TA10 Microbial Remediation of Acid Mine Drainage Wastes
D135-136
8:00 AM - 12:00 PM, Tuesday
() Sustainable approach for the remediation of groundwater contaminated by heavy metals: an overview of Permeable Reactive Barriers and Zones.
Vanbroekhoven, K1, Diels, L1, Gemoets, J1, Geets, J1, Vos, J1, Van Roy, S1, Dejonghe, W1, Bastiaens, L1, 1 Vito, Boeretang 200, Mol, Belgium
ABSTRACT- Former mining activities, non-ferrous metals processing, surface treatment and electronic industries lead to the contamination of soils and groundwaters with heavy metals. Also the presence of natural iron (or even arsenic) can play a role in this contamination. After long periods of exposure the heavy metal plumes can become very large and are threatening groundwater reserves. This paper will deal with the use of immobilisation techniques for the reduction of risks related to the presence of heavy metals._CR__LF__CR__LF_In case of groundwater pollution the metals can be treated in situ in the aquifer in a way that they become immobilised. This immobilisation can be done by inducing Sulphate Reducing Bacteria (SRBs) to reduce sulphates into sulphides which will precipitate the heavy metals as metal sulphides. In order to induce the bacteria a carbon source (electron donor) must be provided to grow these bacteria and to remove the oxygen. It is important to make good evaluations about the feasibility of this technology as a quite low ORP is necessary and methanogenic activity must be avoided. Good chemical analysis of the inorganic and organic content are necessary (evaluations will be presented). _CR__LF_Batch test systems and column test systems will be presented. Evaluations of the in situ precipitates will be discussed. Special attention will be paid to the addition of ORP reducing compounds. The results will be compared with another in situ technology being immobilisation by sorption to zerovalent iron, zeolites, silicates, compost and other adsorbing materials in so called adsorption barriers. Also special attention will be paid to alkalinity generating barriers able to increase the pH. _CR__LF__CR__LF_The upscaling of the process towards injection and diffusion of carbon sources will be discussed in detail. The influence of the carbon source and concentration on the microbial ecology of sulphate reducing bacteria versus methanogenic bacteria will be presented. Also the treatment design will probably consist of some kind of virtual barrier or treatment curtain at the border of the industrial site to avoid the high costs for complete remediation of the whole site. Feasibility tests and the results of a pilot study work for in situ bioprecipitation and sorption will be presented and compared. All the results will be accompanied by molecular biological results concerning the identification of specific groups of Sulphate Reducing Bacteria in the process._CR__LF__CR__LF_Special attention will be paid to case studies and special approaches apart from PRBs based on adsorption and the in situ bioprecipitation process (ISBP), combinations of ISBP with redox manipulation or with adsorbents will be illustrated for specific cases. Also attention will be paid to the fate of the immobilized metals by changing the operation conditions of the column systems and by determining the metal binding to the aquifer by a sequential extraction process._CR__LF__CR__LF_A general approach for mining sites, non-ferrous sites or surface treatment sites will be presented. Special attention will be paid to prevent possible disasters and to remediate large areas of contaminated groundwater and even surface water._CR__LF_
Key words: sulfate reducing bacteria (SRB), metal toxicity and inhibition measurements, heavy metals, groundwater