Monitoring Wastewater Overflows and Bypasses

Wastewater Treatment Plant Bypasses
The Wastewater Treatment Plant (WWTP) operations staff can bypass the WWTP at four locations, a total plant bypass, headworks bypass, primary bypass, and secondary bypass.

Plant Bypass
A plant bypass sends untreated sewage from the main pumping station (MPS) wet-well directly to the natural environment. This type of bypass would only be initiated if there was danger of flooding the MPS, or if there was significant maintenance or other works taking place for downstream WWTP processes.

Headworks Bypass
A headworks bypass sends partially treated sewage to the natural environment, bypassing the majority of the WWTP processes.  In the event of a headworks bypass, large solids and heavy grit have been removed from the sewage, and chemicals have been added for phosphorous removal. This type of bypass would be initiated if the maximum primary and secondary bypass capacity was reached and flows continue to increase.

Primary Bypass
A primary bypass sends partially treated sewage to the natural environment, bypassing the majority of the WWTP processes. In the event of a primary bypass, large solids and heavy grit have been removed from the sewage, and chemicals have been added for phosphorous removal. Between May 15th and October 15th each year, primary bypasses will also be disinfected with chlorine, and then the chlorine will be removed. This type of bypass would only be initiated if there was danger of flooding or damage to the primary treatment processes, or if there was significant maintenance or other works taking place for downstream WWTP processes.

Secondary Bypass
A secondary bypass is the most common type of bypass event at a WWTP. A secondary bypass sends partially treated sewage to the natural environment, bypassing the WWTP’s secondary treatment processes (biological treatment and final clarification). In the event of a secondary bypass, large solids and heavy grit have been removed from the sewage, chemicals have been added for phosphorous removal, and the majority of settleable solids and floatable materials have also been removed. Between May 15th and October 15th each year, secondary bypasses will also be disinfected with chlorine, and then the chlorine will be removed. This type of bypass is initiated when WWTP flows exceed the WWTP capacity risking non-compliance of the Environmental Compliance Approval (ECA) for the WWTP and ‘wash-out’ of the WWTP’s biological treatment processes (which would result in partially treated sewage being discharged from the WWTP continuously for days or weeks until the biological processes can be restored), or if there was significant maintenance or other works taking place for downstream WWTP processes.

Combined Sewer Overflow (CSO) Tank Events
Hamilton has nine CSO tanks that were built from the 1980’s through 2010 to help add capacity to the combined sewer system The nine large storage tanks hold more than 314,000 cubic metres of diluted wastewater. During rain events the combined sewer overflow tanks will fill and store the excess water. If the storm continues the combined sewer system - now being full and at capacity, will then overflow into the environment.

When the storm stops, and the sewer system and treatment plant have capacity for the volume of wastewater inside the combined sewer overflow tanks, the water is then put back into the sewer system to head to the treatment plant for cleaning.

If the combined sewer system didn’t have the designed overflow option to release wastewater to the harbour, large areas of Hamilton would experience flooding -  which would impact homes, business, roadways, public spaces and public health.

Public Health services monitors beaches in accordance with the Ministry of Health and Long-Term Care’s Operational Approaches for Recreational Water Guideline 2018 and the Recreational Water Protocol 2018 under the Ontario Public Health Standards. As outlined in the above protocols, beach samples are collected and tested for E. coli bacteria at least once per week during the swimming season.

Beach sampling results cannot be guaranteed accurate as conditions can change quickly depending on the weather. You should not swim at the beach during and after storms, floods or heavy rainfall. Cloudy water may indicate high levels of bacteria.

For more information on ways to stay safe at the beach, visit the Canadian Red Cross’s website. 

The Government of Ontario provides fish consumption advisories for Ontario’s lakes and rivers which are available in the Guide to Eating Ontario Fish. You can use this guide and the interactive map to help you identify the types and amounts of fish that are safe to eat from more than 2,400 fishing locations.

There are 2 Wastewater Treatment Plants in Hamilton:

All bypasses are promptly reported to the Ministry of Environment, Conservation and Parks (MECP) Spills Action Centre and to Public Health Services as required by the WWTP’s ECA.