Thermal and Thermochemical Hydrolysis (THP/TCHP) systems offer a variety of benefits—reduced polymer usage, improved digestion, and enhanced dewatering performance, to name a few. But to fully unlock these advantages, one critical step is often overlooked: effective pre-dewatering through sludge thickening.
In the second session of our Sludge Treatment Webcast Series, Centrisys CEO Michael Kopper and CNP President Gerhard Forstner explored how upstream sludge thickening directly enhances the efficiency and stability of hydrolysis and biosolids treatment systems.
How sludge is prepared before it enters the reactor affects everything from polymer usage and pump reliability to energy efficiency and downstream process consistency.
A thickening step is needed before sludge enters a hydrolysis reactor. The method and degree of thickening influence how efficiently the sludge can be heated, pumped, and ultimately digested.
In traditional high-pressure THP systems, sludge typically needs to be thickened to approximately 17% total solids. Achieving this level often requires significant polymer dosing and presents mechanical challenges that many facilities are not equipped to handle.
For facilities using or considering Centrisys/CNP’s Thermochemical Hydrolysis Process (TCHP), the pre-treatment requirements are less demanding. TCHP is optimized for sludge in the range of 6–10% total solids and operates under atmospheric pressure using moderate heat and alkaline pH adjustment. This allows for a simpler and more manageable thickening strategy—without compromising performance.
Not all sludge thickening technologies perform the same, and the differences become even more important when preparing sludge for hydrolysis. In the webcast, our experts examined several commonly used thickening methods and what to consider for each including but not limited to the following equipment:
Choosing the right thickening solution depends on your facility’s specific constraints—such as space availability, sludge type, and processing goals. But when aligned with the overall system requirements, well-matched equipment can boost process reliability and set the stage for smoother, more efficient downstream operations.
Polymer usage is a major operational cost in both sludge thickening and dewatering. If polymers aren’t mixed properly or sludge isn't uniformly conditioned, downstream hydrolysis and digestion performance will suffer. Inconsistent thickening leads to uneven feed characteristics, which in turn stress pumps, slow digestion, and reduce biogas yield.
One of the main advantages of the TCHP system application in many plants is due to the fact that this process doesn’t require extreme solids concentrations prior to treatment. This means that the polymer dosage during pre-thickening is significantly reduced. In most installations, facilities have cut polymer usage by several folds compared to conventional high-pressure THP systems.
Lower and more consistent polymer demands allow operators to fine-tune chemical dosing and optimize equipment settings, instead of constantly reacting to fluctuations. The result will be smoother performance and better control of operating costs.
Spending too much on polymer? Input your plant data into our polymer savings calculator to see how you can improve polymer savings.
Sludge isn’t always predictable. Feed composition can shift due to collection schedules, seasonal weather changes, or even community behavior. Systems that lack flexibility often become bottlenecks.
This opens the door to smarter system design. With fewer pressure-related constraints, facilities can avoid overbuilding their thickening systems. In many cases, they can use existing thickening infrastructure with only minor upgrades, lowering the upfront cost of implementing hydrolysis while reducing the learning curve for operators.
During the webcast, we shared two real-world examples where sludge thickening strategies directly improved performance:
Sludge thickening is a core component of overall process performance. Getting it right means fewer problems downstream and a system that’s easier to run, optimize and sustain.
Sludge thickening should never be treated as an afterthought when planning for thermal hydrolysis. Whether you’re using traditional THP or exploring the advantages of TCHP, upstream preparation has a significant influence on the efficiency, reliability, and cost of the full biosolids treatment process.
Centrisys/CNP’s experience in designing and optimizing end-to-end solutions has shown that the best results start with informed decisions about thickening. Facilities that plan for variability, align equipment with their unique needs, and manage inputs carefully are more likely to realize the full benefits of hydrolysis—without the setbacks caused by overlooked pre-treatment factors.
Below, we answer the questions asked during the webinar about the Centrisys' THK Series Sewage Sludge Thickener, including the ROI of the equipment, installation process, and more.
Watch the full webinar here to dive deeper into these insights and see how your facility can benefit from a smarter approach to sludge thickening.