• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.121-132
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• 2000

This study is to investigate the performance of a new BNR process using predenitrification scheme focusing on nitrogen removal and the possibility of adapting a computer simulation scheme in BNR process development. By using a pre-denitrification basin, higher $COD/NO_3-N$ ratio could be sustained in this BNR process. The results of the investigation showed a SDNR value of 9.04mg/gMv/hr. In the anoxic tank, the average value of SPRR of 6.25mgP/gMv/hr was observed to be very sensitive to SCOD load of influents. By calibrating internal parameters (stoichiometric and kinetic parameters) of the simulation model, the results of simulation for various BNR processes gave good agreement with observed data. The major adjustment was given with three parameters, maximum specific growth rate of heterotrophic biomass, short chain fatty acid (SCFA) limit, and phosphorous release rate. With the series of simulations on varying operational conditions, the simulation by computer program can be a useful tool for process selection, and design and operation of municipal wastewater treatment plant.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.780-786
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• 2010

The bacterial community structure in biological reactor in wastewater treatment system was investigated by denaturing gradient gel electrophoresis (DGGE) and fluorescent in situ hybridization (FISH). Samples were collected at different three points in wastewater treatment system. Through treatment processes, BOD (biochemical oxygen demand) and COD (chemical oxygen demand) of was removal efficiency was 83.1~98.6%, 67.2~85.2% respectively. Microbial community of aerobic tank and oxic tank were similar but anoxic tank was different (RRP group was increased about tripple) by DGGE and FISH in sludge (2007 October and 2008 January). Samples in 2007 October and 2008 January were dominant ${\alpha}$-Proteobacteria and CF group respectively. Sludge in 2008 April were different comparing former results dominant others as 65~80%. Others group was dominant. Eubacteria by FISH with the probe EUB338 was about $1.7{\sim}7.6{\times}10^9\;cells/mL$. It could be successfully observed bacterial community in biological wastewater system.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.548-555
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• 2007

The control of wastewater treatment has two merits; one is to regulate water quality of effluent and the other is to reduce the cost of wastewater treatment. The purpose of this study was to control the ammonium nitrogen in effluent that is known to cause eutrophication. The control was based on simplified ASM No. 1 which had 3 component materials and 8 coefficients, and the control method was as following. Firstly the ammonium concentration of inflow was measured and the optimal aeration time in effluent was determined according to simplified ASM No. 1 to be 1.0 mg/L. If ammonium concentration of effluent was not equal to 1.0 mg/L, the influent ammonium was corrected by adaptive control. These processes above were repeatedly performed. The SBR running aerobic-anoxic phase had been controlled for 1 month with this method. As a result, the ammonium concentration of the effluent showed in the range of $0.22\sim3.1$ mg/L with an average concentration of 1.1 mg/L. The adaptive control method used in this study was found very useful to control and predict the effluent concentration of ammonium.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.724-729
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• 2013

Simultaneous nitrification and denitrification (SND) occurs concurrently in the same reactor under micro dissolved oxygen (DO) conditions. Anaerobic zone was applied for phosphorus release prior to an aerated membrane bio-reactor (MBR), and anoxic zone was installed by placing a baffle in the MBR for enhancing denitrification even in high DO concentration in the MBR. Phosphorus removal was tested by alum coagulation in the anaerobic reactor preceding to MBR. DO concentration were 2.0, 1.5, 1.0, 0.75 mg/L in the MBR at different operating stages for finding optimum DO concentration in MBR for nitrogen removal by SND. pH was maintained at 7.0~8.0 without addition of alkaline solution even with alum addition due to high alkalinity in the raw sewage. Both TCODcr and $NH_4^+$-N removal efficiency were over 90% at all DO concentration. TN removal efficiencies were 50, 51, 54, 66% at DO concentration of 2.0, 1.5, 1.0, 0.75 mg/L, respectively. At DO concentration of 0.75 mg/L with addition of alum, TN removal efficiency decreased to 54%. TP removal efficiency increased from 29% to 95% by adding alum to anaerobic reactor. The period of chemical backwashing of the membrane module increased from 15~20 days to 40~50 days after addition of alum.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.694-702
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• 2013

The purpose of this study is to evaluate a de-watering filtrate treatment and the possibility of securing biological treatment capacity by changing the structure of the secondary clarifier. Accordingly, the column test was conducted to determine the effect of polymer in the de-watering filtrate on sludge sedimentation. Also, the characteristics of de-watering filtrate processing was evaluated through batch test and continuous processing operation. The results showed that sludge settling velocity increased with higher polymer concentration, and that effluent SS concentration was found to decrease. Regarding processing characteristics of de-watering filtrate, the removal efficiency of TSS and TBOD5 increased as the length of secondary clarifier was longer. Also, comparing injections into anoxic tank and secondary clarifier, de-watering filtrate by continuous infusion treatment process showed stability in both conditions. Therefore, by modifying the structure of secondary clarifier, efficient processing of de-watering filtrate is expected to be possible and processing capacity of small sewage treatment plants is considered to be improved.

• Journal of Animal Science and Technology
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• v.46 no.2
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• pp.251-260
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• 2004

The feasibility and stability of ORP, pH(mV) and DO as a real-time control parameter for SBR process were evaluated in this study. During operation, NBP(nitrogen break point) and NKP(nitrate knee point), which reveal the biological and chemical changes of pollutants, were clearly observed on ORP and pH(mV)-time profiles, and those control points were easily detected by tracking the moving slope changes(MSC). However, when balance of aeration rate to loading rate, or to OUR(oxygen uptake rate), was not optimally maintained, either false NBP was occurred on ORP and DO curves before the appearance of real NBP or specific NBP feature was disappeared on ORP curve. Under that condition, however, very distinct NBP was found on pH(mV)-time profile, and stable detection of that point was feasible by tracking MSC. These results might mean that pH(mV) is superior real-time control parameter for aerobic process than ORP and DO. Meanwhile, as a real-time control parameter for anoxic process, ORP was very stable and more useful parameter than others. Based on these results, a stable real-time control of process can be achieved by using the ORP and pH(mv) parameters in combination rather than using separately. A complete removal of pollutants could be always ensured with this real-time control technology, despite the variations of wastewater and operation condition, as well as an optimization of treatment time and capacity could be feasible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.251-259
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• 2016

This study examined the DO concentration distribution and ORP distribution using microbubbles on pilot-scale aeration tanks. As a result of MLSS mixing and oxygen transfer phenomenon using microbubbles, different DO concentrations were observed depending on the circulation of the liquid with the microbubble supply location on the lateral of an aeration tank. The simulation results of CFD (computational fluid dynamics) program showed that MLSS mixed with a microbubble supply in the middle the reactor is much better than on the left side of the reactor. A single reactor containing an anaerobic, anoxic, and aerobic zone, was evaluated without partition according to the location of the microbubble supply based on the experiments and CFD analysis. MLSS was separated into solid-liquid by the microbubble supply in the aeration tank. Consequently, selecting the appropriate microbubble size is important for MLSS mixing and was maintained at the proper DO concentration for biological treatment.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.79-89
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• 2006

The survival rate and tube number of Monocorophium uenoi, one of the dominant species in Lake Sihwa, was investigated under laboratory condition with salinity gradients (1, 5, 10, 15, 20, 25, 30, 35, 40‰). Another laboratory experiments were conducted to investigate the survival rate of Monocorophium uenoi in sulphide-rich sediment with oxic overlying water, and the effect of amphipod bioturbation on sulphide and oxygen profiles. The survival rate and tube-forming number of the amphipod were high in salinity range of 20 to 30‰. The amphipod survival rate was also high in sulphidic sediment when the water column was oxic. The amphipod bioturbation affected the oxygen and sulphide content in the sediment; oxygen conditions in the upper sediment layers were improved, and simultaneously the concentrations of sulphide were reduced. And their depth was clearly dependent on amphipod density. In Lake Sihwa, previously anoxic bottoms with sulphidic sediment during summer turn oxic with pycnocline disappearance during autumn. Amphipods seem to have the capability to quickly invade such areas, and their tubing of the sediment may play an important role in preparing the sediment for further recolonisation of other macrobenthos.

• 한국해양학회지
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• v.26 no.3
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• pp.204-222
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• 1991

The annual cycles of plant major nutrients and dissolved oxygen in a nutrients-rich semi-enclosed coastal inlet, chinhae Bay, of the southern coast of the Korean Peninsula are first presented. The water column of the bay is stratified during summer (April-late September) and well0mixed during winter (October-March). During the summer stratification period, dissolved oxygen contents exceed 400uM in the surface but diminish to less than 50uM in the near bottom waters, which often results in an anoxic environment in the inner part of Chinhae Bay. After the breakdown of the stratification in October, dissolved oxygen concentration remains undersaturated until February. The evidence of allochthonous input of N-nutrients throughout the year is readily seen in the water column: however. crude budget calculations show that the nutrients are efficiently utilized within the bay ecosystem, and that export of the nutrients from the bay to the shelf must be negligible. There is no sign of the enrichment of the nutrients in the water column. The eutrophication phenomenon sensu stricto is not observed in chinhae Bay. Using the standing stock of dissolved oxygen and estimation of the oxygen fluxes across the air-sea boundary, a benthic oxygen respiration rate during winter is estimated conservatively at 21-24 mmol Cm/SUP -2/d/SUP -1/. this oxygen respiration rate accounts for about 20% of the total phytoplankton production in winter.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.1-9
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• 2014

Lake Suwa is a natural lake which is well-known for sightseeing and fisheries. It had suffered severe eutrophication during 1960s and 1970s with the occurrence of cyanobacterial blooms and the extinction of some benthic animals. Since 1980 water quality has been improved due to efforts of local government, scientists, and citizens. Of various methods that were attempted to improve the water quality of Lake Suwa biological methods received much attention, because it can improve the lake ecosystem integrity and fisheries in addition to the water quality. The aim of this paper is to introduce the biological methods for water quality improvement that had been employed in Lake Suwa, Japan, and their contribution to the economic benefit of local residents. Until now a significant restoration of water quality has been achieved, but there are insufficient recovery of the sediment and biota due to anoxic hypolimnion of the lake. This study proposed suspended cage culture of bivalves as a feasible method of water quality improvement. Increased grazing by bivalves will contribute to the improvement of water quality and fisheries production, which will contribute both to the ecological restoration and economy of local residents.