• Membrane and Water Treatment
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• v.14 no.1
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• pp.1-10
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• 2023

This study explored the feasibility of calcium-rich food waste, Mactra veneriformis shells (MVS), as an adsorbent for phosphate removal, and its removal efficiency was enhanced by the thermal activation process. The CaCO3 in MVS was converted to CaO by thermal activation (>800 ℃), which is more favorable for adsorbing phosphate. Thermal activation did not noticeably influence the specific surface area of MVS. The MVS thermally activated at 800 ℃ (MVS-800), showed the highest phosphate adsorption capacity, was used for further adsorption experiments, including kinetics, equilibrium isotherms, and thermodynamic adsorption. The effects of environmental factors, including pH, competing anions, and adsorbent dosage, were also studied. Phosphate adsorption by MVS-800 reached equilibrium within 48h, and the kinetic adsorption data were well explained by the pseudo-first-order model. The Langmuir model was a better fit for phosphate adsorption by MVS-800 than the Freundlich model, and the maximum adsorption capacity of MVS-800 obtained via the Langmuir model was 188.86 mg/g. Phosphate adsorption is an endothermic and involuntary process. As the pH increased, the phosphate adsorption decreased, and a sharp decrease was observed between pH 7 and 9. The presence of anions had a negative impact on phosphate removal, and their impact followed the decreasing order CO₃^2- > SO₄²- > NO₃^- > Cl^-. The increase in adsorbent dosage increased phosphate removal percentage, and 6.67 g/L of MVS-800 dose achieved 99.9% of phosphate removal. It can be concluded that the thermally treated MVS-800 can be used as an effective adsorbent for removing phosphate.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.4
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• pp.453-462
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• 2010

Nowadays, the challenges of ensuring good water quality and quantity of river are becoming more important for human society, but there has been troublesome for purifying river water. In this study, we performed the fundamental study of a river water treatment system using riverside soil and eco-friendly optimal media for improving river water quality and can also treat a large amount of river water. As the results of the physical and chemical characterization of the two different soils (Kyungan and Chungrang, The Republic of Korea), which were collected from real stream sides in the Han River basin, and five kinds of media (zeolite, perlite, steel slag, woodchip and mulch), both soils were all classified as a sand, and effective size ($D_{10}$) and uniformity coefficient (U) of the soil were about 0.2 mm and 4 or so, respectively. Through the batch and column experiments with the soil and eco-friendly media, zeolite and mulch were found to be efficient for decreasing nitrogen. In addition, steel slag was especially superior to the other media for phosphorus removal. From soil reforming tests volume ratios were 2.8, 1, and 1 of Kyungan soil, zeolite, and steel slag hydraulic conductivity of mixed soil was increased $1.30{\times}10^{-2}$ from $2.85{\times}10^{-3}$ of Kyungan soil, and the removal efficiencies of nitrogen and phosphorus were also improved. These results show that reforming of the soil enhanced the purification of a large amount of water, and zeolite, mulch, and steel slag might be facilitated as proper functional media.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.939-947
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• 2000

Enhanced biological phosphorus removal (EBPR) was performed in an anaerobic/aerobic sequencing batch reactor (SBR). Influent was a synthetic wastewater based on acetate as a carbon source. The sludge age and hydraulic retention time were kept at 10 days and 16 hrs, respectively, Phosphate release during the anaerobic period and phosphate uptake in aerobic period were increased gradually with time. and after about 200 days, steady-state operation could be achieved with complete removal of influent phosphate. Number distribution of microbial community in the sludge performing EBPR was investigated during the steady state operation. 17 rRNA targeted oligonucleotide probes were designed and slot hybridization technique was used to determine the number distribution of each microorganism. In the acetate fed SBR, rRNA belonging to the beta subclass of proteobacteria was the most dominant in total rRNA and rRNA matching to CTE probe was the second, rRNAs of Acinetobacter, Aeromonas and Pseudomonas, which are usually thought as phosphorus accumulating organisms in EBPR processes, constituted less than 10% of total rRNA. From this community analysis, it was inferred that microorganisms belong to the beta subclass of proteobacteia (BET) and CTE such as Rhodocyclus group were important in biological phosphorus removal. Therefore, the role of Acinetobacter, Aeromonas and Pseudomonas in the EBPR might have been overestimated.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.992-998
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• 2008

Recently, a new concept for nitrogen removal that is simultaneous nitrification and denitrification(SND) has been studied for wastewater treatment process. The DMR(Daiho Microbic Revolution) process that used in this study consists of two suspended anoxic, anaerobic reactors and an aerobic biofilm reactor. The function of aerobic environment and the intensity of air flow rate(2.0, 1.0, 0.5, 0.4, 0.2 L/min) were studied in the biofilm reactor; also SND and nutrient removal efficiencies were investigated. Experimental results indicated that the change in air flow did not affect COD$_{Cr}$ removal significantly. Thus sustained at 93%. The lower the air flow rate, the higher T-N removal efficiency was attained(i.e.80% at 0.2 L/min). SND efficiency was 62, 65, 72 and 78% corresponding to each air flow rate. T-P removal was sensitive to aeration intensity and removal enhanced from 75% to 96% when the air flow rate was changed from 2.0 to 0.5 L/m; however second release occured in the clarifier at 0.2 L/min. Phosphorus content of activated sludge was 5.0%, as P releases and acetate uptake a ratio of 0.75 mg P/ mg HAc.

• Korean Journal of Environmental Agriculture
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• v.17 no.4
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• pp.352-357
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• 1998

This experiment was conducted to find out the effects of major nutrient levels(N, P, K) on ozone susceptibility of tomato plants(Lycopersicon esculentum Mill, cv. Pink Glory). Plants were grown in water culture system. A half-strength of Hoagland's nutrient solution was considered as a standard formulation($N_{100}$ $P_{100}$ $K_{100}$). The levels of major nutrients were adjusted through addition or removal of several fertilizer salts from the standard solution. Top growth was significantly decreased at the low nitrogen level or phosphorus removal condition. P- and K-contents of leaves were greatly decreased by removal of salts containing P and K from the nutrient solution. The rate of ozone injury was significantly increased when potassium was removed. However, the influence of nitrogen and phosphorus levels or high potassium level on injury occurrence did not show statistical significance compared to the standard solution. Ozone exposure resulted in reduction of chlorophyll, and increase of ethylene production, electrolyte leakage and malondialdehyde(MDA) contents. These changes were much more enhanced in plants grown at the potassium removal solution. Whereas the activity of superoxide dismutase(SOD) was low at the potassium removal treatment and this tendency remained after ozone exposure. These results indicated that potassium nutrient level in tomato plants is closely associated with the susceptibility to ozone injury.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.105-108
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• 2000

Enhanced biological phosphorus removal (EBPR) is not always successfully achieved by anaerobic/aerobic operation. It has been reported that the EBPR deterioration was caused by the outgrowth of glycogen-accumulating organisms (GAO) over polyphosphate-accumulating organisms (PAO). It was found that pHcould be a tool which might induce the success of EBPR in a sequencing batch reactor (SBR) supplied with acetate. When the pH of anaerobic phase was controlled at 7.0, the operation resulted in failure of EBPR. However, when the pH of anaerobic phase increased up to 8.4, complete EBPR was achieved. We explained the mechanism of pH effect on the competition between GAO and PAO with experimental results and previously proposed biochemical models.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2007.05a
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• pp.383-389
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• 2007

호기시간 변경에 따른 SBR에서의 영양염류제거특성과 MLVSS의 변화를 본 이번 연구에서는 다음과 같은 결론을 얻었다. 1) 충분하지 못한 산소의 공급은 미생물의 wash-out으로 인한 영양염류 제거 효율의 저조를 나타냈다. 2) 산소 공급량이 $0.045m^3$였던 R2에서 저조산 질산화가 나타났으나, 인을 과다 축적하는 EBPR(Enhanced Biological Phosphorus Removal)을 나타냈다. 3) 산소 공급량이 $0.06m^3$이상이었던 R3, R4에서는 60%이상의 질산화 및 탈질화와 약 100%에 달하는 인 제거 효율을 나타내었다. 4) 단위 미생물당 $1.5{\sim}1.8ml/mg$의 공급 산소량이 인 흡수에 유리한 것으로 나타났다. 5) 공급되는 산소에 있어 유기물 분해>인흡수>질산화에 우선적으로 소모되는 것으로 나타났다.

• Journal of Korean Society on Water Environment
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• v.21 no.4
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• pp.398-402
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• 2005

The enzyme Xeronine was investigated as a microbial activating substance in biological wastewater treatment processes. Xeronine as bio-stimulant was injected in the anaerobic sludge and the activated sludge treating wastewater in order to examine the effect of hidden benefits. Bio-stimulant did not show significant improvement of anaerobic treatablity. In the aerobic system, higher bio-stimulant dose condition resulted in slightly more removal of nitrogen and phosphorus. Floc aggregation and zone settling velocity as solid-liquid separation factors in activated sludge systems was enhanced by bio-stimulant. Effects of bio-stimulants injection on improvement of water quality and microbial activity did not clear in terms of normal operation conditions.

• Analytical Science and Technology
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• v.35 no.2
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• pp.41-52
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• 2022

The leaching of nitrate from soil increases the concentration of elements, such as nitrogen, phosphorus, and potassium, in water, causing eutrophication. In this study, the feasibility of using clinoptilolite as an ion-exchange material to reduce nitrate leaching in soil was investigated. Soil samples were collected from three soil depths (0 - 30, 30 - 90, and 90 - 120 cm), and their sorption capacity was determined using batch experiments. The effects of contact time, initial concentration, adsorbent dosage, pH, and temperature on the removal of NO₃^- were investigated. The results showed that an initial concentration of 25 mg L^-1, a contact time of 120 min, an adsorbent dosage of 5.0 g/100 mL, a pH of 3, and a temperature of 30 ℃ are favorable conditions. The kinetic results corresponded well with a pseudo-second-order rate equation. Intra-particle diffusion also played a significant role in the initial stage of the adsorption process. Thermodynamic studies revealed that the adsorption process is spontaneous, random, and endothermic. The results suggest that a modification of clinoptilolite effectively reduces the leaching of nitrate in soil.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.40-46
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• 2006

This study was initiated to evaluate the inhibitory effect of selected heavy metals on the growth of Acinetobacter sp. Down as one of the phosphorus accumulating microorganisms (PAO) involved in the enhanced biological phosphorus removal (EBPR) process of the wastewater treatment plant. Acinetobacter sp. was initially selected as a starting model microorganism and was grown under aerobic condition for this experiment. The heavy metals selected and investigated in this study were cadmium (Cd), copper (Cu), mercury (Hg), nickel (Ni), and zinc (Zn). Median $(IC_{50})$ and threshold $(IC_{10})$ inhibitory concentrations for Cd, Cu, Hg, Ni, and Zn were 2.95 and 1.45, 4.92 and 2.53, 0.03 and 0.02, 1.12 and 0.43, 14.84 and 5.46 mg $L^{-1}$, respectively. We demonstrated that most of heavy metals tested in the experiment inhibited the growth of Acinetobacter sp. in the range of predetermined concentrations. Based on the data obtained from the experiment, Hg was the most sensitive to Acinetobacter sp., then Ni, Cd, Cu, and Zn in order.