• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.6
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• pp.690-695
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• 1994

Simultaneous removal of phosphorus and nitrogen from wastewater was studied by the anaerobic-aerobic system of activated sludge. In the anaerobic stage, most of the influent glucose was removed and orthophosphate was released, when the nitrate and/or nitrite concentration in the wastewater was almost zero. The amount of the released phosphorus was found to be directly proportional to the amount of the removed glucose. When the ratio of phosphorus to glucose in the influent was less than 0.04, the phosphorus in the wastewater was almost completely removed during the aerobic state. Under the anaerobic condition, activated sludge released phosphate and excess removal of phosphate occurred during the aerobic condition. Namely, the stress received in anaerobic period stimulated the uptake of phosphorus in aerobic period. The amounts of phosphorus release in the anaerobic and uptake in the aerobic stage were less in proportional to the concentration of $NO_x-N$. Further, if the initial ratio of $NO_2-N$/glucose was less than 0.37, the inorganic nitrogen in the influent could be completely removed.

• Journal of Microbiology and Biotechnology
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• v.22 no.9
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• pp.1288-1295
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• 2012

Exposure to bioaerosols causes various adverse health effects including infectious and respiratory diseases, and hypersensitivity. Controlling exposure to bioaerosols is important for disease control and prevention. In this study, we evaluated the efficacies of various functional filters coated with antimicrobial chemicals in deactivating representative microorganisms on filters or as bioaerosols. Tested functional filters were coated with different chemicals that included (i) Ginkgo and sumac, (ii) Ag-apatite and guanidine phosphate, (iii) $SiO_2$, ZnO, and $Al_2O_3$, and (iv) zeolite. To evaluate the filters, we used a model ventilation system (1) to evaluate the removal efficiency of bacteria (Escherichia coli and Legionella pneumophila), bacterial spores (Bacillus subtilis spore), and viruses (MS2 bacteriophage) on various functional filters, and (2) to characterize the removal efficiency of these bioaerosols. All experiments were performed at a constant temperature of $25^{\circ}C$ and humidity of 50%. Most bacteria (excluding B. subtilis) rapidly decreased on the functional filter. Therefore, we confirmed that functional filters have antimicrobial effects. Additionally, we evaluated the removal efficiency of various bioaerosols by these filters. We used a six-jet collision nebulizer to generate microbial aerosols and introduced it into the environmental chamber. We then measured the removal efficiency of functional filters with and without a medium-efficiency filter. Most bioaerosol concentrations did not significantly decrease by the functional filter only but decreased by a combination of functional and medium-efficiency filter. In conclusion, functional filters could facilitate biological removal of various bioaerosols, but physical removal of these by functional was minimal. Proper use of chemical-coated filter materials could reduce exposure to these agents.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.599-607
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• 2000

In this research, ${NH_4}^+-N$ and ${PO_4}^{3-}-P$ in wastewater were removed by crystallization. Nitrogen and phosphate have been regarded as key nutrients in the eutrophication of rivers and lakes. Struvite, $MgNH_4PO_4{\cdot}6H_2O$, is insoluble in alkaline solutions. Fertilizer industry wastewater contains organic and nitrogen concentration of 330 mg/L and 550 mg/L, respectively. Nitrogen in this wastewater cannot be treated by conventional biological treatment without physicochemical pretreatment, because nitrogen concentration is relatively high compared to organic concentration. Magnesium ions used in this study were from bittern and commercial magnesium salts of $MgCl_2$ and $Mg(OH)_2$. Bittern obtained as a by-product of seasalt manufacture contains $8,000mg\;Ca^{2+}/L$ and $32,000mg\;Mg^{2+}/L$. Optimum initial pH was 10.5~11.0 and the reaction was complete or done in 2 min. Nitrogen removal efficiency using bittern, $MgCl_2 $ and $Mg(OH)_2$ (as source of $Mg^{2+}$) was 71 %, 81% and 83%. respectively. Phosphate removal efficiency was 99%, 98% and 93%, respectively. Therefore, bittern, $MgCl_2$ and $Mg(OH)_2$ can be efficiently used as $Mg^{2+}$ source for crystallization of nitrogen and phosphate. However, bittern is economically favorable $Mg^{2+}$ source for removing nitrogen and phosphate in wastewater.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.4
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• pp.251-258
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• 2019

The physical treatment such as chemical precipitation or adsorption was usually added after biological treatment in wastewater treatment process since it was enforced to reduce the concentration of phosphate for wastewater effluent to 0.2 mg/L as P which was well known as one of main nutrient causing eutrophication in waterbody. Therefore, the new material functioned for both adsorption and disinfection was prepared with Fe and Cu, and $TiO_2$, respectively, by changing the ratio of concentration referred to tri-metal (TM). According to SEM-EDS, $TiO_2$ was 30~40% composition for any TM regardless of any synthesis condition. However, the ratio of composition for Fe and Cu was dependent on the initial Fe and Cu concentration, respectively. The removal efficiency of phosphate was obtained to 15% at low initial concentration and the maximum uptake (Q) was calculated to ~11 mg/g through Langmuir isotherm model using TM1 which was synthesized at 1000 mg/L, 1000 mg/L, and 2 g (10 g/L) for $Fe(NO_3)_3$, $Cu(NO_3)_2$, $TiO_2$, respectively. In disinfection test, the efficiency of virus removal using TM was increased with increase of dosage of TM and can be reached 98% at 0.2 g.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.861-867
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• 2000

The feasibility of simultaneous phosphorus and nitrogen removal by enhancing anoxic phosphorus uptake was investigated in a sequencing batch reactor (SBR). By introducing an anoxic phase into an anaerobic-aerobic SBR (AO SBR), significant amounts of denitrifying phosphorus accumulating organisms (DPAOs) which can utilize nitrate as electron acceptor could be accumulated in the reactor (anaerobic-aerobic- anoxic-aerobic SBR, $(AO)_2$ SBR). A direct comparison of phosphorus uptake rate under anaerobic and aerobic conditions showed that the fraction of DPAOs in P-removing sludge were increased from 10% in the AO SBR to 64% in $(AO)_2$ SBR. The $(AO)_2$ SBR showed stable phosphorus and nitrogen removal efficiency: average removal efficiencies of TOC, total nitrogen, and phosphorus were 92%, 88%, and 100%. respectively. Results of the $(AO)_2$ SBR operation and batch tests showed that nitrite (up to 10 mg-N/L) was not detrimental to anoxic phosphorus uptake and could serve as good electron acceptor like nitrate.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.3
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• pp.339-349
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• 2013

Biological treatment of RO concentrate from wastewater reuse process is known to be very difficult due to its high concentration of non-degradable organics and salt ions such as chloride, nitrate and phosphate. In this research, the treatment performance of MBR was examined using RO concentrate mixed with raw wastewater as the influent of MBR. Addition of PAC (powdered activated carbon) to MBR was also evaluated in order to enhance the treatment performance and stability. The performance of MBR for treating only RO concentrate decreased gradually although external carbon source was added. The average removal performance of MBR with and without PAC decreased from 99.1 %(98.8 %) to 94.9 %(91.4 %) for COD, 81.3 %(80.3 %) to 42.0 %(41.9 %) for T-N and 57.3(55.0 %) to 30.0 %(21.0 %) for T-P with the increase of RO concentrate mixing rate of 0 % to 20 % in the feed water. Addition of PAC showed positive effect on the performance of MBR for the removal of COD and phosphorus in case that the ratio of RO concentrate to feed water increased.

• Journal of Wetlands Research
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• v.7 no.4
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• pp.43-50
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• 2005

Wetlands can transform or remove pollutants from water body, such as nitrogen, phosphate, and organics. Many researches were conducted in relation to uptake process by aquatic plants in wetlands. However, water purification processes in wetlands are the results of physical, chemical and biological, especially microbiological reactions. As such, understanding on microbial processes is of great importance. In this study, we used pondor marsh-type wetland microcosms for investigating the water purification capacity and microbial functions, namely, extracellular enzyme activities, nitrification and denitrification. In a pond system, removal efficiencies of $NO_3{^-}$ and $PO{_4}^{3-}$ were 96% and 100 % respectively, while those in a marsh system were 94%, 100% respectively. These high removal efficiencies appeared to be caused by high adsorption ability to soils and microbial functions in wetland.

• Clean Technology
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• v.8 no.2
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• pp.77-83
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• 2002

The purpose of this study is to develop the efficient nutrient removal process and to verify operation and design parameters in domestic sewage. Endogenous nitrate respiration (ENR) was used for denitrification of nitrate in return sludge without additional organic carbon source. ENR reactor before the anaerobic tank enable to reduce nitrate below 3 mg/L and increase phosphate release at anaerobic reaction. Primary effluent during pilot scale plant were shown as TCOD/TP ratio of 40~60 and TCOD/TKN ratio of 5~7. Effluent concentrations were 10 to 12mg/L as TN and 1mg/L as TP respectively. In lab scale experiments endogenous denitrification rate of ENR reactor ranges from 0.042 to $0.057gNO_3-N/gMv.d.$ $SP_{rel}/SCOD_{rm}$ was shown as from 0.13 to 0.17 in anaerobic reaction. These kinetic parameters are expected to be available for BNR(Biological Nutrient Removal) plant design and ENR reaction is available for nutrient removal in low strength wastewater.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.462-467
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• 2006

An improvement of nitrogen and phosphorus removal in SBR using the elutriated acids from the food waste as an external carbon source was investigated in this study. The food waste was elutriated at $35^{\circ}C$ and pH 9 to produce the external carbon source. The elutriate of food waste were continuously collected. The elutriated liquid contained VFAs of 39,180 mg/L representing soluble COD of 44,700 mg/L. The SBR showed poor denitrification and EBPR (enhanced biological phosphorus removal) without elutriated VFAs addition. An average denitrification rate was 0.4 mg NOx-N/g MLVSS/day. In turn, EBPR was also inhibited by this poor denitrification because the remaining nitrate in anaerobic phase resulting a poor denitrification. On the other hand, the denitrification in anoxic phase significantly improved with an elutriated VFAs addition. Nitrate removal was 82% while the denitrification rate was 2.9 mg NOx-N/g MLVSS/day with 18.4 mL/cycle of elutriated VFAs. With the enhanced denitrification, nitrate concentration in anaerobic phase could effectively be controlled to a very low level. The elimination of nitrate inhibition in anaerobic phase resulted enhancement of EBPR. The specific phosphate release rate was $1.9mg\;PO_4^{3-}-P/g\; MLVSS/day$ with less than 0.5 mg/L of $PO_4^{3-}-P$ concentration.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2303-2309
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• 2007

Expressed protein ligation (EPL) technique, joining recombinantly expressed proteins to polypeptides, has been widely adopted for addressing various biological questions and for drug discovery. However, joining two recombinant proteins together is sometimes difficult when proteins are expressed insoluble and unrefoldable, because ligation-active proteins via intein-fusion are obtainable when they are folded correctly. We overcame this limitation coexpressing target protein with additional methionine aminopeptidase (MAP) which enhances removal of the initiation methionine of recombinantly expressed protein. Our approach demonstrated that two domains of 46 kDa 5-Enolpyruvylshikimate-3-phosphate (EPSP) synthase, a target of herbicide glyphosate, were successfully joined by native chemical ligation, although its C-terminal domain was expressed as an inclusion body. The intein-fused N-terminal fragment of EPSP synthase (EPSPSN, residues 1-237) was expressed and the ligation-active thioester tagged N-terminal fragment (EPSPSN-thioester) was purified using a chitin affinity chromatography and mercapto-ethanesulphonate (MESNA) as intein thiolysis reagent. Its Cterminal fragment (EPSPSC, residues Met237-238CYS-427), expressed as an inclusion body, was prepared from an additional MAP-expressing strain. Protein ligation was initiated by mixing ~1 mM of EPSPSN-thioester with ~2 mM of EPSPSCCYS (residues 238CYS-427). Also we found that addition of 2% thiophenol increased the ligation efficiency via thiol exchange. The ligation efficiency was ~85%. The ligated full-length EPSP synthase was dissolved in 6 M GdHCl and refolded. Circular dichroism (CD) and enzyme activity assay of the purified protein showed that the ligated enzyme has distinct secondary structure and ~115% specific activity compared to those of wild-type EPSP synthase. This work demonstrates rare example of EPL between two recombinantly expressed proteins and also provides hands-on protein engineering protocol for large proteins.