Venice is a unique city, and has unique problems that are difficult to solve. Trash collection is one of them. Trash in Venice has to be collected on foot which is labor intensive and expensive. Men with wheelbarrows cruise the alleys and canals collecting trash. A large number of plastic bottles end up in the canals each day.

From October 4th, 2016, Venice has changed their trash collection system. It’s now illegal to leave trash bags on the street or in front of one’s building door, as they attract mice, seagulls and pigeons, who open the bags and spread the trash around.
The new law allows two methods to getting rid of one’s trash:
1) Take your trash bags between 6:30 and 8:30 am from Monday to Friday (Sunday and holidays excluded) to the trash boats located on certain streets.
2) Wait for the trash men to buzz your building between 8:30 am and 12:00 (noon) to collect the trash.
If you’re caught disposing trash anywhere else, it’s a 167 euro fine!
Each “Sestiere” has its own trash collection site, which you’ll have to inform yourself about.
Regarding the issue of plastic bottles, there are over 100 drinking fountains with good, safe, free water in the city, so buy your own re-usable bottle, or just keep using one plastic bottle, during your travels.
You can find a map of Venice’s fountains with the “Fuorirotta the other map of Venice“, which are called “Fontanelle Pubbliche”