(a) the test method prescribed in section 221 of the publication Standard Methods for the Examination of Water and Waste Water, 13th edition (1971), published jointly by the American Public Health Association, American Water Works Association and the Water Pollution Control Federation; or
a) par la méthode d’essai décrite à la section 221 de la publication intitulée Standard Methods for the Examination of Water and Waste Water, 13 édition (1971), publiée conjointement par l’American Public Health Association, l’American Water Works Association et la Water Pollution Control Federation; ou