Governor Johnson Sakaja has announced a major expansion of Nairobi's sewerage infrastructure after the Ruai Sewerage Treatment Plant doubled its wastewater treatment capacity from 160,000 cubic metres per day to 320,000 cubic metres, as the county also moves to triple the capacity of the Kariobangi Sewer Treatment Plant.
The Kariobangi facility is being expanded from 30,000 cubic metres to 90,000 cubic metres per day, in a move aimed at improving sanitation services, protecting the environment and supporting the city's growing population.
The projects form part of the county's broader plan to modernise Nairobi's sewerage network and reduce pollution caused by untreated wastewater flowing into rivers.
Speaking during the announcement, Sakaja said the expanded facilities are necessary to keep pace with the city's rapid growth.
"This is important because we are in a growing city that now hosts more than seven million people during the day and over five million at night. It is paramount that we expand our treatment capacity, and that is exactly what we have achieved through the efforts of our teams in collaboration with the National Government," he said.
According to the Governor, the increased capacity at Ruai and Kariobangi will allow the county to treat more wastewater, reducing illegal sewage discharges that have for years polluted Nairobi's rivers and surrounding environment.
The expansion comes as Nairobi City County and the National Government continue implementing a 54-kilometre trunk sewer project along the Nairobi River corridor. The new sewer network is expected to eliminate illegal sewer connections that currently release untreated waste directly into the river while strengthening the city's long-term sanitation system.
"The new trunk sewer line will serve Nairobi for the next 50 years. It will help clean the Nairobi River and permanently address illegal sewage discharges. Beyond environmental restoration, we are transforming the river corridor into an attractive public space with boulevards, walkways and cycling lanes, changing the story of a capital city that for decades has been defined by a polluted river running through it," Sakaja said.
County officials said the expanded Ruai treatment plant will also produce safer treated water for downstream agricultural use, benefiting farming communities that rely on reclaimed water while improving public health.
They added that the Kariobangi expansion will strengthen wastewater treatment in the northern parts of the city, complementing the wider sewerage upgrades and positioning Nairobi to meet future demand as its population continues to grow.