Arcata Wastewater Treatment Plant and Wildlife Sanctuary - Sewage Treatment

Sewage Treatment

The sewage treatment process takes place in stages:

1. Primary Treatment (completed in 1949): Sewage is held in sedimentation tanks where the sludge is removed and processed for use as fertilizer.
2. Secondary Treatment (completed in 1957): Primary effluent is pumped into oxidation ponds (here bacteria break down the waste).
3. Disinfection (completed in 1966): Secondary effluent is chlorinated to kill pathogens and dechlorinated to avoid damage to natural environments.
4. Tertiary Treatment (competed in 1986): Disinfected secondary effluent is put into artificial marshes where it is cleansed by reeds, cattails, and bacteria.
5. Disinfection: Tertiary effluent is chlorinated to kill pathogens from bird droppings and dechlorinated to avoid damage to natural environments.