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By G. Upadhya

Of late, solidification modeling has progressed considerably to emerge as a viable simulation tool for the foundry engineer. A wide variety of tools exist in the commercial market to cater to the various needs of the design/ foundry engineer. In fact, recent developments in the area of solidification modeling have been so rapid that a comprehensive review of the state-of-the-art is very much needed. In this paper, an attempt is made to summarize the various issues of solidification modeling, at the same time addressing the historical evolution of the subject. The various phenomenological issues covered in this paper include: heat transfer, fluid flow during mold-filling, solidification kinetics and microstructural evolution, quick-analysis schemes for approximations, porosity prediction models, and the phenomena of fluid flow in the mushy zone. Modeling issues related to the development of solidification stresses which lead to defects such as hot tears and the development of artificial intelligence concepts in the area of rigging design are also discussed. Due emphasis is given to the various phenomena which add to the complexity of the whole subject, and the various alternatives available for solving a particular problem. For example, the heat transfer problem can be approached by the use of simple modulus schemes or by solving the conduction equation to obtain a more accurate temperature distribution. Similarly the microstructural evolution can be handled in a deterministic way by use of nucleation and growth models, or in a probabilistic way by use of empirical models. The main goal of this paper is to put the multi-faceted problem of solidification modeling in proper perspective so that it can serve as a guide for future developments in this area.

Jan 1, 1994

By Wander. L. Vasconcelos, Virgínia. S. T. Ciminelli, Angela. M. F. Guimarães

"The present work was aimed at synthesizing nanostructured hybrid materials derived from the functionalization of smectite clays with ligands containing thiol (-SH) groups for application in cadmium adsorption processes. An in nature Brazilian bentonite was investigated. The modification route was based on the grafting reaction between hydroxyl groups present on clay surface and the hydrolyzable alkoxy group of the (3-mercaptopropyl)trimethoxysilane in dry toluene under reflux. The present work showed that the proposed modification route was effective for the grafting of the thiol groups in the clay structure. The thiol-functionalized bentonite samples showed average binding capacities 160% higher with respect to Cd2+ to those obtained with the ungrafted material. These results support a mechanism of adsorption involving primarily ion complexation by the thiol groups (specific) instead of cation exchange (unspecific). The proposed modification processes are suggested for the preparation of novel adsorbent materials with controlled selectivity and specificity and therefore with good potential for separation and pre-concentration purposes.IntroductionMany efforts have recently been devoted to the design and preparation of inorganic-organic nanomaterials because of their potential application in novel functional materials. The intercalation of organic species within the spaces between interlayers of inorganic layered crystals provides nanostructures consisting of alternating layers of inorganic and organic compound. The intercalation reactions occur by insertion of mobile guest species (neutral, molecules, or ions) into the accessible crystallographic-defined vacant sites located between the layers (interlayer spacing) of the layered host structure [1}.Silane coupling agents, used widely for the modification of silica surfaces, have also been employed more recently for modification of layered silicates [2,3,4,5]. Modification with organosilane involves grafting reactions by establishing covalent bonds between the reactive groups of the layer, normally hydroxyl groups, and silane molecules. These reactions can be restricted to the external surface (the basal spacing remains unchanged) or to the interlayer surface, in which case an interlayer expansion occurs. The resulting material can be defined as a hybrid material or, more specifically, functionalized inorganic layered material [1]."

Jan 1, 2008

By Batric Pesic

The interactions of mineral-pyrite with T. ferrooxidans were studied by using a cyclic voltametry technique. The interactions with bacteria were carefully examined during the entire growth stage of bacteria (fermentation). Several very important discoveries were made. For example, the pyrite surface invariably drastically changed its properties at the second day of fermentation. Beyond two days of fermentation, the cyclic voltamograms were insensitive to convective diffusion produced by stirring. The SEM study revealed that bacteria populated the pyrite surface at an extremely high density levels. The high density of bacteria, and the solid reaction products formed on the pyrite surface created conditions for pore diffusion which explained why the CVs became insensitive to convective diffusion in solution (stirring).

Jan 1, 1990

By Yukio Ishikawa

Sumitomo Metal Mining Co,. Ltd. (SMM) has been producing 22,000 t/y of electrolytic nickel at Niihama by nickel matte electrorefining process since 1970. Although the matte electrorefining is an established process and the productivity has been greatly improved in the last 20 years, SMM has intensively developed the chloride process for the nickel production since 1970's. The nickel and cobalt refining process involving solvent extraction and electrowinning from the chloride solution has been successfully developed for the treatment of the mixed sulphide in 1975. The first application of chlorine leach to the anode slime has been succeeded since 1986. Based on those technology, the matte chlorine leach electrowinning process (MCLE) has been developed as an alternation to the relatively old technology of matte electrorefining. The new process offers significant cost down and excellent quality of the product. In 1986, the feasibility of MCLE was confirmed by the test work using the integlated pilot plant. The innovation of the chlorine leach process has been undertaken by this work. The new refining process can be divided into three stages including chlorine leach stage, purification stage and electrowinning stage. More than 99 % of nickel was extracted in atmospheric chlorine leach. Although copper ion was used for electron carrier in the chlorine leach, the excess copper from the feed matte is bled off from the leach circuit by de copperizing electrolysis. The copper ion of the pregnant solution is fixed on nickel matte by the cementation reaction. The nickel matte containing copper is processed in the chlorine leach. In the purification circuit, cobalt, iron and other impurities were removed from the nickel chloride solution. The nickel chloride solution is then fed into the electrowinning cell. Based on the process established, the new plant with a capacity of 330 t/M electrolytic nickel was commissioned in order to obtain the engineering data for design of the full scale plant in 1989. The performance of the plant was fully satisfied and the new process demonstrated the potential application of modern process control.

Jan 1, 1992

By A. H. Rhoades

The modern polarizing microscope with such accessories as cameras, infrared devices, reflectance and/or transmission photometers, indention hardness, and heating stage is used to characterize coal, coke, and other carbon forms. It allows characterization of coke by-products, such as tars and pitches and their insoluble residues. A useful product of the microscopic approach is the coal petrographic analysis which permits the prediction of coke strength carbonization pressure and volume change. Carbonization tests are expensive, time-consuming and require large amounts of coal. Tests on the coke show it to be strong or weak but give no indication of why. Petrographic analysis requires grams of coal and yields data that indicates why the coal produces coke of a given quality. Small samples from drill cores are sufficient for petrographic analysis. These data are also used to optimize blends for coke production. When coke-plant problems occur, ~he microscope can be used to check the coal blend proportions, as well as for weathered coal. Microscopy is useful in spore correlation work which may be a prerequisite to sound coal reserve estimates. Dispersed vitrinoid reflectance studies are used to determine the degree of organic metamorphism which serves to establish oil and gas deadlines. Tars and pitches are examined microscopically for the amount of normal solids as well as the size of undesirable carry-over solids resulting from pollution abatement practices in coke works. The microscope is also used to study coals for gasification and liquefaction.

Jan 1, 1981

By B. Willit, J. Martin

"Continued emphasis on water and energy conservation with less operator attention has created a need for more sophisticated cooling tower controls. A joint Betz/ASARCO project has produced a computerized water parameter controller and automated pumpless feed unit. Interfacing the unit via radio modem to the operator control room computer allows real time system status monitoring. Incorporating SPC principles to monitor and regulate all pertinent parameters yielded enhanced water control. This paper described the system design and present the results of a six month trial.BackgroundReducing operating costs and better manpower utilization are two of the largest concerns confronting maintenance managers today. At the ASARCO plant in Amarillo, a trial has been initiated to prove that it is possible to accomplish both of these objectives by using automated cooling tower control. The system is being adapted from a unit that was designed for continuously operating cooling towers in refineries and power plants by Betz Equipment Systems Division, a subsidiary of Betz Laboratories, Inc. The System l3000™ is designed to continually monitor conditions in the cooling system and to provide adjustments to the chemical balance for corrosion and deposition control. At Asarco, the unit was installed on the Rodline cooling system which operates on an intermittent basis.The primary justification for this project is to reduce costs of the five cooling systems in the plant. Current procedures require an operator to make visual checks every two hours on the five cooling towers as well as run lab tests on the water to insure proper treatment levels. This manpower can be better utilized by controlling the towers and collecting all the data available at one central location, in this case, the boiler house."

Jan 1, 1989

By R. G. Hilton

This paper deals with application of Super Detox? stabilization technology to the treatment of electric arc furnace dust (US-EPA listed hazardous waste KO61 ). The process has been used on approximately 170,000 tons of electric arc furnace dust. In addition to the nearly four years of commercial experience at Sterling, Illinois, the process is now being permitted for application at two other locations. The process was originally developed by the Bethlehem Steel Corporation and then further improved by Conversion Systems, Inc. (Bethlehem Steel's Licensee). The treatment process offers many unique bases for its selection, including: A) Low cost compared to the treatment alternatives; B) Lowest available TCLP leachate levels for any process treating K061. Many other processes leave some residue that represents a disposal requirement, although often not addressed; C) Produces minimized final waste disposed, including the fact that the total volume of dust generated and less than the volume occupied by the residue slag from HTMR; and, D) Opportunities for the beneficial utilization of part or all of the waste stream through the development of chemical and physical characteristics. Each of these aspects will be specifically discussed in the paper, including that status of the operations now under permit.

Jan 1, 1994

By Terry Mandziak

Typical leach mine operations recover gold values through the application of a dilute cyanide solution onto ore within an engineered facility. Key to the success of mining operations is the, containment and management of the cyanide solutions within the facility. Properly engineered' facilities will have containment systems that are both protective of the environment while enhancing solution recovery. This paper not only discusses general containment standards, but identifies state-of-the-art containment and monitoring practices;

Jan 1, 1998

By Larry M. Southwick

There is much ongoing work in research and development of new processes for the recovery and recycling of met.a.ls and other materials from various waste and scrap streams. Commercialization of such new technologies requires the bringing together and successful execution of a considerable effort involving a variety of activities. These include process conceptualization, research and development, detailed design and construction, and then plant startup and operation. Processes evolve through all of these steps by engineering due diligence, making objective and critical analyses of results, and troubleshooting processing steps to, hopefully, arrive at a sequence that has the best chance to succeed operationally and economically. After a summary review of the above steps, several processes will be described in more detail that provide mostly successful examples of the above procedures. Finally, some observations will be made on areas that will become critical in the near future to the success of new processes for wastes and residues.

Jan 1, 2000

By Kerri-Ann Hue, Kerry Hasapidis, Ken Babcock, Patrick O'Hagan

"Metallic nanoparticles exhibit properties that are significantly different from individual atoms or bulk materials. Their applications are diverse and have varying uses in areas such as cancer treatment, biochemical sensors, nanoelectronics, and drug delivery. For each application extensive characterization must be performed in order to probe the unique properties of these nanoparticles. In this study, ultra-high resolution mass sensors consisting of MEMs-fabricated, suspended microchannel resonators (SMRs) were used to determine the size and concentration of metallic nanoparticles. With femtogram (10- 15 g) mass resolution, ultra-high resolution mass sensors can weigh individual particles suspended in fluid, and so measure their mass, density, and size. Particle size analysis with these sensors provides excellent accuracy and resolution compared to mature technologies such as light scattering. This technique also provides quantitative information via the ability count particles.IntroductionThe unique electronic, chemical, and optical properties associated with nanoparticles vary with their size, shape, and composition[ 1-4]. These properties are attributed to increased surface area and nanosized mean free path of electrons to the particle surface. Nanoparticle colloidal solutions have been prepared and are commercially available. In recent years, noble metals such as gold, copper, and silver have been extensively researched[5-7]. In order to tailor the optical, electronic, and electrical properties of nanoparticles, size and shape must be controlled. For many applications a monodisperse colloidal solution is ideal. Methods of size characterization include Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), and Electrophoretic Mobility Measurements to name a few[6, 8]. Although TEM can provide shape and size distributions, sample preparation requires that samples be dried on a metal grid and cannot be analyzed in solution. DLS uses curve fitting algorithms that while useful for determining mean particle diameters are not ideal for polydisperse colloidal solutions. New technologies are therefore needed to accurately determine the particle size distributions of metallic nanoparticles."

Jan 1, 2011

By Blas Melissari, Stavros A. Argyropoulos

"In this paper a computational approach was employed to estimate the melting of solid spheres immersed in different liquid metals and under different convective conditions. The spheres are made from the same material as the liquid metal. The SIMPLER algorithm was implemented using a three-dimensional system in Cartesian co-ordinates. Experimental validation of the dimensionless correlation was carried out in two fluids with vastly different Prandtl numbers. The dimensionless heat transfer coefficient (Nusselt number) is obtained as a function. of the Reynolds and Prandtl number.IntroductionThere is a paucity of dimensionless convective heat transfer correlations applicable to fluids like liquid metals. The existing correlations cover single Prandtl number metals [l] or at most two different Prandtl number metals [2]. A knowledge of heat transfer rates from particles at high flux levels has become increasingly important to the design of energy transfer systems. Melting of solid particles has been studied extensively as it relates to many engineering and environmental applications, such as materials processing, space applications, water resource and energy conversion. When objects are immersed in a fluid with a temperature higher than their melting point, they melt and produce molten material that then mixes with the surrounding fluid. These objects experience not only size variation but also changes in their shape. This observation is more pronounced when the melting occurs in a forced convective flow.Yuge performed pioneering experimental work on the heat transfer from a sphere to air under mixed convection [3]. He suggested procedures for predicting the Nusselt number. Hieber et al [4] studied the spherical system analytically, but their study was limited to flow with small Reynolds numbers. Many researchers studied the melting dynamics of ice spheres in water at different convective regimes. Aziz et al [5] and Hao et al [6] performed measurements of the heat transfer coefficient in the water system by measuring the melting time of ice spheres in forced convection. Hao et al [7] performed visualization studies of ice spheres melting in water under mixed convection regime. All of this groundbreaking work, however, did not involve the use of liquid metals"

Jan 1, 2004

By Lin Yang, Minjun Tang, Shuishi Liu, Jianfeng Zhou, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"The dynamics of oolitic hematite magnetic roasting was studied. The results show that oolitic hematite magnetic roasting was controlled by the internal diffusion, and the diffusion coefficient was 9.018x10-7 m2·s-1when the oolitic hematite was roasted at 650°C. Magnetic susceptibility improves when temperature increases and roasted time prolonges under the condition of roasting at 650°Cfor 50min, with the magnetic susceptibility is 39.88%. CaF2 and Na2C03 can significantly improve the magnetic susceptibility at the same roasting condition, and the magnetic susceptibility was 63.35% and 57.99% respectively, thus the reduction of oolimic hematite was promoted.IntroductionWith the continual depletion of free-milling iron ores and its rising price, developing the abundant resources of oolitic hematite has become one of the main research areas. The oolitic hematite accounts for 10% of China's iron ore reserve, and it also accounts for 30% of red ore reserve in China [1]. In order to exploit the oolitic hematite, there are many beneficiation research methods, including fine grinding/selective flocculation/high intensity magnetic separation or flotation, high-gradient magnetic separation, low intensity magnetic separation/high intensity magnetic separation/reverse flotation, chloridizing roasting/acid pickling, magnetic roasting/leaching process etc [2]. However, the oolitic hematite is easy to slim and the valuable mineral is covered by the slim, because of the tiny granule of value mineral, then the ooides are formed due to the state of layer morphology formed by iron ore and ganaue minerals [3, 4]. Fairly good separation indexes were hard to be obtained by traditional separation due to its structural features, so the magnetic property of the iron minerals will be changed with the use of the magnetic roasting [5, 6], which result in hematite variably altered to magnetite and simplified technological process so that a good separation indexes will be obtained by using the low intensity magnetic separation. Therefore, in order to provide theoretical direction of how to use the oolitic hematite effectively through the magnetic roasting, the oolitic hematite of GuiZhou province was studied, which emphasized on researching the dynamics of oolitic hematite magnetic roasting."

Jan 1, 2013

By Chris Doyle

From 1997-2000. PT INCO undertook the Fourth Line Expansion Project (FLEX) to increase annual production rates from 90-100 to 150 Mlbs Ni/year (68,000 MT Ni/yr). In 2003, PT INCO nickel production underwent a major sustainable step jump that finally exceeded the targeted rate. This paper presents the changes that led to this achievement. The focus of mining changed. Improving Ni grade was important but only if electric furnace feed met target chemistry so that on-specification slag could be produced. The intensity of diamond core drilling for exploration was dramatically upgraded, mine planning strategy was totally re- vamped and an ore chemistry quality assurance team was formed. In the processing plant, measurement systems were upgraded for better control. Teamwork between sections vastly improved. The final step jump in production occurred when the fifth hydro-electric power generator was added to the furnace grid to allow the power-starved furnaces to cruise in operation at 70+ MW. Keywords: Free cash flow, Ore Chemistry, Measure, Control, Improve

Jan 1, 2004

By Muhammad Abid, Kh. .. S. Karimov

"In this study, design and investigation of biogas digester consisting of methane tank with built-in solar collector to utilize solar energy for the heating of the slurry prepared from the dung and heat exchanger is designed, developed and tested. The digester was laboratory type and consists of cylindrical metallic tank of size of 0.5 m in diameter; 1 m in height and 200 liters in volume. The surface of the digester from outside was covered by thermo insulated material a glass wool, except of south side (in northern hemisphere). This side played the role of built-in collector and was blackened to increase absorption of solar irradiation and covered under 45o by glass. In the blackened side of the digester on the different heights it was installed metallic pipes for the inlet and outlet of the air, connected with heat exchanger installed inside of the digester. The heat exchanger was fixed in the level above of the inlet pipe. The horizontal plane reflector concentrates solar beams to blackened side of the digester. In the winter period, it was found that the retention time of this digester is shorter on 15% and produced biogas volume is larger on 20% with respect of ordinary biogas digester. This digester is used for the demonstrative purposes and as a teaching aid presently and base on the results it may be used for the construction of large volume digesters for use in the farms, especially located in the remote and mountain areas where the climate in the winter period is cold. Introduction At present many experts around the world have focused their efforts to energy crises because energy is one of the most important factors for the development of the society. It is known that consuming energy is proportional to quality or standard of life. There is a close relationship between energy consumption and the Gross National Product (GNP). It is obvious that for further development of the country additional sources of energy is required, which are cheap, safe and environmentally compatible with respect to the action on possible wastes. Utilization of renewable energy is one route to help in solving the above mentioned problems. In particular, biogas as a source of renewable energy is produced by biotechnology and used wide on residential scale [1]. The biogas was produced for the very first time in 1814 by Deivy from organic wastes. In 1900 production of biogas was started in Bombay (India) [2, 3]. Biogas consists of 55-70% methane (CH4) and around of 27-44% carbon dioxide (CO2) and less than 1% H2 and H2S. At present biogas is used widely in some countries for lighting, machines, and vehicles, generators, cooking and heating. Biogas generation is suitable for small to large scale operation and at present is realized in a number of developed and developing countries as USA, Hungary, China, India etc. Since 1990s biogas projects construction in China has developed steadily by the end of 1998, there were altogether 6.88 million household biogas digesters [4]. In Russia biogas digesters are used for processing of hard dung into biogas [5]. Over the last few years the very first biogas digesters were constructed in Tajikistan as well [6,7] and it was found that the digesters can work with sufficiently high efficiency in mountain areas as well ."

Jan 1, 2008

By M. Drozd

Multi-use pad operators require an efficient and economic method to destroy cyanide in their process residues so new material can be stored on the pad and leached. Operators of the dedicated or single-use pads require an effective cyanide destruction method for pad closure. Cyanide destruction can be accomplished by utilizing oxidants such as hydrogen peroxide or calcium hypochlorite, or by utilizing ferrous sulfate which sequesters the cyanide in strong acid dissociable complex. Ferrous sulfate can be the preferred method of cyanide destruction because it is a less costly chemical, reaction rates are almost immediate and unlike oxidants, it can penetrate the total depth of a pile without being destroyed by side reactions. Literature indicates that the (Fe(CN)6)-4 com~lex is produced slowly but it appears that complexes such as Fe(CN)4(H20)2-or Fe(CN)4(OH)2)-4, are formed quickly and should have no U.V. sensitifity, unlike (Fe(CN)6)-4. Stoichiometry of the testwork indicates that Fe«CN)4(OH)2)-4 complex may be the species formed. The usage of ferrous sulfate has the advantage of being able to bring ~ level down that divalent metal ions such as Cu++, Cd++, Hg++, Pb++ and Zn will form insoluble complexes and precipitate from solutions does not destroy weak acid dissolvable complexes and can leave a heavy metal problem behind after cyanide destruction.

Jan 1, 1990

By J. C. Agarwal

Most metals are produced from minerals containing one or more of the desired metals, some contaminating metals, silicate, oxides, carbonates, and sulfides. Therefore, in the production of metals, there is generally a gaseous effluent in pyrometallurgical processes and a liquid effluent in hydrometallurgical processes. There are also solid residues such as waste ore, tailings, dust, and slag, created by the metal recovery processes. There are two important distinctions between the effluents and the residues: I. Effluents ? gases and liquids ? affect the neighboring environment for miles from the point of emission, while residues affect only the soil on which they are stored or dumped. 2. The environmental and economic effects of effluents are known and felt essentially immediately. By contrast, the environmental effects of the residues may not be known for a long time. For these reasons, the economic impact and the potential corrective actions required are very different for effluents and residues.

Jan 1, 1992

By K. Morsi, P. Mehra

"Spark plasma sintering has gained a considerable amount of attention over the past decade, due to its rapid sintering rates, and low temperature requirements, but has so far been usually limited to the production of simple geometries. The present paper examines the current-activated production of extended geometries through the process of spark plasma ""extrusion"". Of interest in the present study is exploratory research into the effect of electrical current activation on the reactive consolidation of powder systems to form intermetallic materials.IntroductionSpark Plasma Sintering (SPS) has been the subject of intense research over the past decade [ 1,2, 3,4,5,6]. The process boasts unique advantages which include ultra fast heating rates, shorter sintering times and lower sintering temperatures than needed in conventional sintering. The process is however limited to the generation of predominantly simple geometries. Recently one of the authors investigated the spark plasma extrusion of aluminum, where an aluminum powder compact is directly (Joule) heated through an applied DC electric current. Here extended geometries can be generated under the influence of electric current. A number of heating sources were identified including the heat source from current, i.e. Joule heating, frictional heating and heat from the deformation energy. However in the case of reactive powder systems, an extra ""one-time"" transient heating source can be supplied. By considering combustion synthesis of powders, this heating source is derived from the reaction between elemental powders to exothermically form a product at some ignition temperature [7]. This exothermic energy heats the compact to the maximum ""combustion temperature'', which could be hundreds of degrees higher than the ignition temperature. Hence a high temperature processing window (of short duration due to heat losses to the surroundings) becomes available in which the material is most suitable for stress-induced deformation and consolidation. For reactive spark plasma extrusion, two scenarios can be envisioned. The first is where the reactive powder compact is ignited through the application of current, and extruded within the high temperature processing window (also under the influence of current). The second scenario is to allow the heat of deformation/friction to heat the material during extrusion, to simultaneously force a reaction and consolidation. Here it is expected that the processing window will be very small if feasible."

Jan 1, 2011

By S. G. Kumar

The performance of nickel based high temperature materials is directly related to their microstructure, which is controlled by the various processing steps. Nickel base alloys are melted and refined by a variety of processes that include Vacuum Induction Melting (VIM), Vacuum Arc Remelting (VAR) and Electroslag Remelting (ESR). The limitation of VIM is that the metallrefractory reactions lead to the disintegration of the crucible and hence contamination of the product due to macrosegregation. This macrosegregation is alleviated to some extent by controlling the solidification in VAR. The main attraction of ESR is its ability to produce a clean product by controlling the deleterious inclusions. In recent years Electron Beam Melting (EBM) is emerging as an alternative to the VIM, VAR and ESR. This paper reviews the current status of these processes and outlines the scope for further improvements in the processing technology.

Jan 1, 1993

By Jewel A. G. Gomes

Lead has long been an USEPA priority pollutant and an important environmental and health concern because of its toxicity at ppb levels. In light of health and exposure data for lead, the EPA has set standards for Maximum Contaminant Level (MCL) and a MCL Goal (MCLG) as 15 ppb and 0 ppb, respectively. An accurate and rapid measurement of lead in the field remains a technical challenge. In this work, a relatively new method of deploying a nanoband electrode system using anodic stripping voltammetry has been optimized by changing deposition potential, electrolyte, and plating time used for the measurement of Pb(II) in water samples. Green rust has been proven to be an efficient intermediate matrix for removal of lead contaminants. We also report here the removal efficiency of lead using green rust produced by electrocoagulation, both directly and indirectly. Lead containing floc was also characterized through XRD, SEM, and EDAX techniques.

Jan 1, 2008

By James L. Whitlock

Biological treatment of mining and industrial effluents reached full scale commercialization around 1980. These proven, low cost, technologies have been limited in application due to a number of factors, including extended periods of time and cost required for pilot testing as compared to chemical treatment technologies, lack of biological expertise in metallurgical personnel, longer treatment periods in some cases, and performance failures based on improper application. Renewed interest in biological treatment technologies is being driven by permits with lower effluent concentration criteria, permits with bioassay evaluation, the need to remove thiocyanate, nitrates, sulfates and? other parameters. Chemical treatment processes, in general, have not been able to meet these present requirements, or require elaborate? combinations of processes, in terms of effluent quality and treatment economics. This paper addresses biologieal treatment of mining and industrial waste waters and selected recent advances in these technologies. The future looks very bright for application of these low capital and operating cost technologies,

Jan 1, 1998