This research proposes an optimal flushing operation technique in an effort to prevent secondary water pollutions and accidents in aged pipes, and to improve the cleaning effect of unidirectional flushing. Water flow directions were analyzed using EPANET 2.0, while flushing and air scouring experiments in forward and reverse directions were performed in the field. In 42 experiments, average residual chlorine concentration and turbidity were improved after cleaning compared to before cleaning. It was found that even when the same cleaning method was used, further improvement of cleaning effect was possible by applying air injection and reverse direction cleaning techniques. By means of one-way ANOVA(Analysis of variance), it was also possible to statistically verify the need of actively utilizing air injection and reverse direction cleaning. Based on correlation between turbidity and TSS, the total amount of suspended solids removal was estimated for 874 flushing operations and 194 air scouring operations. The result showed that air scouring used more discharge water than flushing by an average of 4.9 m3 yet with larger amounts of suspended solids removal by an average of 145.9 g. The result of analysis on turbidity values from 887 flushing operations showed low cleaning effect of unidirectional flushing for the pipes with diameters over 300 mm. In addition, the turbidity values measured during cleaning showed an increasing tendency as pipe age increased. The methodology and results of this research are expected to contribute to the efficient maintenance and improvement of water quality in water distribution networks. Follow-up research involving the measurement of water quality at regular time intervals during cleaning would allow a more accurate comparison of discharge water quality characteristics and cleaning effects between different cleaning methods. To this end, it is considered necessary to develop a standardized manual that can be used in the field and to provide relevant trainings.

ABSTRACT
1. 서 론
2. 연구방법
    2.1 연구 대상 관로 선정 및 세척 실험 설계
    2.2 상수도 관로 세척 현장실험 방법
    2.3 플러싱 수행 자료를 이용한 탁질 제거 효과분석 및 관리 방안 마련
3. 연구결과 및 고찰
    3.1 세척 공법별 전·중·후 수질 측정 결과 비교 분석
    3.2 물 흐름 방향을 고려한 세척방법별 효과분석
    3.3 세척방법별 세척수 수질측정 결과에 대한 일원분산분석
    3.4 세척수의 수질분석을 통한 탁질 제거 효과분석
    3.5 관로 조건별 세척 효과분석 및 관리 방안
5. 결 론
References

• 서지원(서울시립대학교 일반대학원 환경공학과) | Jeewon Seo (Department of environmental engineering, University of Seoul)
• 이규상(서울특별시 상수도사업본부 시설안전부) | Gyusang Lee (The office of waterworks Seoul Metropolitan Government)
• 김기범(서울시립대학교 일반대학원 환경공학과) | Kibum Kim (Department of environmental engineering, University of Seoul)
• 형진석(서울시립대학교 일반대학원 환경공학과) | Jinseok Hyung (Department of environmental engineering, University of Seoul)
• 김태현(서울시립대학교 일반대학원 환경공학과) | Taehyeon Kim (Department of environmental engineering, University of Seoul)
• 구자용(서울시립대학교 일반대학원 환경공학과) | Jayong Koo (Department of environmental engineering, University of Seoul) Corresponding author