7. Once-through cooling water: For the application of the standard relative to the deposit of petroleum hydrocarbons (C10-C50), prescribed in section 6, the liquid effluents of an existing petroleum refinery shall not include once-through cooling water containing petroleum hydrocarbons (C10-C50) in a concentration of 5 mg/litre or less.
R.R.Q., 1981, c. Q-2, r. 6, s. 7; 994-2023O.C. 994-2023, s. 31.