Effect of organic carbon in MSWI bottom ash on the mobilization of

heavy metals

Ruggero Maria Cavallino

Supervisors: Dr. U. Eggenberger, Dr. N. Waber, G. Weibel

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1904: First plant in Zürich

2000: Prohibition of the disposal of untreated waste

2014: 30 MSWI plants

2014: Incineration of 3’816’753 t waste

• Household waste (702 kg per person)• Industrial/commercial waste • Sewage sludge

Municipal solid waste incineration (MSWI)

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Destruction of organic compounds

Mass (80%) and volume (90%) reduction

Energy and heat production

Recovery of valuable metals

Most environmentally friendly method

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Municipal solid waste incineration (MSWI)

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Bottom ash: 20 wt.% Fly ash: 2 wt.%

Waste input

850-950°C

Household waste (MSW) Industrial/commercial waste Sewage sludge

Municipal solid waste incineration (MSWI)

Bottom Ash

Bottom AshBA major components:

Mineral Fraction >2mm (glass, porcelain, tiles, cement,...)

Slag >2 mm (partially molten material)

Native Metals >2 mm (Al-nuggets)

Ash particles < 2mm

Unburnt Organic Matter >2 mm (e.g. books, leather, wood...)

Background MSWI Bottom ash are

composed of inorganic and organic material.

TOC = EC + OC

Dissolved Organic Carbon (DOC) is known to form DOC-metal complexes in the leachates produced by the bottom ash, once disposed into the landfill.

Cu2+ is known to built preferentially complexes with organic acids in the bottom ash leachates (e.g. Meima et al. 1999a/b; Eggimann 2008).

Total Organic Carbon (TOC)

Elemental Carbon (EC)

Organic Carbon (OC)

Dissolved Organic Carbon (DOC)

Which method is suitable for the determination of OC and EC in BA

Is there a dependence of OC/EC and DOC

Is there a simple dependence of DOC and HM mobilisation/complexation

and/or has the DOC to be characterized more in detail (speciation, HA, FA..) ?

What can we learn from experiments in comparison to leachates of aged bottom

ash from deposits?

The aim of my study is to reveal the transition from TOC in the solid material to DOC in the bottom ash leachates and their correlation to heavy metals mobility.

Questions addressed

Aim

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MSWI Switzerland

N° Company

Where Age

1 MÜVE Biel/Bienne 40 years 2 Kebag Zuchwil 20 years3 Ewb Bern 1 year4 AVAG Thun 10 years

Different Sampling Methods3 Weeks 2x / Day 1x ≈ 40Kg

Sample Reduction

Roller Crusher

Sieve 2 cm

Splitting 1:2 Splitting 1:4 Splitting 1:4

Step 1 Step 2 Step 3 Step 4

Metal and organic

particles are then

removed for separate analysis

(5-8 % of the total)

Roller Crusher

Roller Crusher

Sieve 1 cm Sieve 0.5 cm

Sample Reduction Inorganic waste material

Aluminum nugget

Organic waste material

X-Ray Fluorescence Analysis

TVA Mobilization Test

CO2 Leaching test

L/S: 10

pH: 6.1 - 6.3

EC: 2.1-8.4 mS

H2O leaching Test

L/S: 10

pH: 11.6 – 12.4

EC: 3.7-4.5 mS

Organic Carbon-Heavy Metal Complex

Total Organic Carbon (TOC) &

Dissolved Organic Carbon (DOC)

Heavy Metal (Cu2+)&

Dissolved Organic Carbon (DOC)

Summary

Material must be collected, at least per three weeks, two times per day, with a minimum amount of 20 Kg per sample. The most efficient sampling procedure is based on 3 main steps: Crushing – Sieving – Splitting.

The results shown support the hypothesis, that organic molecules (TOC) favor heavy metal mobilization through DOC-metal complexes, especially with Cu which can lead to a potential risk of soil and groundwater contamination.

Thun and Bern MSWI show DOC concentrations above the Swiss threshold value suggested form the VVEA ordinance (20 mg/L).

Outlook

Column leaching tests Comparison of leachates from the Teuftal

Deponie-D deposit to laboratory tests TOC speciation (EC, OC, AOC, etc. ) Size-exclusion chromatography (LC-OCD)

Outlook

Thank you for the attention

Irving - Williams series: 1953

Cu2+ > Ni2+ > Zn2+ > Co2+ > Cd2+ > Ca2+ > Mg2+