In Situ Treatment of Contaminated Water Environments: The Experiment of the Arsenale Vecchio, Venice Lagoon, Italy

We report on the results of an experiment of in situ bioremediation by forced aeration, carried out in the Arsenale Vecchio shipyard dock basin of the Venice Lagoon, Italy. The experimental area is characterized by its limited size and reduced boat traffic. The forced aeration technique chosen for the oxygenation of the highly polluted bottom sediments and of the water column above does not obstruct harbor activities and is unique due to its innovative use of a system of porous pipes laid on the bottom sediments. The general recovery of the polluted shipyard dock basin resulted in the documented return of small fish to the area as an indication of a less polluted environment. Most important the bioremediation of the water body above the bottom sediment favours, with time, the formation of a clean natural sediment capping over the bottom contaminated sediments. Post-experiment control after fifteen months of aeration with no extra oxygen added, shows the presence of clean light grey sediments with no foul septic smell, deposited over the polluted bottom sediments. The experiment has indicated that oxygenation by porous pipe forced aeration could represent a cost effective and environmentally feasible way for the recovery of shallow marine and fresh water systems, in situations where other techniques may not be economically and/or environmentally feasible.