• Korean Journal of Hydrosciences
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• v.2
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• pp.115-126
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• 1991

The anaerobic digester with sludge from sewage treatment plant was operated in the laboratory for two year to investigate the enumeration and activity of methanogenic microorganisms. In this experimental study, the effects of HRT on the degradation characteristics of organic materials and on the number of methanogenic bacteria produced were investigated. By making the media with the repeated wxperiment, the number and activity of methanogenic bacteria were measured. The increase of the removal rate of organic acid in the digester was oberved at HRT of 2 days. The total number of methane forming bacteria estimated by the MPN method showed 2.3 $\times$ $ at HRT of 3 days, 7$\times$$ of 5 days and 7.9$\times$$ $/ml of 10 days. The optimum incubation time for measuring the number of methanogenic bacteria was found as more than four weeks. The PMA revealed 161ml CH$/l day at HRT of 10 days and the PUA 290mg COD/l day. At the incubation time 4.3 days, the maximum value of CH$ *59.1%) was found. At this time, $ was found as 15.3% and $ 25.6%.

• Journal of Aquaculture
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• v.12 no.1
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• pp.47-56
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• 1999

Denitrification by anaerobic bacteria is one of the most common processes of removing nitrate from recirculating aquaculture systems. This process is affected by many factors such as external carbon sources, hydraulic retention time (HRT), and $COD/NO_3-N$ ratio. Although external organic carbon sources are essential for the denitrification process, these also contribute to increase dissolved organic carbon concentration in recirculating aquaculture systems. So these external organic carbons must be removed from the systems. This study was conducted to find out the optimum operating conditions for the removal of external organic carbons in a submerged denitrification biofilter. Combinations of two external carbon sources (glucose and methanol), two HRT (4- and 8-hour), and four different C:N ratios (3, 4, 5, and 6) were used in this experiment. The removal efficiencies of organic carbon sources at 8-hour HRT were always better than those at 4-hour's (P<0.05). Maximum removal efficiencies were achieved when C:N ratio was 5 in both glucose and methanol. The removal efficiencies of methanol were always better than those of glucose. The maximum removal efficiencies of glucose and methanol were 76.5% and 84.0%, respectively and the removal rates were 223.5 $g/m^2/day$ and 247.1$g/m^2/day$. The maximum removal rates of glucose (290.9 $g/m^2/day$) and methanol (355.6 $g/m^2/day$) were achieved at 4-hour HRT and 5 C:N ratio. But the concentrations of SCOD in the effluent of both glucose ($52.5 mg/\ell$) and methanol ($40.9 mg/\ell$) were too high for rearing fish. Therefore, the optimum operating conditions for the removal of external carbon in a submerged denitrification biofilter were 8-hour HRT and 5 C:N ratio. And methanol showed better efficiency as an external carbon sources.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.911-916
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• 2006

The influence of substrate concentration and hydraulic retention time(HRT) on the hydrogen production by anaerobic microflora was investigated by conducting three series of continuous experiments the individual influences of substrate concentration and HRT. In series I, substrate concentration was increased from 3 to 27 g-glucose/L keeping HRT at 8 hr. Series II and III carried out same condition with series I at HRT of 16 hr and 24 hr, respectively. The effects of HRT and substrate concentration on the hydrogen production yield were analyzed by quadratic model. The maximum hydrogen production yield of 2.05 mol $H_2/mol$ glucose was found at the HRT of 9.6 hr and the substrate concentration of 15.4 g/L. The relationship between HRT and substrate concentration on hydrogen production yield as displayed a saddle shape in the response surface plot. Optimum HRT and substrate concentration are observed at in the range of 5 and 14 hr, at between 13 and 17 g/L, respectively, for the hydrogen production yield being 2 mol $H_2/mol$ glucose. The concentrations of organic acids increased with the increase of the amount of glucose consumption. Acetic acid and butyric acid were the main by-products from the glucose degradation.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.781-788
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• 2008

This study shows how to find out optimum co-substrate conditions and continuous operating parameters for maximum acidification of three different organic wastes - livestock wastewater, sewage sludge and food waste. Design of experiments and statistical analysis were revealed as appropriate optimization schemes in this study. Analyses of data obtained from batch tests demonstrated the optimum substrate mixing ratio, which was determined by maximum total volatile fatty acids(TVFA) increase and soluble chemical oxygen demand(SCOD) increase simultaneously. Suggested optimum mixing ratio of livestock wastewater, sewage sludge and food waste was 0.4 : 1.0 : 1.1 based on COD, respectively. Response surface methodology(RSM) contributed to find out optimum operating parameter - hydraulic retention time(HRT) and substrate concentration - for the semi-continuous acidogenic fermentation of mixed organic wastes. The optimum condition for maximum TVFA increase was 2 days of HRT and 29,237 mg COD/L. Empirical equations obtained through regression analysis could predict that TVFA increase would be 73%. To confirm the validity of the statistical experimental strategies, a confirmation experiment was conducted under the obtained optimum conditions, and relative error between theoretical and experimental results was within 4%. This result reflects that using statistical and RSM technique can be effectively used for the optimization of real waste treatment processes.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.69-74
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• 2002

This study was performed to evaluate an applicability of the SMMCMAS system for reuse of the sewage from spa area and was operated to HLR(Hydraulic loading rate) of 211.3 to 126.8 $\ell$/㎥/d. The operating HRT(Hydraulic retention time) ranges were 2.5 to 1.5 hours. Conclusions are as follows; At the optimum HLR of 158.5 $\ell/\m^2$/d (HRT of 2.0 hours), the maximum BOD removal efficiency was 94% and the effluent BOD concentration was 1.1mg/$\ell$ in result. As the HLR was increased to 211.3 $\ell/\m^2$/d, BOD removal efficiency was decreased to 75% and BOD removal efficiency was also reduced to 74% at lower HLR of 126.8 $\ell/\m^2$/d. It shows that the maximum BOD removal efficiency occurs at an optimum HLR value and that the removal efficiency decreases when the HLR is either higher or lower than the optimum value. Sludge production rates were ranged 0.01 to 0.24gVSS/gBODrem/d and accomplished to 0.01gVSS/gBODrem/d at the optimum HLR of 158.5 $\ell/\m^2$/d.

• Journal of Environmental Science International
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• v.8 no.2
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• pp.177-182
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• 1999

Nitrifier consortium entrapped in Ca-alginate bead were packed into aerated packed bed bioreactor and non aerated packed bed bioreactor and the performances of two bioreactors were evaluated for the removal of ammonia nitrogen from synthetic aquaculture water. Total ammonia nitrogen(TAN) removal rate was decrease in aerated packed bed bioreactor below 0.3hr of hydraulic residence time(HRT), but increased in non aerated packed bed bioreactor until 0.5hr of HRT. At HRT of 0.05hr, TAN removal rate of non aerated packed bed bioreactor was about 335g TAN/㎥/day and the optimum ratio of packing height and inside diameter of reactor (H/D) was 4. The performance of two bioreactors indicated that non aerated packed bed bioreactor was better than aerated packed bed bioreactor in ammonia removal from synthetic aquaculture water.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.98-102
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• 2000

The aim of this study was to evaluate on the removal effect of total nitrogen in municipal wastewater by decreasing hydraulic retention time(HRT) from 6 hour to 4 hour on CNR process. CNR-A(Cilia Nutrient Removal) is the process combining A2/O process with cilium media of H2L corporation. The removal efficiencies for T-N were 63.1% in A-1 reactor, and 73.5% in A-2 reactor and 77.0% in A-3 reactor. The specific nitrification(g-NH3-N/g-MLVSS.d) of Oxic in CNR-A process was 0.07-0.32. The specific denitrification in Anoxic and the specific nitrification inOxic was higher in HRT 4 hour because of optimum F/M ratio.

• Korean Journal of Environmental Agriculture
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• v.19 no.2
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• pp.183-187
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• 2000

Removal rate of nitrogen compound containing swine wastewater was 97 percent in case of high loading rate treatment of swine wastewater at studies for process development using soil microorganism. Minimum hydraulic retention time(HRT) for nitrification process was 11 days and solid retention time was 25 days. Nitrification was between 5 and 11 days but this time $NO_2-N$ was remained. Reactor condition was injured to nitrosomonas according to pH, $NO_2\;^--N$, and $NH_3\;^--N$ concentration but this condition was recover to pH controlling.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.5-14
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• 2010

A pilot-scale biological aerated filter (BAF) was operated with an anaerobic, anoxic and oxic zone at $23{\pm}1^{\circ}C$. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 hours with recirculation rates of 100, 200 and 300% in the column was more than 96%. Total nitrogen removal was consistently above 80% for 4 and 6 hours HRT at 300% recirculation. For 3 hours HRT and 300% recirculation, total nitrogen removal was approximately 79%. Based on fitting results, the kinetic parameter values on nitrification and denitrification show that as recirculation rates increased, the rate of ammonia and nitrate transformation increased. The ammonium loading rates for maximum ammonium removed were 0.15 and 0.19 kg $NH_3$-N/$m^3$-day for 100% and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3 hours with 200 - 300% recirculation rates with more than 96 % removal of sCOD and ammonium, and at least 75% removal of total nitrogen.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.85-93
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• 2018

Semi-dry anaerobic digestion experiment using dairy cattle manure collected from dairy cattle house was conducted to analyze efficiency of biogas production. As a first experiment, Biochemical Methane Potential (BMP) test was carried out according to certain ratio of sample mixtures: dairy cattle manure, pig slurry, and mixture of dairy cattle manure and pig slurry. The amount of methane accumulated during BMP test period was high in the experimental groups containing dairy cattle manure. As a second experiment, semi-dry anaerobic digestion experiment was carried out using only the dairy cattle manure collected from floor of the dairy cattle house. Judging from the experimental results, the optimum hydraulic retention time (HRT) of semi-dry anaerobic digestion for dairy cattle manure containing 13% of TS was 25 days. The amount biogas generated from the semi-dry anaerobic digestor with the TS of 13% of the dairy cattle manure ranged from 1.36~1.50v/v-d and the average was 1.44v/v-d. The optimum HRT of the semi-dry anaerobic digestor for dairy cattle manure containing TS of 15% and the semi-dry anaerobic digestor for dairy cattle manure containing TS of 17% was the same as 30 days. The amount biogas generated from the semi-dry anaerobic digestor with the TS of 15% of the dairy cattle manure ranged from 1.42~1.52v/v-d and the average was 1.47v/v-d. The amount biogas generated from the semi-dry anaerobic digestor with the TS of 17% of the dairy cattle manure ranged from 1.50~1.61v/v-d and the average was 1.55v/v-d.