IMWA 2010 Sydney, Nova Scotia Mine Water & Innovative Thinking. 2 Outline Introduction / Recent works summary Introduction / Objectives

Transcription

1 /8/11 IMWA 1-9 September 1 Cape Breton, Nova Scotia Canada Outline Session : Passive treatment Passive treatment of high-iron acid mine drainage using sulphate reducing bacteria: comparison between eight biofilter mixtures Thomas Genty Chemical engineer from ENSCR Ph.D. student Materials and methods - Results and short discussion Genty, 9 Supervisor : Bruno Bussière Co-supervisors : Mostafa Benzaazoua, Gérald Zagury 1- Introduction / Acid mine drainage production neutral : FeS / O H O Fe SO H <, : catalyzed by bacteria FeS 1Fe 8H O 1Fe SO 1H For rich pyrite and pyrrhotite base metal mines, iron and sulfates concentrations ti are often high: h For examples in Québec : Lorraine : [Fe]=, [SO ]= 9 (Potvin, 9) Manitou: [Fe]=, [SO ]= 11 (Molson et al., 8) Genty, 1- Introduction / Recent works summary Recent works by our research group on high iron treatment showed : An anoxic limestone drain followed by a step of aeration and settling pond was not efficient to remove metals (Genty, ) Potvin (9) obtained similar results with a L dolomite reactor Potvin (9) and Neculita () showed that sulfate reducing biofilter could treat well with iron concentration of approximately and lower However, Neculita () observed that downflow biofilter columns could clogg mainly with iron precipitates. This phenomenom was not observed by Potvin (9) who used a horizontal flow in a L biofilter In these studies, SRB biofilters seemed to be the best option to treat. Material and methods Material and methods 1- Introduction / Sulfate reducing bacteria (SRB) biofilter 1- Introduction / Objectives Degradation of a carbon source and sulfates to produce hydrogen sulfide : CH CHOHCOOH SO HCO H S Precipitation of metals as metal sulfides : M H S MS H Other treatment phenomena can occur in biofilter (Neculita,, Karathanasis et al., 1, Sheoran et al., 1 ): Sorption, hydroxide and carbonate precipitation Important design parameters are : Hydraulic retention time HRT, carbon source SRB (Langumier et al., 9) The main objectives of this study are : Evaluate the capacity of SRB biofilter to treat high iron Optimize the biofilter carbon source mixture and the hydraulic retention time Evaluate biofilter clogging Evaluate the effect of iron concentration on the treatment efficiency Material and methods Material and methods 1

2 /8/11 Outline 8 Materials and Methods / synthetic production Materials and methods Concentrations mg/l Al 1 Cd, Cr 1 Fe (in ) Two were investigated : - : Fe = - light : Fe = 1 - Results and discussion Genty, 9 Fe (in light) 1 Mg 1 Mn 1 Ni Pb, SO 9 Zn, (Genty, 8) 9 Materials and Methods / Biofilter mixtures Mixtures summury: Cellulosic wastes, organic materials, compost, structural agent, inoculum, neutralizing agent, nutriments (more information in the proceedings) : sawdust (%), wood chips (1%), chicken manure (1%), compost (%), sand (%), river sediments (1%), calcium carbonate (%), urea (%) (Neculita, )., #, #, # : comparison between organic material sources # = without inoculum from sediment #8 = not boost by urea #, # = % % sand or calcite sand SRB present in compost, sediments, organic materials Mixture # (Genty, 1) 1 Materials and Methods / Batch tests Mixture characterization in batch conditions Nitrogen mixture ml / g 1 L erlenmeyer Genty, 8 Nitrogen sampling port Mesurements :, redox potential, metal concentrations, sulfates during days 11 Materials and Methods / Column tests 1 Outline Three mixtures were selected from batch tests 1 L columns Genty, 8 Materials and methods HRT : and days, upflow OUT - Results and discussion and light The saturated hydraulic conductivity was measured during the experiment to evaluate clogging IN Genty, 9

3 /8/ Results / Batch test results Results / Column tests / After 1 days, for most mixtures, increased up to. Eh decreased below mv for most mixtures and provided reducing conditions Metal concentrations reduced around 99% Mixture based on chicken, cattle, sheep manures or municipal wastes = similar results SRB inoculum coming from sediments was not essential Mixtures containing % of calcite or sand performed well Mixture not boosted by urea was less efficient Three mixtures selected to evaluate hydraulic properties in column test :, #, # Eh mv Fe mg/l # # # # # # #8 1 # # # # # # # # # # # # # #8 a 9 8 HRT days Iron : HRT days Iron : 1 HRT days Iron : 1 HRT days Iron : HRT days Iron : Neutralization at a of approximately whatever the column and conditions 1 1 Time (Days) # # light 1 - Results / Column tests / Eh 1 - Results / Column tests / Iron b d Eh mv 1 # # light % ir ron removal # # Time (Days) Decrease from mv to mv whatever the column and conditions Small removal when is treated (%) No difference with High removal when light is treated (8%) HRT or days 1 - Discussion / Column performances 18 Outline Al, Cd, Cr, Ni, Zn removal was up to 9%, Pb removal was between 8% and Mn removal varied between 1 and 8%. Sulfates removal was - %. No significant difference between each operational condition. Role of biofilter mixture : No signifiant change in terms of iron removal No signifiant change in terms of saturated hydraulic conductivity. Values stayed quite stable around 1 cm/s for and #, and.1 cm/s for #. SRB biofilter with upflow seemed not clogged (contrary to downflow columns of Neculita, ) Role of HRT No signifiant change for iron treatment efficiency for or days Role of iron concentration 8% when 1, 1-% when Materials and methods - Results and discussion Genty, 9

4 /8/11 19 Single bioreactor improved significantly water quality but did not treat high iron concentrated Multi-step treatment systems could be an available option : We are runing a L reactor (tested previously in columns): wood ash filter (for iron sorption) Next year : based on laboratory results, a field size passive treatment system for high iron concentration will be constructed SRB biofilter # (combination of SRB and ALD) SRB biofilter (polishing step). m m Wood ashes sampling port # Genty, 1 Genty, 1 Column performances Thank you for your attention Effluent decreased related to the high iron concentration of mg/l: Decrease of due to iron hydrolysis and precipitation in effluents, C1 C C, Sampling time, Fe H O Fe(OH) H Fe,O 1,H O FeOOH H 8 time h Genty, Biofilter mixtures Methodology Dry weight % # 1 # # # # # Mixture ## (Genty, # 81) Maple chips Maple sawdust 1 11 Chicken manure Catle manure 1 Sheep manure 1 Compost 1 1 sand 1 Sediment Urea Calcium carbonate Calcite sand Municipal sludges 1 Collect data on Collect data on availability of local carbon source, neutralizing agents Batch test : optimize queeklymsoffice1 Material reactive mixtures characterization Column test : optimize HRT Evaluate clogging If treatment is not efficient, combine with other treatments Medium size test Field test

5 Slide MSOffice1 Qu'est-ce que tu veux dire? "weekly", 1-9-1