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Overview Processes Phytoremediation 4... · Overview Processes ... Phytoremediation Techniques...

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1 Phytoremediation Principles and studies done at Overview Processes Processes summary Change of water balance (2/3rd transpired) Change of soil conditions (Redox, pH) Root zone degradation (100times more bacteria) Uptake into plants (water soluble compounds) Metabolism by plants (?) Toxicity to plants (?) Definition: Phytoremediation = healing of soils with plants Engineer! Phytoextraction Rhizo- and phytodegradation Hydraulic control ”Pump and tree” Phytovolatilization Phytoremediation Techniques Phytoremediation projects at DTU - Tankstation Axelved (1999, gasoline) - Asphalt work Vassingerød (1999, PAH) - Gas works Søllerød (2000, cyanide) - ENDEGRADE (2001-2004, toluene) - Harbour sludge Antwerp (2003-2004, TBT) - Kalvebod Miljøcenter (2005- 2006, copper, PAH) - Airport Szprotava (kerosin) 2014
Transcript

1

Phytoremediation

Principles and studies done at

Overview Processes

Processes summary

Change of water balance (2/3rd transpired)

Change of soil conditions (Redox, pH)

Root zone degradation (100times more bacteria)

Uptake into plants (water soluble compounds)

Metabolism by plants (?)

Toxicity to plants (?)

Definition:

Phytoremediation = healing of soils with plants

Engineer!

Phytoextraction

Rhizo- and phytodegradation

Hydraulic control

”Pump and tree”

Phytovolatilization

Phytoremediation Techniques Phytoremediation projects at DTU

- Tankstation Axelved (1999, gasoline)

- Asphalt work Vassingerød (1999, PAH)

- Gas works Søllerød (2000, cyanide)

- ENDEGRADE (2001-2004, toluene)

- Harbour sludge Antwerp (2003-2004, TBT)

- Kalvebod Miljøcenter (2005- 2006, copper, PAH)

- Airport Szprotava (kerosin) 2014

2

General conclusions from field tests

+ Phytoremediation is helpful,

but not a „wonder weapon“

- - - Time scale is very long (> 10 years)

if something happens at all!

+++ The method is very cheap

(~5% of conventional costs)

-- - Engineering companies don‘t like it

(nothing to earn)

--- Take care! some engineers promise too much

++ Many abandoned sites might be used for

biofuel production, as parks ...

Experiments & Real Life at DTU

The Challenge

Phytoremediation has a good reputation (green, cheap, in situ).

The processes at site are very complex and difficult to predict.

Does it work?

and if so, why?

Toxicity test

soil or solution

Metabolism

closed bottle

Mass balance

model Mass balance

experiment

Toxicity

very toxic to

trees?

Kinetics

Michaelis-

Menten?

Monod?

Calculation

Mass

balance

Experiment

Mass

balance

Test bacterial

metabolism

yes

no

none

Test scheme phytoremediation

no

phyto-

remediation no

degradation

Acute toxicity test with trees Principle: healthy trees transpire more

Loss of weight compared to controls

fast, cheap, reliable

3

Toxicity of KCN to willow trees

in hydroponic solution in sand

(toxic at > 5 mg/L) (toxic at > 20 mg/L)

% T

ran

sp

irati

on

Toxic at

< 1 mg/L ?

yes

no

Willow tree acute toxity test

Results in water // in soil

KCN, KCN, PAH, BTX, Cd

3,5-dichlorophenol, detergents

Toxic at

< 100 mg/L ?

yes

no

MTBE, phenol,

Nano-TiO2,

antibiotics

diesel, gasoline,

TBT, PAH, FeCN

2,4-D

Cu

TBT

Closed-bottle test for metabolism

2 grams leaves, roots or stem in 100 ml solution

Concentration tracked by chemical analysis here done by Morten Larsen, Ex-PhD, now COWI

Degradation kinetics bacteria and trees

MTBE, PCB

Michaelis-

Menten

Monod

none

Plants

Bacteria

HCN, FeCN

chlorobenzoic acid

BTX, phenol

(TBT, oil, PAH,

detergents, Cl-phenol)

and many more …

Plants are usually bad degraders. Bacteria needed.

Idea: Symbiosis

Plants transport bacteria sitting on

roots down to deep soil and distribute

them. Plants suck the polluted water

towards root-colonizing bacteria.

Bacteria grow and degrade pollution.

And protect plants.

Test in laboratory and practical

application outside.

Bacteria can either be added (dip roots

into a suspension with cells) or develop

naturally.

For shallow contamination only.

How can we bring plants and bacteria together?

4

Test of concept: protection of lupin by endophytic bacteria

(Barac et al.)

Toluene in

water Bacterial

degrader

added

Ford Genk: BTEX from fuel and solvents in groundwater

275 poplar trees planted in 1999 to stop the shallow BTEX plume.

Monitoring for 6 years. Tree roots and associated bacterial

community degraded toluene. After remediation, bacteria died off.

Monitoring of

Remediation Ford Genk

Plume after

13 month (A)

42 month (B)

50 month (C)

55 month (D)

Field study TIMBRE project

"wild" phytorem at the former Russian airport Szprotawa in

Poland - jet fuel and BTEX

Lauge PW Clausen, Stephan Bartke, Mariusz Kalisz, Janusz

Krupanek, Eugen Martac, Nicolas Fatin-Rouge, Mette Algreen and

Stefan Trapp

Department of Environmental Engineering DTU (DK), Helmholtz

Centre for Environmental Research – UFZ (D), Institute for Ecology of

Industrial Areas (PL), Fuegro (D), Université de Franche-Comte (F)

Regeneration of a brownfield mega-site –

Review of technologies available for a former

military airport Table of Contents

1 Historical evaluation

2 Site characterisation

3 Clean-up technologies

5

History The site we deal with is a former Sowjet military airport (nuclear) in

Silesia/Poland in use until 1992. The Russians voluntarily retreated and

left an abandoned airfield.

26

TIMBRE test site: Szprotawa, Poland

Former Soviet airbase

200 ha

Site Impressions

Fueling of a Mig 29

Main pollution at Szprotawa airport is from jet fuel

What is jet fuel?

"Most aviation fuels available for aircraft are kinds of petroleum

spirit, petroleum ether, also known as benzine, naphtha".

Petroleum ether is a mixture of light alkanes, e.g., pentane,

hexane, and heptane.

Historical Evaluation Site characterisation tools

Geological profiles

Contaminants in groundwater

Soil gas

Risk assessment

Tree core sampling

Contaminants in soil

6

Spatial distribution

more to site characterization please see poster Mette Algreen

Highest pollution at the fuel station - a 200 tons kerosin NAPL (80 000 m3)

+ wide diffuse pollution near the air field (engine heating)

What to do ?

III Remediation options

Experience from the past: Airport Hradcany (CZ)

Former Russian military airport contaminated with kerosin etc.

Remediation by Kap = Earth Tech = Aecom since 20 years

Hradcany remediation: combination of several methods

I. stage

– Soil vapour extraction + dual phase extraction – removal of

extractable oil phase

– 1 – 2 years in the source zone

II.stage

– In situ aerobic biodegradation with oxygenation and

nutrient supply for 6 years (bioventing/biosparging)

– > 90 % of hydrocarbon removal

Evaluation of options for Szprotawa remediation

Approach Considered technologies Criteria of evaluation

time costs sustainability

Quick remediation

(based on ex-situ techniques)

Polluted soil replacement, eventual on-site soil remediation.

Supporting techniques could be needed (ISCO)

+ + + - - - - - -

SHORT-term remediation

ISCO based techniques - + + - - + - - +

LONG-term remediation

Bioremediation combined with ISCO techniques,

enhanced bioremediation.

- - + - - + - + +

Soil vapour extraction, and/or bioventing

- + + - + + + + +

Phytoremediation supported by humification, lime treatment (land farming)

- - - + + + + + +

Suspended usage

MNA, phytoremediation/ forestation, continuous risk control

- - - + + + + + +

7

Cheap Solutions I

CO2 Methane

Soil gas indicates ongoing natural attenuation

Cheap solutions II

Trees remove VOC and aerate soil - stimulate natural

oxidation with trees?

Remediation options

Vapour extraction and bioventing are two proven successful

methods, only neither cheap nor fast.

Alternatives

"Slurping" (sucking of free phase)

ISCO in situ chemical oxidation (of the source zone)

Natural attenuation (of the diffuse pollution)

Phytoremediation (of the diffuse zone)

Decision to be made in Poland

Questions?

Field Study: Full-Scale Phytoremediation Project

Gas Works Holte

Holte / Søllerød (near Holte Midpunkt)

Pollution from old gas works (tar and PAH; cyanide)

In the 1990ies, CN was found in drinking water wells in 60

m depth

Cyanide (Blåsyr)

Free cyanide (HCN, CN-) is

extremely toxic

World production is

1.4 mio tons/year

Environmental sources are

- Gas works waste (iron CN)

- Gold mine effluents (free CN)

- Chemical industry (Bhopal)

- Others

8

Søllerød gasworks site (1955) The problem at former gas works

is the waste from

gas cleaning.

It contains 1- 20 g CN/kg

and was dumped at site …

Cyanide is iron complexed

(Prussian blue).

This is a solid (blue powder)!

Geochemistry of FeCN

start

here

The waste persists for decades and decomposes to

… HCN

250 000 tons alone in Denmark!

Frequently, gas works were close to water works

... and iron cyanide leaches into wells

Map of Contamination Holte gas works

9

Remember: Trees take

up HCN and FeCN and

degrade it to harmless

amino-acids.

In vivo HCN metabolism by willows

Metabolism pathway of cyanide (HCN) by plants

Metabolism kinetics by plant enzymes

where

v (mg/d) is the removal velocity of

substrate with concentration C (mg/L),

vmax (mg/kg/d) is the maximal removal velocity,

KM (mg/L) is the half-saturation constant and

M (kg) is the mass of the plant.

MCK

Cvv

dt

dm

M

max

Michaelis-Menten kinetics

Michaelis-Menten enzyme kinetics

CK

Cv

dt

dC

M max

maxvdt

dCKC M C

K

v

dt

dCKC

M

M max

"zero order", linear "first order", exponential

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6

Time (d)

Sub

str

ate

C (

mg

/l)

0

2

4

6

8

10

12

0 2 4 6

Time (d)

Sub

str

ate

C (

mg

/l)

low C high C

Michaelis-Menten parameters

vmax

mg/kg/h

KM

mg/L

Roots 6.9 0.44

Leaves 9.6 0.59

Results for HCN and willows

10 mg per kg plant and hour is 50 kg per ton plant and year

10

Michaelis - Menten in the mass balance

Steady-state gives a non-linear

(quadratic) equation

with two solutions

RM

RRR

RWR

W

R

R

CK

CvCk

KM

QC

M

Q

dt

dC

max

02 cbCaC

inflow to roots outflow from roots metabolism

Example calculation (cyanide, willow trees, with metabolism)

The relation between external concentration and

concentration in roots is non-linear !

0

10

20

30

40

50

0 20 40 60 80

CW (mg/L)

Cro

ot

(mg

/kg

)

metabolism

= uptake metabolism

< uptake

toxic effects

Model versus Experiment

Trees dead

Trees metabolize HCN – or they die!

6000 trees were planted at the former gas

works site - and survived!

Gas works Holte 2002 and 2005

rapid growth of poplars

2002 2005

Holte 2005/6

Remediation and public park at the same time

11

Holte 2007

Trees have grown up to 15 m

Søllerød 2000 - 2010

Trees pump off contaminated water

year L / m2/

year

2001 12

2002 82

2003 217

2004 267

after 2004 267

> 40% of the rain is

pumped off by trees

Cost efficiency

Traditional remediation: about 40 mio DKr

> 50% for pumping of polluted groundwater

Phytoremediation:

about 50% cheaper (savings for pumping)

Søllerød

2000 2002

Measured concentration of CN in leachate

source: L.C. Larsen, ATV-meeting DTU 2005

Total CN (mg/l) in GW < 15 m depth, together with success criteria

Source: documentation report Orbicon

CN in water < 15 m depth

Total CN (mg/l) in GW > 15 m depth Well B97.16 is in the center of contamination

CN in water > 15 m depth

12

Geochemistry of FeCN

slow dissolution of solid complexed CN Prussian blue

start

here

1955

2001

Summary Results Gasworks Holte

• The primary goal was reached (no more CN in well water)

• The target for the upper aquifer wasn’t met.

• Costs were reduced (50%)

• It took long (> 4-5 years) before concentrations of CN in GW

fell (close to ) the success criteria

• There were no particular difficulties (accidents etc.)

BUT

• The source of pollution (solid iron cyanide) is still there

• The problem holders are not satisfied, not at all.

Any questions?


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