Kent Bioresources Request for Information

Project Purpose

Southern Water Services Limited (SWS) is initiating the Kent Bioresources Project to modernise and consolidate its sludge treatment operations across Kent. The project forms a key part of SWS’s long-term bioresources strategy to deliver a more efficient, resilient, and compliant asset base aligned with future environmental standards and the company’s AMP8 priorities.

Background

Southern Water currently treats approximately 6 million m³ of sewage sludge per year across its wastewater treatment network, operating 16 sludge treatment centres (STCs) supported by a large transport and recycling operation. In Kent, the current system comprises seven STCs processing around 42,000 tonnes dry solids (TDS) annually.

A combination of ageing infrastructure, evolving regulation, and tightening environmental standards — including restrictions on landbank use, air-emission limits, and emerging contaminants such as PFAS — necessitates a shift toward advanced, centralised treatment solutions.

Project Vision

The Kent Bioresources Project proposes to consolidate seven existing sludge treatment centres into three new “super-sites” that will employ Advanced Anaerobic Digestion (AAD), CHP biogas utilisation, or biomethane upgrading for grid injection. The indicative preferred sites are:

• Ashford STC (South Kent)

• Ham Hill STC (North Kent)

• Motney Hill WTW (Medway) – this has been added since the last market engagement.

Sites are expected to require full redevelopment, including new reception, digestion, dewatering, and energy recovery infrastructure.

We also have commenced feasibility studies for plants in Hampshire and Sussex to be upgraded to AAD too.

Delivery Approach

Southern Water is exploring delivery through a single third-party DBFOM (Design, Build, Finance, Operate, Maintain) contract, though alternative contracting structures remain open for market input.

Indicative features include:

• Long-term, performance-based contract structure.

• Off-balance-sheet treatment of capital investment preferred.

• Potential Special Purpose Vehicle (SPV) or consortium delivery model.

• Opportunities for collaboration among civil contractors, technology providers, funders, and operators.