• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.866-871
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• 2006

The nutrient recovery in phosphate crystallization process was investigated by using laboratory scale uptlow reactors, adopting sequencing batch type configuration. The industrial waste lime was used as potential cation source with magnesium salt($MgCl_2$) as control. The research was focused on its successful application in a novel integrated sludge treatment process, which is comprised of a high performance fermenter followed by a crystallization reactor. In the struvite precipitation test using synthetic wastewater first, which has the similar characteristics with the real fermentation effluent, the considerable nutrient removal(about 60%) in both ammonia and phosphate was observed within $0.5{\sim}1$ hr of retention time. The results also revealed that a minor amount(<5%) of ammonia stripping naturally occurred due to the alkaline(pH 9) characteristic in feed substrate. Stripping of $CO_2$ by air did not increase the struvite precipitation rate but it led to increased ammonia removal. In the second experiment using the fermentation effluent, the optimal dosage of magnesium salt for struvite precipitation was 0.86 g Mg $g^{-1}$ P, similar to the mass ratio of the struvite. The optimal dosage of waste lime was 0.3 g $L^{-1}$, resulting in 80% of $NH_4-N$ and 41% of $PO_4-P$ removal, at about 3 hrs of retention time. In the microscopic analysis, amorphous crystals were mainly observed in the settled solids with waste lime but prism-like crystals were observed with magnesium salt. Based on mass balance analysis for an integrated sludge treatment process(fermenter followed by crystallization reactor) for full-scale application(treatment capacity Q=158,880 $m^3\;d^{-1}$), nutrient recycle loading from the crystallization reactor effluent to the main liquid stream would be significantly reduced(0.13 g N and 0.19 g P per $m^3$ of wastewater, respectively). The results of the experiment reveal therefore that the reuse of waste lime, already an industrial waste, in a nutrient recovery system has various advantages such as higher economical benefits and sustainable treatment of the industrial waste.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.343-352
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• 2013

In this study, we have evaluated the effect of efficient microorganisms on odor-removal efficiency and early stabilization of the burial sites. We have developed an efficient microorganism designated as 'KEM' which have the ability to degrade organic compounds and remove odor effectively. Other efficient microorganisms already used on site, such as EM and Bacillus sp., were also compared. We preceded these experiment using lab-scale reactors under three conditions (control, only media and only body) and comparing the effect of with or without the application of tree efficient microorganisms separately. Analysis was focused on eight components (ammonia, TMA, $H_2S$, methyl mercaptan, dimethyl sulfide, dimethyl disulfide, $CO_2$ and $CH_4$), and as a result, efficient microorganisms were shown efficiency in the removal of ammonia and methyl mercaptan. The applied KEM decayed up to 71.2% of the buried meat. We were unable to observe significant differences in microbial communities between efficient microorganisms-treated and non-treated reactors due to the large presence of microorganisms in both soil and carcasses. However, it was possible to observe the effect on odor control and decay rate through the application of efficient microorganisms.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.207-212
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• 2008

This study focused on shorten the period of the struvite crystal birth and development by adding seed materials. For this purpose, three different seed materials were selected: sand, anthracite and struvite. The experiments has been conducted to evaluate the effect of the particle size of the selected seed material on the struvite crystallization, and to study the mixing effect which can be expressed by the value of $G{\cdot}t_d$(the multiple of mean velocity gradient(G) and mixing time($t_d$)). It was observed in this study that the removal efficiency of ammonia nitrogen increased by 9%, 11%, and 20% for sand, anthracite, and struvite added as the seed material, respectivley. This indicated that the struvite crystallization efficiency had a close correlation with the specific surface area of the seed particle. It was found that when struvite was selected as the seed material, the struvite crystallization proceeded at lower $G{\cdot}t_d$ value as compared with other seed materials. This observation implied that the secondary crystal birth would be dominated in this reaction. It was concluded in this study that the particle size was not significant factor on the struvite crystallization, while the $G{\cdot}t_d$ value was a considerably important factor in terms of the theory of the struvite crystal birth.

• Membrane Journal
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• v.28 no.1
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• pp.31-36
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• 2018

The purpose of this study is to investigate the changes of sludge characteristics according to the changes of influent sewage flowrate in the advanced wastewater treatment processes including MBR, SBR, and $A_2O$. The ratio of the actual sewage flowrate to the design flowrate is decreased from 100% to 70, 40%, and 10%, and the specific denitrification rate and ammonia oxidation (nitrification) rate was measured. The specific nitrification rate of the sludge collected from the aeration tank of each process was measured at a similar value ($0.10gNH_4/gMLVSS/day$) in all three process under the condition of 100% of sewage flowrate. It has tended to decrease significantly as the sewage flowrate decreased from 70% to 40%. The specific denitrification rate was also decreased by ~50% as the sewage flowrate decreased. However, considering the total nitrogen concentration in the influent and the microbial concentration in the reactor, the changes in kinetic parameter did not affect overall nitrogen removal. Therefore, it can be concluded that stable nitrogen removal will be possible under low influent flowrate condition if the MLVSS concentration is kept high.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.330-336
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• 2005

The ozone injection method was proposed to improve the catalytic process for the removal of nitrogen oxides ($NO_x$). Nitric oxide (NO) in the exhaust gas was first oxidized to nitrogen dioxide ($NO_2$) by ozone produced by dielectric barrier discharge, and then the exhaust gas containing the mixture of NO and $NO_2$ was directed to the catalytic reactor where both NO and $NO_2$ were reduced to $N_2$ in the presence of ammonia as the reducing agent. A commercially available $V_2O_5-WO_3/TiO_2$ catalyst was used as the catalytic reactor. The $NO_2$ content in the mixture of NO and $NO_2$ was changed by the amount of ozone added the exhaust gas. The effect of reaction temperature, initial $NO_x$ concentration, feed gas flow rate, and ammonia concentration on the removal of $NO_x$ at various $NO_2$ contents was examined and discussed. The increase in the content of $NO_2$ by the ozone injection remarkably improved the performance of the catalytic reactor, especially at low temperatures. The present ozone injection method appears to be promising for the improvement of the catalytic reduction of $NO_x$.

• Journal of the Korean Wood Science and Technology
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• v.33 no.3 s.131
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• pp.45-52
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• 2005

This research was performed to evaluate adsorption behavior of woody charcoals obtained from wood powder, fiber and bark of spruce (Abies sibirica Ledeb). The wood materials were carbonized at various temperatures for 1 hour using experimental rotary kiln without any inert gas. The adsorption capacity of iodine and toluene, specific surface area and removal efficiency of acetic acid and ammonia gas of those charcoals were measured. The higher was the temperature for carbonization, the lower yields of charcoals were. Ash content of bark charcoal was higher than that of wood powder charcoal or fiber charcoal. Elemental analysis of woody charcoal revealed that the content of carbon was gradually lincreased as carbonization temperature was higher. When carbonization temperature was higher, adsorption capacity of woody charcoals for iodine was much improved. Wood powder charcoal and fiber charcoal were more effective for iodine adsorption rather than bark charcoal. Capacity of toluene adsorption was the highest in the charcoal of $600^{\circ}C$. Charcoals produced at high temperature efficiently removed acetic acid gas, while charcoals carbonized at low temperature such as $400^{\circ}C$ were proper to remove ammonia gas. This difference may be explained that the acidity of charcoals depends on the carbonization temperature: charcoals of low temperature indicate acidic property, while those of high temperature turned to alkaline.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.117-127
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• 1983

An experimental research was performed employing the two stage anaerobic digestion of the mixture of the nightsoil and septic tank sludge to determine the effects of various hydraulic retention time of the digestion on chemical characteristics and treatment effeciency, thus determining the proper retention time. Results of the research are as follows, 1. Volatile-acid decreased as HRT increased. 2. Alklinity and ammonia-N tended to increase as HRT increased as did pH values, however, were observed to be constant at higher HRT values than 15 days. 3. The removal efficiencies of TBOD, TCOD and VS increased as HRT increased. 4. The removal efficiency of volatile solid decreased as VS loading increased. 5. It was observed that the rates of gas production were: 0.33 with HRT of 5 days, 0.58 with HRT of 15 days and $0.57m^3/kg$ VS fed/day with HRT of 25 days respectively. It is believed that the highest rate of gas production was at HRT of 15 days. 6. The sludge settling experiment showed that the minimum settling time required to ensure the desired underflow concentraton was estimated to be 8.6 days.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.199-206
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• 2001

Behavior of nutrients along the salinity gradients in the Seomjin River estuary was investigated in March July, September and November, 1999. Sampling sites were set based on the surface salinity during each cruise rather than geographic locations. The results suggest that source of nitrate and silicate was the Seomjin River discharge, while that of nitrite and phosphate was waste disposal from the Gwangynng Bay near the mouth of Seomjin River estuary. Ammonia was supplied inside the estuary at the region about $6\~8$ km far from Nancho Island. Strong removal behavior of some nutrient such as ammonia, phosphate and silicate was observed at $5\~15$ psu salinity area in November, where high concentrations of $chlorophyll\;a\;(>8{\mu}g/L$) occurred. High N : P ratios and entirely removal of phosphate at chlorophyll a peak region suggest that phosphate is the limiting factor for phytoplankton growth. Relatively high ratios of Rb to Ra (Rb: Fluorescence before acidification, Ra: Fluorescence after acidification) at $5\~15$ psu salinity region in November indicate that phytoplankton were in good physiological condition.

• Clean Technology
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• v.12 no.3
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• pp.165-170
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• 2006

When ammonia ($NH_3$) and hydrogen sulfide ($H_2S$) in binary mixture gases were supplied to a biofilter packed with biomedia made of polyurethane, PVA, and worm cast. No odor gases were detected on the outlet of the biofilter when $NH_3$ and $H_2S$ were separately supplied to the biofilter at space velocity(SV) of $50h^{-1}$ until inlet $NH_3$ concentration was increased up to 300 ppmv and inlet $H_2S$ to 428 ppmv. While, inlet $NH_3$ concentration maintained at 50 ppmv, inlet $H_2S$ concentration increased from 1 to 489 ppmv, and the removal efficiency of each gas was investigated. After that, $NH_3$ concentration increased step by step such as 80, 100, 200, 300, 400 and 500 ppmv. $H_2S$ concentration increased gradually when $NH_3$ concentration was set up at each condition. Under each condition, removal efficiency of $NH_3$ and $H_2S$ gas was investigated by analysing the gases sampled from the inlet and outlet of the biofilter. When binary gases were supplied to the biofilter and inlet $NH_3$ concentration was increased from 50 to 300 ppmv, elimination capacity of $NH_3$ increase linearly as inlet loading increased to $11.14g\;N{\cdot}m^{-3}{\cdot}h^{-1}$. However, as inlet $NH_3$ concentration increased over 300 ppmv, both removal efficiency and elimination capacity decreased while inlet loading increased. $H_2S$ removal efficiency was not affected seriously by the simultaneous supply of $NH_3$ when maximum inlet loading of $H_2S$ was under $40.27S{\cdot}m^{-3}{\cdot}h^{-1}$ and maximum inlet loading of $NH_3$ was under $15.25N{\cdot}m^{-3}{\cdot}h^{-1}$.

• KSBB Journal
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• v.18 no.3
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• pp.211-216
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• 2003

The removal yield of dissolved organic matter in drinking water by biological activated carbon (BAC) process was investigated. The tested processes wer raw water-AC process (BAC1), raw water-ozonation-BAC process (BAC2), and raw water-ozonation-coagulation/sedimentation-BAC process (BAC3). The amounts of organic matter was measured as dissolved organic carbon (DOC), ulta-violet radiation at 254 nm wavelength ($UV_{254}$), total nitrogen (T-N), ammonia nitrogen (NH_3$-N), and total phosphate (T-P). As a results, 30.7% DOC was removed by BAC2 process, which showed higher removal efficiency than BAC1 or BAC3 processes. The removal yield of $UV_{254}$ in BAC1, BAC2, and BAC3 processes were observed as 45.3%, 44.6%, 58.4%, respectively. And the removal yield of ammonia nitrogen were 66%, 81%, 29% in each BAC processes. The optimal empty bed contact time (EBCT) of BAC processes was estimated as 10 minute. This study has shown that BAC process combined with ozone treatment was efficient for removing dissolved organic matter in water.