Sludge dewatering polymer reduction on a centrifuge
Sludge dewatering polymer reduction was the goal at a Yorkshire wastewater treatment works dosing heavily with polymer on its dewatering centrifuges. The works could not simply dose less: cutting polymer risked floc loss, cake dryness had to be held near 21% to feed the thermal hydrolysis plant, and centrate quality had to stay within process limits. During an October to November 2018 trial, one HydroFLOW® i160 was fitted to the incoming sludge feed pipe before polymer injection on centrifuge 3. Polymer dosing fell by 11%, with cake dryness and centrate quality both holding and no change to the downstream process.
The Challenges
- Sludge dewatering polymer reduction was needed, with high dosing on the centrifuges
- Any cut in polymer dosing risked floc loss
- Cake dryness had to stay near 21% to feed the thermal hydrolysis plant (THP)
- Centrate quality had to remain within process limits
- Any change had to be proven on a live centrifuge
The Solution
- Unit installed: one HydroFLOW® i160
- Installation point: incoming sludge feed pipe, before polymer injection on centrifuge 3
- Trial: October to November 2018 on a live centrifuge
The works needed sludge dewatering polymer reduction without upsetting a live centrifuge, so the unit was fitted to the sludge feed pipe on centrifuge 3, ahead of polymer injection. The signal improves flocculation, so polymer demand falls. The polymer saving was then measured against the two constraints: cake dryness near 21% and centrate quality within process limits.
