Southern Water is investing nearly £8 million to upgrade the Battle Wastewater Treatment Works in East Sussex.
The project aims to reduce phosphorous levels, improve water quality and reduce storm overflows.
The latest milestone, managed by contractor CMDP, includes constructing an additional secondary settlement humus tank and installing a scraper bridge.
These additions help remove solids in the final stages of wastewater treatment.
A new storm tank is also being installed to increase storage capacity during heavy rainfall, ensuring more wastewater is fully treated and storm overflows are less frequent.
Project Manager for Southern Water Sunday Odusola said: “We are pleased to see this project progressing well, we’re keen to continue investing in our treatment works to improve our environmental performance improve water quality and reduce the number of storm overflows.”