This study was performed to investigate the effects of water molecules on ozone oxidation of acetaldehyde using a manganese oxide catalyst at room temperature. The catalytic ozone oxidation was conducted at different relative humidity (RH) conditions of 0%, 50%, and 80%. As the RH increased, both ozone and acetaldehyde removal efficiencies dropped due to competitive adsorption on the surface of the catalyst. At the highest RH of 80%, the oxidation reaction was severely retarded, and oxidation by-products such as acetic acid were formed and adsorbed on the surface. After the ozone oxidation of acetaldehyde, the regeneration of the catalyst using ozone alone was tested, and the further oxidation of accumulated organic compounds was investigated under the RH conditions of 0%, 50%, and 80%. When the highest relative humidity was introduced in the regeneration step, the ozonation reaction with the by-products adsorbed on the catalyst surface decreased due to the competitive reaction with water molecules. These findings revealed that, only when relative humidity was low to minimize the formation of by-products, the ozone oxidation of acetaldehyde using the manganese oxide catalyst at room temperature can be feasible as an effective control method.

In this study, a manganese catalyst on the surface of a ceramic support was developed for the removal of odor emitted from barbecuing restaurants. Its ozone oxidation at room temperature was tested using acetaldehyde (CH3CHO), the most dominant compound in the barbecuing odor, and the ozonation efficiency under wet conditions was also studied. The manganese catalyst was made with the honeycomb-type ceramic support, and an acid pretreatment was applied to increase its specific surface area, resulting in an increase of the degree of dispersion of manganese oxide. The acetaldehyde removal efficiency using the manganese catalyst on the acidpretreated support (Mn/APS) increased by 49%, and the ozone decomposition rate and the CO2 conversion rate also increased by 41% and 27%, respectively. The catalyst without surface pretreatment (Mn/S) showed a low efficiency for the acetaldehyde ozonation, and other organic compounds such as acetic acid (CH3COOH) and nonanal (CH3(CH3)7CHO) were found as oxidation by-products. In comparison, CO2 was the most dominant product by the ozonation of acetaldehyde using the Mn/APS. When the relative humidity was increased to 50% in the influent gas stream, the acetaldehyde removal efficiency using the Mn/APS decreased, but only the production rates of CO2 and acetic acid were changed. As a result, the manganese oxide catalyst on the surface of the acid-pretreated honeycomb support manifested high acetaldehyde ozonation even at humid and room temperature conditions.

Odor emitted from food waste is commonly known as a severe problem, and needs to be controlled to minimize public complaints against food waste collection systems. In this study, ozone oxidation with manganese oxide catalyst, which is known to effectively treat odorous substances at room temperature, was applied to remove acetaldehyde and hydrogen sulfide, the model odorous compounds from food waste. In addition, the effect of relative humidity (RH) on the ozone/catalyst oxidation was tested at 40%, 60%, and 80%. When the catalyst was not applied, the removal of acetaldehyde was not observed with the ozone oxidation alone. In addition, hydrogen sulfide was slowly oxidized without a clear relationship under RH conditions. Meanwhile, the ozone oxidation rates for acetaldehyde and hydrogen sulfide substantially increased in the presence of the catalyst, but the removal efficiencies for both compounds decreased with increasing RH. Under the high RH conditions, active oxygen radicals, which were generated by ozone decomposition on the surface of the catalyst, were presumably absorbed and reacted with moisture, and the decomposition rate of the odorous compounds might be limited. Consequently, when the ozone oxidation device with a catalyst was applied to control odor from food waste, RH must be taken into account to determine the removal rates of target compounds. Moreover, its effect on the system performance must be carefully evaluated.

Climate change is believed to increase the amount of dissolved organic matter in surface water, as a result of the release of bulk organic matter, which make difficult to achieve a high quality of drinking water via conventional water treatment techniques. Therefore, the natural water treatment techniques, such as managed aquifer recharge (MAR), can be proposed as a alternative method to improve water quality greatly. Removal of bulk organic matter using managed aquifer recharge system is mainly achieved by biodegradation. Biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) can be used as water quality indicators for biological stability of drinking water. In this study, we compared the change of BDOC and AOC with respect to pretreatment methods (i.e., ozone or peroxone). The oxidative pretreatment can transform the recalcitrant organic matter into readily biodegradable one (i.e., BDOC and AOC). We also investigated the differences of organic matter characteristics between BDOC and AOC. We observed the decreases in dissolved organic carbon (DOC) and the tryptophan-like fluorescence intensities. Liquid chromatographic - organic carbon detection (LC-OCD) analysis also showed the reduction of the low molecular weight (LMW) fraction (15% removed, less than 500 Da), which is known to be easily biodegradable, and the biopolymers, high molecular weight fractions (66%). Therefore, BDOC consists of a broad range of organic matter characteristics with respect to molecular weight. In AOC, low molecular weight organic matter and biopolymers fraction was reduced by 11 and 6%, respectively. It confirmed that biodegradation by microorganisms as the main removal mechanism in AOC, while BDOC has biodegradation by microorganism as well as the sorption effects from the sand. O3 and O3 + H2O2 were compared with respect to biological stability and dissolved organic matter characteristics. BDOC and AOC were determined to be about 1.9 times for O3 and about 1.4 times for O3 + H2O2. It was confirmed that O3 enhanced the biodegradability by increasing LMW dissolved organic matter.

Oxidation of erythromycin, sulfamethazine and sulfathiazole by ozone was experimentally investigated to see the effects of background water quality such as ultrapure water, humic acid and biologically treated wastewater and water temperature on the removal rate, consequently to provide design information when the ozone treatment process is adopted. Initial concentration of the antibiotics was spiked to 10 μg/l and ozone dose was 1, 2, 3, 5, 8 mg/l. While the removal rate of erythromycin under ultrapure water background by ozone oxidation was over 99%, that under humic acid and biologically treated wastewater background was markedly reduced to the range of 59.8%~99% and 17.0%~99%, respectively. When water temperature is decreased from 20℃ to 4℃, the removal rate is reduced from the range of 17.0%~99% to the range of 9.4%~97.4% under biologically treated wastewater background. The effects of background and temperature on the removal rate of sulfamethazine and sulfathiazole were similar to erythromycin, but the degree was different. Therefore, it is concluded that the background of water to be treated as well as water temperature should be taken into consideration when the design factor such as ozone dose is determined to meet the treatment objective in the ozone treatment process.

Optimal processes to remove chromaticity at E water treatment plant(WTP) mainly caused by algae of E lake in Jeju island were investigated based on lab-tests of chlorine and ozone oxidation. 42.9% of chromaticity of filtered water was removed by chlorine oxidation under pH 7.0∼8.0, dose of 1.0 mg/L with contact time of 30∼60 min. On the other hand, chromaticity removal was 71.4% when post-ozone dose of 0.9∼1.9 mg/L and pH 9.0, while it was increased to 86.7% under post-ozone dose of 3.1∼7.3 mg/L and pH 9.0. However, there was no significant chromaticity removal efficiency increase when ozone doses were higher than 5.0 mg/L regardless of feeding point(i.e., pre-ozonation and post-ozonation) and pHs(i.e., 7.0 and 9.0.) under the experimental conditions. Based on the results, chlorine oxidation using existing chlorination facilities at the WTP is recommended for lower chromaticity while ozone oxidation is recommended for higher chromaticity by installing new ozone feeding facilities.

Microfiltration (MF) and Ultrafiltration (UF) membrane processes capable of producing highly purified water have been extensively applied as a pretreatment process in the wastewater reuse field with the improvement of membrane properties and resistance, development of operating protocols, and improvement of technologies of backwashing and physicochemical cleaning, and improvement of scale and antifoulants. However, despite of the development of membrane production and process technologies, fouling still remains unresolved. This study confirmed that foulants such as polysaccharides, proteins and humic substances existed in final treated effluent (secondary effluent) by fluorescence excitation emission matrix (FEEM) and fourier transform infrared spectroscopy (FTIR) analysis. In addition, when constructing ozone oxidation and coagulation processes as a hybrid process, the removal efficiency was 5.8%, 6.9%, 5.9%, and 28.2% higher than that of the single process using coagulation in turbidity, color, dissolved organic carbon (DOC), and UV254, respectively. The reversible and irreversible resistances in applying the hybrid process consisting of ozone oxidation and coagulation processes were lower than those in applying ozone oxidation and coagulation processes separately in UF membrane process. Therefore, it is considered possible to apply ozonation/coagulation as a pretreatment process for stable wastewater reuse by and then contributing to the reduction of fouling when calculating the optimal conditions for ozone oxidation and coagulation and then to applying them to membrane processes.

The aim of this study was to evaluate the chemical quenching system for residual ozone and to determine the operating condition for the quenching system. Hydrogen peroxide (H₂O₂) and sodium thiosulfate (Na₂S₂O₃) were investigated as quenching reagents for ozone removal, and the tendency of each chemical was notably different. In the case of H₂O₂, the degradation rate of ozone was increased as the concentration of H₂O₂ increase, and temperature and pH value have a significant effect on the degradation rate of ozone. On the other hand, the degradation rate of ozone was not affected by the concentration of Na₂S₂O₃, temperature and pH value, due to the high reactivity between the S₂O₃²- and ozone. This study evaluates the decomposition mechanism of ozone by H₂O₂ and Na₂S₂O₃ with consideration for the water quality and reaction time. Furthermore, the removal test for the quenching reagents, which can be remained after reaction with ozone, was conducted by GAC process.

We used a conventional activated sludge process to treat a paper wastewater, and then the effluent was treated with an ozone oxidation process as advanced process to remove non-degradable materials. It was found that the removal efficiency rates of the organic matter has been rapidly increased initially, and then it was almost constant after this period. The concentration of ozone should be recommended to maintain approximately 8.3 mg/L during this operation to keep the CODmn value below 100 mg/L and ozone contact time longer than 60 min.

Ozonation was performed for an effective removal of bisphenol A in laboratory scale batch reactor under various experimental conditions including the Al2O3 catalysts dosage, UV irradiation and temperature. Flow rate of ozone 1.0 L min−1 and ozone concentration of 75 ± 5 mg L−1 was maintained constantly, and the pH, COD and TOC were measured in 10 min intervals during oxidation processes for 60 min at 20oC. Our results confirmed that the O3/UV, O3/UV/Al2O3 in the ozonation improved the removal efficiency of both COD and TOC in solution compared with O3 process alone. The pseudo first-order rate constants for the elimination of COD and TOC were calcluated to be 3.58 × 10−4 sec−1, 1.58 × 10−4 sec−1 and 7.98 × 10−4 sec−1, 3.42 × 10−4 sec−1 and activation energy was 1.44 kcal·mol−1 and 2.32 kcal·mol−1 at 20oC, respectively.

엄격해져가는 수질기준과 수자원 확보를 위하여 정수처리시설 및 하폐수처리시설에 나노막(Nanofiltration, NF)과 RO(Reverse Osmosis, RO) 멤브레인 적용이 증가하고 있다. 멤브레인 공정의 경우 오염물질이 지속적으로 농축됨에 따라 고농도의 농축수를 발생시키는 문제점을 지니고 있다. 이러한 NF/RO 농축수의 경우 용존 고형물로 구성되어 있으며, 유입수 대비 경도 물질(Ca2+, Mg2+), 난분해성 유기물 및 미량오염물질 등이 4~10배 농축되어 고농도이므로 별도의 처리가 요구된다. 본 연구에 적용한 CaCO3 결정화 기법은 유동상 반응기 내 seed를 충진하고, 반응기 하단부에서 상향류식 흐름으로 원수를 주입함과 동시에 NaOH, Ca(OH)2 등의 약품을 주입하는 방법이다. 약품 주입으로 pH는 증가하고, 이 과정에서 CaCO3, Mg(OH)2 의 형태로 경도 유발물질을 결정화시켜 회수가 가능하다. 반응기 내부의 seed는 반응 표면적을 증가시켜 반응속도를 증가시키는 역할을 하며, 이 과정에서 seed 표면에 결정이 성장하게 된다. 성장한 seed는 회수하여 석회생산, 산성폐수 중화제 등으로 재활용이 가능하다. 또한, 후단의 Ozone 산화 공정(1mg O3/mg DOC)을 연계하여 추가적으로 유기물 제거를 위한 연구를 진행하였다. 실험은 NF 농축수와 RO 농축수(G, D)로 진행하였으며, NF 농축수와 G RO 농축수의 경우 Ca 85%, Mg 13~32% 제거율을 나타났다. 그러나 D RO 농축수의 경우 상대적으로 경도 제거가 낮게 확인되었으며, 이는 수중의 알칼리도가 낮아 결정화 반응이 충분히 이루어지지 못한 것으로 판단된다. EDS-SEM 분석으로 seed 표면을 관찰하여 결정물질의 형성과 사용 전․후 seed의 구성 원소 분석을 통하여 Ca함량 변화를 확인하였으며, 경도 제거율이 높을 경우에 seed 표면에서의 Ca함량이 증가하는 것으로 나타났다. 이는 경도 제거시 seed 표면에서 올바르게 결정화 반응이 이루어짐에 따라 회수 가능성을 확인하였다. PS 후단에 오존 산화를 연계하여 농축수를 처리한 후, COD, DOC, LC-OCD, UV254, SUVA, F-EEM 분석을 진행하였다. 그 결과 COD, DOC는 크게 변하지 않았으나, LC-OCD의 경우 biopolymer peak가 감소하고 humic peak가 증가하는 경향을 나타내었다. 이는 유기물의 무기화가 아닌 비교적 고분자 물질인 biopolymer가 상대적으로 저분자 물질인 humic 등으로 저분자화된 것으로 사료된다. 또한, UV254 값은 원수대비 전체적으로 감소하였으며, SUVA 값의 경우 NF 농축수 34.5±2.7%, G RO 농축수 43.2±1.1%, D RO 농축수 45.2±10% 감소한 것으로 확인되었다. F-EEM 경향은 LC-OCD, UV254, SUVA와 유사한 경향을 나타냈으며, 모든 영역(Aromatic protein-like, Tryptophan Protein-like, Humic-like)에서 80% 이상의 높은 intensity 감소율을 보였다. 이는 오존 산화에 의하여 불포화 결함이 깨짐에 따라 저분자화가 이루어진 것으로 보인다. 위와 같은 결과를 통하여, 본 연구에서 멤브레인 농축수에서의 경도 물질의 결정화를 통한 회수 가능성을 확인할 수 있었다. 또한, 오존 산화 공정과의 연계를 통하여 유기물질의 저분자화를 통하여 추후 연구시 고려되어지는 MBR 공정과 같은 생물학적 처리 공정에 긍정적으로 작용 가능할 것으로 예상된다.