Rotorua mayor Steve Chadwick spoke at the commissioning.
"The health of our water is about the health of the people and the health of the land, and today marks a key milestone on this journey.
"Sustainability and how we look after our natural assets couldn't be more important to us as a council. As we look to the future, we are so dependent on the good health of our lakes.
"Working in partnership is enormously important as we continue down this path. The work under way here in Rotoiti to protect our water and land is both deeply spiritual and enormously practical, and it is symbolic of the investment in our relationship with iwi."
The East Rotoiti Rotomā Sewerage Scheme project has been led by the Rotoiti Rotomā Sewerage Steering Committee since its inception in 2014 after the council's resource consent for its chosen scheme failed in the Environment Court in 2012.
The scheme involves the construction of the Wastewater Treatment Plant behind the Rotoiti Emery Store and the installation of a reticulation network to the plant to cater for homes in Rotomā and east Rotoiti.
Some locals have previously voiced concerns about not knowing the final cost of the scheme, while others complained they already had adequate and long-lasting septic tank systems.
To date, $24.5 million of a $35.3m budget has been invested in the project.
