Scottish Water has gone out to tender with a contract for bioresource treatment framework at Kinneil Kerse with an estimated total value of £6.4 million (ex VAT).

The water company is looking to appoint a supplier to de-water and treat liquid wastewater sludge with lime to produce a biosolid that meets an enhanced treated standard as defined in the Biosolids Assurance Scheme (BAS). Scope of the procurement includes the supply of an appropriately sized centrifuge, lime treatment and storage equipment, treating, conveying the sludge cake to a storage location agreed on site, and operators.

The cake storage bay will be configurated by the supplier to meet their needs and be their responsibility. There are prefabricated “tombstones” that may be used - any additionally required material for creating the cake bay will be provided by the supplier. It will also be the supplier’s responsibility to ensure the placement of any materials to create the cake bay are positioned safely.

Scottish Water also specify that the type of lime used in the process must not be liquid and that any powdered or granulated lime is acceptable. All equipment must be suitably sized to deal with daily production levels of indigenous and imported bioresource.

The supplier will also be required to have an odour management plan which must satisfy all parties, namely Scottish Water, SEPA (Waste Management Licence) and the Local Authority (The Odour Code of Practice) and commit to adhere to this for the duration of the framework.

Other requirements the supplier must meet include:

• All prices should include supply of documentation and data with respect to operational performance and relevant legislation, codes of practice and other relevant standards.
• Full transparency of all activities performed by the supplier is expected. Daily communications with the local Scottish Water Operations team will be required, and a weekly meeting held. 
• The supplier must comply with the Sludge Treatment Facilities - Waste Management Licence Odour Management Plan, and other site associated Scottish Water processes and procedures.
• Electrical, water and wastewater services will be made available within the sludge storage/treatment area for use in providing the required service. It is the supplier' responsibility to confirm the available services are suitable.
• The supplied centrifuge should be capable of dealing with peaks in the sludge production.
• Equipment should be able to operate at approx. 40m3 per hour flow throughput through the supplied centrifuge and lime plant, of sludge whilst maintaining a solids capture rate of 97% +/- 2% in the return liquors.
• Equipment breakdown should not impact the ability of the successful supplier to accept business as usual cake imports.

Sludge from the onsite holding tanks will be a mixture of indigenous SAS from the onsite sequencing batch reactor (SBR) tanks and imported sludge from various satellite sites.

The sludge holding tanks do not currently have mixing capabilities and the total make up of sludge will likely be a high ratio of SAS and potentially lower than ideal dry solids. This should be taken into consideration by the supplier when providing suitable equipment.

In addition to indigenous sludge, there will be a requirement for cake import equipment able to treat up to an approximate additional 13,500 wet tonnes of imported cake per annum which is estimated to be between 20-24% dried solids. This is an estimate only using recent output figures following decommissioning of digesters at Stirling and Dalderse WWTWs and the figure may fluctuate.

Scottish Water also say that any additional capacity for cake imports would be welcomed to provide contingency for import restrictions elsewhere in the network.

Contract term will be eight years.

Time limit for receipt of tenders or requests to participate is 14 January 2026. All criteria are stated in the procurement documents which are available from: 

https://atamis-scottishwater.my.salesforcesites.com/ProSpend__CS_PublicLandingPage?SearchType=Projects