Phosphate mineralogy controls microbial hydrocarbon degradation - - PowerPoint PPT Presentation

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Presenting Members

Phosphate mineralogy controls microbial hydrocarbon degradation

Steven D Siciliano, Tingting Chen, Courtney Phillips, Jordan Hamilton, David Hilger, Blaine Chartrand, Jay Grosskleg, Kris Bradshaw, Trevor Carlson and Derek Peak

• The soils are full of clay.
• The soils freeze.
• The soils have fractured flow.

Why did your remediation stall?

1.Supply electron acceptors (oxygen, nitrate, iron, sulfate) 2.Supply the building blocks that microbes need to grow (nitrogen, phosphorus)

How to remediate hydrocarbons in two easy steps

Phosphate Fate in Soil during Biostimulation

HPO4

• 2

(aq)

Adsorbing on Mineral Surfaces Transport (macro and micro scale) Microbial Uptake for bioremediation Forming New Minerals

If sorption controls phosphorus reactivity. In soils, this really means mineralogy dictates sorption which controls phosphorus reactivity. Microbes require phosphorus to degrade hydrocarbons. In soils, this really means that mineralogy sways microbial hydrocarbon degradation.

It logically follows that if microbes need phosphorus then……

Biostimulatory solutions worked at some sites but not others due to variation in phosphate speciation, Hypotheses

whereas site‐specific effects not linked to phosphate are secondary.

Site History

Remedial Approach: Large (1m) bore 5.5m infiltrators

2013 Activities – Infiltrator Installation

2013 Activities – Infiltrator Installation

Biostimulatory Solution

• circumneutral pH
• 11 mM MgSO4,
• 1 mM H3PO4,
• 0.08 mM HNO3 in potable water.

Concentrations were selected to:

• 1. match local groundwater sulfate,
• 2. be at the maximum allowed

concentration of nitrogen,

• 3. be below solubility for any phosphate

mineral formation. It was pumped into the infiltrators 0.5 m below ground at a flow rate of approximately 5000 L/day.

Step 1. Alter soil mineralogy

Collect Soils from 8 Different Contaminated Sites Amorphous Phosphorus Nothing Hydroxyapatite Hematite Natural Phosphorus Crystalline Phosphorus Most soluble (adsorbed Phosphorus) Least soluble (crystalline phosphorus minerals)

2014 Activities – Soil Sample Placement

• Amendment delivery began on

August 14th, 2014

• Premade soil bags placed in the

infiltrators August 22nd

Step 2. Amend with orthophosphate for six months

Amorphous Phosphorus Hydroxyapatite Hematite Natural Phosphorus Crystalline Phosphorus Aerobic & Anaerobic Mineralization Living Diesel Degraders

• 1. Diesel dissipation
• 2. Degradation gene prevalence
• 3. Community Structure

Pulling the Soils Back Out

After 3 months all 8 different sites had responded to the biostimulatory solutions.

Calcite was dissolved when we acid washed, but there was no consistent effect on the pools of phosphorus in these soils

Three principal phosphate phases formed: a) Adsorbed phosphate b) Brushite (CaHPO4 ∙ 2H2O) c) Newberyite (MgHPO4 ∙ 3H2O)

Indicator Type Mineralogy Phosphate Adsorption Catabolic Genes Non‐significant P < 0.05 Mineralization Assays Non‐significant P < 0.10 Culturable Diesel Degraders P < 0.01 P < 0.01 BTEX Degradation Rate P < 0.04 Non‐significant CCME F1 Degradation Rate P< 0.01 P < 0.01

What was more important: mineralogy or phosphorus adsorption?

But remember that mineralogy and phosphate adsorption are not independent; rather it is what dominated in our system.

Anaerobic phenanthrene degradation and the catabolic gene bzdN were promoted by adsorbed phosphorus.

Mineralogy influences microbial community composition.

Microbial community composition influences degradation.

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• 1. Total amount of adsorbed phosphate controls

hydrocarbon degradation.

• 2. Relative proportions of adsorbed versus

mineral phosphorus controls community composition.

Take Home Messages

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Thus, small amounts of phosphorus injected in the subsurface will increase degradation but large amounts may inhibit degradation.

Site Management Lessons

Total Phosphorus Relative Proportions Hydrocarbon Degradation Phenotype Microbial Community Composition Genotype Newberyite bzdN (denitrifiers) Hydrocarbon Stall Excess Phosphorus Carbonate Dissolution