Riot police on Saturday used batons to beat back protesters in central Beirut, while others were carried away, overcome by tear gas.
An online group calling itself "You Stink!" and other civil society groups organized the rallies, calling on Lebanese to join them in a revolt against a corrupt system, Al Jazeera reported on Sunday citing other agencies.
Shots were echoing through the streets of the capital Beirut into the night, but it was not immediately clear if this was live fire, blanks, or rubber bullets.
Private television station LBC reported police attacked one of its crew.
Lebanese Red Cross spokesman George Kattaneh told the AP news agency that at least 15 protesters were wounded, and one of them was in a critical condition.
Kattaneh said the number of injured was likely to rise as security forces continued to battle with protesters.
Police said 35 officers were wounded as they tried to disperse protesters trying to break into a security zone near parliament and the government building.
Saturday saw the biggest demonstrations by far since rubbish began piling up on the streets after the capital's main landfill was closed a month ago.
Nour Samaha, reporting for Al Jazeera from Beirut, said more than 4,000 people had joined the protest, adding that about 1,500 people remained on the streets by 10pm local time.
"Protesters are calling the security forces ‘shabiha’ [thugs] for their heavy handed action against the protest," she said.
Demonstrators said they planned to stay near the government building and parliament through the night.
"We want to live in our country," read one poster carried by a protester. Another read: "Some trash should NOT be recycled," written in red above photos of Lebanese politicians.
The government has been unable to find an alternative system for waste management as a result of government paralysis.
Some residents have resorted to burning rubbish on the streets, sending toxic fumes over the city's skyline and into homes.
The health minister has warned of a catastrophe as some have started dumping waste in valleys, rivers and near the sea.