EFFECT OF A FURTHER MATURATION PHASE ON THE LEACHING BEHAVIOUR OF MBT - - PowerPoint PPT Presentation

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EFFECT OF A FURTHER MATURATION PHASE ON THE LEACHING BEHAVIOUR OF MBT - - PowerPoint PPT Presentation

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6 th International Conference on Sustainable Solid Waste Management EFFECT OF A FURTHER MATURATION PHASE ON THE LEACHING BEHAVIOUR OF MBT WASTE Daniela Zingaretti, Alessio Lieto, Francesco Lombardi, Renato Gavasci DEPARTMENT OF CIVIL ENGINEERING AND

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EFFECT OF A FURTHER MATURATION PHASE ON THE LEACHING BEHAVIOUR OF MBT WASTE

DEPARTMENT OF CIVIL ENGINEERING AND COMPUTER SCIENCE ENGINEERING University of Rome “Tor Vergata”

Daniela Zingaretti, Alessio Lieto, Francesco Lombardi, Renato Gavasci

6 th International Conference on Sustainable Solid Waste Management

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Consumption Waste Resources Manufacturing Landfill

For reducing the organic waste disposal in landfill:

Production Collection and Transport Bio‐stabilization treatment Bio‐stabilized material

Introduction

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Residual mixed MSW Mechanical‐Biological Treatment MBT WASTE

Bio‐stabilization treatments: Introduction

Source‐segregated MSW Bio‐stabilization stage Maturation stage

MECHANICAL BIOLOGICAL TREATMENT COMPOSTING

COMPOST USE AS FERTILIZER LANDFILL

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Aim of the study:

Evaluation of the effects of a secondary maturation stage on the main chemical properties and environmental behaviour of a MBT waste

Experimental activities:

  • Simulation of a maturation stage;
  • Monitoring of organic matter, elemental composition and carbon content;
  • Characterization of samples collected at 0, 90 and 180 days

Introduction

  • A stabilization step is adopted in both Composting and Mechanical Biological

Treatment

  • However a further 6 months maturation phase to enhance the chemical properties
  • f the material is applied only in the composting plants
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Material

MBT waste Residual mixed Municipal Solid Wastes Metal removal Bio‐stabilization Dry material removal (D>90 mm) Dry material removal (D>30 mm)

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Material and methods Simulation of a Maturation stage

  • a 300 kg‐sample of MBT waste was collected at the end of its treatment and

stored indoor for 180 days

  • Each 10 days the sample was manually overturned and humidified simulating

the typical maturation phase of a compost

  • Samples were collected at specific time intervals

MONITORING

MATURATION PHASE

CHARACTERIZATION

30 60 90 120 150 180 days 90 180 days

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Material and methods

  • Biological stability degree
  • Elemental composition
  • Total metal content
  • Metal speciation
  • Leaching behaviour
  • Organic matter content
  • Elemental composition

MONITORING: Samples collected each 30 days Dynamic Respiration Index (DRI) ‐ UNI TS 11184 (2016) CHNS‐O analysis Acid Digestion Tessier Method Batch Leaching Test (BLT) ‐ UNI EN 12457 (2004) Volatile Solids (VS) ‐ UNI TS 11184 (2006) Total Organic Carbon (TOC) ‐ UNI EN 13137 (2002) CHNS‐O analysis CHARACTERIZATION: Samples collected after 0, 90 and 180 days

Chemical analysis

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  • D. Zingaretti - Effect of a further maturation phase on the leaching behaviour of mbt waste
  • The concentration of VS decreases from 59% to 40% in the first 60 days and then

remained almost constant

  • The Total carbon content passes from 31 to 20 % in the first 60 days
  • The inorganic carbon content showed a 60% increase (from 1.25 to 2 %)

Results: Monitoring

10 20 30 40 50 60 70 30 60 90 120 150 180 % Time (d) Volatile Solids Total Carbon Inorganic Carbon

Volatile Solids (VS) and Total Carbon (TC)

Percentage

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Days C [%] H [%] N [%] S [%] O [%] C/N 29,43 ± 0,53 4,45 ± 0,04 1,94 ± 0,06 0,75 ± 0,15 2,51 ± 0,1 15,11

30

25 ± 0,38 3,51 ± 0,05 1,72 ± 0,02 0,63 ± 0,15 2,21 ± 0,03 14,48

60

22,11 ± 0,42 2,89 ± 0,04 1,62 ± 0,02 0,43 ± 0,28 2,13 ± 0,1 13,61

90

20,38 ± 1,59 2,87 ± 0,17 2,17 ± 0,07 0,56 ± 0,11 3,66 ± 0,09 9,36

120

21,55 ± 1,08 2,88 ± 0,13 2,14 ± 0,07 0,48 ± 0,14 3,53 ± 0,29 10,05

150

22,28 ± 4,23 2,66 ± 0,41 1,8 ± 0,06 0,45 ± 0,26 3,46 ± 0,21 12,31

180

21,67 ± 1,86 2,98 ± 0,26 2,27 ± 0,11 0,45 ± 0,05 3,24 ± 0,13 9,54

Results: Monitoring

Elemental Composition

  • Decrease in the carbon content and increase in the nitrogen content due to the

degradation of organic matter

  • Decrease in the C/N ratio
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Results: Characterization

0 days 90 days 180 days DRI mg O2 / h*Kg VS 1503 369 267 pH ‐ 8.01 ± 0.04 8.13 ± 0.03 8.07 ± 0.03

Dynamic Respiration Index (DRI) Dissolved Organic Carbon (DOC)

1000 mg O2/h*kg VS is the threshold value suggested for bio-stabilised organic wastes (European Commission, 2001)

50 100 150 200 250 300 350

0 days 90 days 180 days

g/kg Time

DOC Residual OC

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  • High concentrations of Al and Fe (>10000 mg/kg) and Ba, Cu, Mn, Pb and Zn (>100 mg/kg)
  • The weight loss due to organic matter degradation entails an increase in the heavy metals

concentration

Results: Characterization

0,1 1 10 100 1000 10000 100000 Al Ba Cd Co Cr Cu Fe Li Mn Mo Ni Pb Zn Total Content [mg/kg] 0 days 90 days 180 days

Total metal content

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Results: Characterization

1^ Exchangable 2^ Carbonates 3^ Fe & Mn 4^ Organic 5^ Residual

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Cd Co Cu Fe Mn Ni Pb Zn Total Content (mg/kg) 0 Days 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Cd Co Cu Fe Mn Ni Pb Zn Total Content (mg/kg) 90 Days 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Cd Co Cu Fe Mn Ni Pb Zn Total Content (mg/kg) 180 Days

  • The metals are mainly related to Carbonates and organic matter
  • Only the exchangable metals are influenced by the applied further maturation step

Metal content speciation (Tessier method)

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0,001 0,01 0,1 1 10 100 1000 10000 Al Ba Cd Co Cr Cu Fe Li Mn Mo Ni Pb Zn Concentration (mg/kg) 0 days 90 days 180 days

Results: Characterization

Leaching batch tests

  • The concentration of metals in the eluate from the leaching tests decreases for

increasing maturation times

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  • The metal release proved to generally decrease for increasing maturation times

Results: Characterization

leachate totalcontent

C Release (%) C 

0,1 1 10 100 Al Ba Cd Co Cr Cu Fe Li Mn Mo Ni Pb Zn

Release [%]

0 days 90 days 180 days

Metal release

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Results: Characterization

0 days 90 days 180 days Values for Mature compost* C/N 15,11 9,36 9,54 < 12 C water soluble (Cw) g/kg 33,30 5,99 4,42 < 5 CW/C organic % 11,28 3,06 2,39 <1.7 HI % 2,8 7,4 5,8 > 3.5 HR % 10,7 14,3 11,2 > 7 PHA % 25,8 52,1 51,5 > 50 CHA/CFA g/g 0,35 1,09 1,06 > 1

Maturation indices and Humic substances

HA

  • rganic

C HI (%) 100 C  

Humification Index Extraction of Humic acids (HA) and Fulvic acids (FA) by alkaline digestion (0.1 M NaOH)

extracted

  • rganic

C HR (%) 100 C  

Humification Ratio

HA extracted

C Pha (%) 100 C  

Percentage of Humic Acids

HA FA

C C

Polimerization Rate

* Bustamante et al., 2012; Garcia‐Gomez et al., 2005; Bernal et al., 1998

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The high heavy metal content and limited biological stability hindered the reuse of MBT waste so far.

Conclusions

The further maturation phase proved to enhance the chemical properties of the MBT waste by:

  • Increasing the biological stability;
  • Lowering the organic carbon content;
  • Decreasing the release of carbon and metals .

The effects exerted on the characteristics of the material are mainly observed in the first 90 days of the treatments while afterward the properties remained almost constant This study showed that the environmental characteristics of the MBT waste could be improved adopting a further maturation phase similar to the one used for the compost