This note is the twelfth installment in the structural analysis series from the Public Asset Utilization Research Lab (ISVD-LAB-005). It compares three leading domestic water and sewerage concession cases from a design-structure perspective and clarifies the conditions and limits of private operational transfer.
What Is Happening
Water and sewerage infrastructure is one of the largest categories of public asset held by municipalities across Japan. The number of water utility operators nationwide stands at approximately 1,300, and a substantial share face a double burden: declining tariff revenues from population loss combined with aging infrastructure requiring replacement.
In response, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and the Ministry of Health, Labour and Welfare (before the post-reorganization into the Ministry of Children and Families) have promoted the adoption of concessions — the operational rights-setting model. Under a concession, ownership of the infrastructure remains with the municipality while a private operator is granted a concession right (jiei-ken), enabling that operator to recoup its investment from operational revenues.
MLIT has developed the regulatory framework for sewerage concessions since 2015, and Hamamatsu City launched Japan's first sewerage concession in April 2018. Miyagi Prefecture subsequently implemented an integrated water, industrial water, and sewerage concession (launched April 2022) that far exceeded the earlier model in both scale and structural sophistication.
Background and Context
Why Are Concessions Needed for Water and Sewerage?
Capital expenditure for water and sewerage infrastructure renewal is rising sharply as pipes and treatment facilities installed during Japan's high-growth era (1960s–1970s) simultaneously reach the end of their service lives. The proportion of sewerage pipes that have exceeded their statutory useful life of 50 years continues to rise year by year.
At the same time, municipalities experiencing sustained population decline face shrinking tariff revenues, making it increasingly difficult to secure financing for renewal. This structure — rising renewal costs against declining revenues — is the backdrop for concession adoption.
Under a concession, a private operator acquires the operational right under a long-term contract (typically 20–30 years) and funds all required renewal and maintenance from its own capital during that period. The municipality receives an upfront consideration for the operational right, and the private operator recovers its investment from long-term operational revenues. The structural reason concessions are chosen is that the municipality's cash-flow problem and the private operator's long-term investment recovery needs coincide.
Overview of the Three Cases
| Case | Scale | Start | Contract Period | Private Revenue Source |
|---|---|---|---|---|
| Hamamatsu City (sewerage) | Processing volume: 310,000 m³/day | April 2018 | 20 years | Sewerage usage fees |
| Miyagi Prefecture (integrated: water, industrial water, sewerage) | Three utilities combined | April 2022 | 20 years | Water tariffs, industrial water tariffs, sewerage usage fees |
| Susaki City (water supply) | Population approximately 20,000 | April 2020 | 15 years | Water tariffs |
Reading the Structure
Hamamatsu City: Japan's First Sewerage Concession
The Hamamatsu City case launched in 2018 as Japan's first sewerage concession. Seven treatment facilities and associated infrastructure within the sewerage service area were designated, and the administrator (Hamamatsu City) granted the concession right to the private operator Hamamatsu Water Symphony Co., Ltd.
The defining design feature is performance-based contracting. Hamamatsu City specifies minimum standards for treated water quality and facility maintenance in the contract, leaving the method of achieving those standards to the private operator. The operator's profit comes from efficiency gains above that minimum threshold.
Hamamatsu City conducts regular monitoring to verify water quality, facility condition, and financial status. Penalty provisions for failure to meet treated water quality standards and the conditions for terminating the 20-year contract are explicitly codified.
The challenge the Hamamatsu model exposed is that "for a single municipality operating a single utility, the private operator's investment recovery is thin." In a mid-sized city with limited processing volume, the margin available to a private operator is small, and the pool of willing private entrants is correspondingly narrow.
Miyagi Prefecture: Integrated Design Across Three Utilities
Miyagi Prefecture's project transfers operational control over three utilities — water supply, industrial water supply, and sewerage — to a single private entity. Known as the Miyagi-Type Management and Operations Model (Miyagi-gata kanri-un'ei hōshiki), the concession right was acquired from Miyagi Prefecture in April 2022 by Mizumusubi Management Miyagi Co., Ltd. (a special purpose company centered on Veolia Japan Co., Ltd.).
In terms of scale, it substantially exceeds Hamamatsu. The design places on the private operator the combined processing and supply volume across three utilities and the full capital burden for facility renewal over the 20-year contract period.
The Miyagi Prefecture model incorporates two key design elements.
First, revenue stabilization through three-utility integration. By bundling water supply, industrial water, and sewerage under one contract, the private operator diversifies its revenue base. If water demand declines, revenues can be supplemented by strong industrial water utilization — a built-in cross-subsidy structure.
Second, graduated tariff revision authority delegated to the private operator. Miyagi Prefecture grants the private operator the right to apply for tariff revisions within defined limits. This is a design provision to ensure operational continuity over the full 20-year horizon.
Susaki City: Water Supply Concession in a Small Municipality
Susaki City (Kōchi Prefecture) is a small municipality of approximately 20,000 residents. Facing fiscal deterioration of its water utility, the city initiated a water supply concession in 2020. The case attracts attention as an application of the concession model to a small municipality — but its structural constraints are equally clear.
The smaller the population, the thinner the private operator's profit margin. Because the total tariff revenue base is limited, a model in which the private operator funds all facility renewal from its own capital is difficult to sustain. In Susaki's case, the design adopted involves partial municipal subsidy for renewal costs — it differs from a fully private-funded model.
| Design Variable | Hamamatsu City | Miyagi Prefecture | Susaki City |
|---|---|---|---|
| Utility integration | Sewerage only | Three utilities: water, industrial water, sewerage | Water supply only |
| Facility renewal costs | Full private burden | Full private burden | Partial municipal subsidy |
| Tariff revision | Municipality determines | Private operator has application rights | Municipality determines |
| Termination conditions | Explicitly codified | Explicitly codified | Explicitly codified |
What emerges from comparing these three cases is a structural insight: the viability of a concession depends heavily on the municipality's scale, the revenue margin available in the utilities involved, and the allocation design for renewal costs. The label "concession" is shared, but the underlying design logic differs fundamentally from case to case.
As the 2030s approach and renewal costs for water and sewerage infrastructure are certain to increase, the design choices available to municipalities reduce to three variables: whether to integrate utilities or treat them separately; whether to place the full renewal burden on the private operator or combine it with subsidies; and how much tariff revision authority to delegate to the private operator.
References
Promotion of PPP/PFI in the Sewerage Sector (Including Concessions) — MLIT Water Management and Land Conservation Bureau, Sewerage Division. Ministry of Land, Infrastructure, Transport and Tourism
Miyagi Prefecture Miyagi-Type Management and Operations Model (Integrated Water, Industrial Water, and Sewerage Concession) — Ministry of Land, Infrastructure, Transport and Tourism. Ministry of Land, Infrastructure, Transport and Tourism
Hamamatsu City Sewerage Concession Project — Ministry of Land, Infrastructure, Transport and Tourism. Ministry of Land, Infrastructure, Transport and Tourism
Current State of Public Enterprises (FY2022 Edition) — Ministry of Internal Affairs and Communications. Ministry of Internal Affairs and Communications