BANGOR – Computers, monitors, televisions and other electronic equipment dropped off on Saturday at the Bangor recycling center filled four tractor-trailers.

Oil products, fertilizer, pesticides and paint filled a fifth as nearly 1,000 Bangor area residents participated in the annual Household Hazardous Waste Collection Day held at the city’s facility on Maine Avenue.

Bangor and 24 communities in Penobscot and Waldo counties joined together to give residents the opportunity to drop off items that contain hazardous materials such as oil, mercury and lead that cannot be safely disposed of in landfills or by incineration.

The cost of the collection is expected to be between $75,000 and $80,000, according to Jerry Hughes of Bangor Public Works, who coordinated the program. People dropping off items filled out paperwork that included their addresses and what they were recycling.

Participating towns will be billed for their share of items collected, he said on Saturday. Bangor’s cost is expected to be between $30,000 and $35,000 for the 330 residents who participated.

The number of used computers and other electronic equipment being recycled has increased dramatically since Bangor held the first household hazardous waste collection nine years ago, Hughes said on Saturday.

Onyx Environmental, a Massachusetts firm, will break down and recycle the components of the computers and other electronics.

What cannot be recycled will be incinerated in a hazardous waste facility, Robert Cappadona, the firm’s general manager, said on Saturday.