Removal of diesel hydrocarbons by constructed wetlands Isotope methods to describe degradation

Transcription

1 Removal of diesel hydrocarbons by constructed wetlands Isotope methods to describe degradation Watzinger A. a, Kinner P. a, Hager M. a, Gorfer M. b, and Reichenauer T.G. a a Environmental Resources and Technologies, Health and Environment Department AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430 Tulln, Austria; andrea.watzinger@ait.ac.at, phone: +43 (0) ; fax: +43 (0) b Bioresources, Health and Environment Department, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430 Tulln, Austria.

2 Task In-situ remediation of a hydrocarbon (diesel) contaminated site in Vienna (Austria) unsaturated and saturated zone were affected Introduction Hydrocarbons can easily be degraded by microorganisms biological remediation strategy was proposed Remediation of the unsaturated zone by bioventing (addition of nutrients was tested) Remediation of groundwater by constructed wetlands

3 Construction of the four wetlands on-site vertical flow and intermittent operation

4 Construction of the wetlands August 2012

5 Construction of the wetlands Planting: Salix viminalis 4 constructed wetlands: Sand (0-4 mm) + Sand (0-4 mm) Liapor HD Biochar (3w/w%) & Sand

6 Bioremediation Results Sand

7 Constructed wetlands hydrocarbon removal efficiency Treatment efficiency

8 Hydrocarbons in the substrate January 2014

9 Microbial biomass in the substrate January 2014

10 Degradation of 13 C labelled hexadecane Microcosms experiment Material and Methods 50 µl of hexadecane (δ 13 C = ) 50 g of substrate from the constructed wetland (δ 13 C = ) 4 replicates + 2 sterile controls per substrate: sand+, sand, liapor, biochar & sand Pre-incubated 2 weeks Addition of hexadecane Incubated for 40 days Measurements of 13 C CO 2 during incubation Measurement of 13 C PLFAs (microbial biomass) after 40 days

11 Mineralization of 13 C hexadecane 13 C CO 2 13 C hexadecane

12 Microbial respiration - CO 2 concentration in the microcosms 13 C hexadecane

13 Mineralization of 13 C hexadecane mass balance calculation

14 Uptake of 13 C hexadecane into microorganisms sterile controls

15 Uptake of 13 C hexadecane into microorganisms

16 Uptake of 13 C hexadecane into microbial PLFAs - concentration and δ 13 C values

17 Uptake of 13 C hexadecane into microbial PLFAs

18 Mineralization and microbial uptake of hexadecane in percent of the added hexadecane 40 days after labelling 50 g substrate with 50 µl hexadecane substrate mineralisation microbial biomass hexadecane & metabolites sand sand liapor biochar & sand < 0

19 Conclusions and Outlook Diesel hydrocarbon removal from groundwater by constructed wetlands is very efficient (> 90% removal) removal this winter ok permanent operation proposed Mineralisation of 13 C hexadecane in the lab was around % for sand and sand & biochar but only 20% for liapor. Retarded degradation of hexadecane in liapor was likely responsible for the high 13 C labelling of the microbial biomass. Does the higher microbial biomass of the liapor substrate in the field compensates for it? A method to quantify biodegradation in the field based on the natural stable isotope fractionation is still needed

20 Fractionation during hydrocarbon degradation Microcosms experiment Material and Methods 150 ml of groundwater + 40 µl of decane (solved in ethanol 1:10) + 30 g of substrate from the constructed wetlands Measurements of the concentration and δ 13 C and δ 2 H decane during incubation

21 Fractionation during hydrocarbon degradation Microcosms experiment Results and Outlook Removal of decane was monitored Degradation was indicated because of oxygen depletion and the presence of decane degrading bacteria Removal was different between different substrates adsorption processes might have also occurred Neither carbon nor hydrogen isotope were discriminated Does decane diffusion through the water column or ethanol masks the proposed microbial driven fractionation? Work is continuing

22 Thanks for your attention! Work was conducted within the project BIOSAN Biostimulation und bepflanzte Bodenfilter zum Abbau von Mineralölkohlenwasserstoffen in Boden und Grundwasser Biostimulation and constructed wetlands for enhancing degradation of petroleum hydrocarbons in soil and groundwater Funded by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management