Study on secondary dewatering of centrifugal sludge and control of residual chloride in sludge cake

July 8, 2026

Over the past decade, urban wastewater treatment plants in China have significantly expanded their treatment capacity, leading to a sharp increase in sludge production. To optimize sludge management and meet the requirements for sludge cake reduction and co-incineration, it is crucial to control both the moisture content and chloride ion concentration in sludge. This study addresses the limitations of conventional coagulants such as PAC by proposing a composite conditioner that enhances dewatering efficiency while reducing the residual chloride load. The results show that, after PAC treatment, the chloride ion content in sludge cakes increased markedly, reaching up to 2560 mg/kg. In contrast, the organic modifier G1, resulted in the lowest chloride ion content, demonstrating a significant capacity for chlorine control. Under pilot-scale conditions, using a 10 m² plate-and-frame filter press, the technical and economic analysis showed that combined conditioning with PAC and G1 significantly reduced the residual chloride ion content in the sludge cake by 86%, to approximately 310 mg/kg, while dewatering efficiency remained essentially unchanged, with a moisture content below 60%. This result meets the co-incineration standard of less than 400 mg/kg, with only a limited cost increase of 19% compared with conventional PAC use.

Authors in the community:

• 

  M

  Maxin Yan

  ist1115702

Supervisors of this institution:

• 

  M

  Maryna Taryba

  ist90317

other-engineering-and-technologies - Other engineering and technologies

eng - English

Instituto Superior Técnico