoxic and oxic tank. Therefore, the solid separation process should be redesigned to fit the BNR processes in case of the application of the DAF (dissolved air flotation) process as an alternatives because the solid-liquid separation characteristics of microbial flocs produced in the BNR processes are also different from that of activated sludge system as well. The results of this study revealed that the microbial floc of the anaerobic tank was the hardest to be separated among the three steps of the unit tanks for the BNR processes. On the contrary, the oxic tank was best for the removal efficiency of nutrients as well as suspended solid. In addition, the removal efficiency of nutrients was much improved under the chemical coagulation treatment though coagulation was not indispensable with a respect to the solid separation. On the other hand, in spited that the separation time for the microbial floc from the BNR processes were similar to the typical particles like clay flocs, over $2.32{\times}10^3$ ppm of air volume concentration was required to keep back the break-up of the bubble-floc agglomerates.

• Membrane Journal
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• v.25 no.1
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• pp.7-14
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• 2015

In this study transmembrane pressure (TMP) was measured with respect to operational time in order to estimate fouling of the submerged membrane in the membrane bioreactor(MBR). The microfiltration flat sheet module which has $0.02m^2$ of effective area and $0.15{\mu}m$ nominal pore size was submerged in the activated sludge solution of MLSS 5,000 mg/L. The permeate experiments were carried out simultaneously to compare TMP of the run/stop (R/S) with that of the sinusoidal flux continuous operation (SFCO). TMP for SFCO mode was up to 93% lower than that of R/S mode, and the effect of TMP drop reduced as permeate flux increased. Also, TMP of the SCFO mode was maintained below 40% of the limited operating TMP 55 kPa until the permeate operational time extended to longer than 5 times for the case as the coagulant $FeCl_3$ was dosed into the activated sludge solution with 500 mg/L concentration.

• Journal of Korean Society on Water Environment
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• v.33 no.4
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• pp.387-393
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• 2017

A chemical batch tests were conducted to evaluate if microwave heating enhances phosphorous release from waste activated sludge (WAS) at pH 2.5, 5, 7, 9 and 11. Polyphosphate-accumulating organisms have a unique physiological feature, which releases intracellular polyphosphate granules when they are exposed under high temperature environments. Microwave irradiation was found to encourage large amount of phosphorus release from WAS, depending on pH and temperature conditions. Most of phosphorus was released below $59^{\circ}C$ within 30 min. A marked increase in phosphorus release was observed under alkaline or acidic conditions. However, based on control tests for phosphorus release under different pH conditions without microwave heating, the largest amount of phosphorus released by microwave irradiation was found at pH 7, followed by 5, 9, 11. On the other hand, crystallization was conducted to obtain magnesium ammonium phosphate (MAP) from phosphate released by microwave heating at pH 7. X-ray diffraction analysis confirmed that the recovered crystalline materials were MAP. MAP is an environmentally friendly fertilizer, which slowly releases ammonia and phosphorus in response to the demand of plant root. Thus, the recovered MAP as a phosphate fertilizer is fully expected to play a important role in the reduction of agricultural non-point pollution.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.371-379
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• 2018

The lack of seed sludges for Ammonium Oxidizing Bacteria (AOB) and slow-growing ANaerobic AMMonium OXidation (ANAMMOX) bacteria is one of the major problem for large-scale application. In this study, $24m^3$ of single-stage SBR (Sequencing Batch Reactor) was operated to remove nitrogen from reject water using AOB and ANAMMOX bacteria cultivated from activated sludge in the field. The ANAMMOX activity was found after 44 days of cultivation in the ANAMMOX cultivation reactor, and then $0.66kg\;N/m^3/d$ of the nitrogen removal rate was achieved at $0.78kg\;N/m^3/d$ of the nitrogen loading rate at 153 days of cultivation. The AOB cultivation reactor showed $0.2kg\;N/m^3/d$ of nitrite production rate at $0.4kg\;N/m^3/d$ of nitrogen loading rate after 36 days of operation. The cultivated ANAMMOX bacteria and AOB was mixed into the single-stage SBR. The feed distribution was applied to remove total nitrogen stably in the single-stage SBR. The nitrogen removal rate in the single-stage SBR was gradually enhanced with an increase of specific activities of both AOB and ANAMMOX bacteria by showing $0.49kg\;N/m^3/d$ of the nitrogen removal rate at $0.56kg\;N/m^3/d$ of the nitrogen loading rate at 54 days of operation.