Biosolids Study and Testing in China

Client: City of Hengyang
Location: Hunan, China

With a population of 7.1 million, Hengyang is one of the fastest growing cities in China. Due to the requirement of new stringent national biosolids quality standards, the City of Hengyang is seeking advanced biosolids treatment to meet the new sludge quality limits. The City currently operates 11 WWTPs, including the 40-mgd Song Ting WWTP, built in 2011.

The city of Hengyang currently operates 11 WWTPs, including the 40-mgd Song Ting WWTP, built in 2011.

Hengyang is located in the central south region of China. With a population of 7.1 million, Hengyang is one of the fastest growing cities in China.

The wasted activated sludge is dewatered by a total of three centrifuges.

The average cake solids content is approximately 20%, which is disposed in landfills.

Project Outcomes and Benefits

  • Providing biosolids study and testing services
  • Evaluating historical biosolids treatment performance
  • Selecting potential treatment methods
  • Testing potential biosolids treatment methods

Currently, the wastewater influent first is filtered through coarse mechanical screens, then fine mechanical screens. After the screening processes, the wastewater goes through a grit removal process, and then it is treated by a biological process through two oxidation ditches with blowers and diffusers. The mixed liquor is discharged to four secondary clarifiers. The wastewater effluent is disinfected with chlorine in a contact basin before it is discharged into the Xiang River. The wasted activated sludge is dewatered by a total of three centrifuges. Polymer is added as the dewatering aid. The average cake solids content is approximately 20%, which is disposed in landfills.

For more information on this project, or to discuss a similar project in your area, contact Michael Wang at mwang@hazenandsawyer.com