The De Hoxar Spiral Separator Gravity Wastewater Solution – Saving up to 97% Footprint on Conventional Tanks

The problems associated with conventional means of separating out waste sludge are well known to the industry – traditionally it involves using large settlement tanks taking up huge areas of land. Once the sludge has been settled, it then requires thickening for transport to anaerobic digester sites. The thickening process involves additional equipment and buildings which require large capital and operational investment.

The spiral solids separating technology, performs the same task as traditional settlement tanks, but requires as little as 3% of the space.  It also has the added advantage of producing thickened sludge which saves the requirement for additional thickening equipment. The capital investment is greatly reduced – saving money as well as space.

Space Saving Solution

One of the first installations of the de Hoxar Spiral Separator was at Shoreham for Southern Water as part of an environmental improvement scheme. The innovative spiral separators use deceptively simple technology comprising of giant plastic fins formed into interlocking spirals in circular treatment tanks. In this case the Spiral Separators were installed as additional plant to upgrade the original plant from primary to secondary treatment. 

The aerial view at Shoreham shows the size of the spiral separators in yellow, compared to the settlement tanks in red.

The spiral solids separating technology, performs the same task as traditional settlement tanks, but requires as little as 3% of the space.

Our Spiral technology saves money and helps in the delivery of a low carbon future.

Environment & Economy

The economic and environmental benefits of these kind of reductions are significant, and the uses for this technology are many – across municipal, potable and non-municipal wastewater treatment processes.  Applications include washwater recovery at water supply works, use on a range of industrial processes and several different uses within sludge treatment centres.

The technology has also been integrated with PWS’ other flagship technology, a biological nutrient removal (BNR) process called NUTREM®. For this application, it will be used to provide primary settlement to generate fresh sludge to use in the NUTREM® hydrolysing system, as well as a smaller version of the technology being offered to clients to provide SAS thickening.

In addition to the space and cost savings, the reduced visual impact makes the Spiral suitable for urban sites next to areas with public access. It is also an ideal solution for efficient extraction of high calorific primary sludge for Anaerobic Digestion as part of utilities CHP programs.

Further design updates are in progress to reduce the cost of production and improve the accessibility for maintenance and repair. Mobile units have also been designed to enable efficient installation and significantly reduce the time spent on site during the construction period.

Saving money and helping to deliver a net zero carbon future…

Plantwork Systems Chief Engineer, Dave deHoxar, invented the Spiral Separator whilst working at Southern Water, taking it from concept, all the way to market ready technology. Several Spirals were delivered on sites in the UK and Japan, ranging from small 1.5m diameter units, up to 7m diameter units performing primary settlement for wastewater treatment works serving populations >50,000 PE.

For more information, please get in touch!

Article by Robert White, Managing Director, PWS