• 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.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.587-595
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• 2000

The most problems of domestic sewage for BNR(Biological Nutrients Removal) process are deficiency of carbon source and low C/N ratio. Primary sludge fermentation is seemed to be one of the best solutions producing biodegradable organic substrates. Soluble organic materials from sludge fermentation are mainly SCFAs(Short-Chain Fatty Acids) with 2~5 carbon atoms. In this research, it was attempted to apply $A_2/O$ process with the side-stream acid fermenter to improve the nutrients removal efficiency. The result showed that proper SCFAs production is about 3.000mg/L with SRT of 4~5 days. SCFAs yield of approximately 0.10~0.16 mg SCFAs(as COD) per mg of primary sludge(as COD) were achieved. The ratio of acetic. propionic. butyric and valerie acid were 1, 0.7, 0.5 and 0.6. Significant improvements of nutrients removal over 70% in BNR process were observed. thus will reduce the demand for chemical dosing to increase nutrients removal efficiency. When the fermentate was entered $A_2/O$ process, the ratio of phosphate release to substrate uptake amounts to $0.34gPO_4-Pg^{-1}COD$.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.675-680
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• 2004

This study was conducted to remove organics and nutrients using 2 stage intermittent aeration reactor. First reactor, using suspended microbial growth in intermittent aeration instead of anaerobic reactor in the typical BNR process, used minimum carbon source to release P, and it was possible to reduce ammonia loading going to second reactor. In the second reactor, using moving media intermittent aeration, it was effective to reduce nitrate in non-aeration time by attached microorganisms having long retention time. In aeration time, nitrification and P uptake were taken place simultaneously. From the experiment, two major results were as follows. First, the removal of organics was more than 90%, and optimum aeration/non-aeration time ratio for organic removal was corresponded with aeration/non-aeration time ratio for nitrogen removal. Second, in the first reactor, optimum aeration/non-aeration time ratio was 15/75 (min.) because it was necessary to maintain 75 min. of non-aeration time to suppress of impediment of return nitrate and to lead release of phosphate. In the second reactor, optimum aeration/non-aeration time ratio was 45/90 (min.).

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1757-1763
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• 2000

To consider the nutrient removal characteristics of BNR process activating soil microorganisms under the influence of DPB and to clear the characteristics of DPB under anoxic condition was investigated in the this study. The batch tests were conducted using sludge sampled from the BNR process activating soil microorganisms during operation periods. The results of this study were summarized as follows: - The DPB(Denitrifying Phosphorus removing Bacteria) performing denitrification and phosphorus uptake in the anoxic phase plays an important role in removing nitrogen and phosphorus in the BNR process activating soil microorganisms. - The PUR(Phosphorus Uptake Rate) of DPB in the anoxic phase was to be about 50% of PUR in the aerobic phase. - The DPB in the BNR process turned out to be increasing nutrient removal efficiency of BNR process.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.872-878
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• 2009

Advanced Phase Isolation Ditch (APID) process was studied to develop economic retrofitting technology, for the plants where retrofitting of common activated sludge process is required. In this study, to develop and apply the modified intermittently aeration mode as process control conditions for treating municipal wastewater, a demonstration plant was installed and operated in the existing sewage treatment plant of P city. During this study, the average effluent $BOD_5$, SS, T-N, and T-P concentrations were 6.3, 4.5, 10.0, and 1.3 mg/L. The modified mode decreased the nitrification capability more than the conventional mode in the application period. Nitrate in the anaerobic condition can have a negative effect on biological phosphorus removal. In the decreasing nitrate levels, the modified mode increased the biological ability of removal phosphorus more than the conventional mode in this study. Therefore, newly developed APID process with modified intermittent aeration mode can be one of the useful processes for stable organic matter and nutrients removal.

• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.451-461
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• 2006

Laboratory scale experiments were conducted to study the conversion of sludge from conventional activated sludge to nitrogen-phosphorus removal sludge using two types of sequencing batch reactor (SBR) systems, a conventional SBR and sequencing batch biofilm reactor (SBBR). The nitrogen and phosphorus removal characteristics were similar between SBR and SBBR and the removal efficiencies were very low when the influent TOC concentrations were low. The nitrogen and phosphorus removal efficiencies in SBR were 96% and 77.5%, respectively, which were higher than those in SBBR (88% and 42.5%) at the high influent TOC concentration. In SBBR, the simultaneous nitrification-denitrification was occurred because of the biofilm process. The variations of pH, DO concentration and ORP were changed as the variation of influent TOC concentration both in SBR and SBBR and their periodical characteristics were cleary shown at the high influent TOC concentration. Especially, the pH, DO concentration and ORP inflections, were cleary occurred in SBR compared with SBBR.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.6
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• pp.628-636
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• 2008

Anaerobic denitrification in a two phase anaerobic digestion(TPAD) process combined with biological nutrients removal (BNR) system was studied for a piggery wastewater treatment. Denitrification efficiency and the effects of the nitrified effluent on acidification was investigated by recycling the nitrified effluent to the acidogenic reactor. Recycle of the nitrified effluent to the acidogenic reactor enhanced the conversion efficiency of the influent COD into volatile fatty acids(VFAs) in the TPAD-BNR system treating the piggery wastewater. Acidification rate of the acidogenic sludge acclimated with the nitrified effluent showed 6 times higher than that acclimated without it. VFA could be used for denitrification as carbon sources, however, nitrate could enhance acidification activity in the acidogenic reactor. VFA production rate was affected on the COD/Nitrate(COD/N) ratio, however, it depended much more whether the acidogenic sludge acclimated with nitrate or not. Denitrification with the acidogenic sludge acclimated without nitrified effluent followed zero-order reaction and the reaction rate constants were in the range of 1.31$\sim$1.90 mg/L$\cdot$h. Denitrification reaction rate constants of the acidogenic sludge acclimated with nitrified effluent were 3.30 mg/L$\cdot$h that showed almost twice of them evaluated from the previous tests. The stoichiometric ratios of utilized COD to removed nitrate showed similar in both tests which were in the range of 5.1$\sim$6.4 at COD/N ratio of 10.