The City’s Environmental Services team oversees the treatment of wastewater collected via the sanitary and combined sewers.
Wastewater is processed at the St. Andrew Street Wastewater Treatment Plant (SAWTP) and the Bright’s Grove Wastewater Treatment Plant (BGWPT) where it is treated before being returned to the environment.
A total of 51 pump / lift stations across Sarnia and Bright’s Grove — five in Bright’s Grove and 46 in Sarnia — are used to transport wastewater to treatment plants.
St. Andrew Street Wastewater Treatment Plant
The STWTP is a Class 3 facility that treats wastewater through a multi-phase process.
STWP wastewater treatment process:
- Preliminary treatment: screening via two mechanical bar screens with 15 mm openings; and grit removal via two aerated grit tanks
- Primary treatment: six primary clarifiers; and four primary sludge pumps
- Secondary treatment: biological treatment via four aeration tanks; and secondary sedimentation via four secondary clarifiers
- Supplementary treatment: phosphorus removal via alum feed system and polymer feed system; and disinfection via UV disinfection system
On average 10,229 megalitres of wastewater is treated annually at the SAWTP.
Biosolids
Biosolids generated at the SAWTP are processed into organic-rich materials that is sold as fertilizer.
Bright’s Grove Wastewater Treatment Plant
Wastewater is treated at the BGWTP through a multi-phase process.
BGWTP wastewater treatment process:
- Preliminary Treatment System: influent distribution chamber; and two lagoon cells
- Secondary Treatment System: biological treatment; aeration system in lagoon cells; Submerged Attached Growth Reactor (SAGR)
- Post Secondary Treatment System: six cloth media disk filters; and filter backwash system
- Supplementary Treatment Systems: phosphorus removal alum feed system
On average, more than 560 megalitres of wastewater is treated annually at the BGWTP.