• Journal of Korean Society on Water Environment
• /
• v.24 no.4
• /
• pp.458-464
• /
• 2008

Bulking phenomena and scum formation are common problem in suspended growth system like the activated sludge plants for wastewater treatment. Apart from wastewater composition, operating conditions, such as mechanical stress by insufficient oxygen supply, are often decisive for the occurrence of a bulking or scumming problem. There were the comparative aeration tanks in terms of sludge bulking caused by the difference of mechanical aeration facilities in the wastewater treatment plant of N paper mill company. In this study the cause of bulking was investigated through not only the biological isolation and identification but also a series of operational data consideration. On the basis of the investigation results for bulking cause, the operational criteria on dissolved oxygen concentration was derived to decrease the bulking problem.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.7
• /
• pp.719-725
• /
• 2005

Anaerobic fill time and feeding pattern in SBR operation were investigated to find way of minimizing poor nitrogen removal efficiency in BNR process without external carbon addition. The three types of the modified SBR operations that were CO-SBR, IA-SBR, and SF-SBR were tested by lab-scale and pilot-scale SBR processes($2\;m^3/day$). In addition, practical equation for biological nitrogen removal was suggested and the equation considered the effect of ratio of fill volume over whole SBR volume and the ratio of step-feed in SBR. The denitrification efficiency of the SF-SBR was best among the three SBRs and followed by IA-SBR, and CO-SBR. The efficiency was 95%, 61%, and 19%, respectively. Looking at the change of sludge floc density by the length of anaerobic fill time, the density of sludge floc at 1 hour and 2 hours of anaerobic fill time were greater than 3 hours of one. The floc size distributions were $100{\sim}300\;{\mu}m$ and $200{\sim}400\;{\mu}m$ with respect to anaerobic fill time 2 hours and 3 hours, respectively.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.05a
• /
• pp.275-276
• /
• 2001

한반도에 자생하는 해산현화식물인 거머리말속 (Zostera, 잘피)의 거머리말 (Zostsra marina), 애기거머리말 (Z. japonica), 수거머리말(Z. caulescens)과 포기거머리말 (Z. caespitosa)들은 연안의 사질과 사니질에 생육하며 생태계에 중요한 역할을 담당한다. 이들 식물의 군집들은 조간대와 조하대에 침수 또는 노출되어 생육하면서 영양염과 중금속 순환에 중요한 역할을 수행한다. 식물체는 유기쇄설물을 먹이연쇄에 공급하는 기능을 하며, 중금속을 고등 영양단계로 수송하는 역할을 한다. (중략)

• Journal of the Korea Organic Resources Recycling Association
• /
• v.13 no.4
• /
• pp.128-135
• /
• 2005

This study was done to improve the effectiveness of nitrification and denitrification using the aeration-anoxic combination method using CFSTR(continuous-flow stirred-tank reactor) attached with an anoxic reactor filled with a media. In order to calculate the concentration of nitric acid within the aeration tank proportional to the anoxic rate within the reactor, supernatant within the inflow and precipitation tanks were influxed into the anoxic reactor. The rate of nitrogen removal was calculated using the concentration of inflow and flow of returned supernatant. From the results of this experiment, the carbon source needed in the anoxic reactor came from the inflow so that anoxification was achieved completely using the inflow source without the introduction of an external carbon source. However, as the ratio of nitric acid becomes large in inflow and nitric acid flow, the carbon source within the input source decreases so that the concentration of carbon source is important.

• Membrane Journal
• /
• v.14 no.4
• /
• pp.289-297
• /
• 2004

In this study, membranes were coupled to a sequencing batch reactor for simultaneous removal of organic matter and nitrogen, and the influences of MLSS (mixed liquor suspended solid) concentration and the sludge loading rate on membrane fouling and bioactivity were investigated. The amount of membrane fouling slightly increased with MLSS concentration at both non-aeration and aeration conditions, but effect of MLSS concentration was more significant at aeration condition. Although the effect of MLSS concentration on membrane fouling was found to be insignificant at low concentration level, extremely low sludge loading, which were generated by the maintenance of large amount of biomass in the reactor, caused severe membrane fouling, and air scouring effect decreased significantly in this condition. Specific bioactivity was constantly reduced as sludge loading rate decreased. In spite of high MLSS concentration over 17,000 mg/L, the activity of the reactor decreased at extremely low sludge loading rate presumably due to the lower oxygen transfer and the competition of biomass to deficient substrate.

• Journal of Arbitration Studies
• /
• v.28 no.1
• /
• pp.3-26
• /
• 2018

This article examines whether parties may agree to contractually waive the right to bring annulment proceedings. Alternately it looks at whether certain grounds of annulment may be waived. The ability for parties to resolve this issue contractually by waiving this element of Article 52(1)(b) ICSID offers a potentially powerful solution. For parties to agree beforehand to the circumstances where tribunals have not 'manifestly exceeded their power' could allow them to remove the unpredictability of annulment on this foundation. Even in the event that an ad hoc committee is against the validity of waiver, it may be possible for a party to frame this restriction as an interpretative agreement by the parties rather than strictly as waiver of a ground of annulment. Ultimately, the wish to enter into such an agreement would likely only be driven by a few exceptional commercial need or prior negative experience with the remedy of annulment. In that cases, and depending on the nature of the specific concern with annulment, a limited waiver or interpretative agreement on certain Article 52(1) ICSID grounds may certainly be appropriate.

• Journal of Korean Society on Water Environment
• /
• v.26 no.1
• /
• pp.140-147
• /
• 2010

In existing design method for aeration tank water temperature was considered as governing variable for applying safety factor. This study tried a few new approach of aeration tank design using SOUR at various temperature conditions. Specific substrate utilization rate (U) and specific oxygen uptake rate (SOUR) both were analyzed at various temperature and SRT. The laboratory scale reactor was operated on various temperature ($10^{\circ}C$, $20^{\circ}C$, $25^{\circ}C$) and SRT (5day, 10day, 20day, 30day). In this study, SOUR tended to increase with the temperature increased. On the other hand, SOUR tended to decrease when SRT increased from 5 days to 30 days. Empirical equations were obtained SOUR=a/SRT+b and $SOUR=(a/m){\cdot}U+(b-a(n/m))$ from the relationship between SRT, U and SOUR. Empirical equations shows the possibility as a new design method for the aeration basin.

• Journal of Korea Water Resources Association
• /
• v.35 no.2
• /
• pp.213-220
• /
• 2002

This reserch was focused upon experimental study for wastewater reuse and conducted to evaluate optimum operating conditions of rapid filtration process such as filter flow rate, filtration time and backwashing condition for reuse of secondary-treated effluent using the pilot plant installed in real wastewater treatment plant. Also, the experiment on treatment char-acteristics of coagulant-added activated sludge process was performed to compare with activated sludge succeeded to rapid filtration. As the filtration velocity was 100m/day, the filtration time of the rapid filter connected with activated sludge system was revealed to 40 hours. Backwashing of filter was conducted by water wash and air scour. The optimum backwashing time and backwash flow rate were 10min and 10LPM, respectively. The quantity of backwashing water of the rapid filter was about 2% of total treated water.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.2
• /
• pp.181-189
• /
• 2008

Phosphate is the limiting factor leading to the eutrophication in nature and has been usually removed by the luxury uptake of PAOs(Phosphate accumulating organisms). The purpose of this study was the control of wastewater treatment removing phosphorus. The control of wastewater treatment process was performed by optimal and adaptive control. They were performed as followings. Firstly the inflow phosphate concentration was measured and the optimal aeration time was calculated by simplified ASM No. 2 for the phosphate to be 1.0 mg/L in effluent. It was optimal control. But when the phosphate concentration in effluent was not 1.0 mg/L, adaptive control was necessary to coincide the objective of control with real value. Then it was performed as the objective phosphate concentration in effluent was changed according to calculation of errors and it was adaptive control. The wastewater treatment process had been controlled by them for about one month. The range of phosphate concentration in effluent 0.2$\sim$3.2 mg/L and the average of it was 1.0 mg/L. The limitation of luxury uptake occurred two times while wastewater treatment process was running. After the analysis of laboratory tests, we knew the reasons were the shortage of ammonia nitrogen and the excessive aeration.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.3
• /
• pp.129-138
• /
• 1988

In order to develop the design and operational criteria in sewage treatment by indirect aerating submerged biofilter, experimental investigations were performed for the reasonable oxygen supply and effecting factors of treatment efficiency. The experiments were executed for the up-flowing synthetic wastewater and aerated water in the submerged biofilter at $20^{\circ}C$. The obtained results are as follows: 1) Appropriate mean diameter of gravels was about 11mm. 2) $BOD_5$ loading rate based on biofilter volume was more reasonable than that on surface area of gravel for operational criteria. 3) To remove the influent $BOD_5$ more than 90%, $BOD_5$ loading rate must be less than $1.0kg-BOD_5/m^3{\cdot}d$ and circulating flowrate must be more than $189m^3/m^3{\cdot}d$. 4) Reaction rate coefficient $K_1$ is related to diameter of gravel and circulating flow rate based on biofilter volume.