Wastewater treatment is essential to protect our water resources, the environment, and human health. Treated wastewater can also produce useable resources such as water, biosolids, heat, and electricity.
Wastewater drains into a network of pipes maintained by sewer serviced municipalities and the Regional District of Nanaimo. Sewer systems are built to follow the natural slope of land, generally flowing towards the sea front. This design allows gravity to do most of the work transporting the wastewater to one of four wastewater treatment plants. For residential areas that are lower than adjacent lands or treatment plants, the wastewater must pass through a pumping station to pump the liquid into the plants. Treatment of our wastewater is an essential process that prevents contamination and destruction of our waterways, and our natural water resources.
Primary treatment allows for the physical separation of solids and grease from the wastewater, and removes approximately 50% of Biological Oxygen Demand (BOD) and 60-70% of Total Suspended Solids (TSS) to produce an effluent with BOD and TSS not exceeding 130 mg/L.
Chemically-enhanced Primary Treatment provides the addition of a chemical or chemicals at the primary sedimentation stage. During this step, a coagulant (e.g. alum) and flocculants (e.g. anionic polymer) are added to the effluent to enhance the settling of solids, further reducing TSS and BOD levels.
Presently, Greater Nanaimo and Nanoose Wastewater Treatment Plants provide Chemically Enhanced Primary Treatment. The final effluent after treatment is discharged to the Strait of Georgia.
Secondary treatment is a biological treatment process that removes up to 90 percent of BOD and TSS and produces an effluent quality with BOD and TSS not exceeding 45 mg/L.
The French Creek and Duke Point Treatment Plants discharge secondary treated effluent into the Strait Georgia.
Tertiary treatment is typically used when there is discharge to lakes or rivers and the phosphorus levels need to be significantly reduced, or if there is a desire to reclaim effluent. Currently, no treatment plants in the RDN that use tertiary treatment.