A HUBER Technology Sludge Thickening case study at Basildon WRC (Anglian Water)

Working with I.O.S., a delivery arm of Anglian Water, together we developed a solution utilising HUBER Rotary Screw Thickeners S-DRUM and investigated how these well proven sludge thickeners might replace existing centrifuges.

Existing Centrifuge plant – Intention is to re-utilise this elsewhere within Anglian Water

Photograph of HUBER Rotary Screw Thickener S-DRUM installed at Galashiels STW in 2005 i.e. 15 years old when site visit took place

Finished installation at Basildon WRC

Typical platform layout for horizontally mounted drum thickeners

In addition, concrete plinths are required to support horizontally mounted drum thickeners


At their water recycling centre at Basildon WRC HpH technology (heating, pasteurisation & hydrolysis) has been operational for a number of years. The first step in the process uses hot water and steam to heat the sludge, typically this is recovered from the combined heat and power (CHP) engines that generate electricity from the biogas. The second step is pasteurisation, after which the sludge goes through a hydrolysis and acidification process, which pre-conditions it for efficient biogas conversion in the anaerobic digester.

HUBER Technology were approached in 2020 to investigate how the well proven S-DRUM sludge thickeners might replace the existing Centrifuges to provide an average output of 8% DS, which is the ideal feed for the HpH process. Although the Centrifuges had provided a good service the cake output was often well above 8% DS.

Before committing to scheme delivery, Anglian Water needed to gain confidence around the use of the S-DRUM thickeners, so a visit was arranged to see a very similar S-DRUM to those that would be required to meet the throughput and output requirements for this project.

Scope of the project

Working with I.O.S., a delivery arm of Anglian Water, together we developed a solution utilising duty/standby S-DRUM 4L sludge thickeners. Prior to the new equipment being ordered a design contract was awarded, which allowed all parties to see and understand exactly what the finished installation would look like. Following a design review a subcontract was awarded and work began to deliver the agreed solution. 

Due to having to maintain sludge thickening throughout the duration of the project it was necessary to phase the installation of the new S-DRUM thickeners. With supervision from Huber engineers I.O.S. carried out the work. The trickiest part of the project was integrating the controls for the S-DRUM thickeners with existing SCADA etc. However, with excellent teamwork this obstacle was overcome.   

Sludge thickening process parameters

Sludge type Raw indigenous & imports
Maximum dry solids content of incoming sludge 3.5 %
Average outlet sludge concentration 8.0 %
Maximum throughput required 45 m³/hour at maximum DS content
Operating periods Up to 24 hours per day 7 days per week
Mode of thickener operation Duty/standby
Minimum solids recovery 95%

HUBER Technology scope

The design, manufacture, supply, delivery, the supervision of the phased mechanical installation, of:

  • 2 x (duty/standby) HUBER S-DRUM 4L sludge thickeners c/w flocculation reactors.
  • 2 x sets of polymer mixing valves and injection rings.
  • 2 x Anglian Water compliant control panels.
  • Commissioning and training of O&M staff.

Unlike other drum thickeners that are predominantly installed horizontally, the S-DRUM is installed at an inclined angle. This has several advantages, the main one being there is no requirement to elevate them on support platforms to enable thickened sludge pumps to be located under the sludge discharge point. As can be seen above, some deem it necessary to erect permanent access platforms, however, this is on a significantly smaller scale when compared to what is required for conventional, horizontally mounted drum thickeners that also require kit specific concrete plinths onto which the thickeners are fixed – See below. This can significantly reduce the cost and the time taken to complete the installation of the overall solution as well as reducing the overall carbon footprint.

Other advantages of the S-DRUM thickeners include:

  • 20% reduction in operating costs versus GBT’s.
  • 50% reduction in maintenance costs.
  • Low energy requirements.
  • Lower volume and pressure washwater demand.
  • Less susceptible to ragging.
  • Slow rotation/operation results in significantly less wear.
  • Robust stainless steel wedge wire ‘screen’ built to last the asset life of the equipment. 

Dale Foster, HUBER Technology’s Area Manager commented: “It was great to secure the first contract to supply our S-DRUM sludge thickeners within the Anglian Water area for this project. It is our expectation that once the kit has operated well for a long period of time sufficient interest will be generated for others to consider this technology for their sites. There are already interested parties. Word of mouth is why we have almost 100 S-DRUM installations in the UK and Ireland and 1,000’s globally.“

For more information please contact Rachael Harvey on 01249 765052 or email Rachael.Harveyhuber.couk.