The average age of the wastewater treatment stock has followed a similar trend as for the water supply systems. It peaked at 19.7 years in 2003 and then dropped by 2.9 years to an average of 16.8 years in 2007, following recent large investments. Wastewater treatment facilities thus accounted for a slightly larger share of public infrastructure stock in the province standing, 8% in 2007.
There has been a trend toward ageing of the wastewater treatment infrastructure since 1985, both nationally and in Nova Scotia. However, as a percentage of estimated useful life, the provincial rate has fallen from 70% in 2003 to 60% in 2007, which was less than the national average of 63%. Nova Scotia ranked first followed closely by Ontario and British Columbia in terms of youngest wastewater treatment assets.