• 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.

• 상하수도학회지
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• 제25권6호
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• pp.839-846
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• 2011

To investigate corrosivity characteristics of raw water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Annual average values of LI at 30 WTPs were all negative, which means raw water in Korea is very corrosive. LI results for 4 major rivers showed that raw water from Han and Nakdong had relatively high values compared to those of Sumjin and Keum. On the other hand, LI values of raw water from the tributaries of four major rivers were relatively low presumably due to geological characteristics, and in some cases the values were less than -4.0 which means increase of LI is urgently needed to minimize red water problem. Based on the correlation results among LI and water quality parameters, pH, water temperature, calcium concentration were confirmed as major components for LI. Therefore, pH and calcium concentration control is an effective method for the improvement of LI in water treatment processes.

• 상하수도학회지
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• 제25권5호
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• pp.731-739
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• 2011

To investigate corrosivity characteristics of tap water in Korea, Langelier index (LI) of 30 multi-regional water treatment plants (WTPs) were evaluated. Weekly LI values of 30 WTPs were all negative, which means tap water in Korea might be very corrosive. Maximum LI decrease through water treatment processes was 0.95 under no additional corrosion control process. Based on the correlation results between LI and tap water qualities, pH and calcium concentration were confirmed as major parameters for LI control. Addition of calcium hydroxide with $CO_{2}$ or calcium hydroxide or sodium hydroxide can be chosen based on water quality. Continuous monitoring of LI and related parameters is recommended in water distribution system.

• 상하수도학회지
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• 제32권2호
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• pp.183-192
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• 2018

Applicability of corrosion inhibitor was evaluated using pilot scale water distribution pipe simulator. Calcium hydroxide was used as corrosion inhibitor and the corrosion indices of the water were investigated. Corrosion indices, Langelier saturation index (LI) increased by 0.8 and calcium carbonate precipitation potential (CCPP) increased by 9.8 mg/L. This indicated that corrosivity of water decreased by corrosion inhibitor and the effects lasted for 18 days. Optimum calcium hydroxide dose was found to be 3~5 mg/L for corrosion inhibition. We suggest that monitoring of CCPP as well as LI need to be conducted to control corrosivity of water.

• 상하수도학회지
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• 제25권2호
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• pp.193-199
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• 2011

A method to improve internal corrosion control efficiency by adding lime and carbon dioxide, which, in turn increases the Langelier Index (LI) for filtered water at a conventional drinking water treatment plant (WTP) was investigated. The SJ WTP (Q=100,000 $m^{3}$/d) has been operating an internal corrosion control system since 2006. The system has achieved stable operation through technical development and trial and error over a period of several years. As a result of the operation, the LI of treated water has increased up to 29% by adjusting pH of filtered water to 7.8 with the addition of lime and carbon dioxide. Coupon tests in the distribution system indicated that the corrosion rate has been delayed by 24% when the internal corrosion method was implemented. The increase of LI by lime and carbon dioxide has been proven to be a practical method for controlling corrosion.

• 상하수도학회지
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• 제25권5호
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• pp.707-717
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• 2011

Replacement of old water distribution pipes for protecting water quality induced by pipe corrosion requires enormous budget. Even after the replacement, however, corrosion can occur again at any times and, therefore, inhibitive measure of the corrosion will be not only economical but needed to diminish the consumers' distrust on tap water quality. In 2008, National Environmental Research Institute did a survey on 8 major drinking water source and proposed to establish the Langelier Saturation Index(LI) as a corrosion index in Drinking Water Quality Criteria. Among the water industries of Korea, K-Water is the only one that set up the level of pH over 7.0 and LI above -1.5 on yearly average basis. However, no systematic regulation including LI to inhibit the corrosive tendency has been established yet. In this paper, LI values out of 31 drinking water treatment plants were analyzed and two-stage control of LI value as a measure of corrosive tendency of water is proposed. Primarily, water treatment facilities may operate the system at a target LI value below -1.5. Following the investigation on the effect caused by adjusting the LI value on water quality and corrosiveness, it will be desirable to improve LI value below -1.0 in the long run. In addition to the LI, supplemental use of Larson's modified ratio (LMR) which incorporates hydraulic detention time will be necessary. Several methods to prove the inhibitive effect of improving the LI value on water quality have been also suggested.

• 공업화학
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• 제16권3호
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• pp.372-378
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• 2005

탄산칼슘 포화지수(LI: Langelier Index)는 탄산칼슘의 포화정도로서 수돗물의 부식성을 나타내며 수도관 부식방지를 위해 미국, 유럽, 일본 등은 수도법에 의해 관리되고 있지만 국내는 아직 도입되지 않았다. 본 연구는 LI의 국내 도입 타당성을 검토하기 위해 LI인자(5개항목: 수온, pH, 총알칼리도, 칼슘이온, 전기전도도)들을 측정하고 LI값을 산출하였다. 수온은 연간 $2.0{\sim}26^{\circ}C$, 연평균 $23.9^{\circ}C$로 나타났다. 총알칼리도는 30 mg/L (as $CaCO_3$)로 나타났으며, 총알칼리도를 $HCO_3{^-}$ 농도 값으로 대체가능성을 검토한 결과 농도 차가 거의 없는 것으로 나타났다. LI값은 2.0~-0.5로 나타나 부식성을 가지고 있는 것으로 나타났으며, 수돗물 부식성을 감소시키기 위해 정수장에서 $Ca(OH)_2$, $CaCO_3$, NaOH, $NaHCO_3$ 등을 투입할 필요가 있는 것으로 나타났다.

• 상하수도학회지
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• 제32권3호
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• pp.235-242
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• 2018

Corrosion inhibitors including calcium hydroxide have been used to prevent corrosion in the pipes for tap water supply. The corrosion index (i.e., Langelier Index) differs by area and water quality. The corrosion indices of the areas studied differed by more than 2.0. The 'homogenized' calcium hydroxide was added to the treated water at the K water treatment plant, in order to increase the value of the corrosion index and the concentration of calcium. As the result, the concentration of calcium was increased while the turbidity and pH changed little. The corrosion rate of the tap water with the 'homogenized' calcium hydroxide could be slowed down pretty much. The results suggested that the technology of 'homogenization' of calcium hydroxide can applied to tap water and desalinated water to prevent corrosion in water pipes even in corrosive pipes.

• 상하수도학회지
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• 제28권6호
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• pp.725-733
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• 2014

16 water treatment plants(WTPs) in Jeju province were investigated to evaluate the corrosivity of tap water. In addition, the impacts of lime and carbon dioxide on LI changes at ES WTP were analyzed. The average of LI in Jeju tap was -1.78 which was similar to that of in-land multi-regional WTPs. The recommended process to improve LI of ES WTP which has high corrosivity(i.e., LI = -2.61) was to combine lime and carbon dioxide with the dosages of 20 mg/L and 5 mg/L respectively to meet LI of -1.0 ~ 0. pH was confirmed to be a major water quality parameter that determined LI based on the correlation results among LI and water quality parameters. Precaution on turbidity increase by lime addition should given to minimize particle breakthrough in the distribution system. Turbidity increase can be controlled by the addition of lime prior to filters.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.529-536
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• 2011

본 연구는 수돗물과 SWRO 생산수의 수질 특성을 분석하여 SWRO 생산수가 지닌 강한 부식성을 확인하였으며, 이를 근거로 해수담수화 시설의 유지관리 및 부식제어를 목표로 진행되었다. 연구 초기 과정에서는 철 시편(mild steel coupon)에 대한 회분식 실험(Batch test)과 전기화학 실험을 통해 수돗물과 SWRO 생산수의 부식성을 비교하였다. SWRO 생산수의 부식성 제어를 위한 수단으로써 액상소석회(liquid lime, $Ca(OH)_2$)와 이산화탄소(Carbon Dioxide, $CO_2$)를 주입하는 방법과 액상소석회와 인산염계 부식억제제(Phosphate Corrosion Inhibitor, $P_2O_5$)의 조합에 이산화탄소를 주입하는 두 가지 방법을 비교하였다. 실험을 통한 각 수질의 평가는 부식성 평가 지수인 LSI(Langelier Saturation Index)를 통해 비교하였고 그 결과를 통해 액상소석회와 인산염계 부식억제제의 최적 주입량을 선정하여 모의배관 실험(Loop system test)에 적용하였다. 모의배관 운전 평가 후 장착된 금속배관(steel pipe)은 내부의 스케일에 대한 기기분석(SEM, EDX, XRD) 평가를 수행하여 형성물의 주성분과 산화상 및 원소 함류량을 비교 할 수 있었다. 실험 결과, SWRO 생산수에 부식제어기술을 적용하지 않은 대조군과 비교하여 적정량의 단일 액상소석회를 주입한 경우 평균 97.4%의 높은 부식억제 효과를 나타내었고, 액상소석회 와 부식억제제 조합이 주입된 경우 평균 90.9%의 부식억제 효과를 나타냈다. 모의배관 실험 과정 중 금속배관 내부에 형성된 스케일은 대조군의 경우 주로 철 산화물인 반면, 실험군의 경우 탄산칼슘($CaCO_3$) 피막이 형성되어 부식방지에 효과적임을 확인하였다.