• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2023년도 학술발표회
• /
• pp.170-170
• /
• 2023

Providing safe and readily available water is vital to maintain public health. One of the most prevalent methods to prevent the spread of waterborne diseases is applying chlorine injection to the treated water before distribution. During the water transmission and distribution, the chlorine will experience a reduction, which can imply potential risks for human health if it falls below the minimum threshold. The ability to determine the appropriate initial intensity of chlorine at the source would be significant to prevent such problems. This study proposes two methods that integrate hydraulic and water quality modeling to determine the suitable intensity of chlorine to be injected into the source water to maintain the minimum chlorine concentration (e.g., 0.2 mg/l) at each demand node. The water quality modeling employs the first-order decay to estimate the rate of chlorine reduction in the water. The first method utilizes a backtracking algorithm to trace the path of water from the demand node to the source during each time step, which helps to accurately determine the travel time through each pipe and node and facilitate the computation of time-dependent chlorine decay in the water delivery process. However, as a backtracking algorithm is computationally intensive, this study also explores an alternative approach using a water age. This approach estimates the elapsed time of water delivery from the source to the demand node and calculate the time-dependent reduction of chlorine in the water. Finally, this study compares the outcomes of two approaches and determines the suitable and effective method for calculating the chlorine intensity at the source to maintain the minimum chlorine level at demand nodes.

• Advances in environmental research
• /
• 제9권2호
• /
• pp.97-107
• /
• 2020

The indiscriminate growth in global population poses a threat to the world in handling and disposal of Municipal solid waste. Rapid urban growth increases the production, consumption and generation of Municipal solid waste which leads to a drastic change in the environment. The methane produced from the Municipal Solid waste accounts for up to 11% global anthropogenic emissions, which is a major cause for global warming. This study reports the methane emission estimation using IPCC default, TNO, LandGEM, EPER and close flux chamber from open dump yards at Perungudi and Kodungaiyur in Chennai, India. The result reveals that the methane emission using close flux chamber was in the range of 8.8 Gg/yr-11.3 Gg/yr and 6.1Gg/yr to 9.1 Gg/yr at Kodungaiyur and Perungudi dump yard respectively. The per capita waste generation was estimated based on waste generation and population. The waste generation potential was projected using linear regression model for the period 2017-2050. The trend of CH₄ emission in the actual field measurement were increased every year, similarly the emission trend also increased in IPCC default method (mass balance approach), EPER Germany (zero order decay model) where as TNO and Land GEM (first order decay model) were decreased. The present study reveals that Kodungaiyur dump yard is more vulnerable to methane emission compared to Perungudi dump yard and has more potential in waste to energy conversion mechanisms than compare to Perungudi dump yard.

• 상하수도학회지
• /
• 제35권3호
• /
• pp.227-235
• /
• 2021

This study examined the effect of ultraviolet (UV) application on bacterial disinfection in a commercialized humidifier using ultrasonic wave (UW). To accurately examine disinfection kinetics in tap-water condition, tap-water was sterilized using a filter, and then inoculated with pure cultures of E. coli and P. putida with known viable counts. The disinfection kinetic characteristics were experimentally compared when UV alone, UW alone, and UW+UV together were applied in disinfecting the added bacteria in the commercialized humidifier. When UV alone was applied, bacterial disinfection kinetics followed a first-order decay reaction, and showed an approximately 10-time weaker disinfection compared to the typical UV disinfection in water treatment or wastewater treatment. When UW alone was applied, bacterial disinfection kinetics followed a second-order decay reaction with a low disinfection rate constant of 0.0002 min^-1(CFU/mL)^-1. When UV and UW were applied together, however and interestingly, the disinfection rate constant (0.0211 min^-1(CFU/mL)^-1) was approximately 100 times increased than that for the UW alone case. These results revealed that the co-use of UV and UW can provide synergistic effect on bacterial disinfection in a tap-water condition in household humidifiers.

• 대한환경공학회지
• /
• 제27권6호
• /
• pp.663-669
• /
• 2005

본 연구에서는 정수처리 공정에서 오존을 보다 효율적으로 적용하기 위하여 수중의 오존소비특성을 파악하고자 하였다. 오존의 소비특성을 측정하기 위하여 흐름주입분석법(FIA: Flow injection analysis)의 원리를 이용하여 오존분해속도 측정 자동화장치를 제작하였다. 수중의 오존농도를 연속적으로 측정함으로써 오존의 소비 경향은 순간적으로 오존이 소모되는 구간(I.D: instantaneous ozone demand)과 의사 1차 반응($k_c$: pseudo first-order rate constant)으로 소모되는 두 구간으로 나누어지며, 각 구간에서 오존 주입량에 의하여 영향을 받는 것으로 나타났다. 또한 I.D와 $k_c$값을 이용하여 구한 모델식으로부터 시간에 따른 오존 잔류농도를 예측할 수 있었으며, 예측된 모델간은 실험값과 비교하였을 때 거의 일치하는 것을 알 수 있었다. OH 라디칼의 농도 및 $R_{ct}$는 OH 라디칼 probe compound를 이용하여 간접적으로 계산하였다. I.D와 $k_c$ 구간에서 OH 라디칼 생성 경향을 파악할 수 있었으며, OH 라디칼 생성 또한 오존 주입량에 의하여 영향을 받는다는 것을 확인하였다. 마지막으로 정수처리 공정 및 계절에 따른 수질 차이에 의해서 오존소비인자가 변화하는 것을 확인하였으며, 이에 따라 오존공정의 적절한 도입위치 및 주입량을 효과적으로 결정해야 할 것으로 판단되었다.

• 유기물자원화
• /
• 제19권3호
• /
• pp.44-53
• /
• 2011

유기규소화합물인 siloxane은 물리화학적으로 우수한 특성으로 인하여 화장품이나 세제 등과 같이 우리 생활에서 다양한 제품 형태로 사용된다. 이러한 제품의 사용 후 매립되어 분해되는 과정에서 매립가스에 포함된 siloxane은 매립가스 자원화 시설의 운영 시 악영향을 미친다. 본 연구에서는 국내 여러 매립지 특성에 따른 매립가스 내 실록산 발생특성을 파악하기 위하여 매립연령과 매립폐기물에 따른 siloxane 발생특성을 실록산의 농도, 구조 및 성분별로 고찰하였다. 시간에 따른 실록산 발생특성은 매립종료 전 후와 각 매립지의 매립연령별로 12개 매립지를 대상으로 검토하였으며, 매립폐기물에 의한 siloxane의 발생특성 변화는 6개 매립지를 대상으로 매립폐기물의 발생원 및 물리적 조성의 비율과 siloxane 농도를 비교하였다. 매립가스 내 total-siloxane의 농도는 평균 $6.75mg/m^3$ 이었으며, cyclic-siloxane이 이 중 93% 이상을 차지한 것으로 나타났다. 성분별 실록산은 매립연령과 관계없이 D4 및 D5가 순서대로 가장 높은 비율을 차지하였다. 본 연구에서 매립폐기물의 종류(조성)가 실록산 발생에 미치는 영향은 확인할 수 없었으나, total-siloxane 및 cyclic-siloxane의 농도는 매립가스 일차분해모델과 같이 매립연령이 증가함에 따라 감소하는 것으로 나타났다.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
• /
• pp.102-105
• /
• 2002

A new finite difference model is developed for solute transport in a fractured medium that can consider advection, adsorption, first-order decay, and scale-dependent dispersivity of individual fractures. In the model, the dispersivity of individual fractures is employed as a variable increasing with travel distance from a source. The model is verified using an analytical solution for a single fracture. A solution from the new model is independent of the outlet boundary condition of fractures, and has little numerical dispersion error.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
• /
• pp.371-374
• /
• 2005

We accomplished optimization for pump and treat (P&T) designs in consideration of degradation processes such as retardation and biodegradation, which are significant for contaminant fate in hydrogeology. For more desirable remediation, optimal pumping duration and minimum pumping rate constraint problems are studied. After a specific P&T duration, it replaces the P&T with the enhanced natural attenuation (ENA), which induces aerobic biodegradation by maintaining oxygen concentration. The design in this strategy carries out the optimization for the number and locations of oxygen injection wells.

• Nuclear Engineering and Technology
• /
• 제28권6호
• /
• pp.542-550
• /
• 1996

Nuclear ship reactors have several features different from land-based PWR's. Especially, effects of ship motions on reactor thermal-hydraulics and good load following capability for abrupt load changes are essential characteristics of nuclear ship reactors. This study modified the RETRAN-03 to analyze the thermal-hydraulic transients under three-dimensional ship motions, named RETRAN-03/MOV in order to apply to future marine reactors. First Japanese nuclear ship MUTSU reactor have been analyzed under various ship motions to verify this code. Calculations have been peformed under rolling, heaving and stationary inclination conditions during normal operation. Also, the natural circulation has been analyzed, which can provide the decay heat removal to ensure the passive safety of marine reactors. As results, typical thermal-hydraulic characteristics of marine reactors such as flow rate oscillations and S/G water level oscillations have been successfully simulated at various conditions.

• Korean Chemical Engineering Research
• /
• 제57권2호
• /
• pp.289-300
• /
• 2019

We have conducted a preliminary numerical analysis to understand the effects of double-diffusive convection on the molar flux at the crystal region during the growth of mercurous bromide ($Hg_2Br_2$) crystals in 1 g and microgravity (${\mu}g$) conditions. It was found that the total molar fluxes decay first-order exponentially with the aspect ratio (AR, transport length-to-width), $1{\leq}AR{\leq}10$. With increasing the aspect ratio of the horizontal enclosure from AR = 1 up to Ar = 10, the convection flow field shifts to the advective-diffusion mode and the flow structures become stable. Therefore, altering the aspect ratio of the enclosure allows one to control the effect of the double diffusive natural convection. Moreover, microgravity environments less than $10^{-2}g$ make the effect of double-diffusive natural convection much reduced so that the convection mode could be switched over the advective-diffusion mode.

• 대한화학회지
• /
• 제34권5호
• /
• pp.404-412
• /
• 1990

시간분해 ESR 분광법에서는 CIDEP법과 흡수 ESR 분광법을 사용하였다. 2-프로판올과 트리에틸아민 혼합용매에서 anthraquinone이 레이저 광선에 의해서 생성된 anthraquinone 라디칼 음이온을 시간분해 ESR 분광법으로 측정하였다. 이 semiquinone 라디칼은 대단히 안정하여 cw ESR을 측정할 수 있었다. 분극된 semiquinone 라디칼이 열적 평형상태로 소멸되는 속도상수는 스핀-격자 완화시간의 역수로서 2.6 ${\times}\;1-^5$ sec$^{-1}$이다. 그리고, 그 라디칼의 소멸속도상수는 300.0 sec$^{-1}$이다. CIDEP스펙트럼의 시간의존성에 대한 강도 변화는 마이크로파 출력이 강할수록 일반적으로 증가하였다. 그러나, 지나치게 출력을 높이면 감소 곡선상에 Torrey 진동이 뒷따라 일어났다.