Tap water vs. distilled water test Cote St Luc, Montreal. What is that black stuff! Lead?

Testing Cote Saint Luc, Montreal water with Aaron, our son. We used an Electrolyzer we bought from Amazon. There are similar tests on my playlist done in other cities with similar results. What exactly is in our water? We compared tap water from Montreal, Quebec to distilled bottled water. The city of CSL said we should use filters. Is the black stuff heavy metals? Cote st luc has a history of lead pipes https://globalnews.ca/news/8270071/cote-saint-luc-lead-pipe-problem/ and https://cotesaintluc.org/services/maintenance/water-network/lead-pipes/