North Sewage Treatment Plant (NSTP) – Lagoons

Wastewater from the north end of Castlegar travels over the CPR bridge and into the headworks structure at the North Sewage Treatment Plant (NSTP).

From there, flow passes through the treatment lagoons, where microorganisms break down waste and take up nutrients. The NSTP is mainly comprised of a series of three lagoons or cells. The first two cells are aerated by submerged air diffusers that provide oxygen for the microorganisms. The third cell is classified as a facultative cell and relies on wind and wave action for aeration. Effluent from the last cell is treated with UV before final discharge to the river.

Wastewater entering the lagoons can take up to 70 days before it is discharged to the Columbia River. The NSTP also provides a habitat for many species of waterfowl and reptiles, such as blue herons and turtles.