Calendar Year

	2002	2003	2004	2005	2006	2007
Sulphate (tonnes)	4	9.5	16.9	1.7	19.1	6.4
Sanitary Effluent ('000's m3)	104	109	97.5	97.5	88.3	105.9
Total Potable Water Use – Buildings		NR	NR	NR	NR	125

Typically from late-May through mid-December, marine-sourced cooling water used at the Burrard Generating Station is chlorinated to reduce biofouling in the cooling system from mussel larva. Before the chlorinated water is discharged, it is treated with sulphur dioxide at the rate of 20 to 50 micrograms per litre to remove the residual chlorine that can be harmful to aquatic life. The treated discharge contains primarily sulphate and chloride as the products of the dechlorination reaction. Because the sulphate concentration in Burrard Inlet is approximately three per cent by weight, the additional sulphate discharged does not change the local concentration detectably.

Total water use volume is the sum of estimated and measured volumes at individual facilities. Total volume of sanitary effluent is primarily estimated as a percentage of potable water use at each facility, with a small number of facilities reporting actual metered volumes.