Innovative treatment by bioremediation of contaminated sediments from the Venice Lagoon, Italy: the Arsenale Vecchio case study.

Sediments in industrialized and/or urbanized coastal shallow waters have reached an alarming and harmful level of contamination that requires the development of new cost effective technologies. We report on the in situ forced aeration experiment in the Arsenale shipyard dock basin of the Venice Lagoon, Italy. This study follows the promising results obtained by similar experiment carried out in the Industrial Harbor of Marghera, where sediment reworking and mixing are strong. The study site of the Arsenale shipyard was chosen in order to test a new forced aeration system aimed at oxygenating the surficial sediments with a minimum of reworking and mixing. The aeration technique, chosen for the oxygenation of the highly polluted bottom sediments, is unique due to its innovative use of a system of porous pipes laid on the bottom sediments, therefore it is non intrusive and does not obstruct harbor activities. Forced aeration consists in the introduction of a great quantitative of oxygen at the surficial sediment-water column interface with the aim of stimulating aerobic bacterial communities to create an adapt environment for the biodegradation of organic and inorganic pollutants. The general reduction of organic pollutants and heavy metals in the surficial sediments resulted in the documented return of small fish to the area as an indication of a less polluted environment. The experiment has indicated that tangential forced aeration could represent a non intrusive and cost effective way for reducing organic and heavy metal pollutants in coastal environments where other techniques may not be environmentally and/or economically feasible