Wastewater sludge processing and utilization at the wastewater treatment facilities of Saint-Petersburg: best practices and prospects

Summary

Best practices of processing and utilization of wastewater sludge at the wastewater treatment facilities of Saint-Petersburg is presented. Centrifuging is used as the main dewatering technology. The dewatering equipment for 40 years has been continuously upgraded; at present decanters – latest generation equipment are used that provide for 72–75% dewatered sludge moisture content and sludge incineration without any fuel addition. All sludge generated at the municipal treatment facilities in the city is incinerated at three incineration plants. Sludge is incinerated in fluidized bed furnaces at 800–850 °С. Ash after sludge incineration is classified as hazard class IV. The amount of sludge is reduced 12-fold. As a result storing dewatered sludge at special landfills was abandoned; consequently the need of constructing new ones was no longer valid. Flue gas cleaning is carried out by wet scrubbing (incineration plants at the Central Wastewater Treatment Facilities and South-Western Wastewater Treatment Facilities) and dry scrubbing. At present the project of upgrading the incineration plant at the Central Wastewater Treatment Facilities has been designed.

Key words

treatment facilities , wastewater sludges , ash , centrifuges , sludge incineration plant , dewatered sludge