• 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.

• Environmental Engineering Research
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• v.9 no.6
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• pp.269-278
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• 2004

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.787-791
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• 2004

We investigated field-effect ion-transport devices based on carbon nanotubes by using classical molecular dynamics simulations under applied external force fields, and we present model schematics that car be applied to the nanoscale data storage devices and unipolar ionic field-effect transistors. As the applied external force field is increased, potassium ions rapidly flow through the nanochannel. Under low external force fields, ther nal fluctuations of the nanochannels affect tunneling of the potassium ions whereas the effects of thermal fluctuations are negligible under high external force fields. Since the electric current conductivity increases when potassium ions are inserted into fullerenes or carbon nanotubes, the field effect due to the gate, which can modify the position of the potassium ions, changes the tunneling current between the drain and the source.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.663-668
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• 2012

The feasibility of enhancing biological nutrient removal from an industrial wastewater was tested with food waste leachate and sugar liquid waste as external carbon sources. Long term influences of adding external carbon sources were investigated to see how the biological nutrient removal process worked in terms of the removal efficiency. The addition of the external carbons led to a significant improvement in the removal efficiency of nutrients: from 49% to approximately 76% for nitrogen and from 64% to around 80% for phosphorus. Approximately, 20% of the removal nitrogen was synthesized into biomass, while the remaining 80% was denitrified. Though the addition of external carbon sources improved nutrient removal, it also increased the waste sludge production substantially. The optimal observed BOD/TN ratio, based on nitrogen removal and sludge production, was around 4.0 in this study.

• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.79-83
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• 2001

The sludge wastes fermentation process reactors were operated to produce the VFAs(volatile fatty acids) as supplemental carbon sources and to determine the optimum operating conditions. The experiment was carried out by varied mixture ration of 400:0 350:30 300:100 200:200 and operating temperature 2$0^{\circ}C$ 3$0^{\circ}C$ and 4$0^{\circ}C$ The results were as follows: Higher VFAs production rate observed at higher mixed ratio of primary sludge. When the mixed ratio of primary sludge and return sludge were 400:0 350:50 300:100 200:200 respectively. VFAs production are were 829.6mg/l 944.2 mg/l 597.9mg/ml an d441.6 mg/l , respectively. the yield of VFAs increased with temperature, but decreased with initial TSS concentration Because fermented sludge has relatively low nitrogen and phosphorus and relatively high VFAs it can be used as a substitute for external carbon in biological nutrient removal process.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.687-692
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• 2006

This experiment was performed to evaluate the characteristics of BNR system performance, behavior of pollutants as organic and nitrogen at each basin and the effects of C/N ratio on biological nitrogen removal with methanol as an external carbon source for a low C/N ratio municipal wastewater. A lab-scale $A_2O$ system by employing the aerobic basin with the fluidized polyurethane media, which was $10{\sim}20$ mm rube type like a sponge, was used. The aerobic basin was hybrid type to be suspended and fixed biomass. The obtained results from this study were as follows; When no methanol was added, suspended biomass was 3 times more than that of the fluidized media in this system(total biomass 80 g). Biomass growed by an external carbon was firstly attached on media, and then suspended. $COD_{Cr}$ concentration for the effluent was a range of 13 to 29 mg/L regardless of pouring an external carbon. For nitrogen, the effluent concentration was $20.0{\sim}35.9mg/L$(removal efficiency; 18%) in case of no addition of an external carbon, but was $2.5{\sim}9.0mg/L$(removal efficiency ; $71{\sim}83%$) with addition of methanol. For the characteristics of pollutants removal, most of $COD_{Cr}$ were removed at the anaerobic basin when no external organic carbon was added, and were removed at the anoxic basin in case of adding external organic carbon but at the aerobic basin in case of adding excess external organic carbon. On the other hand, most TIN(total inorganic nitrogen) were removed at the anaerobic basin when no external organic carbon was added, but when an external organic carbon was added, they were removed at the anaerobic basin under unstable condition and at the anoxic basin under stable condition.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.461-466
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• 2011

The feasibility of utilizing food waste leachate as an external carbon source was tested to enhance biological nutrient removal from an industrial wastewater with an average flow rate of $164,800m^3/d$ and a low carbon/nitrogen ratio of 2.8. A considerable improvement in the removal of nitrogen and phosphorus was observed when a certain amount of the leachate, ranging from 70 to $142m^3/d$, was supplemented to the biological industrial wastewater treatment process. The addition of the leachate led to an increase in the BOD/N ratio (4.5) and the removal efficiency of nutritents from 29.7% to 71.7% for nitrogen and from 34.8% to 65.6% for phosphorus. However, an excessive dose of the leachate that significantly exceeded $120m^3/d$ caused serious operational problems, like oil-layer formation in the grit chamber and scum layer in the primary clarifier. Thus, an supplement of food waste leachate at a dose acceptable to an existing facilities can be a practical and effective means to enhance the nutrient removal from industrial wastewater and to dispose of the food waste leachate.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.641-646
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• 2008

In this research, recovery of high quality organics from excess activated sludge and its potential as a external carbon sources for BNR process was studied. By simultaneous treatment of alkali and ozone, TSS concentration was reduced by 32%, and RBDCOD fraction was increased by 76.2%, and major constitute of produced organic were acetic acid and propionic acid. Also, nitrogen and phosphorus were greatly solubilized. However, because acid-hydrolyzable phosphorus(AHP) was major part of solubilized phosphorus, $NH_4{^+}-N$ and $PO_4{^3}-P$ concentration were insufficient for effective formation of crystal like as MAP(Magnesium Ammonium Phosphate) and hydroxyapatite. By placing BPR reactor before alkali-ozone treatment reactor, $PO_4{^3}-P$ concentration in pretreated sludge was increased by 1.8 times, and improved potential of phosphorus recovery by crystallization. In experiment of crystallization, hydroxyapatite formation was more easily applied than MAP. By hydroxyapatite formation, $SCOD/PO_4-P$ ratio was greatly increased from 32.7 at control to 141.9 at $Ca^{2+}/PO{_4}^{3-}-P$ mole ratio of 2.4. The results based on this study indicated that the proposed system configuration has potential to reduce the excess sludge production, to recover phosphorus in usable forms as well as utilize organics as a external carbon source in BNR process.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.551-558
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• 2007

From the view point of biological wastewater treatment, C/N ratio is one of the most important factor in biological nutrient removal process. However, municipal sewage in Korea is characterized by extremely low content of carbon source and relatively higher portion of N source. Accordingly, it is necessary to dose external carbon source in order to obtain higher degree of carbon source within the process. In this study, the effects of pH pretreatment as an alternative plan for increasing carbon source on the cell disruption and COD solubility of waste activated sludge were conducted under well defined experimental conditions. During 5 hours, the value of COD solubilization rate ($S_R$) at pH 11.5 is approximately 4.4 times higher than the value of $S_R$ at pH 9.5. It is expected that the level of SCOD increased due to the result from cell disruption. However, VSS/TSS ratio was not significantly changed after 5 hours. As Alkalinity changes gradually from less than 15, 30 and 60 meq NaOH/L, average RBCOD/SCOD fraction showed 34, 36 and 45%,respectively.

• KSBB Journal
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• v.23 no.6
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• pp.535-540
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• 2008

In this study, the effects of several factors such as initial nitrate concentration, C/N ratio, biomass amount and external carbon source on denitrification process were investigated using synthetic wastewater and sludge obtained from wastewater treatment facility. As a result, the condition of lower initial nitrate concentration was increased to the removal rate of nitrate than that of high concentration. The increases of C/N ratio and initial biomass amount were linearly enhanced the removal rate. The use of ethanol as external carbon source was shown the highest removal yield than that of others.