Integrated waste and water management in mining and metallurgical industries

Available online at www sciencedirect.com●CIENCE doinmor.Transactions ofNonferrous Metals骂RSociety of ChinaScienceTrans. Nonferrous Met. Soc. China 18(2008) 1497-1505Presswww.csu.edu.cnu ysxb/Integrated waste and water management in mining andmetallurgical industriesB. K. C. CHAN', S. BOUZALAKOS', A. W. L. DUDENEY!1. Department of Earth Science and Engineering, Imperial College, London SW72AZ, UK;2. Centre for Innovation in Carbon Capture and Storage (CICCS), University of Notingham,Nottingham NG7 2RD, UKReceived 20 September 2008; accepted 5 November 2008Abstract: Extractive operations usually co-produce large quantities of unmarketable materials (mineral wastes), most of which areconventionally discarded to dumps (coarse material) and tailings ponds (fines). Escalating cost and regulation worldwide highlight anincreasing need for reduction and re-use of such wastes. The present paper introduces a new integrated waste management schemefor solids and water. The scheme was exemplified by novel treatment of synthetic waste and process water linked to thebiohydrometallurgical processing of metal sulphide flotation concentrates. Bioleaching of sulphide concentrate leads to two types ofsolid waste: a frrihydrite/gypsum precipitate from neutralisation of the bioleach liquor and un-leached gangue. The paper indicatesthat, depending upon the minor components involved, the solid phases in admixture might be usefully distributed among three typesof product: conventional underground backfill, cermented civil engineering backill (particularly controled low strength material orCLSM) and manufactured soil. It emphasizes CLSM containing simulated mineral waste, showing that such material can exhibit therequired characteristics of strength, porosity and perneability. When toxic components, e.g. arsenic from refractory gold ore, arepresent, encapsulation will be required. Process water is typically recycled as far as possible, although any excess should be treatedbefore re use or discharge. The paper also highlights treatment by reverse osmosis (one of the few methods able to generally removedissolved components), particularly showing that arsenic in oxidation state +6 can be readily removed for discharge (< 50X 10~As), although additional ion exchange is needed for potable water (<10X 10-12 As). .Key words: cementation; waste processing; bioleaching; tailings; refractory gold; arsenic; controlled low strength materials; reverseosmosisconventionally discarded, at significant cost, to1 Introductionengineered structures such as mineral dumps for coarsematerial and tailings dams for fine material. However,Extractive operations, i.e. exploration, mining,increasing emphasis is placed o re-utilisation, rathermineral and metallurgical processes, which are employedthan storage/disposal, of mine waste for the futureintermationally for the provision of primary andthrough innovative solutions and emerging technologiessecondary metal and mineral commodities, usuallydue to increasing cost of disposal and stringentco-produce large quantities of unmarketable orenvironmental regulation. Changes are slow， wituneconomic materials[1]. These wastes, which may be aconservative mine operators continuing to focus onmajor source of polution, include mining waste (topsoil,conventional 'good practice' guidelines. Nonetheless,overburden and waste rock)， processing wastenew opportunities for reduction and re-use of mineral(collectively referred to as tailings), and metallurgicalwaste are becoming possible. In particulat, combinationswaste (slag, flue dust, leach residues and precipitates)of mineral wastes with other bulk industrial products,[1- -2]. In accordance with the European Mine WasteDirective[3] and “best available technology' BAT,in civ中国煤化工typically 30%- -50% of these wastes are back-filed inYHC N M H Groach to integratedmining voids. The remainder of the materials iswaste managermemt in wnicn all significant products ofCorresponding author: B. K. C. CHAN; Te: +4-20-7594-7435; E-mail: bike. cam@inperitalacaul1498B.K.C.CHAN, et al/Trans. Nonferrous Met Soc. China 18(2008)metal production are linked and all are in principleemissions and losses of heat to the surroundings are notutilised. The approach is designed to generalconsidered in the figure. They are likely to be relativelyapplicability, but, of course, the details will differ greatlysmall for unit operations in waste management (evenfrom one process to another. In the present work, thethough upstream energy inputs and losses can be quiteapproach has been exemplified through bioleaching oflarge, e.g, in ore crushing and grinding) because mostsulphide flotation concentrates[4 -5]. As process waterrelevant processes occur in the condensed phase at orand waste solid were not available from operating plant,near ambient temperature. Gaseous emissions and energysynthetic analogues were studied.losscs associated with the production of sewage products,cement, coal fired power station ash, and related2 Theory and objectivesproducts may also be substantial.Aspects of the scheme are already common practiceFig.1 gives a scheme[6] from which the principlesin the industry, particularly mine backfill mentioned)f integrated waste management can be seen. Theabove, and surface restoration, perhaps as mine spoilscheme is meant to have general applicability, althoughamended with lime and sewage products to form athe details would obviously differ greatly in eachgrowing medium for plants. However, a far greaterapplication. The figure shows plausible inputs from avolume of solid is generally produced than can betypical mineral processing operation, proportions forapplied in these ways in the vicinity of a miningwater recycle and examples of the re-use of products,operation. Thus, backfill are limited by the increasedvariously destined for mine backfill, agricultural (orvolume of comminuted products and by inacessibility,restoration) soil and civil engineering construction.e.g., because of subsidence, while surface spreading andAccording to the scheme, the inputs of solids and watersoil amendment is limited by available area near a mine.are parially separated by dewatering and decantation toTo utilise a greater proportion of the solid, artificial soilfacilitate water recycle and/or discharge (someproducts containing mineral waste (which would be70%- -80% of the total water in the system) and totransportable to remote markets)， might also beincrease the solids content of waste to about 70%- -80%formulated with specially treated sewage products[7].by mass (40% -50% by volume). The resulting solids,However, this application remains in its infancy. Anothercontaining some 20%- 30% by mass of water, are mixedapproachwith selected products from other industries, asincorporating waste for the construction industry,exemplified by mineral matter (cement, cement kiln dust,particularly for applications in building and perimeterlime metallurgical slag, wastc gypsum, power station ashfoundations requiring low loading capacity, within, say, aand/or incinerator ash) for engincering products and10 mile radius of a mining operation. Thus, so-calledorganics (various formulations of sewage sludge, e.g..controlled low strength materials(CLSM)， containinganaerobically digested sludge with green waste) for soils.sand, cement and pulverised fucl ash, have beenContaminated soil and subsoil from former industrialdeveloped in recent years in civil engineering, but not sosites might also be of interest. Representativefar for dealing with mineral process waste. One objectivecompositions are given in the scheme for formulatedof the present work was to test rclevant characteristics,soils, and cemented products一viscous pastefll forparticularlycompressive strength, porosity andstabilising voids and 'flowable' controlled low strengthpermeability, of CLSM containing such waste.materials for groundworkconstruction.GaseousMetal extraction from mineral process concentrates,Other industry surplus,| Mineral tailings:Agricultural or35% solids,e.g, sewage sludgereclamation soils65% watere.g, 20% organicsDewaterWater for recycle and/ordischarge (70%-80%)Other industry suplus,e.g.. cement, slag and/oPastefll: e.g. 5% cement, 10% pfa, 68%power station fly ashtailings/waste soilds, 17% water, for void backfill andunderground mining structural suooort中国煤化工Controlled low strength materials: e.g.. 2% cement, 10% rTYHCNMHG78% tailings solids, 10% water forflat surfaces in construction foundationsFig.1 Scheme of integrated waste managementB.K.C.CHAN, et alTrans. Nonferrous Met. Soc. China 18(2008)1499e.g., metalliferous sulphide flotation concentrates, shouldrecycle and 'makce-up'， with or without integralbe especially suited to the application of IWM. Thus,purification linked to amenity use or discharge. Waterupstream processes of comminution and concentrationmake-up is relevant for a process with a negative waterproduce particle sizes suitable for flowable cementedbalance, e.g, less water from sedimentation andproducts (or soils), together with considerably reducedrecycling than needed in the process. Discharge orbulk in comparison with the original ore. However, theamenity use are options when the balance is positiveprocess water and solid waste produced are likely to be(more available than required for recycling to thecomplex and may contain sigmificant concentrations ofprocess). Water purification may then be appropriate.toxic elements, e.g., As. Safe management is necessary,Chemical precipitation, filtration and reverse osmosis areincluding effective removal of deleterious contamninants,examples of unit opcrations used in such purification.when necessary， from process water together withLong-established practice is thus employed througheffective immobilisation or contanment of them in thedewatering and recycling water within the process, as farsolid cemented products. A second objective wasas feasible. A traditional dewatering route is by gravitytherefore to investigate purification of process water bysettlement and decantation using a tailings pond,reverse osmosis (one of the few techniques able toalthough mechanical centrifuging and/or filtration mightremove dissolved species) and to test the stability ofbe employed. Water balance and pulp density (proportionsolid products against leaching under environmentalof solid to water) vary substantially from one mineralconditions.process, and from one part of a process, to another.Fig.2 gives a generalised flowsheet of basicHowever, the water contents and settled densities arerelationshipsbetween directbioleaching, waterelatively steady in tailings ponds. The water content inmanagement and waste treatment in proposed options[6]settled solids, although much lower than in pulp, is stillfor the production of base metals (especially copperlikely to be substantial and may be in excess of thatand/or nickel) and gold from sulphide flotationneeded in integrated waste management. Further waterconcentrates. The figure indicates the options for waterremoval is thus indicated (Fig.2).purification and integrated waste management. FoThe figure also shows the formation of two mainclarity, it excludes details of inputs, e.g-, the compositiontypes of solid residue: a ferrihydrite/gypsum-richof the bioleach pulp, configurations of unit operationsprecipitate ftom limestone neutralisation of barrennd the compositions of outputs. The general termbioleach liquor and a mineral-rich residue from‘extraction' is used to represent the configurations ofbiolcaching. Both might be modified by different metalparticular processes, e.g., selective precipitation (Ni),extraction procedures (mainly solvent extraction/solvent extraction/electrowinning (Cu) and cyanidationelectrowinning for copper, carbonate or hydroxide(Au). The products (designated CuNi and Au) areprecipitationor nickel and cyanidation/carbonvariable depending upon details of process design.absorption for gold,). The waste solids would ideally bePossibilities are refined copper cathode, precipitatedtreated together with imported local materials (othernickel hydroxide and impure gold (the Ni and Auindustry waste) to yield a marketable bulk product. Theproducts to be refined at a smelter).flowsheet shows the link to IWM, apparently as anRegarding water management, the flowsheet showsessentialy a 'pipe end' procedure. However, the variousalternative possibilities of total water recycle or partialbioleach and waste management processes are likely toMake-upAmenity/waterdischargeRecycle| ProcessSulphideBioleach I Leachate Nurasation Pulp SelememconcentratepH2-3_pH6-7 IHiExtractini-+ Cu/NiSettled Watersolid |中国煤化工Extraction;MYHCNMH GDUIKAiindustryproductFIg.2 Ceneralised flowsheet of metals bioleach, water management and waste treatnea processesB.K C.CHAN, et a/Trans. Nonferrous Met. Soc. China 18(2008)be mutually interactive to a greater or lesser extent andhazardous components). Silica sand(SS) was used as thetherefore subject to optimisation to achieve the bestbulk mineral material in the CLSM formulations. Aoverall technical and economic outcome.commercially available cement(PC), PFA and Lime(L)For instance, settlement conditions are designed towere used as binder.take account of particle sizc efects: bioleaching beneftsA conventional mix, 5PC-FA, was initially mixedfrom fine particle sizes (through fine grinding) whilewith a mechanical stirrer, deionised water was addedseparation of solid from water (hrough gravitygradually until the mix gave a spread diameter of (229+sedimentation) is more efficient with larger particles,10) mm. Further mixing was carried out until the mixwith consequent effects on water content going throughhad a uniform consistency and appearance and gives ato waste treatment. Mineralogy is also an importantcompressive strength within the excavatable andconsideration: some minerals, e.g. silica sand and manywalkable limits of 2 and 0.4 MPa respectively. 0MWaluminosilicates, form individual free settling particles,and JR were introduced into the formulation of 5PC-FAwhile fincr-sized hydrous oxides, like ferrihydrite, mayby substituting fixed proportions of ss with waste. Tablesediment very slowly. Sedimentation may be further1 lists the formulation for CLSM mix design.retarded by solids forming colloid or gel structures inThe mix was poured into cylindrical moulds ofwater, e.g., montmorillonite and other smectite phases.appropriate dimensions, depending upon the type of testSuch variables can be optimised using material balancesto be performed. Due to the flowable nature of CLSM,for different operating conditions, once detailedno compaction or vibration was necessary during casting.site-related feasibility studies have been carried out.Specimens were allowed to harden for about 3 d beforemechanically de-moulding. Following de-moulding,3 Experimentalspecimens were cured in scaled plastic bags at roomtemperature until required for testing ater 7, 14 and 28 d3.1 Controlled low strength materialsof curing.CLSM were characterised by very high worbability,The aim of this work was to investigate thelow density, and strength[8- 10], having a flowable andlaboratory-scaled CLSM specimens made from thsel-lelling consistency[11-13]. They are typically aabove materials for physical (hydraulic conductivity &blend of portland cement (PC), pulverised fuel ash (PFA),porosity), mechanical (unconfined compressive strength),fine/coarse aggregates and water; that upon hydration ofand leaching properties (ICP-AES) of the wastethe cementitious and pozzolanic material produces amaterials.solidified geotechnical composite suitable for fillmechanical characterisation,triplicateapplications[9]. A minimum compressive strength ofcylindrical CLSM specimens for each mix design were0.44 MPa (walkability limit) should be achieved in ordersubjected to unconfined compressive strength (UCS)to be excavatable by mechanical equipment[14] andtesting after different curing periods. For physicalmaximum design strength of 2 MPa (excavatable limit)characterisation, Porosity was evaluated using a heliumafter 28 d of curing should also be obtained to providepycnometer according to BS ISO 11599 (1997) [15].sufficient support for construction and vehicle loads.Hydraulic conductivity (K) was determined using aThe model wastes chosen to represent thehigh-pressure permeameter, particularly suitable forneutralisation precipitates were an ochreous mine watercement-based materials[16]. Prior to testing, porositywaste(OMW-fine -grained,Fe- andCa-richspecimens were dried in an oven at 40 C in order toneutralisation precipitates from bioleaching withavoid, as much as possible, interal cracking andrelatively low levels of hazardous components) and anshrinkage. Hydraulic conduetivity specimens wereindustrial jarosite residue (JR- with higher levels ofvacuum saturated in dc-ionised water for 4 h. For leachingTable 1 Material formulation for CLSM mix designDry solids%Ratio of waterMixCFAssOMWJRL10 solidSPC-FA-0.205PC-FA-OMW51570100.30SPC-FA-JR中国煤化工0.2510PC-FA-JR0MHCNMHGl0L-FA-JR65U0.435PC-FA-L-JR0.41B. K.C.CHAN, et al/Trans. Nonferrous Met. Soc. China 18(2008)1501characterisation, specimens were assessed using theincludes units for reverse osmosis (TFM-100 withDutch difusion leach test, commonly known as the 'tankspiral-wound polyamide thin film composite membrane),test',，in accordance to EA NEN 7375 (2005)[17].micro-filtration (Hytrex cardridge filter) and ioDuplicate monolithic cylindrical specimens, for each mixexchange (D340 mixed bed resin). The equipment wasdesign, cured for 28 d, were submerged into closeddesigned to facilitate continuous recirculation of ROpolyethylene beakers containing a leachant (de-ionisedreject via the stock tank using a Purite custom-builtwater with electrical conductivity of 61 μS/cm). Thepump system, and recovery of permeate for furtherdiffusion-leaching test was carried out for eighttreatment by ion exchange, as required. The pumpsuccessive steps of specified length: 0.25, 1, 2.25, 4, 9,typically generated 3 L/min flow at 0.4-0.6 MPa,16, 36 and 64 d. pH and electrical conductivity werecontrolled by a drain flow restrictor valve. Gypsummonitored for all eight periods. Eluates were preservedprecipitated in the reject was recovered by in-lineimmediately after filtration (0.45 um) and collection byfltrationat I or 5 μm.acidifying with HNO3 to pH . <2. Chemical elementalTest solutions were re-circulated in the equipmentanalysis by ICP-AES (Varian VISTA PRO) of the wasteas follows. Neutralised filtrate was pumped from thematerials and leach eluates, was undertaken at theholding tank to the microfiltration and RO units atNatural History Museum, London. Detailed descriptionpre-set pressure while membrane reject was returned tof specimen preparation, mixed formulation,the holding tank. The process was continued until thecharactcrisation and analytical techniques can be foundvolume remaining was too small (about2 Lafter3- 4 h).by BOUZALAKOS et al[4, 18].Permeate was collected in approximately 2 L volumesover 30 min intervals. Samples of reject (500 mL) were3.2 Purified watertaken at hourly intervals. When required, combinedThis second part of the paper deals with the qualitypermeate volumes (10- 14 L) were passed once-throughof liquid streams likely to arise from bioleaching ofthe ion exchange column for further purification.gold-bearing arsenical sulphide flotation concentrateMonitoring during these processes was carried out withwith purification of efMluent after lime neutralisation. Thehand-held probes for pH (WTW pH 330i) andrefractory gold flotation concentrates contain high levelsconductivity(WTW conductity 330i). Bothof arsenate, which is dissolved during bioleaching andinstruments gave temperature measurement. Sampleslargely co-precipitated with ferrihydrite and gypsum(approximately 1 L from each cycle) were retained forduring neutralisation of the leach liquors. The work isICP elemental analysis (ICP-AES and ICP-MS) forprimarily relevant to processes having a positive watercalcium, sulphur, arsenic and other elements arising frombalance, e.g. raw water to a setling pond, or where aimpurities in reagents. Precipitated gypsum waproportion of purified water is required for otherrecovered from the filter cartridge and holding tank.purposes on a site, e.g. washing solids. It considers ROResidues were removed by flushing the equipment withmanagement of residual concentrations remaining afterwater and/or a propriety purite anti-fouling solution. Thethe co-precipitation ( < <0.1 mg/L As) and combineddistribution of arsenic at low concentrations required byreverse osmosis and/or resin ion exchange (IX) treatmentpotable water and groundwater regulations wasunder designed conditions in a re-circulating systemdetermined by ICP-MS and ICP-AES.based on equipment provided by Purite Ltd.Detailed experimental procedure can be found by4 Results and discussionCHAN et al[5]. Fig.3 shows the equipment constructedemploying components provided by Purite Ltd. It4.1 Cementation of wasteFerric sulphate -limePermeate+ Clean中国煤化工. walerMixing tankHolding lankFYHCNMHGSkludgeRejeetFig_3 Equipment for reagent mixing, reverse osmnosis, micrfltration and ion exchange1502B.K.C.CHAN, et al/Trans. Nonferrous Met. Soc. China 18(2008)Fig.4 shows the typical variations of unconfinedFig.6. Concentrations of the heavy elements As, Cd, Co,compressive strength (UCS) in cemented mixtures withCu, Mn, Mo and Ni were below guideline values, evenspecimen age (7, 14 and 28 d). All exhibited increasingfrom specimens containing jarosite waste bhavingstrength with age, as expected for formulationselevated levels of these elements. Adsorption ontocontaining cementitious binders-Portland cement (PC),hydrated iron( II) oxide abundant in the specimensfly ash (FA) andJor lime (L)-in a matrix of silica sandaccounted for the low mobility of arsenate. The metals(SS). Specimens containing 5%, 15% and 80% PC, FAshould also be adsorbed, aided in most cases by lowand SS, respectively, gave UCS of 0.S-1.5 MPa,solubility at the high pH prevalent in lime and cement.satisfactorily within the limits 0.4- -2.0 MPa published forHowever, cationic Ba exceeded guidelines for allcivil engineering CLSM. Replacement of 10% of thespecimens (including the cement/fly ash control) and thesand with neutral ochreous waste resulted in similaramphoteric Cr, Pb and Zn gave excessive concentrationsstrength. However, replacement with acidic jarositefor some formulations, particularly with jarosite.waste resulted in mechanically weak composites havinga tendency to disrupt in water, even with 10% binder,3.0unless both cement and lime were used to neutralise the8 7d2.5B 14dacidity.8 28d2.01.52.0- Exevalable limi.1- 5PC-FA1.- 5PC-OMW- SPC-JR- 10PC-JRg 1.005PC-SL-JR5PC- 10PC- 10L-Walkable .FA OMW JR JRJR 5L-JR0.5上limit_Mix designsFig.S Hydraulic conductivity of CLSM formulations atdifferent curing periods15202530Curing period/dFrom the results, formulations without significantFlg4 UCS ofCLSM formulations at diferent curing periodsconcentrations of toxic elements from fly ash and/ormineral waste can provide credible CLSM. However, inThe porosity of specimens was in the range ofother cases, development of a suitable containment39%-44%, decreasing by about 6% over 7-28 d assystem will be required before cemented mixtures can becrystallization occurred within pores. This behaviour waspromoted for use in the environment. Although detailedtypical of CLSM. Hydraulic conductivity was (0.5- -3.0)research is still required, it is clear that two types ofX 100 m/s, similar to CLSM in analogous studics[13,19]containment can be described: particle and monolith.and in the range expected for granular flls. Examples areThus, particles can be coated with a clean lowshown in Fig.5. Hydraulic conductivity decreased withpermeability layer, such as magnesium carbonate, andaddition of waste ochre and jarosite because of theirlarge blocks of material can be contained within a lining,content of fine sized particles, which in-filled cavities inin a similar way to conventional landfill. The differencethe specimens. Thus, although permeability wasfrom such landfll is, of course, that the ground becormessubstantial in all cases, this was reduced with wasteimmediately stable for use in civil engineeringpresent (leading in principle to reduced loss ofapplications such as foundations for roads, car parks andcontaminants to the environment).low-rise buildings. Technical and regulatory hurdlesActual leachability was compared with groundwaterneed to be overcome.intervention levels for contaminated land[20]. A中国煤化工expected, leachate from specimens immersed in water4.2 wunder standard conditions was alkaline and contained:MYHCN M H G neutralisation osubstantial levels of calcium sulphate. Examples ofsynthetic liquor from bioleaching of gold-bearingcumulative concentrations of other species are given inpyrite/arsenopyrite concentrate gave 0.03-0.09 mg/L AsB.K.C.CHAN, et al/Trans. Nonferrous Met. Soc. China 18(2008)1503(a) 5PCFA0.16(b).一SPC-FA5PC-OMW1一5PC OMW5PC-5LJRs- 5PC-5L-JR.0-0.12 |.5导0.081.0-品0.5Intervention valueg 0.04(VROM 2000)10 20304050 60 7010 20304050 6070Leaching time/d5PC-FA(d)●- 5PC-FA.6-二- SPC-SL-JR二2.5|一SPC-5L-JR.2-2.01.5.8tIntervention value (VROM 2000)20.4旨0.5-102030405060701020304050 60 70Fig.6 Tank leaching test of CLSM formulations over 64 din filtered neutralised leachate-similar to, or in excess of,0.14guidelines for discharge. Reverse osmosis results◆一Permeate0.126●- Rejectinvolving arsenic at low concentration (Fig.7) in suchfiltrate show more or less constant arsenic in permeate0.10|(0.002- -0.003 mg/L As) from sucessive cycles while0.08 |concentrations steadily increased (0.03- 0.13 mg/L As) inthe diminishing volume of reject (separation factor about0.0612). Arsenic was in oxidation state +6, i.e., as arsenate.At the same time, concentrations of calcium and sulphate0.04-(not shown) remained low in permeate ( < 10 mgL)0.02while increasing to saturation (approximately 2.1 g/LCaSO42H2O) in the reject, with excess precipitated inInlet lst 2nd 3rd 4th 5th 6th 7th Leftmineral form. Very high initial concentrations of arsenicin jar(2.9 mg/L As) were reduced to <100 mgL As in oneCycleRO pass, with calcium and sulphate behaving as above.Fig7Concentration of arsenic in reject and permeate withHowever, when arsenic was in partially or fully reducedinitial arsenic concentration of 0.03 mg/Lstate, i.e, much less complete separation was achievedbecause of the neutral characteritics of arsenite. Fularsenic in. the reiect stream. can be recycled tooxidation was necessary.neuta中国煤化工s on precipiaingThus，arsenic levels were readily reduced toferrihyCNMHGtestream,wihthedischarge standards and the proportion of water going tofiltered ueuualscU ICalIalc aga1n leaching about 0.03discharge could be varied widely to suit the watermgL As. As there is currently no evidence thatbalance in a particular flowsheet (Fig.2). Conversely,moderately elevated arsenic levels adversely affect1504B.K.C.CHAN, et al/Trans. Nonferrous Met. Soc. China 18(2008)bioleaching, it may also be possible to employFramework Programme on the development andAs-enriched RO reject as make-up water ahead o1integration of innovative， environmentally frendly,bioleaching.biohydrometallurgical processes such as bioleaching forIn principle, the gypsum precipitate might bethe recovery of metals from primary and secondarymarketed for use in plasterboard. However, it precipitatesresources within Europe (ttp://biormine.brgm.fr). Wefrom the RO system in a lath-like crystalline habitalso wish to thank our various partners for theirunsuited for this purpose. Gypsum also co-precipitatescontributions Mintek, South Africa (John Neal) forwith about one third of the dissolved arsenic. Therefore,supplying data on bioleach liquor; Umicore, Belgium,it should join the solid waste stream, and may possiblyDRAX Power Station, UK and the Coal Authority, UKbe of benefit there for its cementitious properties. Thefor supplying the materials; staff at Purite Lrdremoval of gypsum from water may also help to meet(paricularly David Gray) for RO; Natural Historydischarge criteria, as discharge consents for sulphate canMuseum (Sarah James) for ICP-MS and Imperialbe as low as 0.4 g/L SO2- (0.7 g/L CaSO:2H2O) in EUCollege (Barry Coles for lCP-AES and Graham Nash forcountries.general technical assistance). Thanks also due to EmilyOther metals, not considered in detail here were alsoRiddiford, lrina Tarasova and Rosie Davy fogreatly reduced in permeate by RO, and were potentiallycontributions to experimental procedures.recyclable via the RO reject. Depending uponconcentrations, they may be recoverable (cfFig.2), or, asReferencesin the case of gypsum, simply prevent build-up ofcontaminants in discharged water.[1] LOTTERMOSER B G Mine wastes: Characterisation. treatment andenvironmental impacts [M]. Berlin Heidelberg, New York: Springer,2003.5 Conclusions[2] BRGM. Management of mining. qurying and ore poessing wastein the European Union (DB/CDI, 2001.1) The present work outlined a scheme of integrated[3] European Commission. Mining Waste: Management of Waste fromwaste management and exemplified a relativelythe Extractive Indusries [R]. Directive 200621/EC, 2006. 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Efte of water quality on he strength of flowablecontaminants being returmed to, and integrated with, thefll mixtures [阴. Cement & Concrete Composites, 2005, 27: 33- 39.main process flowsheet. Thus, conditions were outlined [10] DU L. FOLLIARD K I, TREJO D. Efc of cnstitucet matrilsto show how dissolved and precipitated contaminantsand qunties on water demand and compresvse stength ofcontolled low-strength material [小Joumal of Materials in Civilmight join the solid waste stream.Eninering, 2002, 14: 485- 495.[1] TAHA R AL-RAWAS A, AL-JABRI K, ALHARTHY A. HASSANAcknowledgementsH, AL-ORAIMI s. An overview of waste materials recyeling in theThis work was carried out in the frame of BioMine中国煤化工tion & Recyeling. 2004,(Biotechnologies for metal bearing materials in Europe)(European project contract NMP1-CT-500329-1). The[12]YHCNMHGrandcasCyashincntolled lowsrength material (CLSM) aplications [CWauthors acknowledge the financial support given to thisProeedings of Design and Application of Cortrlled Low-Strengthproject by the European Commission under the SixthMaterials (Flowablc Fil). Missoun; ASTM STP 1331, St Louis,B.K.C.CHAN, et al/Trans. Nonferrous Met. Soc. China 18(2008)15051998: 13-26.leaching: The tank test [R]. EA NEN 7375. UK: Environment13] ACI (American Concrete Insitute), Controlled low strengthAgency. 2005.materials (CLSM) []. Concrete Intemational, 1994, 16: 55-64.[18] BOUZALAKOS s, DUDENEY A w L, CHEESEMAN C R. CLSM[14] GABR M A. BOWDERS J1. Controlled lowstrength materal usingfly ash and AMD sludge [几Journal of Hazardous Materials, 2000,Proceedings of 2nd Intermational Conference on Advances in Mineral76(2/3): 251-263.Resources Managcment and Environmental Geotechnology15] BS Iso 1599. Determination of gas porosity and gas permeabliy(AMIREG). Greece: Hania, Crete, 2006: 293 -298.of hydraulic binders containing embedded rnadioactive waste [S] UK:[19] NAIK T R, SINGH s s, RAMME B W. Prfomance and leachingassessment of flowable slurry [0]. Jourmal of Environmental[16] GREEN K M, HOFF w D. CARTER M A, WILSON M A. HYATTJEngineering (ASCE), 2001, 127(4): 359 368.P. A high pressure permeaneter for the measurenent of liquid[20] The Ministry of Housing, Spatial Planning and Environroent,conductivity of porous constnuction matcrials [J- Revicw ofNetherlands. Intervention values and target values- soil qualityScienific Insruments, 1999. 70 (8);: 3397-3401.standards, Department of Soil Protection, the Haque, Netherlands,[17] Leaching characeistis of granular building and waste materals.1994.The determiaion of the availability of iorganic components for(Editedby u Xiang-qun)中国煤化工MYHCNMHG