The sewage treatment plant (13): the secondary sludge tank

Sounds recorded at a secondary tank, where the sludge from mechanical and biological treatment is mixed. The waste will be used for biogas production.

The recording was made at the Płaszów Sewage Treatment Plant. This is one of two mechanical-biological treatment plants belonging to Miejskie Przedsiębiorstwo Wodociągów i Kanalizacji S.A. in Krakow. The sewage treatment plant in Płaszów serves around 500,000 inhabitants and treats an average of 165,000 m3 of sewage per day.

First, the sewage is pre-treated mechanically: solid impurities are retained on coarse and fine grids, sand is removed in a sand trap, sediment settles in the primary settling tanks. Mechanically treated sewage is channelled to biological reactors where the processes of removing organic compounds, nitrogen and phosphorus using the biomass of bacteria, protozoa and higher organisms (the so-called activated sludge) take place. Then they go to secondary settling tanks where active sludge is separated from the treated sewage. Sewage which has been treated and is now safe for the ecosystem is discharged into the Drwina River. Sludge from the purification process is used to produce biogas which powers electricity generators. Finally, after dewatering the sludge is incinerated at the Sludge Thermal Treatment Station.

The information comes from: https://osplaszow.wkraj.pl/#/62657/0

Sound recording: Monika Widzicka
Photo: Piotr Żabicki