BIOBIO22REMEDIATIONREMEDIATION®® : a self-sustainable tool : a self-sustainable tool

for the treatment of shallow polluted basins.for the treatment of shallow polluted basins.

G. RAVAGNAN G. RAVAGNAN aa, S. DE PIERI , S. DE PIERI bb, S. MANENTE , S. MANENTE aa, C. STOCCO , C. STOCCO aa, G. BORDIGNON , G. BORDIGNON aa

aa Molecular Science and Nanosystems Dept. Molecular Science and Nanosystems Dept. bb Environmental Sciences Statistics and Informatics Dept. Environmental Sciences Statistics and Informatics Dept.Calle Larga S. Marta 2137, Dorsoduro 30123 Venice, ItalyCalle Larga S. Marta 2137, Dorsoduro 30123 Venice, Italy

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BIO2REMEDIATION® is a patented technology jointly developed by Ca' Foscari University of Venice and SAPIO Industries. This technology aims to stimulate aerobic biodegradation of pollutants present into sediments; in particular, it involves forced oxygen supply to ensure the aerobic condition’s maintenance, to provide electronic acceptor versus endemic microbial communities required for biodegradation reactions and to create an adapt environment for the organic pollutant biodegradation. This is achieved through both sediments and overlying water column oxygenation through introduction of oxygen enriched water. BIO2REMEDIATION® was applied on the bottom of a shipyard dock called Arsenale Vecchio. It was a basin in Venice chosen for our experiment because of its limited size, shallow water and (nowadays) reduced boat traffic. The study aim was to first assess the status quo of the chosen area treated with BIO2REMEDIATION®, in order to make a comparison with data collected prior to, ongoing and after two years the treatment. It affected both directly the abiotic component, consisting of the sediment, and indirectly, the overlying water compartment, everyone comprehensive of organisms, of course. Results clearly showed that the sediment after treatment has undergone a substantial change: a) a substantial decrease in organic pollutant content (where PAHs have been chosen as pollutant markers); furthermore, b) the creation of an oxidized surficial layer which can act as a <<natural biocapping layer >> in respect of pollutants located in the lower (anoxic) part to step to the interface with the water. At the same time, this re-newed sediment can be a really helpfull substrate for biotic component re-engraftment. It a macroscopic analysis, in fact, it is again verified the presence of animals and plants.In light of these considerations, it intends to conduct an audit of targeted requirements of self-sustainability of the ecosystem through qualification and quantification of the parameters below.

ARSENALE VECCHIO

Fig. 1

ADRIATIC SEA

VENICE

Fig. 3b

Fig. 2a

Fig. 3a

Fig. 2b

O2

cis -dihydrodiolNAD+

dehydrogenase

Fig. 4b

di-oxygenase

O2

di-oxygenase

cis -dihydrodiol

NAD+dehydrogenase

Fig. 4a

RRAATTIIOONNAALLEE

The Venice Lagoon, located in the northern part of the Adriatic Sea, is a shallow basin with a surface area of about 550 Km2 and an average depth of 0.6 m. It is a transitional environment which has suffered an heavy impact of industrial, agricultural and urban pollution during the last century. The ancient venetian shipyard dock (Fig. 1) called Arsenale Vecchio is located in the eastern part of Venice, covering an area of about 46 ha, of which 11 ha are water. Arsenale Vecchio basin was chosen for our second in field BIO2REMEDIATION technology experiment because of its limited size, confined shallow water, reduced (nowadays) boat traffic, and a strongly heavy metals and PAHs polluted sediment. BIO2REMEDIATION technology is a new in situ remediation treatment of polluted sediments. It consists of a 20,000 liter cryogenic evaporator (Figg. 2a and 2b), a main distribution conduit, and a set of 19 porous pipes 21 m long laid on the bottom floor of the basin (Figg. 3a and 3b).The system is able to develop a forced superficial aeration: it consists in the introduction of a great quantitative of oxygen at the superficial sediment-water column interface with the aim of:• stimulating the growing of endemic aerobic bacterial communities by supplying them with oxygen (electron acceptor for aerobic metabolism);• creating a suitable environment for the aerobic biodegradation of organic pollutants (as general example, see anthracene and phenantrene’s biodegradation pathways in Figg. 4a and 4b);• i.e., performing a self-sustainable in situ bioremediation.In Arsenale Vecchio, BIO2REMEDIATION technology was performed with both plain O2 aeration (for 1 year ) and O2 enriched air insufflation (for the next year).

Thermo stabilization or chemical extraction are typical in situ approaches for the treatment of sediments contaminated, but their

environmental impact is doubtless high; and, furthermore, the classical dredging only <<moves>> the problems (i.e. polluted

sediment’s disposal). The modern promising alternative to all these technologies is based on bioremediation processes, in which

microbial metabolism is utilised both to change the metals’ speciation, thus enhancing their mobilisation and solubilization, and

to increase the organic compound’s metabolic pathway by aerobic microrganisms (Figg. 4a and 4b).

Bioremediation strategies depend on the specific conditions created to stimulate bacterial metabolism, including two main approaches: a)

bioaugmentation, in which specific (often genetically modified, then more expensive) bacterial strains are inoculated, and b) biostimulation, in which the

metabolism of autochthonous microbial community is stimulated by inoculating specific substrates. BIO2REMEDIATION technology enforces the endemic

aerobic microrganism’s communities, increasing their engraftment.

EEXXPPEERRIIMMEENNTTAALL

DDAATTA A

Heavy metals (data not shown) and 16 PAHs were measured in sediment samples cores collected in the Bacino delle Galeazze at Arsenale Vecchio, before and after application of in situ remediation treatment with BIO2REMEDIATION technology (treated area); the negative control was the small basin located nearby (non treated area). Applying proportion among different pollutants, i.e. diagnostic ratio for source identification, it has been seen that local contamination was due to naval vehicular traffic and garaging works in the shipyards (Tab. 1).Just to show the BIO2REMEDIATION technology’s effectiveness only a few data are here presented. In treated area sites PAH’s concentration decreases after in situ remediation treatment with BIO2REMEDIATION technology , i.e. aeration involves PAH’s transformation and oxygen presence facilitates both the reduction of their content (Fig. 5) and the different percentage distribution (see Figg. 6a and 6b).

in this work petrogenic pyrolitic diesel

2.22 ± 1.56> 10 petrogenic

sourceBudzinsky et al

1997

1.10 ± 0.1> 1 pyrolitic

sourceBudzinsky et al

19970,5 Diesel

0,73 DieselB(a)P/ B(a)P+Cry

0.61 ± 0.03 Khalili et al 1995, Guo et al 2003

Ratio Reference

Phe/Ant

Fluo/Pyr

Tab. 1 - DIAGNOSTIC RATIO FOR SOURCE IDENTIFICATION

9 sites-TREATED vs 4 sites-NON-TREATED AREAS AT ARSENALE VECCHIO, VENICE

0,0E+00

1,0E+03

2,0E+03

3,0E+03

4,0E+03

5,0E+03

6,0E+03

ng/g

w.w

.

TREATED AREANON-TREATED AREA

Fig.5

TREATED AREA% PAH'S CONGENERES

Naft

Acy

Ace

Flu

Phen

Ant

Fluo

Pyr

B(a)Ant

Cry

B(b)Fluo

B(k)Fluo

B(a)Pyr

B(ghi)Per

Ind

Di(a,h)Ant

Fig. 6a

NON-TREATED AREA% PAH'S CONGENERES

Naft

Acy

Ace

Flu

Phen

Ant

Fluo

Pyr

B(a)Ant

Cry

B(b)Fluo

B(k)Fluo

B(a)Pyr

B(ghi)Per

Ind

Di(a,h)Ant

Fig. 6b

This research was granted with the SAPIO SpA and CORILA. Acknowledgements to: