According to the Balearic Agency for Water and Environmental Quality the bulk of the waste was non biodegradable plastic items and wood.
The majority of the waste was collected off the coast of Majorca where the nine boats plucked 5.9 tons of waste from the sea.
In Minorca, the six boats cleared four tons from the coast while in Ibiza and Formentera two tons and 748 kilos were collected respectively.
According to the agency, calm conditions made it much easier for the boats to carry out their tasks and enabled them to remove the most important rubbish from the coast.
That said, the amount of waste collected from the coast last month was nearly double the 6.5 tons cleared up in July.
All of the 23 boats will continue working until the end of this month.