WATER MANAGEMENT in FORMER URANIUM MINES. UMREG 2014 MEETING FREIBERG Philippe CROCHON AREVA Mines

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1 WATER MANAGEMENT in FORMER URANIUM MINES UMREG 2014 MEETING FREIBERG Philippe CROCHON AREVA Mines

2 Part 1 Quality of uranium mine water Water management in former U mines P. Crochon / UMREG - p.2 2

3 The three classical components of former mining sites Uranium production sites like other former mining sites present three major source terms for water contamination Flooded mine voids (open pit or underground) Waste rock piles Tailings (milling residues) disposals Each one of these source terms is a geochemical reactor with peculiar: Rock/mineral reactive matrix Water inflow Geochemical processes Hydrodynamic regime Mine discharge Waste rock Waste rock pile Rate of evolution Each source term contributes to the overall impact on the hydrogeological environment Underground or open pit mine effluent Ore Treatment plant Tailings concentrate Tailings repository effluent Water management in former U mines P. Crochon / UMREG - p.3

4 Underground mine and open pit discharge water quality (1/3) Characteristics of the mine void reactor: Reactive matrix Host rock and residual/marginal ore with generally reactive U +4 minerals and often sulfides Inflow: Meteoric water and host rock groundwater Hydrodynamic regime: Unsaturated during flooding Saturated (±) in post-mine conditions Constant (but site specific) water renewal Main geochemical process Dissolution of residual ore minerals écoulement flow puits well TMS rivière river Water management in former U mines P. Crochon / UMREG - p.4

5 Underground mine and open pit discharge water quality (2/3) The initial (post-flooding) water quality reflects: Oxidation of reactive phases in unsaturated conditions Sulfides Uranium oxides/silicates During operation AND post-mine flooding The resulting initial water quality is poor AIR ph, SO4, dissolved U and RN, Initial U concentration may vary from a few mg/l to x 10 mg/l Water management in former U mines P. Crochon / UMREG - p.5

6 Concentration en Zn (mg/l) Underground mine and open pit discharge water quality (3/3) Short-term evolution depends on water renewal Q (outflow) vs V (mine water volume) Stabilization is observed after about 8 renewals of mine water Duration may vary between a few months to a few years Temps (mois) Long-term quality of discharge depends on The oxygen content of water inflow and its ability to leach reactive minerals The process will go on for a very long time Meteoric/oxidizing vs deep/reducing groundwater inflow Water management in former U mines P. Crochon / UMREG - p.6

Evolution of waste rock piles and effluent quality (1/2) Characteristics of the waste rock reactor: Reactive matrix Host rock and residual/marginal ore Secondary (weathering minerals) Up to 200 ppm U

7 Evolution of waste rock piles and effluent quality (1/2) Characteristics of the waste rock reactor: Reactive matrix Host rock and residual/marginal ore Secondary (weathering minerals) Up to 200 ppm U Coarse material Water inflow: Essentially meteoric (seepage) water Hydrodynamic regime: Unsaturated flow Main geochemical process Acid mine drainage oxidative dissolution of sulfide minerals and subsequent U solubilisation Water management in former U mines P. Crochon / UMREG - p.7

8 Evolution of waste rock piles and effluent quality (2/2) Main characteristics of early effluents Very low ph (0.9 to 2) Very high sulfate (up to 15 g/l), Al, Fe and often base metals High dissolved U (up to 800 mg/l) But low dissolved Ra Strong seasonal variation of effluent quality Significant annual attenuation Duration influenced by Thickness of waste disposal Climatology (rainfall and T ) Presence of peculiar elements (fluorine, arsenic) Water management in former U mines P. Crochon / UMREG - p.8

Groundwater and minor meteoric water Hydrodynamic regime: Initial fluid expulsion Very low permeability Mainly peripheral leaching Main

9 Behavior of U tailings and effluent quality (1/3) Characteristics of the tailings reactor Reactive matrix Very fine grained material (milling) Residual gangue and ore minerals Secondary minerals (process specific) Water inflow: Initial interstitial process solution Groundwater and minor meteoric water Hydrodynamic regime: Initial fluid expulsion Very low permeability Mainly peripheral leaching Main geochemical process Internal re equilibration Slow leaching of soluble phases, including RN bearing phases Water management in former U mines P. Crochon / UMREG - p.9

10 Behavior of U tailings and effluent quality (2/3) Early evolution and re equilibration of interstitial water Strong attenuation (x ¼) of uranium, sulfate, and radium Return to anoxic conditions Timescale 5 to 10 years Early evolution of peripheral drain water Similar attenuation of contaminants Timescale 2 to 4 years Probably expulsion / rinsing of initial process water Water management in former U mines P. Crochon / UMREG - p.10

11 Behavior of U tailings and effluent quality (3/3) Internal part of tailings Internal part of tailings very close to geochemical equilibrium (interstitial water and solid phase) No sizeable evolution Periphery of tailings repository Under saturated dilute waters Oxidized in topmost horizons Peripheral leaching confirmed by flow modeling Long term evolution of tailings effluents Probably very slow (but strong noise ) Not well documented, especially for RN retention (current research) m 100 m Water management in former U mines P. Crochon / UMREG - p.11

12 Part 2 Water treatment Water management in former U mines P. Crochon / UMREG - p.12 12

Water treatement objectives Longwall mining Open

Run-off water Water treatment plant To limit the

suspended particles, U & Ra, acid ph, Fe River or

13 Water treatement objectives Longwall mining Open pit mining Waste rocks or tailings Mine water Run-off water Water treatment plant To limit the particulate & dissolved pollution caused by suspended particles, U & Ra, acid ph, Fe River or stream Water management in former U mines P. Crochon / UMREG - p.13

14 Regulation Quality of the collected water expected or modelized evolution Stopping of water treatment planified comparison French main regulations for water discharge limits for mining sites : U < 1.8 mg/l (22 Bq/l) Ra < 3.7; 0.74 or 0.37 Bq/l (100; 20 or 10 pg/l) 5.5 < ph < 8.5 if it exceeds 1 limit Water treatment plant (re)built or maintained Based on the technical costs/efficiency ratios of that time Mainly focused on radiological impact Water management in former U mines P. Crochon / UMREG - p.14

15 Water treatment processes at mine closure Useful process : Physico-chemical process New processes Active processes Ion exchange (implemented in Lodève in 1999) Biosorption Membrane technologies (ultra and nanofiltration, reverse osmosis ) Passive processes Trapping of U & Ra by iron oxides Limestone drains (implemented in Beaurepaire, Cérilly and Le Cellier) Artificial wetlands and other biosorption techniques Each process has advantages and drawbacks on economical, environmental and maintenance aspects Water management in former U mines P. Crochon / UMREG - p.15

16 Physico chemical process Most useful technique Barium -> Radium : Add of barium chloride (BaCl 2 ) (10 50 g/m3) with sulfates Ra 2+ + Ba 2+ + SO 4 2- RaBa(SO 4 ) 2 Aluminium sulfate + soda -> Uranium : Add of aluminium sulfate (Al 2 (SO 4 ) 3 ) or clairtan (FeClSO 4 at g/m 3 ) and ph adjustment with soda (NaOH) : part of U sol U insol Floculant for decantation Cleaning of settling ponds (sludge production) Settling pond Collecting pond & baffles Settling pond Tailings pond (pumping system if sewage) Drainage water Monitoring phmeter Treated release Bois Noirs water treatment plant Water management in former U mines P. Crochon / UMREG - p.16

(better settling) Use of neutralizant Augères water

17 Coagulation/flocculation Determination of better coagulant concentration Use of flocculant to increase flocs size (better settling) Use of neutralizant Augères water treatment plant Water management in former U mines P. Crochon / UMREG - p.17

out of particles Use of chemical reagents Monitoring Cost (energy, reagents, monitoring) Years Bellezane :

18 Advantages/drawbacks of physico chemical process Advantages : Good experience feedback Good performances for high grade waters Adapted to fluctuations of waters flows and grades Disposal of muds Drawbacks : Muds Salting out of particles Use of chemical reagents Monitoring Cost (energy, reagents, monitoring) Years Bellezane : Release levels / Treatment plant inlet levels Sludge production Water management in former U mines P. Crochon / UMREG - p.18

19 Ion exchange station de traitement des eaux Resins Uranium recovery and valorisation Water management in former U mines P. Crochon / UMREG - p.19 Lodève water treatment plant

Peristaltic pump Laboratory experiments Column filled with limestone rocks sampling

20 Limestone drains To treat aluminum : Al precipitates in the form of hydroxides In a passive way (without using energy nor reagents) through ph treatment Acid waters Peristaltic pump Laboratory experiments Column filled with limestone rocks sampling Beaurepaire water treatment plant Water management in former U mines P. Crochon / UMREG - p.20

21 Passive treatment Artificial wetlands and others biosorption technique (peat) Results Adsorption of 60% of U Adsorption of 40% of Ra Not for important flows Plugging problem Water management in former U mines P. Crochon / UMREG - p.21

22 Others processes Ion exchange resins : High grade waters, pretreatment (MeS, Fe), U valorisation but important investment, regular flows Biosorption (barks) : Cheap,no chemical reagents,regular flows,management of barks, no current use Reversis osmosis : Important investment, management of concentrate Precipitation on fluided bed (Metclean) : Non adapted for mining waters, not better efficiency Ultra/nanofiltration : Chemical treatment to avoid plugging of filters Water management in former U mines P. Crochon / UMREG - p.22

23 CONCLUSION Water management in former U mines P. Crochon / UMREG - p.23 23

24 Conclusion Long term management of mining waters is required Physico chemical process : Effective, proven,adaptable,muds Passive process : Limited performance New regulatory evolution for water discharge limits underway Chemical impacts, applying in the river (not at the discharge point anymore), U limit (0.3 µg/l) R&D Water management in former U mines P. Crochon / UMREG - p.24

25 Thank you for your attention! Questions? Water management in former U mines P. Crochon / UMREG - p.25

26 ANNEXES Water management in former U mines P. Crochon / UMREG - p.26 26

Source terms for contaminants in Uranium production legacy sites The ideal case Geochemical and hydraulic independency of source-terms Individual monitoring The real case Generally complex mine sites

27 Source terms for contaminants in Uranium production legacy sites The ideal case Geochemical and hydraulic independency of source-terms Individual monitoring The real case Generally complex mine sites with interaction of the different source terms (mixing and cross feeding) ruissellement Run-off MCO B TMS BD apports Direct meteoric météo water directs A difficulty to monitor individual source terms and for planning / evaluating remediation actions Complex modeling required for this purpose Encaissant granitique remblais MCO TMS arrosage Watering Q(MCO), C(MCO) R 570 Q(TMS), C(TMS) constants Water management in former U mines P. Crochon / UMREG - p.27

28 Trapping of U & Ra by iron oxides ph influence : ph = 6-7 : iron oxides positively charged Fe + U : mainly negatively loaded => attracted by positive loads (U - iron oxides) complexes created Ra in Ra 2+ form is not fixed UO 2 (OH) ph = 9-10 : iron oxides negatively charged Ra Ra : presented as Ra 2+ => attracted by negative loads - Fe - (Ra - iron oxides) complexes created The ph is not natural => addition of soda ash or an other chemical base is necessary : It is no more a passive treatment Water management in former U mines P. Crochon / UMREG - p.28

Chemical treatment of acid mine drainage. Anna Gulkova, Water and Environmental Engineering, Aalto University

Chemical treatment of acid mine drainage Anna Gulkova, Water and Environmental Engineering, Aalto University 1 Contents Acid mine drainage formation Problems associated with acid mine drainage Treatment