1. CONVERSION OF DREDGING SEDIMENTS TO GROWING MEDIA BY MEANS OF CO-COMPOSTING
Paola Mattei
Giancarlo Renella

2. …HUGE AMOUNT OF DREDGED SEDIMENTS:
Dredged sediments: minerals and organic materials accumulated in the bottom of water bodies and removed by dredging.
Maintenance dredging: safety and efficiency of shipping and port operations
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?

3. MENEGMENT OF DREDGED SEDIMENTS
Sediments are generally menaged as wastes…
INTERNATIONAL CONVENTIONS:
Oslo Convention (1972)
Convention of London (1972)
Paris Convention (1974)
OSPAR Convention (1992)
Convention of Barcelona (1995)
RECOVERY and REUSE instead LANDFILLING
Reuse without treatments
DREDGED SEDIMENTS
Pollutants analyses
Landfilling
Treatment
Reuse

4. POTENTIAL RECOVERY TREATMENTS AND REUSE
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)
REUSES
“Beneficial use”
(USACE, 1986)
Environmental restoration
Bricks
PRINCIPLE
TREATMENT
Separation of less contaminated dredged materials fractions
Classification
Sorting
Dewatering
Evaporation
Mechanical dewatering
Contaminant separation
Chemical extraction
Thermal desorption
Contaminant destruction
Biological reduction
Chemical oxidation
Thermal oxidation
Contaminant immobilisation
Thermal immobilisation
Chemical immobilisation
Urban parcks
Beaches
nourishment
Strip mine
reclamation
Artificial soil
Nursery,
horticulture

5. REUSE OF DREDGED SEDIMENTS TO PRODUCE ARTIFICIAL SOIL Previous experiences
AGRIPORT (ECO/08/239065/S ): 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 , reuse of phytoremediated river sediments as growing medium in open field for ornamental plants

6. PHYTOREMEDIATION: It works! But…
REUSE OF DREDGED SEDIMENTS TO PRODUCE ARTIFICIAL SOIL Previous experiences
Basil
Rosemary
Mint
Soil
Soil + sediments
Sage
Lavander
PHYTOREMEDIATION: It works! But…

7. 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

8. Production of an artificial soil by co-composting of dredged sediments and pruning residues
Working hypothesis:
Dredged sediments
Pruning residues
Artificial soil
CO-COMPOSTING
from WASTE to RESORCE

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

10. Production of an artificial soil by co-composting of dredged sediments and pruning residues
Materials used:
LEACHING TEST
Sediments
Law limit
(DM )
PCB mg/Kg SS
0.005
0.01
PAH mg/Kg SS
1.36 1
Heavy metals
(Col. A; D.Lgs. 152/2006)
Be ms/Kg ss
2.23 2
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
ZERO INPUT!

11. 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

12. TEMPERATURE TREND
PR, Tr1: °C
COLD COMPOSTING PROCESS: experimental conditions did not allow the achievement of the thermophilic phase of composting (minimum volume for the accumulation of heat: 1m3)

13. ECOTOXICITY BioToxTM Flash Test - ISO STANDARD 21338
Ecotoxicity determination by BioToxTM Flash Test (Aboatox Oy, Turku, Finland):
standardized method based on inhibition of the bioluminescence of Vibrio fischeri (ISO STANDARD 21338)
Further investigation needed to identify compound responsible for the toxicity of treatments containing pruning residues: probably secondary metabolites?

14. 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.

15. CARBON AND NITROGEN CONTENT
TOC and TN content are measured in accordance with ISO (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

16. POLYCYCLIC AROMATIC HYDROCARBONS
0.6%
-26.2%
-56.8%
-24.4%
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

17. HEAVY METALS

18. Analyses on the end-product:
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.

19. Small-scale in vessel experiment
2 ornamental species: Photinia x fraseri, Viburnum tinus
Treatments: Tr1:1, Tr3:1, PR, SED (three replicates)
Control: peat-pumice mix (three replicates)
Fertilization with Osmocote Topdress N/P/K 
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

20. 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.

21. Thanks for your attention!