Acute lethality

Under the Wastewater Systems Effluent Regulations, effluent is considered acutely lethal when at 100% concentration (undiluted) it kills more than 50% of the rainbow trout subjected to it during a 96-hour period.

For all wastewater systems that are subject to the Regulations, the owner or operator is responsible of ensuring that effluent deposited from its final discharge point: 

Small systems that deposit an average daily effluent volume less than or equal to 2,500 m3

Acute lethality testing is not required for wastewater systems with an average daily volume of less than or equal to 2,500 m³ (subsection 11(1)). However, you may decide to test for acute lethality on occasion to determine if the effluent is acutely lethal.

If you test for acute lethality, you must include all test results in your monitoring report for that period (subparagrah19(1)(b)(viii)).

If any sample is found to be acutely lethal, the effluent is considered an unauthorized deposit under the Fisheries Act and you must consider your responsibilities under the Act without delay. You must take all reasonable measures to prevent, counteract, mitigate or remedy any damages that result or that might reasonably be expected to result from such a deposit (subsection 38(6) of the Act). For more guidance on reporting an unauthorized deposit, please consult the following factsheet: procedure for reporting unauthorized wastewater deposits.

Sampling schedule for systems that deposit an average daily effluent volume greater than 2,500 m3

Normal sampling frequency

Acute lethality testing is required for wastewater systems depositing more than 2,500 m3 per day. The minimum sampling frequency, outlined in the chart below, is based on the average daily volume of effluent for the previous calendar year (subsection 11(1))

 

Average Daily Volume Deposited Annually (m3) Minimum Sampling Frequency  Minimum Time Between Samples
> 2,500 and ≤ 50,000 Quarterly  At least 60 days after any other sample
> 50,000 Monthly At least 21 days after any other sample

Reduced sampling frequency

The minimum sampling frequency can be reduced if samples were determined to be not acutely lethal for a specified period of time, as outlined in the chart below (subsection 11(6)).

Average Daily Volume Deposited Annually (m3) Number of consecutive samples not acutely lethal Reduced frequency for sampling 
> 2,500 and ≤ 50,000 4 consecutive quarters where a discharge occurs Yearly, but at least 6 months after any other sample
> 50,000 12 consecutive months where a discharge occurs Quarterly, but at least 60 days after any other sample

Procedure for an acutely lethal sample

If any sample is found to be acutely lethal, the effluent is considered an unauthorized deposit under the Fisheries Act and you must consider your responsibilities under the Act without delay (subsection 38(6) of the Act).

If you have a sample that is acutely lethal, your sampling frequency increases to 1 sample every 2 weeks, with at least seven days between samples (subsection 11(3)). If 3 consecutive samples are found to be not acutely lethal, then the sampling frequency returns to normal sampling frequency (subsection 11(4)). If the effluent continues to be acutely lethal, increased sampling frequency continues.

The last of your 3 consecutive samples can also be used to fulfill your requirements for normal sampling frequency (illustrative example below). The Regulations allow you to fulfill both requirements with only one sample.  

Figure 1: Illustrative example of when regular sampling frequency and increased sampling frequency overlap and fulfill both requirements.
Text version

Figure 1: Illustrative example of when regular sampling frequency and increased sampling frequency overlap and fulfill both requirements. 

Testing methods

The test must be done by an accredited laboratory (section 16) in accordance with:

Reporting

All laboratory test results for acute lethality samples must be included in the monitoring report for the period in which the sample(s) were taken (subparagraph 19(1)(b)(viii)).

The following information is required through the Effluent Regulatory Reporting Information System (ERRIS):

You may request paper reporting forms if electronic reporting is unavailable (subsection 19(5)).

Contact us

If you require further assistance or have any questions, please contact Environment and Climate Change Canada at eu-ww@ec.gc.ca .

Disclaimer

This information does not in any way supersede or modify the Wastewater Systems Effluent Regulations or the Fisheries Act, or offer any legal interpretation of those Regulations or Act. Where there are any inconsistencies between this information and the Regulations or Act, the Regulations or Act take precedence, respectively. A copy of the Regulations is available.

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