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Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix and localization of micropollutants into matrix compartments

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Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix

and localization of micropollutants into matrix compartments

Quentin Aemig, Sabine Houot, Dominique Steyer

To cite this version:

Quentin Aemig, Sabine Houot, Dominique Steyer. Dynamic of organic micropollutants during anaer- obic digestion: link between characterization of the matrix and localization of micropollutants into matrix compartments. Micropol & Ecohazard 2013, International Water Association (IWA). IWA Specialist Group on Assessment and Control of Micropollutants and Hazardous Substances, INT., Jun 2013, Zurich, Switzerland. �hal-01231281�

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Comment citer ce document :

Aemig, Q., Houot, S., Patureau, D. (Auteur de correspondance) (2013). Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix and localization of micropollutants into matrix compartments. Presented at Micropol & Ecohazard

2013, Zurich, Suisse (2013-06-16 - 2013-06-20).

8th Micropol & Ecohazard

Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix and localization of

micropollutants into matrix compartments

Quentin Aemig 1, Sabine Houot 2, Dominique Patureau 1*

1INRA, UR0050, Laboratoire de Biotechnologie de l’Environnement, F-11100 Narbonne, France

2INRA-AgroParisTech, UMR 1091 Environnement et Grandes Cultures, F-78850 Thiverval-Grignon, France

* corresponding author’s email address: dominique.patureau@supagro.inra.fr

Introduction. Many organic micropollutants are toxic and persistent compounds into the environment. They can bioaccumulate and, even though they are found at low concentration, they have huge impacts on environment [1]. These molecules are various: polycyclic aromatic hydrocarbons (PAH), nonylphenols (NP), nonylphenols ethoxylates (NPE), polychlorobiphenyls (PCB), etc. [2]. Emerging contaminants appear also now due to the use of pharmaceutical and personal care products (PPCP), drugs, etc. by the human activities [3].

They enter environment through sewage treatment plants [1], [2]. During the treatment, they are eliminated from wastewater by degradation, volatilization or sorption [4], [5]. It was showed that almost 65 % of the micropollutants removed during treatment by activated sludge were transferred from the liquid phase to the solid phase of the mixed liquor [5]. The contamination levels in sludge depend on the nature of the molecules: detergents and plastizicers have very high levels of contamination (from g to mg.kg-1 dry matter (DM)), others (hydrocarbons, pesticides, flame retardants, pharmaceuticals) have low (100 – 1,000 µg.kg-1 DM) to very low (< 100 µg.kg-

1DM) levels of contamination [5].

Anaerobic digestion is one of the most widely used processes for sludge stabilization, while treated sludge is very often disposed to the soil or reused for agricultural purposes [7]. The removal of micropollutants during anaerobic digestion depends on two processes: sorption and biodegradation [5]. To minimize the risk of micropollutants in soil after agricultural use of the treated sludge, we need to improve the removal by increasing sorption to particules (the molecules can be trapped into the organic matrix and then will not transfer to water or biota) or increasing biodegradation (the compounds are metabolized or cometabolized). To know how to control these processes, it is necessary to better understand the link between both evolutions of the organic matrix and the micropollutants during anaerobic digestion. The particulate phase represents most of the organic matter of the sludge [4] so in this study, we focus on this sludge phase.

Material & Methods. An experience based on batch systems was made to study this concomitant evolution. Three mixtures composed of 80 % DM digested sludge (inoculum) and 20 % DM secondary sludge (substrate) were introduced into bottles flushed by nitrogen (anaerobic conditions), sealed and placed in a thermostated room at 35°C. The ratio substrate/inoculum (S/X) was set at 0.5 g Chemical Oxygen Demand (COD)substrate.g-1 Volatile Matterinoculum (VM).

The quantity of biogas produced was measured regularly and its composition was determined by gas chromatography (Perkin Elmer, GC Clarus 480). The amount of endogenous biogas was substracted with an assay containing only the inoculum (control). The substrate was a secondary sludge from a wastewater treatment plant (WWTP) located in the center of France with a capacity of 285,000 population equivalents. Two inocula were used: the digested sludge from the WWTP and a granular sludge from a sugar effluents treatment plant located in Marseille, France.

The third mixture was made of sludge and digested sludge as the first one but spiked with micropolluants (PAH and NP). After 32 days of incubation, the experiment was stopped and the matrices were gathered for further analysis.

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Version postprint

Comment citer ce document :

Aemig, Q., Houot, S., Patureau, D. (Auteur de correspondance) (2013). Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix and localization of micropollutants into matrix compartments. Presented at Micropol & Ecohazard

2013, Zurich, Suisse (2013-06-16 - 2013-06-20).

Zurich 2013

Part of the initial and final matrices (T0 and Tf respectively) were centrifuged at 18,600 g during 30 minutes at 4°C to separate the aqueous phase form the particle phase. The centrifuged or not matrices were freeze dried and grinded with a mortar. The particle phase was divided into different compartments by using successive extractions with salted and basic solutions. 0.5 g freeze-dried and grinded matrix is placed in a centrifuge tube. 30 mL of the extraction solution is added. The tube is then placed in an incubator at 30°C and shaken at 300 rpm. Then it is centrifuged at 18,600 g during 20 minutes at 4°C. The liquid phase is filtered with a cellulose acetate filter at 0.45 µm (Whatman) and its COD is measured before pooling with the other extracts of the same compartment. The solid phase is used for further extraction or sacrificed for analyses. Four extractions are realized for each compartment. The first two compartments (soluble exopolysaccharides S-EPS and easily extractatable exopolysaccharides RE-EPS) are extracted with 10 mM NaCl/4 mM NaHCO3 and 10 mM NaCl/10 mM NaOH respectively. The extraction time is 30 minutes. The third compartment corresponds to humic like substances (HS- like) extracted during 4 h under nitrogen atmosphere with 0.1 M NaOH. Between the last RE- EPS extraction and the first HS-like extraction, the sample is freeze-dried and washed with 0.1 M HCl and milliQ water (pH adjusted at 7 with NaOH solution). These washing steps extract little COD so the extracts are not considered for the rest of the experiment. Different analyses are made on the different samples collected during the fractionation of the sludge (Table I.).

Sample Analyses

Particulate phase Measure of DM and VM, Total Carbon (TC), Total Kjeldahl Nitrogen (TKN), Lipids, Acid Hydrolysis, quantification of micropollutants (µPO)

S-EPS, RE-EPS, HS- like (solid phase)

TC, TKN, µPO S-EPS, RE-EPS, HS-

like (liquid phase)

COD, Organic Carbon (OC), Inorganic Carbon (IC), Proteins, Total Sugars, Fluorimetry 3D

Table I. analyses made on the fractionation of sludge

Results. The methane productions were the same for the spiked and non-spiked mixtures (Table II). It seems that there is no influence of the spiking procedure on the methane potential.

Contrary to what we expected, the methane potential of the mixture with granular sludge is lower. It can be explained by the inoculum not adapted to the substrate (the organic matter of sewage sludge may be less degradable than the one of the sugar effluents). The significative difference between each methane potential was verified by ANOVA test (Excel 2007) using a p value of 5 %.

Methane production Granular sludge Digested sludge Digested sludge + PAH & NP

mLCH4.g-1CODsubstrate 142±23 169±9 160±19

Table II. Methane production during the experiment

The fractionations of the six matrices were completely different showing the evolution of the matrix during the treatment (T0 versus Tf) and the differences between the inocula. The spiked and non-spiked mixtures have different compartments. This can be explained because the two series were not made at the same time: the inoculum was maintained during three weeks in a room at 35°C before utilization with spiked micropollutants. These results on the different compartments of the matrices will be gathered with the results on the biochemical characterization of the compartments and the localization of the micropollutants (PAH and NP) i.e. concentrations in each compartment. Furthermore, the use of 3D fluorimetry (Figure 1) will

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Version postprint

Comment citer ce document :

Aemig, Q., Houot, S., Patureau, D. (Auteur de correspondance) (2013). Dynamic of organic micropollutants during anaerobic digestion: link between characterization of the matrix and localization of micropollutants into matrix compartments. Presented at Micropol & Ecohazard

2013, Zurich, Suisse (2013-06-16 - 2013-06-20).

8th Micropol & Ecohazard

allow determining the types of molecules extracted in each compartment during the fractionation of the matrix (qualitative and quantitative method).

Figure 1. examples of fluorimetry spectra obtained on the three extracted compartments

Conclusion. In this study, we focused on three different matrices composed of 20 % DM sludge (substrate) and 80 % DM digested sludge (inoculum). Those three matrices were transformed during an anaerobic digestion in batch. The compartments evolved during the treatment and their compositions were different for each matrix. The biochemical characterization of the matrices and the localization of the contaminants will be used in a Partial Least Square regression (PLS regression) to create a model which will give the affinity of a compound for a compartment linked to its biochemical composition.

References

[1] Rowsell, V.F., Tangney, P., Hunt, C., Voulvoulis, N., (2009) Estimating Levels of Micropollutants in Municipal Wastewater. Water, Air, and Soil Pollution 206(1-4), 357–368.

[2] Clarke, B.O., Smith, S.R., (2011) Review of “emerging” organic contaminants in biosolids and assessment of international research priorities for the agricultural use of biosolids. Environment international 37(1), 226–47.

[3] Teijon, G., Candela, L., Tamoh, K., Molina-Díaz, A., Fernández-Alba, a R., (2010) Occurrence of emerging contaminants, priority substances (2008/105/CE) and heavy metals in treated wastewater and groundwater at Depurbaix facility (Barcelona, Spain). The Science of the total environment 408(17), 3584–3595.

[4] Rogers, H.R., (1996) Sources, behaviour and fate of organic contaminants during sewage treatment and in sewage sludges. Science of The Total Environment 185(1-3), 3–26.

[5] Barret, M., Delgadillo-Mirquez, L., Trably, E., Delgénès, N., Braun, F., Cea-Barcia, G., Steyer, J.P., Patureau, D., (2012) Anaerobic Removal of Trace Organic Contaminants in Sewage Sludge: 15 Years of Experience. Pedosphere 22(4), 508–517.

[6] Stasinakis, A.S., 2012. Review on the fate of emerging contaminants during sludge anaerobic digestion. Bioresource technology 121(null), 432–

40.

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