Southern Water is seeking further supply chain input for its proposal to consolidate seven existing sludge treatment centres into three new "super-sites" - known as the Kent Bioresources Project.

The water company is inviting interested suppliers in the wider water sector to participate in further market engagement activities via a Request for Information (RFI).

The RFI follows on from, and has been informed by market engagement activities undertaken in early 2024.

Southern Water said the earlier sessions, including a market engagement event and subsequent one-to-one discussions, had provided valuable insights into market capacity, delivery preferences and potential partnership models.

Southern Water is currently exploring delivery through a single third-party DBFOM (Design, Build, Finance, Operate, Maintain) contract, with aff-balance-sheet treatment of capital investment preferred, although it says alternative contracting structures remain open for market input. 

The water company is initiating the Kent Bioresources Project to modernise and consolidate its sludge treatment operations across Kent. The project forms a key part of the company’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.

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.

The utility says 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.

Image source: Southern Water Bioresources Strategy October 2023

Note: Motney Hill WTW (Medway) subsequently added (see below)

The Kent Bioresources Project would see seven existing sludge treatment centres onsolidated 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) - added since the last market engagement

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

The company has also commenced feasibility studies for plants in Hampshire and Sussex to be upgraded to AAD too.

Delivery approach

Southern Water is currently exploring delivery through a single third-party DBFOM (Design, Build, Finance, Operate, Maintain) contract, although it says 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.

Via the RFI, Southern Water is seeking input from organisations across the wider water sector in order to:

• Gauge market appetite across the investor, construction, and technology supply chain.
• Understand preferred contracting and financing models.
• Explore innovative technical solutions (e.g., alternative advanced treatment processes, resource recovery, or third-party waste integration).
• Identify key delivery risks, interfaces, and opportunities for resilience.

The engagement deadline is 31 March 2026, with both group and 1-2-1 sessions expected to be held in the 1st quarter of 2026

Currently the estimated publication date of a formal tender notice is 1 September 2026 and the current estimated contract start and end dates are 1 April 2027 to 30 March 2055 i.e. a 28 year contract.

The Request for Information is available for download at southernwater.bravosolution.co.uk under "pqq_907 Kent Bioresources Project Request for Information". For organisations who are not already registered with a login, the registration process is simple and free.