CT 값에 의한 정수장의 소독능 평가

윤제용(Je Yong Yoon),변석종(Seok Jong Byun),이상덕(Sang Deok Lee),석관수(Kwan Su Seok) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.4

Disinfection process in water treatment plants is one of the most important step in order to inactivate waterborne disease. However, what is the necessary disinfection which has to be achieved in water plants was not properly established in Korea. In this study, we introduced the concept of CT values and evaluated CT in several water treatment plants to propose reasonable guidelines of necessary disinfection capabilities. The concept of CT was referred to the SWTR(Surface Water Treatment Rule) which is current US-EPA regulation. The necessary disinfection capability is expressed by CT which may be variable depending on the type of disinfectant, temperature, and pH etc. C is the concentration of disinfectant in the effluent of clearwell and T(=T-10) is the detention time at which 90% of the water passing through the unit is retained within the basin. Total of 8 water treatment plants(CJ, SS, BS, KG, BW, YC, KC, YJ) were intended to investigate the necessary disinfection capability in clearwell. For two of them, tracer study to find out T_(10) was not possible due to the unavailability of the port of chemical addition in the clearwell. It was found that T-10/T were varied widely from 0.2 to 0.5 even though all the clearwell in water treatment plants investigated were not baffled. For reference, T_(10)/T of 0.1 were given for unbaffled clearwell in terms of US-EPA recommendation. Considering the operation condition of plants and water quality characteristics at the time of study, 6 of water treatment plants successfully met the necessary disinfection capability based on 90% giardia removal. However, under the scenario of worst case which can be anticipated year round, nearly all the water treatment plants failed to meet CT requirements. Therefore, the necessities for adjusting disinfection process to the condition of various water quality were raised.

금강지역 정수장 원수에서 Cl2/NH3 에 따른 THMs 및 TOXs 생성특성에 관한 연구

윤제용(Je Yong Yoon),변석종(Seok Jong Byun),이상덕(Sang Duk Lee) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.4

Chlorine is currently being used for the disinfection process in nearly all domestic water treatment plants. Trihalomethanes(THMs) and a lot of chlorinated disinfection byproducts(DBPs) are inevitably produced as a result of chlorine use. The chlorinated DBPs other than THMs are hard to measure and regulate individually. Total organic halides(TOXs) which indicate the sum of chlorinated DBPs may be used as a process control variable for the control of DBPs. In this study, the formation characteristics of THMs and TOXs as a function of the ratio of Cl₂ to NH₃-N in two types of raw water which have the different characteristics of ammonia concentration were investigated. The breakpoint chlorination of the drinking water treatment plants was simulated to represent the characteristics of DBPs formation. Breakpoint chlorination curves with naturally occurring ammonia were not significantly different, when compared to those with chemical ammonia. The breakpoint was observed at Cl₂/NH₃-N ratio of 7.0∼7.7. When Cl₂/NH₃-N ratio was below 5, where chloraminations were practiced, THMs & TOXs formation were low, becoming up to 8㎍/L and 78㎍/L respectively. Below Cl₂/NH₃-N ratio of 5, THMs formation was almost identical regardless of water quality presumed and the source of ammonia, while TOXs formation slightly reflected water quality. On the other hand, when the ratio of Cl₂to NH₃-N was above 7.5, the level of THMs & TOXs formation increased significantly, becoming up to 36㎍/L and 259㎍/L respectively. It was found that the overall level of THMs and TOXs formation was not high, considering the organic content and the high chlorine dose applied. The implication of this DBPs formation characteristics could be enormous for the regulation policy of DBPs. THMs that is only the regulated DBPs explained about 8∼14% of TOXs.

추적자 실험에 의한 정수장 침전지내 구조물의 수리학적 영향평가에 관한 연구

윤제용(Je Yong Yoon),변석종(Seok Jong Byun),이상덕(Sang Deok Lee),김정현(Jeong Hyun Kim),권순범(Soon Buhm Kwon) 한국수처리학회 1999 한국수처리학회지 Vol.7 No.1

Sedimentation basin is one of the most common and important units in the conventional water treatment plant. It plays an important role in removing the floc formed in mixing and coagulation basin, and then has a great impact on the backwash cycle of filtration process. Plug flow pattern in sedimentation basin which is the most desirable, never exists on its own in a real basin. It is always accompanied by a certain degree of mixing and dead space. Structures such as the inlet and outlet of basin, the location of baffle wall, the installation of sludge collector may be the obstacles to the horizontal flow when it is poorly designed. Therefore, to know how these structures in the settling basin have an influence on the characteristics of hydraulic flow is beneficial to improve the settling efficiency of the floc. The hydraulic characteristics of the sedimentation basin in the three real WTPs(B, K, I) which have the different structural characteristics inside the settling basin were qualitatively investigated by the tracer test. Quantitative evaluation was not attempted due to the poor recovery of tracer chemical. First plant(B plant) has a plate settler. Second plant(K plant) has baffle wall cut about 60 cm in the bottom for the purpose of installation of the sludge collector. Third plant (I plant) does not have any structure in the basin. It was found that structures such as plate settler(B plant) and baffle wall cut in the bottom had an profound undesirable impact on the horizontal flow in the settling basin. Tracer distributions clearly indicated that any space occupied by plate settler in B plant was the complete dead zone, on the contrary to its intended role. Also, the baffle wall cut in the bottom in K plant was not as good as the plate settler in B plant in having the horizontal flow in the sedimentation basin. Even for I plant which has no structure in the basin, the limited horizontal flow was observed, though showing the best hydraulic performance among the three plants.

국내 정수장에서 염소주입 특성 및 잔류염소 분포에 관한 연구

윤제용,변석종,이상덕 ( Je Yong Yoon,Seok Jong Byun,Sang Duck Lee ) 한국물환경학회 1997 한국물환경학회지 Vol.13 No.3

Chlorine is currently being used to control microorganism, odor, color and inorganics such as Fe, Mn in nearly all domestic water treatment plants. However, an overdose of chlorine can cause the formation of unexpectedly high disinfection byproducts(DBPs) such as trihalomethanes, besides being econonomically not sound. On the other hand, under dosage of chlorine may increase public health risk resulting from waterborne disease. Therefore, it is necessary to investigate the characteristics of chlorine dosage in water treatment plants to provide the proper guideline of chlorine practice. In this study, five water treatment plants were selected for investigating for characteristics of chlorine dosage and distribution of residual chlorine. Three major characteristics of chlorine dosage were found. First, for raw water with high ammonia concentration(3∼5㎎/L), a large quantity of chlorine was added to get rid of ammonia through breakpoint chlorination. Post-chlorination practice in this case becomes unnecessary because the chlorine residual prior to clear well is sufficiently high in maintaining chlorine residual in distribution system. Second, for the same type of raw water with first case in terms of ammonia content, only small amount of chlorine was added to the water two sites (as pre-chlorine & post -chlorine) to form the combined chlorine as residual chlorine. This type of chlorine practice is called as $quot;chloramination$quot;. Chloramination in Korea is unique in two ways. 1) naturally occurring ammonia was used far ammonia source 2) this was chosen due to the shortage of chlorine capacity not for the control of chlorinated byproducts. Third, for the water which does not contain high ammonia content, dual chlorine addition practice was selected. Pre-chlorination is performed to meet the chlorine demand of raw water. Post-chlorination is performed to maintain the proper residual chlorine in distribution system.

UV 법에 의한 안정화 이산화염소 원액 성분 특성에 관한 연구

윤제용,이상덕,안창진,김호순 대한상하수도학회 1997 상하수도학회지 Vol.11 No.2

Chlorine dioxide is being used to control THMs formation or taste & odor in water treatment plant. Recently, some operators or academic circles doubted the effectiveness of stabilized chlorine dioxide which is presumed as a liquid form of chlorine dioxide. In this study, we investigated components which consist of stabilized chlorine dioxide in terms of chlorine dioxide and chlorite. Two analytical methods used in this study are UV method and Iodometric method. Iodometric method is recommended by Korean EPA to check the purity of stabilized chlorine dioxide. The samples of stabilized chlorine dioxide from four water treatments were investigated and compared with that produced from chlorine dioxide generator on-site. This study demonstrated that the component of stabilized chlorine dioxide was overwhelmingly chlorite (CIO_2￣) not chlorine dioxide (CIO_2) by UV method. It was also proved that Iodometric method (2nd method) recommended by Korean EPA could not differentiate between CIO_2 and CIO_2￣. Iodometric method (2nd method) recommended by Korean EPA should be revised accordingly to measure chlorine dioxide properly.

Phenate 법으로 암모니아 분석시 염화아민의 방해 작용에 관한 연구

윤제용,이상덕 대한상하수도학회 1998 상하수도학회지 Vol.12 No.1

The determinations of ammonia in water for drinking purpose served as one basis of judging the sanitary quality of water for a great many years. However, presently ammonia regulation varies depending on countries. In USA and Canada, ammonia is added to water for chloramination process. However, for korea, there is ammonia regulation of treated water in Korea which should not exceed 0.5mg/l as NH_3-N. There was a report exceeding 0.5mg/l of ammonia in chlorinated water when the famous drinking water contamination episode happened in the downstream of Nakdong River, 1994. With lack of sewer distribution system and treatment plants of domestic wastes, many water treatment plants have a difficulty of complying with ammonia regulation in treated water. Breakpoint chlorination is usually performed to get rid of ammonia. The method which is allowed to measure ammonia in Korea is Phenate method. However, it would be undesirable to use Phenate method for measuring ammonia in chlorinated water if Phenate method would not differentiate ammonia from chloramine. A good possibility of interferences in measurement of ammonia exists because Phenate method include the step of the formation of chloramine and would not differentiate chloramine which is formed as a result of reaction between chlorine and ammonia. This study was on inaccuracy of Phenate method for measuring ammonia of chlorinated water when chloramine and ammonia coexist. This study found that Phenate method measured all chlormaine as ammonia. Ammonia measurement by ion chromatography confirmed this results. Finally, the result from this study suggests that ammonia measurement by Phenate method in chlorinated water should be revised accordingly.