• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.451-457
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• 2007

Four parallel $A^2/O$ systems maintaining an MLSS of 3,000 mg/L were operated to investigate the effects of varying an HRT of anoxic reactors and packing Bio contact media (BCM, fixed beds) in aerobic reactors on organic matter removal and nitrification/denitrification efficiencies. All systems were operated under conditions that the external recycle ratio was kept 0.5 Q while the internal recycle ratio was changed 1.0 Q to 1.5 Q with that $NH_4-N$ concentration of feed was increased to 40 mg/L by adding $NH_4Cl$. In terms of TSS and TCODcr removal efficiency, both systems with BCM and a system without BCM, respectively, had a similar level of the removal efficiency under varied HRTs of anoxic reactors (0.6 hr, 1.3 hr, 2 hr, 2 hr; control, without BC M) showing that varying an HRT of anoxic reactors did not affect the removal efficiency. While SCODcr removal efficiency of systems with BCM was improved approximately 4~5% at the same HRT of anoxic reactor, the removal efficiency of system with BCM was slightly decreased by reducing an HRT of anoxic reactor. The nitrification efficiency for both systems with BCM and a system without BCM was above 94% showing that packing BCM in aerobic reactors and varying an HRT of anoxic reactors did not affect the efficiency significantly despite of increasing $NH_4-N$ concentration of feed. The denitrification efficiency increased from 81.4% to 85.4% at system with BCM while the efficiency decreased when a shorter HRT of anoxic reactors was kept. The excellent effluent quality for $NO_3-N$ concentration was observed although the $NO_3-N$ concentration increased in anoxic reactors that $NH_4-N$ concentration of feed sufficiently converted into nitrate through nitrification. As a result, packing 20% BCM to an aerobic reactor with HRT of 1.3 hr of anoxic reactor in $A^2/O$ system can achieve a similar level of nitrogen removal efficiency in $A^2/O$ system which the aerobic reactor had no BCM and HRT of 2 hr for anoxic reactor is maintained.

• 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 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.2
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• pp.163-169
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• 2003

The floating bead filter was tested for treatment of aquacultural water in a pilot-scale recirculating aquaculture system. Performance of floating bead filter on the removal of total suspended solids (TSS) and the treatment of nitrogen sourer such as total ammonia nitrogen (TAN), nitrite nitrogen and nitrate nitrogen were evaluated. The system was stocked with Nile tilapia at an initial rearing densities of $5\%\;and\;7\%$ over 30 days. The average TSS removal rates were $43.0\;g/m^2{\cdot}day\;and\;39.5\;g/m^2{\cdot}day$ for rearing density of $5\%\;and\;7\%$, respectively. As rearing density increased from $5\%\;to\;7\%$. the TAN removal efficiency decreased from $22.0\%\;to\;17.7\%$. At the rearing densities of $5\%\;and\;7\%$, the average TAN removal rates and removal efficiencies were $38.8\;g/m^2{\cdot}day,\;15.6\%\;and\;37.8\;g/m^2{\cdot}day.\;17.7\%,$ respectively. The average TAN removal rate was $37.8-38.8\;g/m^3{\cdot}day.$ The oxygen consumption by floating bead filter was higher than theoretical oxygen consumption rate by nitrification.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.1
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• pp.51-60
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• 1999

An intermittently-aerated, intermittently-decanted single-reactor process (KIDEA process : KIST intermittently decanted extended aeration process) was applied for nitrogen removal from wastewater. Synthetic wastewater with chemical oxygen demand (COD): nitrogen (N) ratio of approximately 5.25: 1 was used. The average COD removal efficiency reached above 95%, and under optimal conditions nitrogen removal efficiency also reached above 90%. This process consisted of 72 minute aeration, 48 minute settling and 24 minute effluent decanting with continuous feeding of influent wastewater from the bottom of the reactor, and did not require a separate anoxic mixing-phase. In this process, nitritation ($1^{st}$ step of nitrification) was induced but nitratation($2^{nd}$ step of nitrification) was suppressed. Main factors responsible for the accumulation of nitrite ion in the experimental condition were free ammonium and dissolved oxygen. This condition of nitrite build-up accelerated by continuous feed flow in the bottom of the KIDEA reactor because of high concentration of ammonia nitrogen in the influent. This research provides one of answers to control nitrate build-up.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.417-423
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• 2018

It analyzed the efficiency of the runoff reduction of artificial reservoir by analyzing the influent and effluent of reservoir located downstream of the livestock area. Production of non point pollutants in livestock feeding areas, which is located at steep slope land, was mainly due to first flushes. Suspended Solid concentration of influent increased due to amount of rainfall, and T-P also increased over four times and 30 % of total nitrogen increased on average compared to those of dry season. While the concentration of nitrate nitrogen showed little variation, ammonia nitrogen increased over two times. The storage style nonpoint reduction facility showed the highest removal efficiency of 53 % for total phosphorus in dry weather, when the removal efficiency was 37 % for suspended solids, 10% for organic compounds, and 5 % for total nitrogen. Since algal bloom grows due to eutrophication in summer, the minus removal efficiencies of nitrogen concentration through the reservoir occurred with high frequency. Removal efficiency decreased during rainfall, showing 60 % for supended solids, and 22 % for total phosphorus. While having over nine times of capacity than the standard of non-point removal facility from Ministry of Environment, it was impounded with water during rainy season, showing not enough nonpoint removal efficiency, which indicates that maintenance is also an important factor to the nonpoint removal efficiency.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.105-111
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• 2012

Manganese (Mn) catalysts were generated using $CeO_2$ and $ZrO_2$supports synthesized by the supercritical hydrothermal method and two different Mn precursors, aimed at an application for a low-temperature selective catalytic reduction process. Manganese acetate (MA) and manganese nitrate (MA) were used as Mn precursors. Effects of the kind and the concentration of the Mn precursor used for catalyst generation on the NOx removal efficiency were investigated. The characteristics of the generated catalysts were analyzed using $N_2$ adsorption-desorption, thermo-gravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. De-NOx experiments were carried out to measure NOx removal efficiencies of the catalysts. NOx removal efficiencies of the catalysts generated using MA were superior to those of the catalysts generated using MN at every temperature tested. Analyses of the catalyst characteristics indicated that the higher NOx removal efficiencies of the MA-derived catalysts stemmed from the higher oxygen mobility and the stronger interaction with support material of $Mn_2O_3$ produced from MA than those of $MnO_2$ produced from MN.

• Journal of Environmental Science International
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• v.18 no.2
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• pp.205-213
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• 2009

A laboratory experiment was conducted to investigate nitrogen removal from plating wastewater by a soil reactor. A combination of soil, waste oyster shell and activated sludge were used as a loading media in a soil reactor. The addition of 20% waste oyster shell and activated sludge to the soil accelerated nitrification (88.6% ${NH_4}^{+}-N$ removal efficiency) and denitrification (84.3% ${NO_3}^{-}-N$ removal) in the soil reactor, respectively. In continuous removal, the influent ${NH_4}^{+}-N$ was mostly converted to nitrate nitrogen in the nitrification soil reactor and only a small amount of ${NH_4}^{+}-N$ was found in the effluent. When methanol was added as a carbon source to the denitrification soil reactor, the average removal efficiency of ${NO_3}^{-}-N$ significantly increased. The ${NO_3}^{-}-N$ removal by methanol addition in the denitrification soil reactor was mainly due to denitrification. The phosphorus was removed by the waste oyster shell media in the nitrification soil reactor. Moreover, the phosphorus removal in the denitrification soil reactor was achieved by synthesis of bacteria and the denitrification under anaerobic conditions. The approximate number of nitrifiers and denitrifiers was $3.3{\times}10^5\;MPN/g$ soil at a depth of $1{\sim}10\;cm$ and $3.3{\times}10^6\;MPN/g$ soil at a depth of $10{\sim}20\;cm$, respectively, in the soil reactor mixed with a waste oyster shell media and activated sludge.

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1670-1679
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• 2015

Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH₄⁺-N/m³/d and 0.10-0.21 kg NO₃^--N/m³/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH₄⁺ or NO₃^- loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.280-286
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• 2005

The purpose of this investigation was to evaluate removal efficiency of $NH_4-N$ using the soil column. Soil, oyster shell and natural zeolite were used as a supporting media of soil column. Removal efficiencies of $NH_4-N$ were $35.9\%,\;41\%\;and\;93.4\%$ for the soil column packed with soil, natural $zeolite(20\%)$ and oyster $shell(20\%)$ at HRT of 72 hours, respectively. The addition of $20\%$ oyster shell to the soil accelerated nitrification in soil column. The influent ammonia nitrogen was mostly converted to nitrate nitrogen in the soil column and little ammonia nitrogen was found in the effluent. When the influent $NH_4-N$ concentration was 200 mg/l, the NIL-N removal was decreased at HRT of 48 hours, while nitrification was significantly increased after mechanical aeration. It was suggested that nitrification from higher $NH_4-N$ concentration was more affected by aeration in soil column process. The number of nitrifiers was approximately in a level of about $10^6\;MPN/g{\cdot}soil$ in the soil column mixed with oyster shell ($20\%$).