CONVERSION OF DREDGING SEDIMENTS TO GROWING MEDIA BY

MEANS OF CO-COMPOSTING

Paola MatteiGiancarlo Renella

DREDGED SEDIMENTS

Dredged sediments: minerals and organic materials accumulated in the bottom of water bodies and removed by dredging.

o Maintenance dredging: safety and efficiency of shipping and port operations

o Environmental dredging: containment of aquatic ecosystem pollution and consequent risks

WHY DREDGE?

…HUGE AMOUNT OF DREDGED SEDIMENTS:•≈ 200 million m3/y in Europe•5 – 6 million m3/y in Italy

POLLUTED SEDIMENTS

HOW CAN WE TREAT AND REUSE DREDGED SEDIMENTS?

MENEGMENT OF DREDGED SEDIMENTS

INTERNATIONAL CONVENTIONS:Oslo Convention (1972)Convention of London (1972)Paris Convention (1974)OSPAR Convention (1992)Convention of Barcelona (1995)

RECOVERY and REUSE instead LANDFILLING

DREDGED SEDIMENT

S

Landfilling

Reuse without treatments

Treatment

Reuse

Pollutants

analyses

Sediments are generally menaged as wastes…

POTENTIAL RECOVERY TREATMENTS AND REUSE

TREATMENTS

Aim: reduce volume or hazardous nature of sediments, facilitate its handling or

enhance recovery (Dir. 1999/31 / EC)

(Dutch-German Exchange on Dredged Material, 2002)

PRINCIPLE TREATMENT

Separation of less contaminated dredged

materials fractions

Classification

Sorting

DewateringEvaporation

Mechanical dewatering

Contaminant separationChemical extractionThermal desorption

Contaminant destructionBiological reduction

Chemical oxidationThermal oxidation

Contaminant immobilisation

Thermal immobilisation

Chemical immobilisation

REUSES“Beneficial use”

(USACE, 1986)

Bricks

Beachesnourishment

Artificial soil

Urban parcks

Environmental restoration

Strip minereclamation

Nursery,horticulture

REUSE OF DREDGED SEDIMENTS TO PRODUCE ARTIFICIAL SOIL

Previous experiences AGRIPORT (ECO/08/239065/S12.532262): sediments reclamation

by phytoremediation

Reuse of phytoremediated harbor sediments as in vessel growing medium for Photina x fraseri

Reuse of phytoremediated river sediments as in vessel growing medium for aromatic plants

CLEANSED project (LIFE-ENV-12-E-000652, http://www.lifecleansed.com/it/): reuse of phytoremediated river sediments as growing medium in open field for ornamental plants

REUSE OF DREDGED SEDIMENTS TO PRODUCE ARTIFICIAL SOIL

Previous experiences

Basil MintRosemary

Sage Lavander

Soil + sedimentsSoil

PHYTOREMEDIATION: It works! But…

Limits of Phytoremediation: Long process (3 – 6 years)

Need for large treatment areas

Scarce ability to modify sediments physical characteristics

Aim of my research: an alternative to phytoremediation

Evaluate co-composting as bio-treatment aimed at conversion of dredged sediments in artificial soil

Advantages and potential of co-composting:• Minimum Input and Minimum inpact• Use of waste materials• Use of existing infrastructures• Custom chemical-physical characteristics to meet

plants and environment needs

Production of an artificial soil by co-composting of dredged sediments and

pruning residues

Dredged sediments

Pruning residues

Artificial soil

CO-COMPOSTING

Working hypothesis:

Sediments co-composting Biological treatment where sediments and organic materials

are subjected to aerobic digestion by microorganisms

Aim: enrich sediments of nutrients, improve their physical property (structure, porosity, water retention) and degrade organic pollutants

Applicability: sewage sludge, soil and sediment contaminated by biodegradable pollutants

Contaminants: Pentachlorophenol, pesticides, explosives, polycyclic aromatic hydrocarbons, ethylene glycol, diols.

Production of an artificial soil by co-composting of dredged sediments and pruning

residues

ZERO INPUT!

Production of an artificial soil by co-composting of dredged sediments and

pruning residuesMaterials used:

Sediments: Sediments dredged in March 2014, From Navicelli canal(Pisa, Italy).

Organic compaund: Pruning residues

from Florence urban green(Quadrifoglio s.p.a., Florence).

Composters: wire mesh and nonwoven fabric;volume: 0.196m3

LEACHING TEST SedimentsLaw limit

(DM 05.02.98)

PCB mg/Kg SS 0.005 0.01

PAH mg/Kg SS 1.36 1

Heavy metals Sediments

Law limit(Col. A; D.Lgs.

152/2006)

Be ms/Kg ss 2.23 2

Production of an artificial soil by co-composting of dredged sediments and pruning

residues Experimental design:2 treatments e 2 controls, three

replicates :

TR1:1 = 40Kg sed. + 40Kg p.r.

TR3:1 = 60 Kg sed. + 20Kg p.r.

PR = only p.r. (control 1)

SED = only sed. (control 2)

Analyses:•Temperature•pH•EC•TC, TOC, N, C/N•Humic substances•PAH•Heavy metals•Eco-toxicity (BioToxTM Flash Test)

Manual turning: end of September, mid-April

TEMPERATURE TREND

COLD COMPOSTING PROCESS: experimental conditions did not allow the achievement of the thermophilic phase of composting (minimum volume for the accumulation of heat: 1m3)

PR, Tr1:1 35.5°C

ECOTOXICITYBioToxTM Flash Test - ISO STANDARD 21338

Further investigation needed to identify compound responsible for the toxicity of treatments containing pruning residues: probably secondary metabolites?

Ecotoxicity determination by BioToxTM Flash Test (Aboatox Oy, Turku, Finland):standardized method based on inhibition of the bioluminescence of Vibrio fischeri (ISO STANDARD 21338)

LEACHATE pH AND CONDUCTIVITY

pH and conductivity were determined on leachate as it is, by, respectively, pH-meter GLP 22 CRISON, conductivity meter COND400 Eutech Instruments.

CARBON AND NITROGEN CONTENT

TOC and TN content are measured in accordance with ISO 10694 (Official Method VII.1), by elemental analyzer CHN-S Flash E1112 (Thermofinnigan). •Initial C/N: optimum in Tr 1:1, acceptable in Tr3:1•TOC: slight reduction during the process in all the treatment •No losses of N

POLYCYCLIC AROMATIC HYDROCARBONS

• Quantification of 18 PAH regulate by D.Lgs152/2006 • PAHs determination by Gas chromatography-mass spectrometry (GC-MS)

GC, using Agilent 6890N inert series/MSD 5973 with DB-35ms column (J&W Scientific, Folsom, CA, USA).

• Initial contamination (Law 152/2006) by benzopyrene, and indenopirene benzoperilene in all treatments containing sediment;

• Reduction of indenopirene concentration in Tr1:1 to value below the law limit after 6 months of treatment;

• PR: No hydrocarbon contamination in pruning residues.• Reduction of PAHs concentration of 26.2% in Tr3: 1 and 56.8% in

Tr1: 1

0.6%

-26.2%

-56.8%

-24.4%

HEAVY METALS

Ongoing analyses:

Microbial community study: extraction of DNA and RNA and analysis by PCR-

DGGE Humic substances content

Analyses on the end-product:

Physico-chemical characterization (C, N, humic substances, pollutants, water

retention, porosity ...)

Further eco-toxicity tests: germination test with Sorghum saccharatum,

Lepidium sativum and Sinapis alba; Tetrahymena thermophila, Daphnia magna,

Selenastrum capricornutum

Small-scale in vessel experiment

CO-COMPOSTING PRODUCTS WILL BE EVALUATED AS GROWTH SUBSTRATES IN

A SUBSEQUENT TRIAL: planting of ornamental plants in urban settings.

Small-scale in vessel experiment

o 2 ornamental species: Photinia x fraseri, Viburnum tinuso Treatments: Tr1:1, Tr3:1, PR, SED (three replicates)o Control: peat-pumice mix (three replicates)o Fertilization with Osmocote Topdress N/P/K 23-5-10o 30 plants in 1l pots

Analyses:•Growth monitoring •Initial and final dry weight•Chlorophyll content•Evaluation of the state of oxidative stress (malondialdehyde assay)•Quantification of metals content in plant tissues

Conclusions:

Dredged sediments could be converted to fertile artificial soils

after appropriate treatments

Co-composting has the potential to be an efficient and

sustainable treatment to convert sediments to artificial soil,

degrading organic pollutants and improving chemical and

physical characteristic of the raw material with minimal input

and impact on the environment

Despite the thermophilic phase has not been reached, the

experiment in progress shows the efficiency of co-composting to

degrade PAHs, expecially in the treatment Tr1:1.

Thanks for your attention!