Q-2, r. 40 - Regulation respecting the quality of drinking water

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5. Water made available to users must have undergone a filtration and disinfection treatment if it originates in whole or in part from surface water or from groundwater whose microbiological quality is likely to be altered by surface water. Groundwater that receives surface water migrating into the soil under such conditions that the soil cannot act as a filtering element of microbiological contaminants is deemed to be likely to be altered by surface water.
The treatment prescribed by this section must be able to eliminate at least 99.99% of viruses, 99.9% of Giardia cysts and 99.9% of Cryptosporidium oocysts.
Notwithstanding the foregoing, the filtration treatment is not mandatory where raw water that supplies the distribution system meets the following conditions:
(1)  its turbidity is lower than or equal to 5 NTU (nephelometric turbidity unit), subject to the provisions of subparagraph 2 below;
(2)  at least one sample of water per week is collected for a period of not less than 120 consecutive days and at least 90% of the samples have 15 Escherichia coli bacteria or less per 100 ml of water collected, and the average turbidity over 30 consecutive days is lower than 1 NTU;
(2.1)  one sample of raw or supplied water is collected at least once a month for a period of not less than 120 consecutive days and none of the disinfection by-product analysis parameters following simulation of the treatment and distribution conditions shows a concentration greater than the standards of quality set out in Schedule 1;
(3)  the quality of the water is not likely to be altered, in respect of one of the parameters provided for in subparagraph 1, 2 or 2.1, by contaminants from a source of contamination located upstream from the water catchment site.
O.C. 647-2001, s. 5; O.C. 467-2005, s. 5; O.C. 70-2012, s. 6.