Replacement of pumps for recirculation and sludge pre-heat at Pomorzany WWTP in Szczecin

Replacement of pumps for recirculation and sludge pre-heat in separated closed digestion chambers (SCDC) at Pomorzany WWTP in Szczecin.

The circulation of fermentation sludge in SCDC was carried out by two pumps on the main thrust and the third one on the reserve. Installed Wilo Emu FA 15.84D pumps with a channel impeller caused operational problems from the very beginning. As a result of agglomeration of fibrous parts in the fermentation chambers, the inlet pump clogged repeatedly. The cleaning consisted in unscrewing the pump so that after lifting it, one would gain access to the lower blocked part of the rotor to clean it, and then to assemble and restart the pump. The frequency of this activity increased over time. And in the seventh year of operation, cleaning of each of these pumps had to be repeated several times a day. The involvement of staff and the number of failures grew. It was decided to replace the pumps with new ones that would cope with fibrous impurities and their size would allow replacement of the old ones without significant changes at the suction and pressure of the sludge installation. After familiarizing with the offer of companies proposing a specific application, the solution offered by Xylem was chosen.

The final choice fell on a Flygt FT 3171 MT3-433 pump. The proprietary solution with the N-rotor spoke behind this solution. The impeller rotates inside the Chopper circular insert with cutting edges. The rotating impeller cuts all hard-to-pump solids such as fibrous materials, fabrics and various other materials into small, easy-to-pump parts. This is all the more important since the Alfa Laval sludge heater Alshe 800 is placed behind the pump, which has a certain tolerance for the size of the pollutants in the recirculated sludge.