(Open the Halifax Water 'where does my wastewater go' map in a new browser window.)
The major aim of wastewater treatment is to remove as much of the pollutants and suspended solids as possible before the remaining water—called effluent—is discharged back to the environment. As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water.
Each treatment facility uses a combination of physical, biological, and chemical treatment stages. The degree or level of treatment required often depends on:
- the nature and quality of the receiving water(i.e., salt water, inland fresh water bodies, etc.)
- federal and provincial regulations
- quantity of flow from the treatment plant
- uses and existing quality of receiving waters
- the amount of mixing between plant effluent and receiving waters
- assimilation capacity of the receiving water
Advanced primary treatment
The Halifax, Dartmouth, and Herring Cove wastewater treatment facilities all utilize advanced primary wastewater treatment technology. The advanced primary treatment process removes up to 70% of the suspended solids in the wastewater.
The solid material collected from wastewater during the treatment process, also known as bio-solids, is a beneficial organic resource. Rather than dump this material in a landfill or the incinerator, the Halifax Regional Municipality puts it through something called the N-Viro process.
The N-Viro process delivers a safe, high-quality product, suitable for a number of applications such as:
- soil amendment
- fertilizer product
- lime substitute
- sod farming
The final product must meet USEPA Class A standards for bio-solids products, and also meet Canadian Food Inspection Agency requirements under the Canadian Fertilizer Act, for labelling as a fertilizer product for sale in Canada.
Ultra Violet (UV) disinfection system
The Halifax, Dartmouth, and Herring Cove wastewater treatment facilities also use Ultra Violet (UV) disinfection. UV disinfection means that high-intensity, ultra-violet lights are used to kill bacteria in the treated flows. This is the final stage in the treatment process before the effluent is released into the harbour.