Exelys™ Continuous Sludge Thermal Hydrolysis System

Exelys is an innovative technology that represents the next generation of biosolids thermal hydrolysis.

Thermal hydrolysis is an anaerobic digestion pretreatment process. The thermal hydrolysis process decreases the viscosity of the material and increases volatile solids or organic loading for anaerobic digestion. Increased volatile content entering the digester increases methane production and reduces the amount of biosolids for disposal. Decreased viscosity alters the rheological properties to improve the digested sludge’s dewaterability and improves dry solids concentration. Other benefits of thermal hydrolysis include lowering downstream process equipment requirements, reducing process chemical costs and production of Class A biosolids for ease of disposal and beneficial use as bio-fertilizer.

The Exelys™ thermal hydrolysis process is a continuous operated anaerobic digestion pretreatment system. Steam is applied to hard to biodegrade wastewater sludge by the means of a dynamic mixer that instantaneously condenses steam on to the sludge. The use of steam applied to dewatered biosolids and the elevated pressure in the reactors causes the microbial cells to rupture and therefore increases the soluble fraction of COD that is available for anaerobic digestion.

The wastewater facility can benefit from amount of solids that will be reduced; the net result being greater biogas production and lower hauling costs. The sludge viscosity is also greatly decreased such that a 12% solids content can be mixed in a standard anaerobic digester, increasing mesophillic digester capacity by more than 200%. Thermal hydrolysis also reduces the dewatering requirements as post-THP sludge is known to yield higher dewaterability using less polymer, and produce a Class A product.

Combination of Thermal Hydrolysis and Anaerobic Digestion

  • Increase the anaerobic digestion capacity of an existing installation, maximizing existing infrastructure
  • Reduce the amount of biosolids produced, offering disposal costs savings
  • Meets Class A requirements, providing a marketable end product
  • Reduce the anaerobic digestion volume of a new installation by up to 50%, decreasing capital costs
  • Increase biogas production, meeting sustainable initiatives

The Veolia Advantage

  • Standard Package Systems
  • Variable configurations to improve energy efficiency
  • Worldwide experience
  • Understanding of full sludge treatment plant


High solids content sludge results in more efficient energy utilization

  • Heating solids, not water

Continuous automated operation allows for optimal performance

  • Effective asset utilization

Higher solids loading in the digester due to the hydrolysate's characteristics, increases capacity of existing digesters by up to 50%

  • Cost effective expansion of digester capacity for the future

Heat recovery and recycling further improving energy efficiency

Simple and efficient maintenance and cleaning of components

  • Decreased O&M costs


Digestion - Lysis - Digestion

DLD (Digestion - Lysis - Digestion) is an innovative process configuration designed to become the powerhouse of your wastewater treatment plant. The DLD optimizes the biosolids anaerobic digestion process, maximizing the production of renewable biogas energy while minimizing biosolids requiring disposal. At the core of the process is the Exelys continuous thermal hydrolysis technology - an energy efficient thermal hydrolysis system. By integrating the Exelys technology, more renewable biogas energy is available for electricity generation. In a modern wastewater treatment plant where energy efficiency is vital, the increased biogas energy available from the DLD solution is enough to make the entire wastewater treatment process energy self-sufficient - decreasing costs and reducing carbon footprint.


Optimized utilization of biosolids

  • Maximized solids destruction - maximized biogas production

First digestion reduces loading on the thermal hydrolysis system

  • Less biogas consumed - more available for other applications

Hard COD production minimized

  • Carbohydrates and ammonia removed in first digestion/dewatering

Energy recovery and recycling is optimized

  • Nothing is wasted