• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.46-52
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• 2007

As flue gas desulfurization (FGD) wastewater contains high concentrations of nitrate and is very low in organic carbon, the feasibility of nitrate removal by autotrophic denitrification using Thiobacillus denitrificans was studied. This autotrophic bacteria oxidizes elemental sulfur to sulfate while reducing nitrate to elemental nitrogen gas, thereby eliminating the need for addition of organic compounds such as methanol. Owing to the unusually high concentrations of dissolved salts $(Ca^{2+},\;Mg^{2+},\;Na^+,\;K^+,\;B^+,\;SO_4^{2-},\;Cl^-,\;F^-,)$ in the FGD wastewater, extensive laboratory-scale and pilot-scale tests were carried out in sulfur-limestone reactors (1) to determine the effect of salinity on autotrophic denitrification, (2) to evaluate the use of limestone for pH control and as source of inorganic carbon for microbial growth, and, (3) to find the optimum environmental and operational conditions for autotrophic denitrification of FGD wastewater. The experimental results demonstrated that (1) autotrophic denitrification is not inhibited up to 1.8 mol total dissolved salt content; (2) inorganic carbon and inorganic phosphorus must be present in sufficiently high concentrations; (3) limestone can supply effective buffering capacity and inorganic carbon; (4) the high calcium concentration may interfere with pH control, phosphorus solubility and limestone dissolution, hence requiring pretreatment of the FGD wastewater; and, 5) under optimum conditions, complete autotrophic denitrification of FGD wastewater was obtained in a sulfur-limestone packed bed reactor with a sulfur:limestone volume ratio of 2:1 for volumetric loading rates up to 400g $NO_{3^-}N/m^3.d$. The interesting interactions between autotrophic denitrification, pH, alkalinity, and the unusually high calcium and boron content of the FGD wastewater are highlighted. The engineering significance of the results is discussed.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1298-1304
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• 2005

This study was performed to evaluate the characteristics of the competition between two electron acceptors, perchlorate and nitrate, with Citrobacter Amalonaticus strain JB101. In addition, the applicability of membrane bioreactor(MBR) for perchlorate removal was evaluated. The maximum growth rate of strain JB101 on perchlorate and nitrate are 0.27 and 0.58 $hr^{-1}$, and maximum substrate utilization rates were 35.1 mg $ClO_4^-/g$ protein-day and 45.6 mg $NO_3^-/g$ protein-day, respectively. Nitrate was a competitive inhibitor for perchlorate, and strain JB101 prefer nitrate to perchlorate as electron acceptor. Complete removal of perchlorate could be achieved up to the surface leading rate of 4.6 g $ClO_4^-/m^2-day$ with the MBR fed with 20 mg $ClO_4^-/L$(HCMBR). When 5 mg/L of nitrate was added to the same influent, perchlorate removal efficiency decreased to 96.5%, while nitrate was completely removed. For the MBR fed with 0.7 mg/L of perchlorate (LCMBR), the maximum perchlorate removal efficiency was 100% up to the loading rate of 0.23 g $ClO_4^-/m^2-day$. Membrane fouling was found to be a problem at high leading rate for both MBRs. The acetate consumption ratio per perchlorate was $13.7{\sim}51.7\;e^-eq./e^-eq.$ in LCMBR, while the value was $2.5{\sim}3.6\;e^-eq./e^-eq.$ in HCMBR. This difference could be related to the acetate consumption with oxygen as electron acceptor. Therefore, the amount of acetate addition must be determined considering the concentrations of other electron acceptors in the influent.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.301-306
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• 2013

This research was conducted to investigate whether sequential anoxic/aerobic biofilm reactors and microfilteration (MF) membrane system can be used as a direct treatment for the removal of perchlorate and nitrate in groundwater. The biofilm process consisted of an anoxic first stage to remove perchlorate and nitrate and aerobic second stage to remove remaining acetate used as a carbon source for dissimilatory reduction of perchlorate and nitrate. In final stage, hollow fiber MF membrane was used to remove turbidity. In this research, perchlorate was reduced from the influent concentration of 102 ${\mu}/L$ to below the IC detection level (5 ${\mu}/L$) and nitrate was reduced from 61.8 mg/L (14 mg/L $NO_3$-N) to 4.4 mg/L (1 mg/L $NO_3$-N). Acetate used as a carbon source was consumed from 179 mg/L $CH_3COO-$ to 117 and 11 mg/L $CH_3COO^-$ in effluents from anoxic and aerobic biofilm reactors, respectively. Turbidity was reduced from 3.0 NTU to 1.5, 0.3, and 0.2 NTU in effluents from anoxic/aerobic biofilm reactors and MF membrane, respectively. It is expected that the sequential anoxic/aerobic biofilm reactors and MF membrane system can efficiently remove perchlorate and nitrate in surface water or groundwater.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.302-308
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• 2005

Nitrate is one of common contaminants frequently found in the bank filtrate. Biological autotrophic denitrification into permeable reactive barrier(PRB) system to reduce nitrate concentration in bank filtrate was implanted. The objectives of research are to investigate effect of inoculation, to evaluate alternative alkalinity sources, and to determine effect of hydraulic characteristics, such as retention time, flow rate on the performance of semi-pilot PRB system. Semi-pilot scale biological PRB system was installed using elemental sulfur and limestone/oyster shell as reactive materials near Nakdong River in Kyoungnam province, Korea. Nitrate concentration in bank filtrate was reduced by indigenous microorganisms in oyster shell as welt as by inoculating microorganisms isolated from the sludge of an anaerobic digester in a wastewater treatment plant. Oyster shell as well as limestone can be used as an alkalinity source. However, oyster shell resulted in suspended solids of effluent. As the flow rate in the system increased from 66 to 132 mL/min and accordingly the residence time decreased from 15 to 7.5 hours, nitrate concentration in effluent increased and nitrate removal efficiencies decreased from 75 to 58% at the fixed thickness of 80 cm of PRB.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.739-745
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• 2005

Simultaneous denitrification and methanogenesis at various influent COD/Nitrate-N(below C/N) ratio was investigated with two different anaerobic sludges of which one was inoculated with glucose only and the other was inoculated with glucose and nitrate. Three different C/N ratios of 30, 20, and 10 were applied with each anaerobic sludge in serum bottles agitated in a rotary shaker to monitor the time related changes of amount of gas production and gas composition. Glucose was used as a single carbon source, which was adjusted to 1,000 mg/L as COD and potassium nitrate was used as a nitrogen source to adjust the each C/N ratio. COD removal by methanogenesis was dominant at higher C/N ratios, while COD removal by denitrification was dominant at lower C/N ratios. With the sludges cultured at C/N ratios below 10, SMA and SDNR rising different carbon substrates were investigated. The most efficient carbon substrate was acetate and the highest SMA and SDNR were 0.76 g COD/g VSS day with pure anaerobic sludge and 1.38 g ${NO_3}^--N/g$ VSS day with sludge cultured at C/N ratio of 5, respectively.

• 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 Microbiology and Biotechnology
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• v.15 no.1
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• pp.14-21
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• 2005

By using PCR with nirS gene primers, three nirSharboring denitrifying bacteria (strain N6, strain N23, and strain R13) were newly isolated from activated sludge of a weak municipal wastewater treatment plant. Small-subunit rRNA gene-based analysis indicated that strain N6, strain N23, and strain R13 were closely related to Arthrobacter sp.,Staphylococcus sp., and Bacillus sp., respectively. In an attempt to identify their roles in biological nitrate and nitrite removal from sewage, we investigated their specific denitrification rates (SDNRs) for $NO_-^3$ - and $NO_-^2$ - in various cultures. All purecultures of each isolated nirS-harboring bacterial strain could remove $NO_-^3$ - and $NO_-^2$ - simultaneously in high efficiency, and the carbon requirements for $NO_-^3$ - removal of strain N6 and strain R13 were effectively low at 3.1 and 4.1 g COD/g $NO_3N$, respectively. In the case of mix-cultures of the strains (N6+N23, N6+R13, N23+R13, and N6+N23+R13), their SDNRs for $NO_-^3$ - were also effective, and their carbon requirements for $NO_-^3$ - removal were also effective at 3.0- 3.8 g COD/g NO3N. However, all tested mix-cultures accumulated $NO_-^2$ - in their culture media. On the other hand, the continuous culture of activated sludge mixed with strain N6 showed no significant increase of $NO_-^3$ - removal in comparison with strain N6's pure culture. These results suggest that nitrate and nitrite removal in biological wastewater treatment might be dependent on complicated bacterial interactions, including several effective denitrifying bacteria isolated in this study, rather than the specific bacterial types present and the number of bacterial types in activated sludge.

• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.436-441
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• 2008

This work experimentally determined the effect of operating parameters such as temperature and solid retention time (SRT) on the phosphorus removal of municipal wastewater with waste-tire media. The experiments were carried out in pilot-scale moving bed biofilm reactor filled at a 0.15 filling ratio with the media. Total phosphorus (TP) removal efficiency was $91{\pm}5$, $75{\pm}16$, and $59{\pm}14%$ at the temperature of 9~10, 10~20, and $20{\sim}26^{\circ}C$, respectively. TP removal efficiency was $71{\pm}17$, $74{\pm}16$, $74{\pm}16$, and $68{\pm}18%$ at the SRT of 3.5~5, 5~10, 10~15, and 15~20 days, respectively. At the nitrate concentration of 1~3, 3~6, and 6~9 mg/L, TP removal efficiency was $82{\pm}9$, $68{\pm}18$, $47{\pm}7%$, respectively. The concentration of total phosphorus in the effluent was $0.1{\sim}1.8(0.8{\pm}0.4)mg/L$ regardless of operating conditions, which meets Korean phosphorus limit value, 2 mg/L, for discharge into receiving waters.

• Korean Journal of Environmental Agriculture
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• v.23 no.4
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• pp.228-233
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• 2004

Nitrate removal was examined from May to October 2003 of a surface flow treatment wetland cell, which was a part of a treatment wetland system composed of four wetland cells and a distribution pond The system was established on rice paddy near the Kohung Estuarine Lake located in the southern part of the Korean Peninsula. Effluent from a secondary-level night soil treatment plant was funneled into the system. The investigated cell, 87 m in length and 14 m in width, was created in April 2003. An open water was designed at its center, which was equivalent to 10 percent of its total area. Cattails (Typha angustifolia) were transplanted from natural wetlands into the cell and their stems were cut at about 40cm height from their bottom ends. Average $25.0\;m^3/day$ of effluent from the treatment plant was funneled into the cell by gravity flow and average $24.1\;m^3/day$ of its treated effluent was discharged into the Sinyang Stream flowing into the lake. Its water depth was maintained about 0.2 m and its hydraulic detention time averaged 5.2 days. Average height of the cattail stems was 42.5 cm in May 2M3 and 117.7 cm in September 2003. The number of stems averaged $9.5\;stems/m^2$ in May 2003 and $16.4\;stems/m^2$ in September 2003. The growth of cattails was good. Temperature of influent and effluent averaged 25.9 and $26.7^{\circ}C$, respectively. $NO_3$-N loading rate of influent and effluent averaged 176.67 and $88.09\;mg/m^2\;day$, respectively. Removal of rf03-N averaged $89.58\;mg/m^2\;day$ and its removal rate by mass was about 50%. Considering its initial operating stage in which cattail rhizomes and litter layer on the bottom were not Idly established, the $NO_3$-N removal rate of the cell was rather good.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.473-476
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• 2003

The effect of oxidation-reduction potential (ORP) level on the denitrification by Ochrobactrum anthropi SY509 was investigated under nongrowing condition. The maximum ORP level of nitrate-containing buffer solution was -70∼-80 mV, under which the denitrification took place. By decreasing the initial ORP level, denitrifying enzyme activity was greatly enhanced, which led to higher denitrification efficiency.