In-situ Bioremediation of oily sediments and soil

Transcription

1 1 Peter Werner, Jens Fahl, Catalin Stefan DRESDEN UNIVERSITY OF TECHNOLOGY In-situ Bioremediation of oily sediments and soil

2 2 WHAT IS OIL? MIXTURE of aliphatic and aromatic hydrocarbons Different composition according to origin and treatment processes

3 3 SPILL Detection Risk Assessment Appropiate Remediation Among others: BIOREMEDIATION (Natural Attenuation > Biodegradation)

4 4 Physical Oil behavior in groundwater and soil Petroleum Hydrocarbons are not miscible with water and weakly soluble. Much lighter than water (lower density) Petroleum hydrocarbons are mixtures of compounds with different water solubilities. And: Volatile components of petroleum hydrocarbons like BTEX-compounds vaporize partially. (at the soil surface as well in unsaturated soil layers). Oil phases in soil move typically in the capillary fringe (border line) between unsaturated and saturated zone. Swimming on the water Laying on the beach Capillary fringe Oil phase Entering the vadose zone

5 5 Spill of a pollutant at the sea - Dissolution - Emulsification - Dispersion - Biodegradation - Volatilization (Evaporation) - Abiotic Transformation (Oxidation/Chemical Reaction)

6 6 NATURAL ATTENUATION Regular Definition: Naturally occurring processes in soil and groundwater that act without human intervention to reduce the mass, toxicity, mobility, volume or concentrations of contaminants (OSWER, 1999) These in-situ processes include biodegradation, dispersion, dilution, adsorption, volatilisation, and abiotic transformation of contaminants. Example: pollutant s concentration reduces over the time: conc. time

7 7 NATURAL ATTENUATION (NA) NATURALLY OCCURING ELIMINATION HAZARDOUS COMPOUNDS IN THE SUBSURFACE WITHOUT ANY HUMAN CONTRIBUTION MONITORED NATURAL ATTENUATION (MNA) THE NATURALLY OCCURING ELIMINATION PROCESSES ARE MONITORED BY A PROCESS RELATED ANALYTICAL PROGRAMME ENHANCED NATURAL ATTENUATION (ENA) THE NATURALLY OCCURING ELIMINATION PROCESSES ARE SUPPORTED BY ENHANCING THE PROCESS OR ELIMINATING LIMITING FACTORS

8 8 NA (Process) MNA ENA Tool to make the process obvious Remediation

9 9 NATURAL ATTENUATION PROCESSES MUST LEAD TO: ORGANIC COMPOUNDS non hazardous end products INORGANICS chemical or biological stabilisation In the case of oil: Mineralization

10 10 WHY NATURAL ATTENUATION BECAUSE NA HAPPENS ANYWAY BECAUSE NA CAN BE A NON DESTRUCTIVE TECHNIQUE BECAUSE NA HAPPENS IN SITU BECAUSE NA IS COST EFFECTIVE BECAUSE NA CAN BE A GOOD REMEDY (MNA, ENA) BECAUSE NA IS AN IMPORTANT PART OF A TREATMENT TRAIN

11 11 NATURAL ATTENUATION A Do-Nothing Approach? Which parameters are necessary for evaluating a plume? Quantitative assessment of a plume s behaviour - amount, extent, and rate of travel, as well as long-term evidence of attenuation N A = No Action? WRONG!

12 12 NATURAL ATTENUATION - Requirements Site assessment - hydrogeology, geochemistry, microbiology High tech approaches - sampling, analytical, modelling techniques Prediction of plume behaviour May be combined with source/hot spot control Containment of dissolved plume A risk management strategy Monitored Natural Attenuation (MNA)

13 13 Monitored Natural Attenuation (MNA) MONITORING CHALLENGES ARE: sensitive precise, reliable, reproducible easy to handle on-site and at the place application continuous control process related quick results data obtained must serve as the base for the decision making process cost effective (not cheap)

14 14 In-situ Bioremediation: Oilspills - Decision Tree

15 PRINCIPLES OF BIOREMEDIATION 15 Bioremediation is the active use of techniques to mitigate the consequences of a spill using biological processes in order to stimulate pollutant biodegradation and/or enhanced ecosystem recovery biodegradation by naturally occurring or added microorganisms to break down hazardous substances into less toxic or non toxic substances Microorganisms are generally bacteria (but also fungi); use organic compounds as source of energy and carbon Microorganisms require also growth factors (nutrients) and an electron acceptor The electron acceptor is usually oxygen but others are accepted too (nitrate etc.) As nutrients nitrogen and phosphorus (although iron, magnesium and sulphur are also needed)

16 16 In-situ BIOREMEDIATION The main factors involved in stimulation of microorganisms growth are: temperature, oxygen and nutritional conditions: In-situ Bioremediation A. Supply of nutrients B. Supply of oxygen C. Supply of surfactants (?)

17 17 CONCLUSIONS (In-situ) Bioremediation: ONE tool among others potential new tool for cleaning of contaminated shorelines low environmental impact More or less long term technology Knowledge on the boundary conditions required Knowledge on the processes behind required

18 18 better expensive slow faster bad cheaper Limitations for the ideal soil remediation