What is bioresources?

Bioresources is the term used to describe all the processes associated with the collection, transport, treatment and recycling or disposal of sewage sludge – a by-product from our waste water treatment works.

We produce approximately 44,000 tonnes dry solids per year from all of our 600+ wastewater treatment works.

Waste water treatment settling phase
Creating bioresources

1. Source

Sludge is the by-product from our 650+ wastewater treatment works. It's the organic material that's collected from the bottom of the settlement tanks that are part of the wastewater treatment process.

More on wastewater treatment
Photo of sludge tanker
Creating bioresources

2. Collection and transport

The sludge is pumped from the settlement tanks into sludge holding tanks.  From there, it's collected by tanker and transported to one of the 29 sludge treatment centres across the region. There it is treated and turned into a bioresource.  

Image of sludge treatment
Creating bioresources

3. Removing pathogens

Sludge is full of nasty bacteria (pathogens), so once it arrives at the treatment centre, it will go through one of these two processes that kills these pathogens.

Lime stabilisation - lime is added to the sludge which raises the pH to 11 or more, which deactivates the pathogens.

Anaerobic digestion - the sludge is heated in sealed tanks to around 37 degrees celsius for a number of days to kill the pathogens. This process has the benefit of generating methane which we can use to create electricity to power our sites!

Photo of sludge treatment
Creating bioresources

4. Dewatering

Part of both treatment processes includes a stage called ‘dewatering’.  Raw sludge is typically in a liquid form (1-3% dry solids), but by using technologies such as centrifuges, means that we can remove some of the water content and create a final treated product that is more like soil (normally 20-25% dry solids)

Tractor and digger doing works
Creating bioresources

5. Recycling

After treatment, sludge has become a safe bioresource. It meets the standards required to be used as a natural fertiliser in agricultural, and helps to recycle valuable nutrients back into the soil. Our bioresources are beneficial to farmland all across Devon and Cornwall.

What do we do with it?

We treat bioresources in our 29 sludge treatment centres (STCs) across the region using either lime stabilisation or anaerobic digestion processes.  This treatment ensures that the pathogen content of the sludge is treated to meet the levels for safe recycling back to agricultural land (meeting the Biosolids Assurance Scheme).

This treated product is beneficially used in agriculture as an alternative to chemical fertilizers and helps maintain the natural cycle of nutrients back to the soil.

How can I get some?

If you are a farm and would like to enquire about using SWW Bioresources please contact our contractors, Gregory's, directly.

Land Management at Gregory's

01884 836666 



Or, for more information, please contact us using the form below.