Temperature difference (ΔT) is the preferred parameter for direct discharge facilities but if this cannot be measured, the absolute temperature of the discharge should be reported instead.

Temperature Difference (ΔT) Measurement: Take the temperature of the discharged wastewater and the receiving body of water upstream. The temperature of the receiving body is subtracted from the temperature of the discharged wastewater to give the delta temperature difference, which can be a positive or a negative value. The discharge limits only refer to a positive value, which produces an overall increase in the temperature of the receiving body of water. This parameter is measured on-site by the sampler and is applicable only for direct discharge.

Exceptions (when ΔT cannot be measured): There may be situations where the sampler is not able to measure the temperature of the receiving body. These situations may include:

• The receiving body may be several kilometres away from the point of discharge and the facility is discharging the effluent into the receiving body through a pipeline.

• Accessing the location of the receiving body to measure its temperature can be risky in terms of injury to the sampler or damage to equipment

• The effluent is discharged directly into the ground

In all such cases where access to the receiving body is not possible or unsafe, the laboratory should report this parameter as “not applicable” and then proceed ahead to check absolute temperature.