Newthorpe STW 

Newthorpe Sewage Treatment Works, in the Erewash Valley in Nottinghamshire, is undergoing a major expansion. The new works will duplicate its current capacity, from 324 l/s and 41,000 population equivalent (PE) to 649 l/s and 100,000 PE, to receive the flows of the Heanor Milnhay STW catchment area. A 2.5 km dual-rising main will connect both sites. Heanor Milnhay STW, a dual-stream site in Derbyshire currently treating 258 l/s (41,000 PE), has reached its maximum capacity and its geographical location makes it impossible to cope with the projected population growth. The process will be decommissioned, and the site will be re-purposed to hold a storm storage capacity that exceeds the current storm storage capacity by more than three times. The client, Severn Trent, and Mott MacDonald Bentley, principal designer and contractor, are the main stakeholders of this project.

Project objectives

The main project objectives align with the current social and economic environment. With the expansion of the works, Severn Trent is aiming to:

• Improve the effluent quality, especially phosphorus content. The new site will reduce the phosphorus concentration in the effluent from 2 mg/l to less 0.2 mg/l.
• Reduce the running costs and maintenance costs of the plant by merging two sewage treatment works and using a less-intensive chemical usage treatment process.
• Reduce the non-treated sewage spillage by increasing the stormwater storage capacity at Heanor from 2,200m3 to 7,000m3. Additionally, all the storm flows will be preliminary treated by physical screening and settlement

Process description: Tertiary treatment

The final stage of the process aims to further reduce the P levels in the effluent by capturing non-organic phosphorus.

Ferric sulphate is dosed upstream of the tertiary solids removal unit to cluster the particles into larger floccules that are then removed by a physical filtration system. The system selected in Newthorpe is FilterClear (mixed media filtration), designed and manufactured by Bluewater Bio Ltd. Once commissioned it will be the largest FilterClear system in wastewater treatment.