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Seasonal Disinfection

Learn more about Seasonal Disinfection

In February 2015, Halifax Water undertook a stakeholder consultation in support of an application to implement a Seasonal Disinfection Program. Since 2017, Halifax Water has turned off the Ultraviolet (UV) systems annually between November 1 and April 30 at the Halifax, Dartmouth, Eastern Passage, and Herring Cove Wastewater Treatment Facilities (WWTFs). Prior to 2020, UV systems at all of these facilities were turned back on between December 24 and January 2 to provide disinfection during the Polar Bear swim in the Herring Cove area.

During the two pilot trials from 2015 to 2017 that were required to permit the Seasonal Disinfection Program in our operating Approvals issued through Nova Scotia Environment and Climate Change (NSECC), the majority of bacteria levels detected remained below recreational swimming limits for E.coli, Fecal Coliform, and Enterococci. However, Halifax Water continued to turn the UV systems on at each facility for the swim in the Herring Cove area. Please click the following link for sample results.

In 2020, NSECC adjusted Approvals to allow for the UV systems to remain off continuously between November 1 and April 30 at Halifax, Dartmouth and Eastern Passage WWTFs. Given the distance these outfalls are away from Herring Cove and the fact that the measured bacteria levels from these facilities are generally within the acceptable swimming limits, this adjustment does not impact water quality in the Herring Cove area. The UV system at Herring Cove WWTF continues to be turned back on between December 24 and January 2 each year.

Halifax Water uses the time when UV systems are turned off at each facility to undertake extensive maintenance and cleaning of the systems to ensure they are properly operating during the summer months when recreational activities are increased. Without the need for the annual two-week period of turning the UV systems back on (between December 24 and January 2) at Halifax, Dartmouth and Eastern Passage WWTFs,  impacts to the efficiency of these maintenance activities have decreased. It should also be noted that turning the systems off also reduces the greenhouse gases (GHG) produced by operations at each of the WWTFs.

Frequently Asked Questions

The final stage in the process of sewage (wastewater) treatment, for the Halifax Harbour facilities, involves disinfection of the wastewater through the use of Ultraviolet (UV) lights. The UV disinfection process kills bacteria. Seasonal disinfection means UV disinfection continues throughout the spring, summer and fall period (May 1 to October 31), but not during the winter period (November 1 to April 30). Full screening of floatables and all other treatment processes will continue to operate year-round.

Seasonal disinfection has been implemented at the Halifax, Dartmouth, Herring Cove, and Eastern Passage Wastewater Treatment Facilities (WWTFs) only. These facilities discharge into waters where there is little direct use or public contact during the winter months.

Due to the nature of water circulation in the Bedford Basin near the Mill Cove WWTF, the area required for mixing of treated plant effluent is more extensive than at the other locations. Therefore, seasonal disinfection is currently not being considered at the Mill Cove WWTF at this time.

The Halifax, Dartmouth, Herring Cove, and Eastern Passage facilities use ultraviolet (UV) light to disinfect wastewater. This process uses large amounts of electricity to run the UV lights. Shutting off the UV systems during the winter months can reduce electricity usage, lower greenhouse gas emissions related to UV light power consumption, increase time for maintenance of the UV systems and potentially extended UV equipment life at these facilities.

The clarity of the water in the Harbour will not be affected, nor will there be any smell related to the implementation of the seasonal disinfection program. Full screening of floatables and all other treatment processes will continue to operate year-round.

Wastewater at each facility will still undergo all the other stages of treatment to remove floating, suspended and settled solids and organic matter. The treated wastewater discharged into the harbour will be of the same quality as always but will have higher bacteria levels during the seasonal disinfection period (November 1 to April 30).

When the UV lights are activated in the spring (and in December at Herring Cove WWTF to accommodate harbour Polar Bear swims) bacteria levels have been observed to drop to safe swimming levels within 2-3 days.

During the winter period, there is little or no direct contact use of the Harbour, other than the Polar Bear swim.

Halifax Harbour is an industrial harbour and is closed year-round to shellfish harvesting. Should people fish or scuba dive during the winter months, proper precautions should be taken in cleaning and preparing fish, and cleaning of scuba gear.

The wastewater will still be treated year-round at the Halifax, Dartmouth, Herring Cove, and Eastern Passage WWTFs to the same levels for solids and organic matter. The bacteria in wastewater do not have any significant impact on other life in the harbour and will not cause any additional environmental impact in the winter.

Nova Scotia Environment regulates wastewater treatment through Approvals issued for all WWTFs in the province and has approved it for the facilities noted. The federal government has regulations for wastewater treatment under the Fisheries Act, however, these regulations do not control bacteria, since bacteria levels do not have any impact on fish.

There are a number of jurisdictions throughout North America that allow for seasonal disinfection. The criteria under which seasonal disinfection is allowed varies in each jurisdiction.

Any questions relating to the Seasonal Disinfection Program can be directed to the Halifax Water Customer Care Centre at (902) 420-9287 or