What are the sources of phosphorous in wastewater?

Fellow Canadian? (I can tell by the "ous" ending!)

Most sources of phosphorous come from household laundry detergents or cleaning products (like dishwashing detergents, etc). If you look on most labels of typical household cleaners, they don't usually list their ingredients. Even the material safety data sheets don't list ALL of the ingredients (instead, they focus on the major hazardous ingredients). But if you do a search for "phosphate free" or "phosphorous free" detergents or cleaners, you'll find a lot of info on just how much phosphorous can be in some of this stuff (one site told me that one bottle of dish detergent holds the same amount of phosphorous as in a bag of fertilizer).

Other sources are industries like production companies that make fertilizers or pesticides (depending on how stringent the discharge limits are in the town or city, different levels of phosphorous can be released to the sewage plant). But the majority of the source of phosphorous for all towns come from the household uses.