• Environmental Engineering Research
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• 제21권4호
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• pp.427-435
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• 2016

In this study, change in water-dissolved oxygen (DO) was analyzed under various synthetic water qualities and nanobubbles (NBs) application conditions, such as gas type, initial DO as well as water dissolved, suspended and organic matters contents. When oxygen, rather than air, was introduced into nitrogen-desorbed ultra-pure water, the stagnation time was significantly increased. It took ten days for DO concentration to drop back to saturation. The higher the initial DO concentration, the longer particles were observed above saturation due to particle stability improvement. The oxygen mass transfer rate of 0.0482 mg/L/min was found to reach a maximum at an electrolytic concentration of 0.75 g/L, beyond which the transfer rate decreased due to adsorption of negative ions of the electrolyte at the interface. High levels of turbidity caused by suspended solids have become a barrier to dissolution of NBs oxygen into the water solution, and thus affected the transfer performance. On the other hand, by applying NBs for just an hour, up to 7.2% degradation of glucose as representative organic matter was achieved. Thus, NBs technology would maintain a high DO extent for an extended duration, and thus can improve water quality provided that water chemistry is closely monitored during its application.

• 한국수소및신에너지학회논문집
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• 제20권4호
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• pp.323-330
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• 2009

Efficiency of a fuel cell is determined by the generated water. If water is not removed sufficiently, water will be accumulated at GDL, which causes flooding. Therefore, water control is regarded as a crucial factor to sustain fuel ell performance. In this study, PTFE coating on the surface of carbon paper was carried out to establish optimum process for hydrophobic treatment of GDL. Carbon paper was immersed at different concentrations of nano-sized PTFE coating solution. Their characteristics were analyzed systematically by FE-SEM, water contact angle, cyclic voltamogam, XRD and FT-IR. The quantitative correlation between the amount of coated-PTFE on a carbon paper and concentration of coating solution was carefully investigated. It is suggested that the amount of PTFE-coating on a carbon paper can be managed by means of controling concentration of coating solution.

• 한국안전학회지
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• 제5권3호
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• pp.39-43
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• 1990

The transport of phenol from waste water through the liquid surfactant membrane containing Aliquat 336 as a carrier was analyzed by a theoretical model. Extraction experiments was carried out to investigate the effect of process parameters, such as mixing intensity, concentration of sodium hydroxide in internal aqueous solution, and counter anions, and initial phenol concentration in waste water at $25^{\circ}C$. It was found that transport rate of phenol increased with increasing pH differents. The transport rate of phenol in waste water was influenced by counter anions.

• 한국수자원학회논문집
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• 제57권3호
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• pp.151-164
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• 2024

상수도 공급을 위한 정수장에서 전염소 또는 중염소 공정이 도입된 수처리 공정의 염소농도 관리에 필요한 공정제어를 위하여 AI 기술을 활용한 수질예측 기법이 연구되고 있다. 본 연구에서는 정수장 수처리 공정에서 실시간으로 관측, 생산되고 있는 수량·수질자료를 이용하여 염소소독 공정제어 자동화를 목적으로 침전지 후단의 잔류염소 농도를 예측하기 위한 AI 기반 예측모형을 개발하였다. AI 기반 예측모형은 과거 수질 관측자료를 학습하여 이후 시점의 수질에 대한 예측이 가능한 기법으로, 복잡한 물리·화학·생물학적 수질모형과 달리 간단하고 효율적이다. 다중회귀 모형과 AI 기반 모형인 랜덤포레스트와 LSTM을 이용하여 정수장의 침전지 후단 잔류염소 농도를 예측하여 비교하였다. 최적의 잔류염소 농도 예측을 위한 AI 모형의 입출력 구조로는 침전지 전단의 잔류염소 농도, 침전지 탁도, pH, 수온, 전기전도도, 원수의 유입량, 알칼리도, NH₃ 등을 독립변수로, 예측하고자 하는 침전지 유출수의 잔류염소 농도를 종속변수로 선정하였다. 독립변수는 침전지 후단의 잔류염소에 영향이 있는 정수장에서 확보가 가능한 관측자료중에서 분석을 통해 선별하였으며, 분석 결과 연구대상 정수장인 정수장에서는 중회귀모형, 신경망모형, 모델트리 및 랜덤포레스트 모형을 비교한 결과 랜덤포레스트에 기반한 모형오차가 가장 낮게 도출되는 결과를 얻을 수 있었다. 본 연구에서 제시하는 침전지 후단의 적정 잔류염소 농도 예측값은 이전 처리단계에서 염소주입량의 실시간 제어가 가능토록 할 수 있어 수처리 효율 향상과 약품비 절감에 도움이 될 것으로 기대된다.

• 상하수도학회지
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• 제19권2호
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• pp.228-237
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• 2005

The main purpose of this study was to investigate the red water reducing effects of phosphate based inhibitor when it was applied to water distribution system. The effects of pH, alkalinity, calcium concentration in the reduction of the red water also studied. The most finished water in Korea showed relatively high corrosiveness and was required to introduce some types of corrosion reducing methods such as addition of alkalinity. The precipitation of $CaCO_3$ by addition of $Ca(OH)_2$ formed porous film on the surface of the carbon steel pipes and was displaced easily from the surface of the pipes; on the other hand, addition of zinc phosphate (ZOP) formed reliable film on the surface and reduced iron release and color. Although the main function of ZOP was to suppress the release of Pb and Cu, it also reduced iron concentration released from water distribution pipes.

• 한국물환경학회지
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• 제22권5호
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• pp.943-951
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• 2006

Spatial distribution of water pollution in the Gap Stream was investigated from October to November, 2005. Sampling was conducted three times including effluents discharged from a wastewater treatment plant (WWTP) and a dam reservoir during the low-flow period. As a typical urban stream, total nitrogen and inorganic nitrogen concentrations increased toward downstream. Ammonia concentration was the highest in the treated water of the wastewater treatment plant and the lowest nitrate concentration was found in the effluent of the dam reservoir. A part of soluble reactive phosphorous (SRP) in total phosphorous was 22~54% in the upstream reach of WWTP in the Gap Stream whereas 68~73% in the downstream reach. Mean chlorophyll-a concentration ranged from 1.6 to $11.0{\mu}g/L$ and it tends to increase toward downstream except for WWTP effluent. As expected, untreated wastewater and WWTP effluent were suggested as the major sources of water pollution in the Gap Stream. In this study, the water pollution of the Gap Stream is a significant undergoing typical eutrophication, caused by excessive phosphorus and nitrogen nutrients from WWTP located in the watershed. As a result, the critical factor for the water pollution was evaluated to dissolved inorganic nitrogen and phosphorus nutrients. Particularly, SRP is a most important for the eutrophication. It suggest that may occur in the most urban streams of Korean peninsula. Therefore, because the necessity of water pollution management in the urban stream, inorganic N and P nutrients should be included as an essential component of water quality criteria in the advanced water quality project of Korean Government by enforcing of water quality assessment and total maximum daily loads (TMDLs).

• 상하수도학회지
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• 제34권6호
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• pp.473-480
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• 2020

High-pressure membrane system like nanofiltration(NF) and reverse osmosis(RO) was investigated as a part of water treatment processes to produce high quality potable water with low organic matter concentration through membrane module tests and design simulation. River water and sand filtration permeate in Busan D water treatment plant were selected as feed water, and NE4040-90 and RE4040-Fen(Toray Chemical Korea) were used as NF and RO membranes, respectively. Total organic carbon(TOC) concentrations of NF and RO permeates were mostly below 0.5 mg/l and the average TOC removal rates of NF and RO membranes were 93.99% and 94.28%, respectively, which means NF used in this study is competitive with RO in terms of organic matter removal ability. Different from ions rejection tendency, the TOC removal rate increases at higher recovery rates, which is because the portion of higher molecular weight materials in the concentrated raw water with increasing recovery rate increases. Discharge of NF/RO concentrates to rivers may not be acceptable because the increased TDS concentration of the concentrates can harm the river eco-system. Thus, the idea of using NF/RO concentrate as the raw water for industrial water production was introduced. The design simulation results with feed water and membranes used in this work reveal that the raw water guideline can be satisfied if the recovery rate of NF/RO system is designed below 80%.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2005년도 국제학술대회
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• pp.263-272
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• 2005

Chlorine disinfection has been used in drinking water supply to disinfect the water-borne microbial disease which may cause to serious human disease. it is still the least costly, relatively easy to use, Chlorination is the primary means to disinfect portable water supplies and control bacterial growth in the distribution system. However, chlorine reacts with natural organic matter(NOM), that presents in nearly all water sources, and then produces disinfection by-products(DBPs), that have adverse health effects. Although the existent DBPs have been reported in drinking water supplies, it is not feasible to predict the levels of the various DBPs due to the complex chemistry reaction involved. 1. The objectives of this study is to investigate seasonal variation difference concentration of DBPs in the plant to tap water. The average concentration of THMs was 20.04 ${\mu}g/{\ell}$ , HAAs 8-15 ${\mu}g/{\ell}$ , HANs 2-4.5 ${\mu}g/{\ell}$ respectively. 2. Distant variation of DBPs furmation by the distance is that THMs concentration increased by 17% at 2km point from the plant and by 28% at 7km and HAAs, HANs also increase each by 16%, 32% at 2 km from the plant and 35%, 56% at 7 km. DBPs increase in water supply pipe continually, 3. The seasonal occurrence of BBPs is that in May and August DBPs concentration is very higher than in march, in May DBPs concentration is highest. The temperature is main factor of DBPs formation, precursor also. 4. Precursor which was accumulated for winter flowed into the raw water by flooding in spring and summer and produced DBPs. 5. Therefore for the supply of secure drinking water, it is required to protect precursor of flowing into raw water and to add to BCAA and DBAA to drinking water standards.

• 한국환경보건학회지
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• 제39권3호
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• pp.223-229
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• 2013

Objectives: In an effort to examine the distribution of THMs (Trihalomethane) generated from chlorine disinfection by the drinking water treatment plants located on the east coast region of Gangwon-do, this study surveyed the distribution and concentrations of each component of THMs twice per month for 5 years from 2008 to 2012. Fluctuation pattern in the seasonal generation amount was identified. In addition, the correlation between the concentration of organic substances in water and THMs was assessed, along with stability of purified water quality supplied by the water treatment plants on the east coast by analyzing the composition ratio of each component that constitutes THMs and the detection frequency. Method: The research was done on purified water supplied by 29 water treatment plants in 7 cities and counties (Goseong-gun, Sokcho-si, Yangyang-gun, Gangneung-si, Donghae-si, Samcheok-si, Taebaek-si) located in Gangwon-do on the east coast. Water samples were collected twice a month from 2008 to 2012 and were investigate for chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform, based on analysis through Purge-Trap (Tekmar 3000) devices using FID-attached GC (HP 6890, Hewlett Packard). Result: THMs concentration detected at Gangneung-si was 0.0086mg/L, Goseong-gun 0.0019mg/L, Donghae-si 0.0099 mg/L, Samcheok-si 0.0016 mg/L, Sokcho-si 0.0057 mg/L, Yangyang-gun 0.0027 mg/L and Taebaek-si 0.0038 mg/L. As the THMs composition rate, chloroform constitutes 51.4% followed bybromodichloromethane 22.3%, bromoform 15.2% and dibromochloromethane 11.1% respectively. Conclusion: Throughout the entire THMs survey areas and period, the maximum concentration was 0.072mg/L, which did not exceed the water quality standards (0.1 mg/L), and the overall average concentration was very low at 0.0044 mg/L.

• 한국농공학회지
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• 제41권2호
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• pp.44-54
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• 1999

Agricultural water quality standards were reviewed through rice culture using treated sewage irrigation . The seqage from school building of Konkuk University was treated by a constructed wetland system, and theeffluent of the systeml was irrigated for rice culutre after nutrient concentration adjusted by dilution. Average concentration of COD, SS, T-N and T-P in irrigated water was 22.3mg/$\ell$, 6.5mg/$\ell$, 25.8 mg/$\ell$and 2.2mg/$\ell$, respectively. Treatment include irrigation of adjusted effluent with conventional fertilization (TWCF), adjusted effluent with no fertilization (TWNF). and effluent of the wetland system as it was with no fertilization (SWNF). These treatment plots were compared with control plot irrigated by tap water with conventional fertilization (CONTROL). Other environmentals for rice culture were identical for all the plots. Among them, TWCF showed the best growth rate and the highest yield, and constituents in the harvested rice showed not much difference among them. Which implies that irrigation with relatively high nutrient concentration compared to the current water quality standards may cause no adverse effect on rice culture and could be even beneficial . Although T-N for this study was 25 times greater than the current standards, rice culture wasnot adversely affected by irrigatino water quality and even beeter results were observed than the CONTROL. It could be mistakenly that clean irrigation water produces better agricultural product, however, it is not necessarily true. Irrigation water with moderate nutrient concentration can enhance the plant growth, and better result might be expected. Therefore, peer review and modification if necessary are needed to the current agricultural water quality standards, especially for the nutrient components.