Since sewer rehabilitation program requires long construction period and enormous capital investment, determination of rehabilitation priorities is important with systematic planning considering appropriate evaluation parameters. In this research, we applied PROMETHEE(Preference Ranking Organization METHod for Evaluations) known as very objective and scientific multi-criteria decision-making analysis, using the weights determined by AHP(Analytic Hierarchy Process) for the selected sewer evaluation items to calculate the rehabilitation priorities for each sewer sub-catchment in basin Gusan 1 of Seoul. Preference functions and preference thresholds were estimated for each criterion of ratio of lack of hydraulic capacity of sewers, defect ratio, ratio of sewers with velocity less than its minimum criteria, and density of sewers in the sub-catchment. As a result, it was found that region d had the first priority among four sub-catchments. For each and every sewer located in region d, we could also rank sewers to be rehabilitated urgently.

Sewer deterioration models are needed to forecast the remaining life expectancy of sewer networks by assessing their conditions. In this study, the serious defect (or condition state 3) occurrence probability, at which sewer rehabilitation program should be implemented, was evaluated using four probability distribution functions such as normal, lognormal, exponential, and Weibull distribution. A sample of 252 km of CCTV-inspected sewer pipe data in city Z was collected in the first place. Then the effective data (284 sewer sections of 8.15 km) with reliable information were extracted and classified into 3 groups considering the sub-catchment area, sewer material, and sewer pipe size. Anderson-Darling test was conducted to select the most fitted probability distribution of sewer defect occurrence as Weibull distribution. The shape parameters (β) and scale parameters (η ) of Weibull distribution were estimated from the data set of 3 classified groups, including standard errors, 95% confidence intervals, and log-likelihood values. The plot of probability density function and cumulative distribution function were obtained using the estimated parameter values, which could be used to indicate the quantitative level of risk on occurrence of CS3. It was estimated that sewer data group 1, group 2, and group 3 has CS3 occurrence probability exceeding 50% at 13th-year, 11th-year, and 16th-year after the installation, respectively. For every data groups, the time exceeding the CS3 occurrence probability of 90% was also predicted to be 27th- to 30th-year after the installation.

This study is to improve the efficiency of BTL (Build Transfer Lease) project operation by comparing the infiltration rate based on the data of 5 years of infiltration of the separate sewer system and combined sewer system. In the survey site, the separate sewer system area consists of eight flowmeters in seven treatment basins, and the combined sewer system area consists of eight flowmeters in five treatment basins. The infillration rate was analyzed by night-time domestic flow evaluation method, and the average infiltration rates of the separate sewer system and combined sewer system were 13% and 16%, respectively. Combined sewer system was about 1.3 times higher than the separate sewer system. The average BOD of separate sewer system was 233 mg/L, which was about 2.4 times higher than the combined sewer system was 107 mg/L. In the comparison of the average pipe diameter-length infiltration of separate sewer system and combined sewer system, the separate sewer system and the combined sewer system were about 0.150 m3/d/mm/km and about 0.109 m3/d/mm/km, respectively. The floating population in mixed residential and commercial areas has been identified as the cause. Therefore, we propose a method to calculate the infiltration rate in consideration of the margin ratio in the area where the night active population is concentrated.

Even though sewers have been conventionally designed to prevent from sediment deposition using a specified minimum velocity or shear stress at a particular depth of flow or with a particular frequency of occurrence, it was appreciated that these methods do not consider the characteristics and concentration of the sediment and the specific hydraulic conditions of the sewer with sediment. In this study, a densimetric Froude number formula was suggested considering particle diameter and volumetric concentration of the sediment as well as flow depth and flowrate, based on several domestic field inspections, which was compared with other formulas proposed by previous investigators. When the sediment concentration was not considered, the calibration coefficient of 0.125-1.5 to the densimetric Froude numbers of this study was needed to obtain the similar ones with previous investigators’. For the densimetric Froude number formula obtained with consideration of sediment concentration, the exponent value of term Cv was almost the same as that of previous results and that of d50/Rh was similar for Fr < 2.2.

If sewage flows for an extended time at low velocities, solids may be deposited in the sewer. Sufficient velocity or tractive force should be developed regularly to flush out any solids that may have been deposited during low flow periods. This study aims to evaluate the periods (T) during which sewage flow greater than the minimum tractive force maintains on a spot in sewer pipe system with lower tractive force or lower velocity than expected in the design step, when a storage tank installed in a place upsteam pours water into the sewer. The effect to T of design factors of storage tank and sewer pipes was evaluated assuming the uniform flow in sewers. When the area of orifice in the storage tank is 0.062 ㎡(or 0.28 m diameter), the maximum T of 31sec was maintained using the usually used preset range of values of several design factors. As the horizontal cross section of storage tank and water depth of storage tank and roughness in sewers increase, T linearly increases. Also, T linearly decreases as the diameter of a sewer pipe increases. Although T gradually decreases as the sewer pipe slope decreases to around 0.005, T decreases sharply when the slope is less than 0.003.

Due to the sewer induced ground subsidence, there is an increasing demand for the advanced visual inspection technique for the existing sewer pipe structures. This study aim to develop a visual inspection device and real-time transmission system of inspection data with precisely evaluated structural and operational conditions of underground sewer pipe structures. In this paper, a high-precision image capturing system that automatically extracts cracks in the large-diameter sewer pipes and sewage culverts with a diameter of 1,000 mm or more, a real-time gas detection sensor for investigator safety were studied. By analyzing the module technology of the visual inspection device, the concept design for system integration was derived, and the real time transmission system of the inspection result was developed to establish the technical basis for the commercialized device. Also the crack detection test using crack calibration was carried out for the proposed image capturing camera system, and the position accuracy using L1 grade GPS module was tested in this study. The inspection technique of the existing structure condition using the visual inspection device in this study can be effectively used for various structures types and advanced composite structures in the future.

This study was performed to propose the sewer defect scoring, and grading protocols for sewer condition assessment. For this, sewer defect scoring methods were comparatively analyzed and reviewed for four international condition assessment protocols, which are established based on WRc manual. As a result, we proposed a new protocol for sewer condition assessment, in which characteristics of sewer pipes are considered by segment. In reference to the PIM-3, the extent of ground subsidence was adopted to be of importance, and renewal scores increased in accordance with weighting of defects causing structural backfill materials. Also, defect grades of ‘Hole’ were extended to 5 levels of the grading, and ‘Surface Damage’ was excluded in defect assessment. The addition of ‘Buckling’ resulted in reduction of weights in ‘Surface Damage’ and ‘Lining Defects’.

Sewer condition assessment involves the determination of defective points and status of aged sewers by a CCTV inspection according to the standard manual. Therefore, it is important to establish a reliable and effective standard manual for identifying the sewer defect. In this study, analytic reviews of the CCTV inspection manuals of the UK, New Zealand, Canada and South Korea were performed in order to compare the defect codes and the protocols of condition assessment. Through this, we also established the standardized method for defect code and revised the calculation method of assigning the condition grade. Analyses of the types and frequencies of sewer defects that obtained by CCTV inspection of 7000 case results, showed that the joint defect and lateral defect were the most frequent defects that occurred in Korea. Some defect codes are found to be modified because those did not occur at all. This study includes a proposed new sewer defect codes based on sewer characteristics.

The purpose of this sudy is to get characteristics of water quality in separated sewer overflows. In dry weather the water quality of sewage in the outfall of the separated sewer was an average BOD of 2.7 mg/L, CODmn of 4.9 mg/L, TN of 3.8 mg/L, TP of 1.9 mg/L, and SS of 5.3 mg/L, Because the quality except for TP was less than the water quality standard of wastewater treatment plant (WTP), a prevention facility was needed to prevent the sewage inflow to interceptor. When the separated sewer overflows (SSO) were overflowed, the maximum pollutant load was be found to be about from 2.7 to 5.4 times as a BOD base, about from 3.2 to 4.6 times as a SS base higher than average load. There was a big difference according to rainfall intensity and rainfall continuous time. In case the quality of SSO was less than water quality standard or water quality in dry season, SSO was required to discharge to the stream not to inflow to WTP by operating the floodgate in the outfall with water quality data using sensors, such as turbidity sensor, etc. Because removal efficiency by an intercepter load was calculated as low as about 10~20% as a BOD base, removal efficiency could be increased by installing a separated wall within the sewer.

최근 이슈가 되고 있는 도심지 지반함몰로 인하여 주기적인 하수관로 조사의 필요성이 강조되고 있다. 일반적으로 수행되는 조사 방법 중 하나인 하수관로 CCTV조사는 상당한 시간과 노력이 소요된다. 기존 연구들은 주로 하수관로 조사에 소요되는 노력을 줄이기 위한 H/W 및 S/W의 개발에 관한 연구가 주를 이루고 있다. 그러나 기존 CCTV 탐사장치를 이용하여 관리담당자가 보관하고 있는 수많은 조사영상 를 활용하기 위한 연구는 진행되지 않았다. 본 연구는 cross-correlation기법 기반의 이미지프로세싱 방법을 적용하여 CCTV 조사영상의 자막 으로부터 장치의 위치정보를 추출하였다. CCTV 장치의 시간-거리 관계를 분석한 결과 탐사 장치가 정지시간과 하수관로의 손상 사이의 강한 상관관계를 확인하였다. 제안된 CCTV영상의 분석법을 활용하는 경우 CCTV조사 보고서 작성 및 관리에 소요되는 노력을 줄임으로써 하수관 로 유지관리의 효율성과 신뢰도를 높일 수 있을 것으로 기대된다.

과거 SWMM 모형은 수십 개소 주요하수관거의 매개변수를 추정하고, 유량측정자료를 활용한 검보정을 통하여 구축된다. 현재 하수관로 관련 수치지도의 양적, 질적 자료 향상으로 분포형 모형과 같은 수준의 SWMM 모형의 초기값 추정이 쉽지만, 매개변수 검보정 시간은 단축되지 않는다. 최적화된 매개변수와 유사한 매개변수의 초기값을 산정하면, 매개변수의 검보정 시간단축으로 분포형 모형과 같은 수준의 SWMM 모형 구축이 쉽다. 본 연구에서는 GIS 툴을 이용하여 SWMM 모형의 소유역의 매개변수를 산정하며, 동일한 산정방법을 적용하여 하수관거 정보를 단순화시킨 관로정보 개소수의 변화와 유역분할 방법에 따른 유출특성의 변화를 비교분석한다. 모의시간과 예측정밀도를 요구하는 홍수예경보시스템의 도시유출모형 구축을 위하여 기존 연구 결과에서 SWMM 모형의 매개변수 민감도 분석결과에서 검토하지 못했던 소유역 분할방법과 모의시간단축과 관계가 깊은 하수관거 정보 개소수 변화에 따른 유출특성의 변화를 도출하는 민감도 분석을 실시한다. 본 연구의 결과는 홍수예경보시스템 구축을 위하여 정밀하고 모의시간이 짧은 최적의 SWMM 모형 구축을 위한 자료로 이용될 것이다.

다양화되는 물 수요와 기상 이변 등의 영향으로 극심해지는 가뭄에 대비하여 대체 수자원의 확보는 수자원 연구의 매우 중요한 부분이 되었다. 다양한 대체 수자원 중 하수처리장의 방류수는 양호한 수질과 비교적 예측이 가능한 방류량으로 인해 농업용수나 공업용수 혹은 공공용수를 대체할 안정적인 수원으로 관심의 대상이 되고 있다. 본 연구에서는 하수처리수 재이용을 위해 미래의 불확실한 용수 수요량을 고려한 최소의 공사비를 최적화하는 방법을 이진변수를 가지는 2단계