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.

폴리설폰 한외여과막 분리막공정을 이용하여 투과유속 상에서의 오존의 효과를 고찰하였다. 처음에는 조제한 페놀용액을 이용해 오존의 농도 10-45 mg/l·min을 가한 후에 분리막내에 막오염 제거를 목적으로 시도하였으며 이후에는 오존과 분리막이 혼합된 연속공정에서 폐수처리를 위해 오존에 의한 통일효과를 고찰하기 위해 시도하였다. 전처리 방법으로는 펜톤 산화법을 이용하여 화학응집을 시도하였고 그 결과 폐수내 용존유기물 제거에 효과가 있는 것으로 나타났다. 실험결과 오존을 이용하게 되면 투과유속이 10% 이상 증가한다는 사실이 조제수와 폐수에 공히 같게 나타났으며 오존과 과산화수소를 이용한 고도처리에서도 투과유속증가에 더욱 효과적이었다. 특히 오존을 이용한 처리수에서는 투과압력이 12% 이상 낮아지는 효과가 나타났으며 분리막 공정에 오존처리는 막오염을 거의 제거하기보다는 막오염을 제한적으로 막는 효과를 얻었다.

The purpose of this study was to develop a recycling system for ozone off-gas. Although the ozone transmission rate of the injector method differs slightly depending on the ozone injection rate, it reaches approximately 99%, which is very high. During the increase in water inflow to the ozone recycling system from 2 L/min to 10 L/min, the average ozone recycling rate was 99.4% at a 1 ppm ozone injection rate, 98.6% at a 2 ppm ozone injection rate, 98.1% at a 3 ppm ozone injection rate. Ozone treatment facility operating costs can be divided into the costs of pure oxygen production, ozone production, and maintenance. The annual operating costs of ozone treatment facilities in Korea are estimated to be approximately 38.9 billion won. The annual savings are estimated to be approximately 5.8 billion won when the ozone transfer rate of the diffuser method, which is mostly employed in domestic water treatment plants, is 85% and 15% of the ozone is recycled.

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.

The main objectives of this research are to investigate characteristics of ozone solubility due to low solubility of conventional bubbles-ozone generators, evaluate the treatment characteristics of reclaiming textile wastewater for industrial water by means of micro/nano bubbles-dissolved ozone flotation(MNB-DOF) process. The textile wastewater used in this research was obtained from final effluent of the textile wastewater in B city. There is a 400L reactor which consists of a micro-nano bubble system and a ozone generator for experiments. As a result of generating micro-nano bubbles (below 0.5 ㎛) by using of MNB-DOF process, it improved ozone solubility due to higher ozone transfer rates. Consequently, the shorter ozonation time clearly indicates the lower power costs. The reported results clearly indicated that MNB-DOF process can be effectively and inexpensively. Results of the experiments through MNB-DOF process in this study satisfy all reclaiming standards as industrial water: pH 6.5～8.5, SS 10 mg/L or below, BOD_5 6 mg/L or below, turbidity 10 NTU or below, Coliforms 1,000/100 mL or below. Therefore there is a possibility of the reclaiming of the textile wastewater as industrial water.

The performance of ozone contactor in ozone-BAC advanced water treatment process was evaluated by the degree of decomposition of organic matters. The degree was measured by the analyses of UV254 absorbance and the concentrations of DOC and BDOC for the sand filtered water and the ozone treated water, respectively. In addition, the ozone concentration in the contactor, required for the maximum BDOC concentration, was selected as the optimum concentration, and the appropriate residential time of ozone treated water in a reservoir was recommended based on the residual ozone concentration in the treated water. The following results were obtained from the pilot scale experiments. By ozonation UV254 absorbance was decreased, and BDOC concentration was increased. The change of DOC concentration by ozonation was negligible, but the excess input of ozone resulted in the removal of the small amount of BDOC by complete oxidation. The optimum ozone concentration was 0.58 mg O3/mg DOC. In order to remove residual ozone, 20 minutes of the residential time were enough after ozonation.

The effect of ozone on the formation and the removal of disinfection byproducts(DBPs) of chlorination process was studied to elucidate the performance of water treatment process. The samples of raw water, prechlorination process, and preozonation process were analyzed quantitatively according to the Standard Methods for the Examination of drinking water. As a result, most of total trihalomethanes(THMs) which were formed in prechlorine treatment process was not removed in the preozonation process. Most of haloacetic acids(HAAs), haloacetonitriles(HANs), and chloral hydrate(CH) was removed in sedimentation and biological activated carbon(BAC) filtration processes. However, DBPs were increased more or less by postchlorine step. In particular, the formation of THMs and HAAs depends on ozone more than chlorine, but, the formation of HANs and CH depends on chlorine more than ozone. The seasonal variation of DBPs concentration for the year needs to be investigated to study the temperature effect because DBPs strongly depend on temperature among various efficient factors.