The paper deals with different strategies that can be adopted for mitigation of pollution from metallurgical industries. It discusses various management aspects in connection with pollution mitigation especially the policy options for environment management. The technology options available have been discussed in details

Joshi, S R

Wate, S R

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PROCEEDINGS: NS-EWM1996e NML , JAMSI UEDPUR , pp.39-44Strategies for mitigation of pollution andenvironmental management in metallurgical industriesS.R.WATE AND S.R. JOSHIScientists . National Environmental Engineering Research Institute , Nagpur, IndiaABSTRACTThe paper deals with different strategies that can be adopted for mitigationof pollution from metallurgical industries. It discusses various managementaspects in connection with pollution mitigation especially the policy options forenvironment management. The technology options available have been discussed indetails.INTRODUCTIONEnvironmental problems in India can be classified into two broad catego-ries : Those arising as negative effects of the very process of development, andthose arising from conditions of poverty and under development. Major problemsin the area of environmental management encompass"' - (i6 High pollutionincrease and its impact on life support system which negate the positive impactsof the developmental programmes, (ii) Rapid growth in the population of domesticanimals over the past few decades accompanied by a loss of area under grasslandand pastures, (iii) Out of total area of about 329 million hectares, 175 millionhectares require special treatment to restore such lands for productive andprofitable usage, (iv) Land degradation is caused by water and wind erosionsalinity and alkalinity, (v) The annual rate of loss of the forest cover is 47,500 -hectares , (vi) Major rivers of the country are facing problems of pollution andsiltation, (vii) The quality of groundwater is being affected due to chemical andbiological pollution and due to the ingress of sea water in coastal areas, (viii) Alarge number of industries and other development projects are sited close toheavily populated urban centres leading to over congestion and over pollution asalso the diversion of population and ecologic resources from rural areas.Policy options for environment managementThe concept of sustainable development2" indicates that the correlationbetween population, poverty and pollution must be analysed against the backdropof ecosystem to provide supportive capacity for development and assimilative38S.R.WATE AND S.R. JOSHTcapacity for maintenance of acceptable quality of environment. Accordingly, theagenda that ensues for sustainable development is : (i) carrying capacity baseddevelopmental planning process, (ii) structural changes in economic sectors, (iii)preventive environmental policy, and (iv) environmental impact assessment. Whilethe first two of the above agenda would be applicable as planning process andsectorial planning, the later two are of more concern to any industrial/developmentalsector. In order to effectively restore the quality of environment, the direction ofenvironmental policy must be shifted towards anticipative and preventive strategieswhich focus on actions necessary to prevent potential environmental damage.Preventive environmental policy should essentially deal with the conditions thatgive rise to environmental problems and should readjust these to obviate environ-mental damage.The concept can be implemented by the prevention of all harmful emissions thatexceed the assimilative capacity of the ecosystem through greater and improvedrecycling, introduction of low/non emission technologies, and pre-emptive substi-tution of environmentally harmful raw materials and products; conservation of non-renewable resource base through its greater use. Efficient use of ecologicallysignificant resource is likely to have a number of positive environmental effects likedecreased resources consumption and reduced production cost; less expensivepreventive environmental protection measures vis-a-vis end-of pipe treatment;more effective environmental control due to use of integrated production technolo-gies vis-a-vis environmental media based technologies.Environmental impact assessmentEnvironmental impact assessment is potentially one of the most valuableinterdisciplinary and objective decision making tools with regard to alternativeroutes for development, process technologies and project sites facilitating internal-ization of environmental concerns. The most appropriate stage for implementingEIA is at the level of district planning since at this stage a reasonable number ofalternatives are available to the developer. Environmental assessment of regionalsupportive and assimilative capacities during formulation of development planscould greatly reduce the requirement for project level EIA.EIA should necessarily include the following steps : Collection of baseline data onall environmental components, identification of impacts with the help of processdetails using cause-condition effect relationship, prediction and evaluation ofimpacts, environmental management plan, disaster management plan and post-project monitoring to be pursued by implementing agency. Technological optionsfor minimization of waste load also need to be identified.39S.R.WATE AND S.R. JOSHITechnological options for Waste ManagementManagement of wastes necessarily should aim at : (i) Resource recovery, (ii)Waste stabilization, (iii) Controlled waste disposal methods based on assimilativecapacity.Resource RecoveryEnvironmental biotechnology refers to waste treatment with emphasis onresource recovery. The emergence and acceptance of the concept of sustainabledevelopment, however, warrants that the scope of environmental biotechnology beenlarged to address issues like environmental monitoring, restoration of environ-mental quality, resource/residue waste recovery/utilization/and substitution of non-renewable source base with renewable resource. Bioleaching of metal containingwastes is one of the options for recovery of resource.Alternatives for recovery and segregation of metalsThere are large number of separation processes applicable for recovery ofmetals from industrial waste (Table-1). Many of these processes have reacheda maturestate of development and are being practiced by many companies. There area numberTable-I : Separation AlternativesSoluble metalsSolid WastesAdsorptionCementationElectrowinningIon exchangeMembrane separationPrecipitationSolvent extractionBiological separationFloataLionMagnetic separationPyrometallurgySolvent partitionof processes that have potential application to secondary metal recovery that can beincorporated by waste generators as a component of their existing manufacturingprocesses. The technologies for separation have been broadly reviewed 131 for widespectrum of nonferrous metals with emphasis on hydro metallurgical processes espe-40SR.WATE AND S.R. JOSHIcially keeping in view the energy conservation during low temperature processing, thephysical character of waste streams and the economics. Consideration is also given topyrometallurgical and biological processes when relevant to the principal emphasis onhydrometallurgy. The primary concern is processing of metals in aqueous or non-aqueous solution or insoluble form as oxide/hydroxide/carbonate/sulphide sludges ordusts, and secondarily the processing of metallic scrap.The separation processes applicable to metals in aqueous , acid or alkalinesolution such as adsorption , cementation , electrowinning ion exchange , membraneprocesses, precipitation and solvent extraction have been reviewed by Brooks°.The separation processes applicable to solid wastes consist of biologicalseparation, flotation, magnetic separation, pyrometallurgy and solvent partition. Theprocesses delineated for liquid wastes can be applied to solids provided solubilizationof solid waste is carried out. Biological processes which are considered as cleaneroptions for metal recovery have been reviewed in greater details in this paper.Biological SeparationsBiological processes play an important role in the separation of metals. Onetype of process arises from the solubilization effect of organisms, (such as certainbacteria), on minerals and various solid wastes. The leaching of copper sulfide ores withThiobaeillus ferrooxidans has been used for some time as a commercial process forcopper recovery. There are a number of other biological systems, such as Sulfolobus,Pseudomonas, Spirogyra, Oscillatoria, Rhizoclonium, Chara, and Synechocus, thathave also received attention as offering promise for the extraction of metal (such as iron,cadmium, copper, chromium, mercury, nickel, manganese, lead, molybdenum, sele-nium, uranium, tin, cesium, radium and aluminum) from ores or solid wastes.Another type of separation process that has been considered is the accumulationby adsorption-ion exchange of metal cations in aqueous solution by algae such asChlorella pyrenoidosa, Spirulina and by fungi such as, Penicilium, and Cladosporium.Accumulation processes on organic substrates offer promise for removal of solublemetals from liquid wastes, and it has been known forsome time thatpassage of pollutedwaters through fresh and marine wet lands provides a significant amount of cleanup.One interesting example"] for purification of nuclear industry wastes is the useof an aerobic recovery ofPu, 2"Am,13''Cs, "Sr, 60Cu, U, Ru, Sr, Co, Cs, Ce, and Zrwith Bacillus subtilis with subsequent recovery of the metals by magnetic separation.In addition, the anaerobic action of Desulfovibrio in a sulfate-lactate culture collectscopper sulfate for subsequent magnetic separation. Another interesting biological41S.R.WATE AND S.R. JOSHIseparation process i nvolves precipitation of copper or other metals from leach solutionsor waste waters as sulfides with Desulfovibrio vulgaris, followed by oxidation of theresultant li2S with Chromatium vinosum bacteriumt5t.Practical success with the biological separation processes requires copingwith large volume reaction systems and patience needed for low-temperaturereaction kinetics. A summary of the various waste and mineral systems that havebeen examined , the types of metals involved, the identified organisms and anindication of whether or not the process is appropriate for leaching or accumulationseparations has been provided in Table 2.Table-2 : Metal Separations Using Biological AgentsWaste system Metal Biological agent Mode of metalactionOres Fe Thiobacillus ferro- LeachoxidansPolluted water Mo, Ra, Se, V Spirogyra , Oscillatoria AccumulateMetal finishing waste Cd, Cu, Pb Chlorella pyrenoidosa AccumulateSewage sludge Cd, Cu, Ni, Zn Chlorella pyrenoidosa LeachWastewater or leachate Cu Desutfavihrio vulgaris AccumulateNuclear wastewater "Am, Ce. Co Cs, Cu, Bacillus subtilis Accumulate2f2Pu, 134Cs, 5Sr, ZrMetal wastewater or Cu, U T.Ferrooxidans, T. Accumulateleachate thiooxidans, Lepto-spirillam fennooxidansMetal wastewater Cd,Cu,Ni,Pb2Zn Penicillium, Cladosporium AccumulateMetal wastewater Ag,AI,Cd,Cr,Co,Cu Chlorella pyreroidosa, AccumulateHg,Ni,Pb,Zn SpirulinaOres Ag,Cd,Cu,Pb,Zn T.ferrooxidans, Chlamy- Leachdomonas reinhardtiBioleaching of OresBioleaching of ores has been widely studied as:o Ores remain unutilized due to iron and other impuritieso Biotechnology presents an economic alternative where- high grade minerals are depleting- energy cost is increasing and- adverse environmental impacts are on the rise42S.R.WATE AND S.R. JOSHIo It is a cleaner technology that minimizes the adverse impacts on the naturalsystems and permits maximum utilization of natural resource for economicdevelopment.Bioleaching ProcessBioleaching is a process where specific micro -organisms are applied forremoval of metal from crude ore. This is effective for leaching of copper, iron,manganese, uranium from ores. The factor which influence bioleaching are :- availability of ores with high metal concentration- selection of proper microbial conditions- optimization of environmental conditions- proper design of a reactorLimitations :- Bioleaching is a slow process- Inorganic matter associated with ore is not used by microbes- microbial culture is usually not competitive- nutrition needs to be supported from outsideDisposal AlternativesA hierarchy of waste disposal priorities commonly accepted consists of thefollowing :o Waste volume reductiono Waste recyclingo Detoxification treatment- Physical- Chemical- Biologicalo Incinerationo Solidification -stabilizationo Landfillo Deep well injectionMetal recovery from waste effluent contributes to instrumentation of the firstthree of these categories.43S.R.WATE AND S.R. JOSHIDelineation of Strategy for ManagementA strategy that can be delineated for any metal processing or ore processingindustry should involve the following steps.Assessment of baseline environmental status and assimilative capacity ofenvironment in the region.Identification of likely impacts due to air emission, waste water discharges andsolid wastes on air, water and land components- Prediction of likely impacts and their quantitative evaluationMitigation of impacts through technological option reviewed with emphasis aspreventive policies rather than end of the pipe treatmentOptions for resource recovery should be given priority over waste treatmentDisposal techniques should be within the frame work of standards and as per thenorms set up by Pollution Control Boards and regulatory agencies.REFERENCESP] P. Khanna, Role of Biotechnology in Environmental Management . Key note address, Interna-tional Conference on Appropriate Waste Management Technologies for Developing CountriesNagpur, Feb. 25-26, 1995.(2] P. Khanna, Role of EIA in Sustainable Development, Proceedings of the Indo-British Workshop,Nagpur, Jan. 8-10, 1994, P-5.[31 C.S. Brookes, Metal Recovery from Industrial Wastes, Lewis Publisher, 1991, pp. 27-29..(41 J.H.P. Watson and D .C. Ellwood, " Bacteria and a magnet separate heavy metals fromsolutions F, Process technologie , 5(11), 21, 1989. 23-26.(5) K.Imai , "Utilization of Sulphate reducing and photolithodrophic bacteria in Biohydrometallurgy,Process Metall., 4 (Fundam. Appl. Biohydromctall.), 1986,383-394.44

Strategies for mitigation of pollution and environmental management in metallurgical industries

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Strategies for mitigation of pollution and environmental management in metallurgical industries

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