The energy consumption of a wastewater treatment plant’s aeration system can be reduced by up to 65% when more energy efficient equipment and expertise in optimising treatment systems is introduced, according to full scale trials carried out by water technology provider Xylem Inc.

Tests conducted by Xylem at the Sternö municipal wastewater treatment plant in southern Sweden revealed that the cost of upgrading the system would be recovered within four years and that the new system decreased the total energy consumption of the entire plant by 13%. This corresponds to annual savings for the test plant of €21,000 or €46,000 if both of the plant’s treatment lines are upgraded.
The Sternö plant, which was built in 1997, is designed to cater for a population of 26,000. Aeration was consuming 44% of the total energy usage of the plant. The test line was upgraded with Xylem’s Sanitare Silver series low pressure diffusers, a new blower and a new control system. The existing aeration system consisting of tube diffusers, lobe blowers and a simple dissolved oxygen (DO) control was kept in the second line which was used as a reference.
With the new system in place aeration efficiency is almost three times as high in the test line compared to the reference line. The required airflow was reduced by 30% and the system pressure reduced by 15%.
These savings were gained by a combination of a more efficient blower, a higher Standard Oxygen Transfer Efficiency (SOTE), a lower headloss and an energy-optimised DO control and DO profile as well as over 40 years’ expertise in optimising wastewater treatment systems.