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.

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.

장수풍뎅이와 흰점박이꽃무지는 국내에서 상업적으로 이용되는 대표적인 부식성 곤충이다. 부식성 곤충을 사육할때 발생하는 응애류는 영양분이 많은 발효톱밥, 곤충의 먹이나 사체 등을 섭식하며 증식한다. 또한 곤충의 몸에부착하기 때문에 질병을 일으키는 매개체가 될 수 있으며, 상품성을 하락시켜 문제가 되고 있다. 본 연구에서는부식성 곤충 사육 중에 발생하는 대표적인 응애류 Sancassania sp.의 초기생활사를 확인하였다. 실험은 온도 25±1℃,상대습도 50±10%, 24시간 암조건 하에 인큐베이터에서 진행되었으며, 물한천배지(water agar, 2%)가 들어있는 36개의페트리디쉬(3.5cm)에 각 1개 씩 응애의 알을 넣고 3시간 간격으로 관찰하였다. 먹이는 곤충전용젤리를 공급하였다.초기생활사는 알(egg), 유충(larvae), 제1약충(protonymph), 제3약충(tritonymph), 성충(adult) 단계가 확인되었으며, 기간은 알 2.2±0.3일, 유충 1.5±0.1일, 제1약충 0.9±0.1일, 제3약충 1.5±0.2일로 성충까지 약 6.2±0.4일이 소요되었다.

In order to prevent secondary pollution of tap water, corrosion characteristics are investigated, and corrosion index are calculated using LI and LR to manage corrosiveness. As targeted water treatment plants from 2014 (July, once) to 2015 (July and October, 2 times), 70 plants are selected by making a division for each area and water system. (treated water samples, n=240, raw water samples, n=72). In result of pH analysis, treated water was lower than raw water to 7.12, and 7.29, respectively. LI were investigated in the order of Seomjin river, Nakdong river, Han river, Geum river, to -2.08, -1.24, -1.11, -1.10 (at raw water), and -2.18, -1.59, -1.51, -1.35 (at treated water), respectively. In case of water quality goal value (LI = -1) in Japan as control of corrosiveness, management object was investigated about 83.3%.

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.

The likelihood of failure for the stress corrosion cracking (SCC) of caustic cracking, which affect to a risk of facilities, was analyzed through the risk based-inspection using API-581 BRD. We found that SCC of the caustic cracking was occurred above 5 % NaOH concentration, and the technical module subfactor (TMSF) was maximized for above 50 % concentration. The heat traced and monitoring were not sensitive to the TMSF with NaOH concentration and temperature. But the steam out was more of less affect minimum value of the TMSF. Also, the inspection number, the inspection effectiveness, and the year since inspection were very sensitive to the TMSF with NaOH concentration and temperature. Therefore, the plan of next inspection will be established with compositively considering those at once.

The tap water is generally known to be corrosive in the pH range at 6.5 ~ 7.5. And the degree of corrosion varies depending on the types of raw water such as river surface water or lake water of the dam. Although several corrosion index represents the corrosivity of tap water, the typical corrosion indexes such as Langelier saturation index (LI) and calcium carbonate precipitation potential (CCPP) were calculated to monitoring the corrosive water quality about raw and tap water in water distribution system. To control the corrosive water quality, the correlation between corrosion index and water quality factors were examined. In this study, corrosion index (LI, CCPP) and the pH was found to be most highly correlated.