From the City of Ottawa website:

What is Household Hazardous Waste?

If it’s corrosive, flammable or poisonous it’s hazardous waste. These types of products contaminate water and landfills and should never be poured down the drain or put out with your regular garbage.

To help you dispose of these products safely, the City of Ottawa operates several one-day Household Hazardous Waste depots for City of Ottawa residents only. 

Liquid or hazardous waste from industrial, commercial and institutional sources will not be accepted. The one-day Household Hazardous Waste Depots are for residential household waste only.

Products to be dropped off at household hazardous waste depots include:  (maximum 100 litres by volume)

• Aerosol containers
• Propane cylinders
• Disinfectants
• Fluorescent bulbs/tubes
• Fire extinguishers
• Fertilizers and pesticides
• Mercury switches/thermometers
• Needles and syringes
• Pharmaceuticals
• Paints and coatings
• Oven and window cleaners
• Pool chemicals

You can also return certain paint products and batteries to Ottawa hardware retailers. Visit makethedrop.ca to find a location near you.