황산은 뛰어난 촉매제로서의 특성과 경제성으로 산업현장에서 다양한 화학 반응에 널리 사용되고 있다. 그러나 황산은 사용 후 재활용이 불가능하고 대량의 폐수를 발생시키는 특성이 있어 폐기과정에서 환경오염의 위험이 있으며 폐수 처리 과정에서 추가적인 비용 과 에너지가 소모된다. 본 연구는 황산을 대신할 수 있는 친환경 촉매제를 활용하여 폐수 의 배출을 줄이고 기업의 친환경 경영을 강화할 수 있는 방안을 모색하고자 실시되었다. 연구에서는 아민 산화반응을 위해 사용되는 말레인산 무수물 기반 고분자 촉매인 PIMA 과 POMA을 평가하여 피리딘 유도체의 아민 산화반응을 최적화하였다. POMA 촉매는 아연 피리치온 합성에 적용되었으며, 98% 이상의 선택성과 93% 이상의 합성 수율로 높은 촉매 활성을 보였다. 또한 촉매는 여과 과정을 통해 쉽게 회수되었으며, 회수율은 99.8% 를 초과하였고, 여러 번 사용 후에도 활성을 유지하였다. POMA 촉매는 전통적인 황산 촉매를 대체하여 폐수 발생에 의한 환경 부담을 최소화하고 기업의 ESG 경쟁력을 높이는 데 기여할 것으로 기대한다.

Strong acidic wastewater containing a radionuclide is generated from the decontamination of radioactively contaminated wastes or equipment. This wastewater is generally treated though a precipitation process using an alkali (alkali earth) hydroxides. In this precipitation process, a significant amount of alkali (alkali earth) sulfates are generated, which is the reason for the increase in the radioactive waste generation. In this study, a method for separating only radionuclides and metal ions from the wastewater was evaluated. For this reason, precipitation behaviors of radionuclides and metal ions by hydrazine injections were investigated using equilibrium calculations. In addition, behaviors of hydrazine decomposition after removal of radionuclides and metal ions were analyzed for recycling the wastewater.

Excess nitrogen (N) flowing from livestock manure to water systems poses a serious threat to the natural environment. Thus, livestock wastewater management has recently drawn attention to this related field. This study first attempted to obtain the optimal conditions for the further volatilization of NH3 gas generated from pig wastewater by adjusting the amount of injected magnesia (MgO). At 0.8 wt.% of MgO (by pig wastewater weight), the volatility rate of NH3 increased to 75.5% after a day of aeration compared to untreated samples (pig wastewater itself). This phenomenon was attributed to increases in the pH of pig wastewater as MgO dissolved in it, increasing the volatilization efficiency of NH3. The initial pH of pig wastewater was 8.4, and the pH was 9.2 when MgO was added up to 0.8 wt.%. Second, the residual ammonia nitrogen (NH4 +-N) in pig wastewater was removed by precipitation in the form of struvite (NH4MgPO4·6H2O) by adjusting the pH after adding MgO and H3PO4. Struvite produced in the pig wastewater was identified by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. White precipitates began to form at pH 6, and the higher the pH, the lower the concentration of NH4 +-N in pig wastewater. Of the total 86.1% of NH4 +-N removed, 62.4% was achieved at pH 6, which was the highest removal rate. Furthermore, how struvite changes with pH was investigated. Under conditions of pH 11 or higher, the synthesized struvite was completely decomposed. The yield of struvite in the precipitate was determined to be between 68% and 84% through a variety of analyses.

최근 신재생에너지의무화제도(RPS: Renewable Portfolio Standard)대상 신재생에너지 항목에 발전소 온배수가 신재생에너지공급인증서(REC:Renewable Energy Certificate)의 수열에너지(가중치 1.5)로 추가되어 온배수 열원에 대한 가치가 높아졌다. 본 연구에서는 고탁도지역 온배수의 직접적인 활용을 위한 방안으로 히트펌프시스템 내 탁도저감장치를 도입하여 열교환기에 가해지는 오염물질의 저감 효과를 확인해보기 위해 한 달 동안 실증테스트를 실시하였다. 실험결과 탁도 저감효과가 80 % 이상으로 고탁도 지역의 온배수 활용을 위한 방안으로 탁도저감장치의 적용가능성을 확인 할 수 있었다. 또한 탁도저감시스템에 따른 열교환기의 오염도 저감 효과를 검증하기 위해 30일간 운전한 열교환기를 해체하여 분석해본 결과 탁도저감시스템을 거친 열교환기보다 그렇지 않은 열교환기의 오염정도가 높은 것을 확인하였다. 열교환기에 유입된 오염물질(스케일)을 분석해본 결과 주로 SiO2, Na(Si3Al)O8, CaCO3, NaCl 성분의 광물이 검출되었는데 이는 높은 탁도로 인해 해양퇴적토가 열교환기에 유입된 것으로 분석되었다. 그 외에도 소량이지만 TiO2, MnO, Cr2O3가 검출되었다. 이는 열교환기를 세척할 때 열교환기 재료로부터 기인한 중금속이 소량 용출된 것으로 판단된다.

합성폐수 내의 유기물(COD), 질산성 질소, 인산이온을 제거하기 위한 폐수처리 시스템 개 발을 위한 연구를 수행하였다. 먼저 COD는 HClO의 산화 반응에 의해 거의 100 % 제거되었으며 전기 화학적 처리에 의해 질산성 질소가 암모니아성 질소로 환원되지만, 암모니아성 질소는 HClO 처리에 의 해 질산성 질소로 재 산화 되었다. 암모니아성 질소는 가열 증발 처리에 의하여 거의 100% 제거 되었 으며 HClO 처리를 하여도 재 산화되는 암모니아성 질소는 나타나지 않았다. 인산 이온은 pH에 따라 금속 착염을 형성함으로써 침전 처리에 의해 제거할 수 있었으며 전기화학적 처리와 HClO 처리를 통 하여 COD 99.5 % 이상, 질소 97.3 %, 인 91.5 %의 제거 효율을 얻을 수 있었다.

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.

This study was performed to improve the foaming generated in the effluent of wastewater treatment plant from March 2015 to July 2016. The main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. Particularly, the foam growth was most active when there is low tide and larger discharge. To solve this problem, we experimented after installing fine mesh screen and the artificial channel device with underwater discharging outlet in the treated wastewater discharge channel and the outlet, respectively. As a result, the effects of foam reduction by devices ranged 85.0~92.0% and 70.7~85.6%, respectively. In addition, the foam and the noise were easily solved, first of all look to contribute to the prevention of complaints. Our device studies were applied to a single wastewater treatment plant. However, it is considered to be able to apply in other similar cases of domestic sewage treatment plants.

Refuse-derived fuel (RDF) produced using municipal solid waste was pyrolyzed to produce RDF char. For the first time, the RDF char was used to remove aqueous copper, a representative heavy metal water pollutant. Activation of the RDF char using steam and KOH treatments was performed to change the specific surface area, pore volume, and the metal cation quantity of the char. N2 sorption, Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and Fourier transform infrared spectroscopy were used to characterize the char. The optimum pH for copper removal was shown to be 5.5, and the steam-treated char displayed the best copper removal capability. Ion exchange between copper ions and alkali/alkaline metal cations was the most important mechanism of copper removal by RDF char, followed by adsorption on functional groups existing on the char surface. The copper adsorption behavior was represented well by a pseudo-second-order kinetics model and the Langmuir isotherm. The maximum copper removal capacity was determined to be 38.17 mg/g, which is larger than those of other low-cost char adsorbents reported previously.

This study was conducted to suggest the cause analysis and mitigation measures of foaming generated in the effluent of wastewater treatment plant. The foam generated in the outlet connected with the tidal river system was identified as structural problems. And the main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. In consideration of these conditions, it present the effective ways such as micro-screen and submerged outlet, to mitigate the foaming generated in the water channel and outlet end.

The Wastewater from the weight reduction process of polyester is more difficult to be treated biologically than the general wastewater from dyeing and finishing processes in textile industries. Above wastewater shows high pH, high organic strength and wide variation of organic loading. These characteristics are due to TPA and EG resulting from alkaline weight-reduction process and make trouble in the operation of activated sludge process. Therefore, the objective of this study is to develop the pretreatment method for the successful operation of treatment process. For the successful pretreatment process, the wastewater from weight-reduction process should be segregated from other wastewater stream and then acidified with concentrated sulfuric acid to precipitate out TPA from DST solution. At the optimum pH of 2. 2, the initial $COD_{cr}$ 60,000mg/l is reduced to 11,500mg/l and the removal efficiency of $COD_{cr}$ is 81.1%. The required amount of sulfuric acid for pretreatment is not greater than the amount for the the existing neutralization process. Moreover, the supernatant of pretreatment process can be reused in acidification of wastewater.

Purpose - The purpose of this study is to apply a cost effective ultrasonic odor reduction method that generated micro-bubbles using ejector to the Southeast Asian wastewater market. Research design, data, and methodology - A leather maker located in Ansan-city, Gyunggi-do, South Korea was sampled from the collection tank to select experimental materials. Experimental setup consisted of circulating water tank-air ejector-ultrasonic device, and circulating wastewater. Sample analysis was performed by CODcr, T-N, T-P, and turbidity by the National Environmental Science Institute. Results - Experimental results show that it is most effective in removing odors when the frequency range of ultrasonic wave is 60∼80 Khz and the output is 200 W. It showed that the concentration of complex odor dropped from a maximum of 14,422 times to a minimum of 120 times. Also, analysis of ammonia and hydrogen sulfide in specific odor substances has shown that they were reduced from 1.5 ppm to 0.4 ppm and from 0.6 ppm to 0.1 ppm, respectively. Conclusions - It is possible to shorten more than 12 hours in the treatment of micro-organisms. It can be seen that the processing time of odor after ultrasonic treatment in the pre-treatment facility is reduced by 25% when compared to the resultant micro-organisms after the chemical treatment, that is, the time of the bio-treatment of micro-organisms. Based on the results, it was confirmed that the pre-treatment method using the ultrasonic and the air ejector device of the experiment shows the effect of reducing the water pollutants and odor more effectively in a relatively short time than the conventional advanced oxidation method.

석탄과 철광석은 산업발달의 시작부터 현재까지 지속적으로 사용되고 있다. 이에 따라 수반된 석탄 및 철광석 정제산업의 발달은 석탄철광폐수의 양적 증가를 초래하여 그 처리가 많은 관심 속에 활발하게 연구되고 있다. 석탄철광폐수는 페놀, 시안과 같은 독성 물질 뿐 만 아니라 혐기성미생물과 경쟁관계에 있는 황산염환원균활성증가를 초래하는 SO42-를 고농도로 함유한다. 이 석탄철광폐수의 처리법으로는 물리적, 화학적, 생물학적 처리가 다양하게 연구되어왔는데, 고농도의 폐수처리에 익히 알려진 혐기성미생물을 이용한 석탄철광폐수의 처리는 경제성과 재생에너지 측면에서 최근 큰 관심을 받고 있다. 하지만 폐수에 함유된 페놀, 시안, 등과 같은 독성물질이 생물학적 처리에 심각한 저해를 초래할 수 있어 문제로 지적되고 있으나 그 독성에 대한 현재까지의 연구는 미진한 형편이다. 이에 본 연구는 입상 혐기성미생물이 석탄철광폐수 소화 시 받게 되는 급성독성에 대하여 실험적 고찰을 진행하고 그 적응 방안을 연구하였다. 석탄철광폐수는 석탄철광정제의 완료시점에 실폐수 샘플을 채취하여 사용하였다. 폐수특성 분석결과 pH 7, 페놀 589±23 mg/L, 시안 49 mg/L, 암모니아성질소 39±9 mg/L, SO4-2는 735 mg/L이며 화학적 산소요구량은 3.9 g/L으로 나타났다. 석탄철광폐수에 대한 물벼룩 급성독성시험 결과 TU가 28로 매우 높게 측정되었다. 이 폐수에 UASB의 입상슬러지를 이용하여 혐기성소화를 수행하였다. 약 20일간 유기물 부하 0.6 g COD/L/day에서 초기 적응을 수행하였고, 혐기성소화조의 정상상태에서 COD 제거율은 98%, 메탄수율은 약 80 mL CH4/g COD로 나타났다. 이 혐기성소화조가 석탄철광폐수 유기물부하 0.76 g COD/L/day에 노출 되었을 경우 미생물의 활성을 모니터링한 결과, 폐수유입 즉시 메탄가스발생이 80% 이상 감소되는 강한 독성이 감지되었으며 COD 제거효율은 점차 감소하여 약 20일 후 10%로 낮아졌다. 유출수 내 페놀은 약 210 mg/L로 제거율 60%을 나타났지만 시안은 106 mg/L로 분해되지 않고 축적되어 유입 대비 2배가량 증가하였다. SO4-2 는 2000 mg/L로 급격하게 농도가 증가한 후 약 20일 후 1000 mg/L 이하로 감소하였다. 이로보아 석탄철광폐수 내 시안과 황화합물로 인하여 혐기성미생물 내의 메탄균의 저해가 이루어짐을 짐작할 수 있다. VFA 분석결과는 산발효균과 메탄발효균의 공생관계가 파괴되었음을 보여주었다. 더불어 높은 SO4-2 농도는 황산염환원균과의 경쟁이 유도될 수 있는 농도로 밝혀졌다. 이러한 석탄철광폐수의 급성독성은 고농도의 독성물질 제거를 위한 전처리 혹은 혐기성미생물의 적응기간이 필요함을 나타내었으며, 후자를 선택하여 약 30일 간 단계적인 미생물의 독성적응절차를 거친 결과 급성독성을 극복하고 유기물 및 페놀 분해가 점진적으로 가능함을 확인 하였다.

The re-emission of mercury (Hg), as a consequence of the formation and dissociation of the unstable complex HgSO3, is a problem encountered in flue gas desulphurization (FGD) treatment in coal-fired power plants. A model following a pseudo-second-order rate law for Hg2+ reduction was derived as a function of [SO32-], [H+] and temperature and fitted with experimentally obtained data to generate kinetic rate values of (0.120 ± 0.04, 0.847 ± 0.07, 1.35 ± 0.4) mM-1 for 40°, 60°, and 75℃, respectively. The reduction of Hg2+ increases with a temperature increase but shows an inverse relationship with proton concentration. Plotting the model-fitted kinetic rate constants yields ΔH = 61.7 ± 1.82 kJ mol-1, which is in good agreement with literature values for the formation of Hg0 by SO32-. The model could be used to better understand the overall Hg2+ re-emission by SO32- happening in aquatic systems such as FGD wastewaters.

Electrochemical reductive extraction of tin from semiconductor plating process wastewater was experimented using synthetic wastewater. Copper and graphite plate were used as a cathode and an anode, respectively. The tin extraction could be optimized in pH 0.5 and polar space of 60 mm. The extraction rate of tin per minute was increased as current and initial tin concentration increased, and more than 87% and 97% of tin could be extracted within 80 minutes at 500 mg/L and 1,000 mg/L of initial tin concentration, respectively. The electrochemical reaction orders and kinetic coefficients were 1.24 ~ 1.26 and 0.004 ~ 0.006 (L/mg)(n − 1)min−1. The residual concentration of tin could be expressed as Ct= (Co −0.246+ 0.0012t)−4.065.

The effect of temperature on the removal process of Cr(VI) ion contained in wastewater by a precipitation method has been investigated for the improvement of its design and operation. The distribution diagram of chromium ion was constructed by employing the MINTEQ program and the quantitative feature of Cr(VI) depending on pH was investigated. As the temperature increases, the relative amount of H2CrO4 was examined to be raised and the pH range in which H2CrO4 exists as a stable form was also investigated to be extended according to the temperature. Cr(VI) ion was shown to be changed from HCrO4 − to Cr2O7 2− as the concentration of Cr(VI) ion is increased in the neutral pH condition and the concentration of Cr(VI) ion which is necessary for the ionic transformation was observed to rise in the acidic and alkaline conditions. The major reactant which involved in the reduction reaction for the removal of Cr(VI) ion was examined to be HCrO4 − and the reduction of Cr(VI) ion to Cr(III) ion was investigated to be influenced much by the temperature change at higher pH conditions. The reduction reaction of Cr(VI) ion for its removal as a precipitate was examined to be promoted as the temperature decreases and pH is lowered. In addition, the stable region of Cr(OH)3 was shown to be enlarged with temperature based on the thermodynamic estimation and it was thought to be necessary to design and control the precipitating process of Cr(VI) ion by considering the thermal characteristics of reduction and precipitation stage.

Electrochemical reductive extraction of copper from LCD manufacturing process and through hole plating process for PCB circuit board wastewater was experimented using synthetic wastewater. Copper plate which could be used as raw material through melting with extracted copper from wastewater and graphite plate were used as a cathode and an anode, respectively. The copper extraction could be optimized in pH 2 and polar space of 45mm. The extraction rate of copper per unit energy was decreased as HRT increased and initial copper concentration decreased. As the optimal HRTs which could maximize the productivity for copper on energy, 80 ~ 110 min at 50 mg/L, 64 min at 1,000 mg/L and 77 ~ 98 min at 3,000 mg/L were determined, respectively.