Biodegradation of organic pollutants in a Biodegradation of organic pollutants in a composting environment in Mauritiuscomposting environment in Mauritius

Vijayalaxmi JumnoodooVijayalaxmi JumnoodooPhD CandidatePhD Candidate

Department of Chemical and Department of Chemical and Environmental EngineeringEnvironmental Engineering

University of MauritiusUniversity of Mauritius

February 2010

OverviewOverview

IntroductionIntroduction ObjectivesObjectives MethodologyMethodology Results and DiscussionResults and Discussion ConclusionConclusion Future worksFuture works

IntroductionIntroduction

Extensive production and use of synthetic organic Extensive production and use of synthetic organic compounds for domestic, municipal, agricultural, industrial compounds for domestic, municipal, agricultural, industrial and military activities has led to a wide distribution of these and military activities has led to a wide distribution of these compounds in the environment compounds in the environment

Contamination of soils, groundwater, sediments, surface Contamination of soils, groundwater, sediments, surface water and air with these hazardous compounds is one of water and air with these hazardous compounds is one of the major problems that the world is facing today the major problems that the world is facing today

Polyaromatic hydrocarbons (PAHs), polychlorinated Polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides and other endocrine disruptors biphenyls (PCBs), pesticides and other endocrine disruptors remain the main pollutants of concern todayremain the main pollutants of concern today

Organic pollutants

IntroductionIntroduction

Environmental pollution due to pesticides Environmental pollution due to pesticides is a global consideration is a global consideration

Herbicides consumption in 2005 in Herbicides consumption in 2005 in Mauritius amounted to about 57% of the Mauritius amounted to about 57% of the average annual consumption (2141 tons) average annual consumption (2141 tons) of pesticides of pesticides

Atrazine, hexazinone, 2,4-D and ioxynil are Atrazine, hexazinone, 2,4-D and ioxynil are commonly used by the planters in commonly used by the planters in MauritiusMauritius

Pesticides

IntroductionIntroduction

The practice of organic farming which includes The practice of organic farming which includes the application of composts allows farmers to be the application of composts allows farmers to be less dependent on synthetic fertilizers and less dependent on synthetic fertilizers and pesticides and hence minimize pollution due to pesticides and hence minimize pollution due to these compoundsthese compounds

However, the detection of clopyralid and picloram However, the detection of clopyralid and picloram in finished composts has aroused concern for the in finished composts has aroused concern for the use of pesticide-contaminated composts made use of pesticide-contaminated composts made from yard trimmings and agricultural residues from yard trimmings and agricultural residues

The application of the contaminated composts The application of the contaminated composts has been found to be detrimental to plant growthhas been found to be detrimental to plant growth

Composting

IntroductionIntroductionCompost bioremediation - technology for treatment of organic pollutants

DegradationCompost-compound interactions

Organic pollutant in compost

Mineralization

ToxicityMobility

Organic matter

Surface sorption-desorption

Entrapment within humic complexes

Increased mobility or toxicity

Decreased mobility or toxicity

Possible interactions between compost and organic pollutant to minimize pollution

AimsAims Study the biodegradation of 3 chlorinated Study the biodegradation of 3 chlorinated

herbicides of different degrees of herbicides of different degrees of persistency during compostingpersistency during composting

Develop theoretical mechanistic pathways Develop theoretical mechanistic pathways of degradation of the herbicidesof degradation of the herbicides

Application of compost bioremediation Application of compost bioremediation technology for treatment of pesticide-technology for treatment of pesticide-contaminated soilcontaminated soil

MethodologyMethodology Herbicides used: Atrazine (moderately persistent), 2,4-D (low Herbicides used: Atrazine (moderately persistent), 2,4-D (low

degree of persistency) and Tordon 101 (persistent)degree of persistency) and Tordon 101 (persistent)

Composting materials: Grass clippings, shredded branches, Composting materials: Grass clippings, shredded branches, brown leaves and finished compostbrown leaves and finished compost

Grass clippings were contaminated with respective herbicide Grass clippings were contaminated with respective herbicide emulsions:emulsions:– Compost A: uncontaminated grass Compost A: uncontaminated grass – Compost B: atrazine-contaminated grassCompost B: atrazine-contaminated grass– Compost C: 2,4-D-contaminated grass clippingsCompost C: 2,4-D-contaminated grass clippings– Compost D: Tordon 101-contaminated grass clippingsCompost D: Tordon 101-contaminated grass clippings

In-vessel composting system: rotary drums of 200L capacityIn-vessel composting system: rotary drums of 200L capacity

MethodologyMethodology

Compost set-upCompost set-up

Green wastes Mixing wastes and adjusting water

Filling wastesin drums

Herbicide application

MethodologyMethodology

Rotating drum (200L)

Compost A (uncontaminated grass clipping)

Compost B (atrazine-contaminated grass clipping)

Compost C (2,4-D contaminated grass clipping)

Compost D (tordon 101-contaminated grass clipping)

Grass clippings (25 kg) + brown leaves (4.5 kg) + dry branches (5.5 kg) + finished compost (5 kg)

Bulk density, pH, respiration test of final compost

Other physico-chemical characteristics:

MoistureTemperature

Biodegradation study:Volatile SolidsCO2 evolution

Mechanism of degradation:NMR and FTIR spectroscopy

Monitoring

Results & DiscussionResults & Discussion

Temperature profile

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 10 20 30 40 50 60 70 80 90 100

Time (Day)

Tem

per

atu

re (

0 C)

Compost A Compost B Compost C Compost D

A maximum temperature range of 55oC for all the composts

Results & DiscussionResults & Discussion

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

0 10 20 30 40 50 60 70 80 90 100

Time (Day)

Moi

stu

re (

%)

Compost A Compost B Compost C Compost D

The moisture content of the composts: 55% to 73%

Moisture content

Results & DiscussionResults & DiscussionVolatile solids content

70.00

75.00

80.00

85.00

90.00

95.00

100.00

3 10 17 24 31 38 45 89Time (Day)

% V

S

Compost A Compost BCompost C Compost D

Presence of herbicides was a limitation to organic matter degradation

Results & DiscussionResults & DiscussionRespiration rate

Same trend for CO2 evolution for Composts A and C;

Acclimatization of microorganisms to herbicide degradates observed

Results & DiscussionResults & Discussion Degradation occurred faster, within 10 Degradation occurred faster, within 10

days, in the case of the 2,4-D-days, in the case of the 2,4-D-contaminated compost due to its low contaminated compost due to its low persistencypersistency

Compost B was associated with a lag Compost B was associated with a lag phase and degradation could only be phase and degradation could only be observed on Day 24 onwards observed on Day 24 onwards (cooling/maturation stage)(cooling/maturation stage)

Tordon 101/picloram was still persistent at Tordon 101/picloram was still persistent at the end of composting processthe end of composting process

Results & DiscussionResults & DiscussionMechanistic pathways of degradation of the herbicides

O CH2 C O

O

2,4-D amine salt

Cl

Cl

OH

Cl

Cl

2,4-DCP

OH

Cl

Cl

OH

3,5-dichlorocatechol

oxidation

+NH2

CH3

CH3

ClCl

COOH

COOH

2,4-dichloromuconate

products

Mechanism of degradation of 2,4-D during composting

Results & DiscussionResults & DiscussionN

N

N

HN

HN

Cl

Chemical hydrolysis

Atrazine

O

H

H N

N

N

HN

HN

OH

Biological hydrolytic dechlorination

Hydroxyatrazine

Humic acid

N

N

N

HN

HN

OH or Cl

O

O

HA

Quinone-like units of HA

e

transferHA-Atrazine orHA-Hydroxyatrazine complexes

desorption

N

N

N

HN

HN

OH

Hydroxyatrazine

N

N

N

HO

HN

OH

N-ethylammelide

N

N

N

HO

OH

OH

Cyanuric acid

N-dealkylation

N-dealkylation

Route 1

Route 2

Mechanism of degradation of atrazine during composting

Results & DiscussionResults & Discussion

The microbial metabolism of 2,4-D during the The microbial metabolism of 2,4-D during the composting process composting process soil systems soil systems

Initial side chain cleavage resulted in the Initial side chain cleavage resulted in the formation of 2,4-Dichlorophenol. Further formation of 2,4-Dichlorophenol. Further degradation of the intermediate occurred through degradation of the intermediate occurred through oxidation. oxidation.

Atrazine degradation occurred mainly due to the Atrazine degradation occurred mainly due to the interaction of the herbicide with compost humusinteraction of the herbicide with compost humus

Biologically mediated hydrolytic dechlorination of Biologically mediated hydrolytic dechlorination of

atrazine has been observedatrazine has been observed

ConclusionConclusion The in-vessel composting system was effective in The in-vessel composting system was effective in

the degradation of pesticides of low to moderate the degradation of pesticides of low to moderate persistency persistency

Degradation of 2,4-D occurred within 10-17 days Degradation of 2,4-D occurred within 10-17 days of composting while that of atrazine was of composting while that of atrazine was associated with lag phases of 24 days associated with lag phases of 24 days respectively. Tordon 101/picloram was still respectively. Tordon 101/picloram was still persistent at the end of composting persistent at the end of composting

The microbial metabolism of 2,4-D was similar to The microbial metabolism of 2,4-D was similar to

that observed in soil systems.that observed in soil systems.

In the case of atrazine, there was a In the case of atrazine, there was a predomination of adsorption mechanism over predomination of adsorption mechanism over microbial metabolismmicrobial metabolism

Future worksFuture works Investigate on the treatment of pesticide-Investigate on the treatment of pesticide-

contaminated soil through composting; atrazine contaminated soil through composting; atrazine would be the target contaminantwould be the target contaminant

Determination of the optimum environmental conditions Determination of the optimum environmental conditions and nutrient amendments for the degradation of atrazineand nutrient amendments for the degradation of atrazine

Study the degradation of atrazine during composting of Study the degradation of atrazine during composting of both contaminated soil with finished composts and primary both contaminated soil with finished composts and primary composting ingredients composting ingredients

Devise a suitable compost bioremediation Devise a suitable compost bioremediation strategy for the treatment of atrazine-strategy for the treatment of atrazine-contaminated soilcontaminated soil

Thank you!Thank you!