In the past, Hazardous Waste was only collected once or twice a year, and was a complete nightmare when it came to waiting lines backed up to Franklin Blvd.  That being said, the 2  day a week collection days give the Hazardous Waste Technicians a chance to process the waste brought in those days besides what is brought in from businesses on another day of the week, whom do not get this service for free. As for making an appointment to discard your haz waste for free, that's so you don't have to wait in line, and the techs know what to expect that day in advance and plan accordingly.