Chelmsford officials are scheduled to collect hazardous waste on Saturday, followed by a townwide cleanup on Sunday. From 9 a.m. to 1 p.m. Saturday, residents may drop off hazardous waste , including paint thinner, gasoline, and fireworks, in the parking lot at Town Hall, 50 Billerica Road. Those who wish to participate in Sunday’s cleanup are encouraged to pick up bags and gloves from 9 a.m. to 1 p.m. Thursday and Friday in the office of recycling and solid waste, Room LL03 at Town Hall, according to recycling and solid waste coordinator Nick Parlee. The cleanup will take place throughout the day Sunday as residents pitch in to remove litter from roads and parks. Residents may clean any area they desire; if the trash bags being provided by the town are left with residents’ curbside trash, it will be collected, Parlee said. For more information, contact Parlee at 978-250-5203.