하수관거정비 임대형 민자사업(BTL)의 시기별 사업 효과 분석

The Sewer Rehabilitation Build-Transfer-Lease (BTL) projects represent a typical model of private investment in public infrastructure; however, comprehensive evaluations of their long-term effectiveness during post-construction operational periods remain limited. This study conducts a time-series analysis from the pre-rehabilitation period (2006) to the operational phase (2011–2021) to quantitatively assess the actual outcomes of a sewer rehabilitation BTL project. The analysis encompasses environmental indicators—including influent flow volume, sewer water quality (BOD, SS, T-N, T-P), and river water quality—as well as financial indicators such as operating costs and facility lease payments. Each indicator was evaluated based on annual variation rates and actual versus planned expenditure ratios. The findings reveal that while influent flow increased sharply immediately following rehabilitation, it gradually stabilized over time. Water quality parameters also showed general improvement after initial short-term fluctuations. Additionally, improvements in river water quality indicate that the rehabilitation project effectively reduced pollutant inflow, resulting in tangible environmental benefits. From a fiscal standpoint, both operating costs and lease payments were largely reduced compared to initial projections, suggesting enhanced financial efficiency. These results demonstrate that BTL projects in sewer rehabilitation can yield significant environmental and economic gains beyond mere infrastructure upgrades. Nevertheless, the study is limited by its reliance on basic time-series methods, which restrict the distinction between short- and long-term impacts. Future research should adopt more advanced time-series methodologies for refined evaluation.