Patent Publication Number: US-10767242-B2

Title: Methods and systems for leaching a metal-bearing ore using a bio-augmentation process

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of and claims priority to U.S. patent application Ser. No. 14/427,535, entitled “METHODS AND SYSTEMS FOR LEACHING A METAL-BEARING ORE”, which was filed on Mar. 11, 2015. The &#39;535 application is a U.S. National Phase filing under 35 U.S.C. § 371 of PCT/US2013/058188, entitled “METHODS AND SYSTEMS FOR LEACHING A METAL-BEARING ORE FOR THE RECOVERY OF A METAL VALUE”, which was filed on Sep. 5, 2013. The &#39;188 application claims priority to U.S. Provisional Application Ser. No. 61/700,718, entitled “METHODS AND SYSTEMS FOR LEACHING A METAL-BEARING ORE FOR THE RECOVERY OF A METAL VALUE”, which was filed on Sep. 13, 2012. Each of the above are incorporated herein by reference in their entirety. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to methods and systems for recovering metal values from metal-bearing ores and, more specifically, to heap leaching methods and systems employing a bio-augmentation process. 
     BACKGROUND OF THE INVENTION 
     Heap leaching provides a low-cost method of extracting metal values from relatively low-grade metal-bearing materials, and has found particular application in the processing of metal-bearing ores. Generally, in traditional heap leaching operations, an ore is mined, crushed, and then transported to a heap location where it is stacked onto an impervious pad. A suitable acidic solution is dispensed onto the heap, and the resulting leach solution trickles slowly under the force of gravity to the pad, which typically has a sloped base to allow the solution to flow into collection drains for further processing, such as, for example, in a conventional, solvent extraction/electrowinning (SX/EW) process or a direct electrowinning (DEW) process. 
     Bio-stimulation, in general, provides a method to improve the efficiency of heap leaching operations. That is, the introduction of a suitable bacterial strain or other microorganism into the process, such as, during an agglomeration step or via a raffinate, may result in catalyzation of the oxidation reaction within the heap. Such bio-oxidation processes typically involve the use of a cultured strain of high-concentration bacteria. 
     Currently known bio-stimulation heap leaching processes are suboptimal in a number of respects. For example, notwithstanding advances in bio-oxidation and agglomeration techniques, these processes generally range from being time consuming to being cost-inefficient. 
     Accordingly, there is a need for methods and systems for bio-stimulation heap leaching that maintain the traditional cost-efficiency and simplicity of heap leaching processes while improving efficiency and metal recovery capabilities. In addition, there is a need for effective management of biological agents that are useful in heap leaching. 
     SUMMARY OF THE INVENTION 
     In accordance with various embodiments of the present invention, a bio-augmentation process is provided. In various embodiments, a method is provided comprising inoculating an agglomerated ore comprising a metal-bearing material with bacteria to form an augmented ore, forming at least a portion of a heap with the augmented ore, leaching the augmented ore in a heap leach to yield a metal-bearing solution, directing at least a portion of the metal-bearing solution to a growth area, adding a nutrient to the metal-bearing solution to yield a fortified metal-bearing solution, and directing at least a portion of the fortified metal-bearing solution to the agglomerated ore before the step of leaching. 
     In accordance with various embodiments, a method is provided inoculating an agglomerated ore comprising a metal-bearing material with bacteria to form an augmented ore, forming at least a portion of a heap with the augmented ore, leaching the augmented ore in a heap leach to yield a metal-bearing solution, directing at least a portion of the fortified metal-bearing solution to the agglomerated ore before the step of leaching, and adding, during the directing, a nutrient to the metal-bearing solution to yield a fortified metal-bearing solution. 
     In accordance with various embodiments, a method comprising incubating a bacterial colony in a bioreactor system, inoculating an agglomerated ore comprising a metal-bearing material with bacteria from the bacterial colony to form an augmented ore, forming at least a portion of a heap with the augmented ore, leaching the augmented ore in a heap leach to yield a metal-bearing solution, and directing at least a portion of the metal-bearing solution to the bioreactor system. 
     Further areas of applicability will become apparent from the detailed description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present invention, however, may best be obtained by referring to the detailed description when considered in connection with the drawing figures, wherein like numerals denote like elements and wherein: 
         FIG. 1  is a flow diagram illustrating a leaching process enhanced through bio-augmentation in accordance with various embodiments of the present invention; 
         FIG. 2  is a flow diagram illustrating a leaching process enhanced through bio-augmentation in accordance with various embodiments of the present invention; 
         FIG. 3  is a flow diagram illustrating a leaching process enhanced through bio-augmentation in accordance with various embodiments of the present invention; 
         FIG. 4  is a graph illustrating data of the recovery of copper in accordance with various embodiments of the present invention; 
         FIG. 5  is a flow diagram illustrating a metal recovery process in accordance with various embodiments of the present invention; 
         FIG. 6  is a flow diagram illustrating a metal recovery process including enhanced bacterial cultivation in accordance with various embodiments; 
         FIG. 7  is a flow diagram illustrating a metal recovery process including an additional bacterial cultivation enhancement in accordance with various embodiments; 
         FIG. 8  is a flow diagram illustrating a metal recovery process including an additional bacterial cultivation enhancement in accordance with various embodiments; 
         FIG. 9  is a flow diagram illustrating a metal recovery process including enhanced bacterial cultivation in accordance with various embodiments; and 
         FIG. 10  is a flow diagram illustrating a metal recovery process including enhanced bacterial cultivation and secondary heap leaching in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. The description of specific examples indicated in various embodiments of the present invention are intended for purposes of illustration only and are not intended to limit the scope of the invention disclosed herein. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features. 
     Furthermore, the detailed description of various embodiments herein makes reference to the accompanying drawing figures, which show various embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, steps or functions recited in descriptions any method, system, or process, may be executed in any order and are not limited to the order presented. Moreover, any of the step or functions thereof may be outsourced to or performed by one or more third parties. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component may include a singular embodiment. 
     The present invention generally relates to methods and systems for recovering metal values from metal-bearing ores and, more specifically, to heap leaching methods and systems employing bio-augmentation. Various embodiments of the present invention provide a process for recovering metals value through bacteria bio-augmented heap leaching, conditioning, and electrowinning. These improved methods and systems disclosed herein achieve an advancement in the art by providing metal value recovery methods and/or systems that enable significant enhancement in metal value yield as compared to conventional metal value recovery methods and systems. 
     In accordance with various embodiments of the present invention, bio-augmentation is provided where a metal-bearing material is mixed with certain substances to form an agglomerated ore. The agglomerated ore is then subjected to bio-augmentation prior to being formed into a heap or transported to an existing heap or leach stockpile system. In an aspect of the present invention, during transportation, between agglomeration and heap formation, an effluent solution generated in a bioreactor or from a heap leaching process is added to the agglomerated ore to produce a biologically augmented ore. The augmented ore is formed into a heap or layered upon an existing heap. Once the heap is formed or at the completion of any stage at which metal recovery may commence, an inoculant may be delivered to the heap. The innoculant may comprise a raffinate and/or nutrients. Finally, a metal value may be recovered from the solution generated by the heap leaching process by utilizing a direct electrowinning (DEW) process or a conventional, solvent extraction/electrowinning (SX/EW) process. 
     Examples of metal values include, but are not limited to, copper, nickel, zinc, silver, gold, germanium, lead, arsenic, antimony, chromium, molybdenum, rhenium, tungsten, iron, ruthenium, osmium, cobalt, rhodium, iridium, palladium, platinum, uranium, and/or rare earth metals. More preferably, the metal values can be copper, nickel, and/or zinc. Most preferably, the metal value is copper. 
     It has been discovered that a bacterial colony that has been exposed to a leaching environment (e.g., a heap leach) may lead to more effective leaching and metal recovery. Stated another way, while not intending to be bound or limited to any particular theory or methodology, the environmental conditions of a given leaching operations (e.g., temperature, pH, mineral composition, etc) may introduce selective pressure to a bacterial colony such that the composition of the bacterial colony shifts to include a greater percentage of a bacterial strains and/or bacterial substrains, or the like, that are best suited to the environmental conditions of a given leaching operation. 
     In this regard, a bacterial colony that has been exposed to a leaching environment may be fortified and/or further cultivated to improve leaching efficacy and efficiency. Accordingly, the selective pressure exerted on the bacterial colony by environmental conditions may be harnessed. 
     Referring now to  FIG. 1 , a bio-augmentation leaching process  200  is illustrated according to various embodiments of the present invention. In accordance with various aspects of the embodiments, a metal-bearing material  202  may be provided for processing from which copper and/or other metal values may be recovered. Metal-bearing material  202  may be an ore, a concentrate, a process residue, or any other material from which metal values may be recovered. Metal values, such as those described herein, may be recovered from metal-bearing material  202 . In an aspect of the present invention, metal-bearing material  202  comprises a refractory metal sulfide. 
     In accordance with various embodiments, the metal-bearing material  202  can comprise chalcocite, pyrite, chalcopyrite, arsenopyrite, bornite, covellite, carrollite, digenite, cobaltite, enargite, galena, greenockite, millerite, molybdentite, orpiment, pentlandite, pyrrhotite, sphalerite, stibnite, and/or any other suitable metal-bearing ore material. Preferably, the metal-bearing ore comprises primary or secondary sulfides such as chalcocite, bornite, pyrite, or chalcopyrite, or a blend of such mineral species. 
     Various aspects and embodiments of the present invention, however, prove especially advantageous in connection with the recovery of copper from copper sulfide ores, such as, for example, chalcopyrite (CuFeS 2 ), chalcocite (Cu 2 S), bornite (Cu 5 FeS 4 ), covellite (CuS), enargite (Cu 3 AsS 4 ), digenite (Cu 9 S 5 ) and mixtures thereof. Thus, metal-bearing material  202  may be a copper ore or concentrate, and preferably, is a copper sulfide ore or concentrate. 
     Metal-bearing material  202  may comprise ore in a number of states. Before an ore deposit is mined, the ore is said to be in an in-situ state. During mining, metal-bearing material  202  may progress through multiple states as it is harvested, collected, transported, and processed. For example, metal-bearing material  202  as harvested at the mining site is often referred to as run of mine (or “ROM”) ore. ROM ore is produced by, for example, blasting, open pit mining, and other surface and subterranean ore extraction techniques. As such, ROM ore includes ore of various sizes from ore as small as powder up to and including boulders. 
     In an aspect of the present invention, all or a portion of metal-bearing material  202  may be further processed via size classification and/or crushing to achieve a desired particle size distribution, such that, substantially all of the particles are of a size to allow effective agglomeration  210  of metal-bearing material  202  during agglomeration  210  and allow for optimal economic recovery of the contained metal values. 
     In accordance with various embodiments of the present invention, metal-bearing material  202  has a particle distribution of any combination of particle distributions. The particle distribution may have a combination of fine and coarse particles. Any particle distribution that maximizes bio-oxidation and metal recovery is useful. A preferred particle distribution allows oxygen and nutrients to permeate through heap  230  for a desirable environment for bacteria  302  growth and optimum bio-oxidation activity, while maximizing copper recovery. 
     In accordance with various embodiments, metal-bearing material  202  is subjected to agglomeration  210  which serves to combine metal-bearing material  202  with water  204  and acid  206  to form an agglomerated ore  208 . As will be appreciated by those skilled in the art, water  204  and acid  206  can be mixed into a solution prior to combination with metal-bearing material  202 . In an exemplary embodiment, raffinate provided from any other metal recovery process (not shown) may be used to form agglomerated ore  208  and as such, raffinate may comprise both water  204  and acid  206 . In an aspect of this exemplary embodiment, at least one of water  204  and acid  206  can be admixed with raffinate and combined with metal-bearing material  202  to form agglomerated ore  208 . In various embodiments, raffinate can be an aqueous product of a solvent extraction process, such as, for example, a SX/EW process. 
     In an aspect of the invention, agglomeration  210  involves metal-bearing material  202  being combined with water  204  and acid  206  in an agglomeration drum. An agglomeration drum may be any suitable agglomeration drum known in the art. In accordance with an exemplary embodiment, water  204  and acid  206  may be combined with the metal-bearing material  202  within the agglomeration drum. The quantity of the water  204  and the quantity and strength of the acid  206  vary with respect to the type of metal-bearing material  202  used. In this regard, raffinate may be mixed with at least one of water  204  and acid  206 , which may optimize the aqueous solution that is utilized during agglomeration  210 . It should be appreciated that in various embodiments, any combination of amounts of water  204 , acid  206 , and raffinate may be utilized. For example, in various embodiments, water  204 , acid  206 , and raffinate may not be used at all. Moreover, the combination of water  204 , acid  206 , and raffinate may change from time to time. Metal-bearing material  202  is mixed with the water  204  and acid  206  in the agglomeration drum to produce an agglomerated ore  208 . Agglomeration  210  may also include the blending of coarse portions and fine portions of metal-bearing material  202 , in order to maximize metal recovery while maintaining heap permeability. 
     In an aspect of the invention, agglomerated ore  208  can be transported to heap  230  via a conveyor belt. It should be understood that any suitable intermediate state would suffice for the transport of agglomerated ore  208  to heap  230 . While agglomerated ore  208  is transported to heap  230 , effluent solution  212  may be applied using any suitable application method including, but not limited to, irrigation lines, streams, sprayers, drip lines, misters, and the like. In an exemplary embodiment, effluent solution  212  may be applied onto agglomerated ore  208  on the conveyor belt via low pressure spray nozzles. A hood over the spray area may be utilized to contain the spray of effluent solution  212  under windy conditions. Bio-augmentation  220  can also be performed at or near the end of agglomeration  210 . In an aspect of the present invention, bio-augmentation  220  occurs at or near the end of the time agglomerated ore  208  is in an agglomeration drum or agglomeration apparatus. 
     Referring again to  FIG. 1  after agglomerated ore  208  has been prepared, it may be transported to a heap  230 . In accordance with the present invention in its various aspects, agglomerated ore  208  is subjected to bio-augmentation  220  prior to being stacked or formed into heap  230 . Bio-augmentation  220 , as used herein, refers to any process or method that provides bacteria or archaea or any other suitable microorganism to agglomerated ore  208 . Other suitable microorganisms suitable for use herein may include eukarya such as protists and/or fungi. For example, bio-augmentation  220 , can be any process or method that inoculates agglomerated ore  208  with at least one strain of bacteria or archaea. In accordance with exemplary embodiments, bio-augmentation  220  comprises augmenting agglomerated ore  208  with effluent solution  212  comprising bacteria to form augmented ore  214 . 
     In accordance with various embodiments of the present invention, any form of microorganism, including but not limited to bacteria or archaea, known or developed hereafter that is useful in leaching a metal may be used to form an effective biological culture to facilitate bio-augmentation  220 . The following bacteria and archaea are exemplary:
         Group A:  Acidithiobacillus ferrooxidans; Acidithiobacillus thiooxidans; Acidithiobacillus organoparus; Acidithiobacillus acidophilus; Acidithiobacillus caldus; Thiobauillus concretivorus; Ferrofefunis bagdadii;      Group B:  Leptospirillum ferriphilum, Leptospirillum ferrooxidans, Leptospirillum  sp.;   Group C:  Sulfobacillus thermosulfidooxidans; Sulfolobus  sp.;   Group D:  Sulfolobus acidicaldarius; Sulfolobus BC; Sulfolobus solfataricus ; and  Acidianus brierleyi  and the like.       

     These bacteria and archaea are generally available, for example, from American Type Culture Collection, or like culture collections, or are known in the art. 
     Alternatively, such bacteria and archaea may be obtained from a naturally occurring source and then cultured, or otherwise grown in any conventional, now known, or hereafter devised method. For example, in certain applications, naturally occurring biological strains may be used. In accordance with various embodiments, mixed bacterial strains occurring naturally in raffinate streams may be initially added to an aqueous solution and allowed to undergo a natural selection process. Such selection process may involve, among other things, the reaction environment. It has been found that such naturally occurring microorganisms may be particularly useful in connection with applications of the present invention in connection with mining activities. However, microorganisms such as the above mentioned bacterial and archeal strains may be selected by any technique now know or developed in the future. In accordance with an exemplary embodiment of the invention, at least one bacterial and/or archeal strain may be selected from the list provided above. 
     These microorganisms may be classified in terms of their temperature tolerances and optimized growth and activity ranges as follows: mesophiles, moderate thermophiles, and extreme thermophiles. Mesophilic bacteria generally thrive under moderate operating temperatures, for example, less about than 40° C.; moderate thermophiles are generally optimized for higher temperature conditions, for example, about 37° C. to about 60° C.; and, extreme thermophiles of the archaea class, generally thrive at higher temperatures, for example greater than about 55° C. Group A and B bacteria are generally considered mesophilic and are grow under conditions at or below about 40° C.; Group C bacteria are representative of the moderate thermophilic type and are preferably operated under conditions at or below about 60° C.; and, Group D archaea are representative of the extreme thermophile group and grow under conditions from about 60° C. to about 80° C. 
     Various mixtures of microorganisms from various groups can also be obtained. For example, various mixtures of mesophilic bacteria and moderately thermophilic bacteria may be mixed together to provide active bacteria variations in temperature of heap  230  during leaching. For example, if the temperature of the heap  230  varies between 35° C. and 45° C., such a mixture of bacteria would allow for leaching of a metal within the range of the temperature variation. 
     In accordance with an aspect of the present invention, a mixture of bacteria can be utilized under varying operating conditions of heap  230 . For example, mixtures of bacteria in groups A and B may be used. For example, if conditions of heap  230  include high ferric-ferrous iron ratios, bacteria group B may be better suited for leaching under such conditions. If ferric-ferrous iron rations are low, bacteria group A may be more efficient in leaching a metal value from heap  230 . Furthermore, if the pH of heap  230  fluctuates, a combination of bacteria in groups A and B may be effective in leaching. Since sulfide oxidation optimally takes place at a pH of less than about 2.5 and may be more efficient in a range from about 1.2 to about 2.0, only bacteria that can survive in such harsh environments may be utilized for leaching metal value from heap  230 . For example, when the pH moves closer to 2, bacteria in group B may be more efficient, as opposed to when the pH moves closer to 1.2, the bacteria of group A may be more efficient. Those skilled in the art will appreciate that any combination of bacteria listed herein as well as any bacteria known in the art or hereafter to follow, may be used individually or in combination for the most effective leaching based on static or varying conditions of heap  230 . As used herein, a bacterial colony may refer to a group of bacteria and/or archaea and may contain one or more strains of bacteria and/or archaea. 
     In accordance with an aspect of the present invention,  Acidithiobacillus caldus  bacteria can be utilized under operating conditions at or about 40° C. For example, a suitable biological environment has been prepared by collecting and culturing mine water containing such bacteria in a conventional manner using methods now known or hereafter developed. In accordance with various embodiments of the present invention, a biomass concentration on the order of from about 1×10 5  to about 1×10 9  cells per milliliter of bacteria is preferred but, as will be appreciated by those skilled in the art, other biomass concentrations may be utilized depending on the individual conditions of a process and/or the configuration of a system. Biomass concentration of individual species of bacteria, archaea, and eukarya may be on the order of from about 1×10 2  to about 1×10 9  cells per milliliter. 
     However, any micro-organism selection and growth processes now known or developed in the future may be used in accordance with the present invention. Moreover, the listings of bacteria and temperature-based classifications set forth herein are provided for illustration only, and are not in any way limiting of the bacteria that may be used in accordance with the present invention. Any biological mediated method that utilizes at least one microbial agents, microorganisms, bacteria, archaea, combinations thereof and the like, which are capable of at least partially oxidizing iron and/or reducing sulfur bearing materials, may be used in accordance with the methods herein described. Growth of micro-organisms may be improved by providing feed sources such as pyrite, sulfur, ferrous, and ore concentrate. 
     As will be discussed in further detail herein, it is desirable to establish a substantially self-sustaining bacteria population to facilitate bio-augmentation  220 . The sustainability of such a population may be promoted by adjusting various parameters of a reaction environment in a bioreactor  310 , including, for example, controlling temperature, oxygen availability, agitation, and nutrient addition. 
     As will be appreciated by those skilled in the art, bioreactors for culturing and/or maintaining a colony or population of active micro-organisms are well-known in the art. Any such bioreactor that may be useful to grow and maintain a population of active bacteria that will be useful in heap  230  may be used in accordance with the present invention. As used herein, a bioreactor is any device or system that supports growth and/or maintenance of micro-organisms such as active bacteria or archaea. A bioreactor typically includes inlets for nutrients, oxygen, carbon dioxide, an acid, and/or a base, of which flow rates can be controlled and, in some cases, monitored. Control of the bioreactor for temperature, pH, and dissolved oxygen content may be desired. In addition, a bioreactor is typically agitated and speeds and circulation rates will be closely monitored and controlled. Typically, bioreactors used in the industry are vessels which include sensors and control systems, such that the environment in which active bacteria are grown and/or maintained is tightly controlled for maximum yield of bacteria and minimal mutation thereof. Further, in various embodiments, a bioreactor may receive a portion of ore, water, or metal-bearing material  202 . The term “bioreactor system” may refer to a bioreactor and other related components, such as a heat exchanger and/or holding tank. 
     As will be appreciated, aeration connected to a bioreactor can provide both oxygen and circulation to the solution in the bioreactor. In general, oxygen delivery requirements are a function of, among other things, the oxygen requirements for optimized bacterial growth and activity as well as oxygen requirements for sulfur and/or iron oxidation reaction. The amount of oxygen dissolved in the solution may affect the kinetics of bacterially augmented leaching. For example, in general, the oxidation rate increases as dissolved oxygen increases, up to a value where mass transfer of oxygen is no longer rate determining. The exact value of this requirement is dependent upon many factors, including concentration of dissolved solids in solution, the bacteria population and activity, the temperature, agitation, and other such solution conditions. Elevation, vessel design, and the amount of dissolved oxygen also affects the active state of bacteria. For example, after reaching the active bio-oxidation stage of its life cycle, bacteria may lapse into dormant stage or die if oxygen concentrations fall below a critical value. Once such a dormant stage is reached, bacteria may be slow to recover once higher oxidation concentrations are subsequently restored. 
     Referring now to  FIG. 2 , in accordance with various embodiments, effluent solution  212  may be produced in bio-augmentation plant  300 . Bio-augmentation plant  300  comprises at least one bioreactor  310  and effluent holding tank  320 . Bioreactor  310  and effluent holding tank  320  comprise any suitable bioreactor or effluent holding tank known in the art or hereafter developed. Bioreactor  310  may comprise a source of bacteria  302 , a source of water  304 , a source of nutrients  306 , and a source of air  308 . Bioreactor  310  can further contain an agitator, which may be utilized to mix the ingredients within bioreactor  310 . Heat exchanger  330  may be coupled with bioreactor  310  to circulate hot liquid  312 , the purpose of which will be further discussed herein. Bioreactor  310  and heat exchanger  330  together comprise a bioreactor system. 
     Effluent solution  212  may be prepared by adding bacteria  302 , water  304 , and nutrients  306  into bioreactor  310 . Various strains of bacteria  302  as discussed herein may be useful depending upon the nature of the Metal-bearing material  202  and the conditions under which bio-oxidation occurs. Examples of bacteria  302  may include  thiobacillus, leptospirillum , and/or  sulfobacillus  sp. as discussed above. Various strains of bacteria or archaea or other appropriate microorganisms  302  may be suitable for catalyzing oxidation reactions, including various mesophiles, thermophiles, and/or the like as discussed above. In general, the kinetics of biological oxidation may be a function of any one or more conditions, such as, for example, but not limited to: ore mineralogy, solution chemistry temperature, pH, dissolved oxygen concentration, mass transfer, and/or metal-bearing material  202  particle size. 
     Though bio-oxidizing biological materials, including bacteria, archaea, or other suitable microorganisms, derive energy, in part, from the oxidation of sulfur or iron, additional nutrients  306  may aid in cell growth and oxidation functions. In various embodiments, nutrients  306  may comprise pyrite, elemental sulfur, ferrous iron, ammonium sulfate, potassium sulfate, ammonia, phosphate, potassium, and/or magnesium. Nutrients  306  may comprise or be derived from ore, such as a raw ore, conditioned ore, cleaned ore or ore concentrate. Nutrients  306  may be mixed prior to entry into bioreactor  310  or may be added individually into bioreactor  310 . Nutrients  306  may be mixed in any manner known in the art. Nutrients  306  provide material to enable population growth and/or energy generation for bacteria  302 . 
     However, other nutrient constituents and concentrations may be used, depending on the precise requirements and conditions of the desired system. For example, the nutrient constituents of ambient air, such as carbon dioxide, may also be used to enrich the reaction media. Other forms of enriched air may also be used in accordance with the present invention, including, for example, enriched carbon dioxide and/or enriched oxygen. Commercially available carbon dioxide, such as carbon dioxide that is distilled from ambient air, may be used as well. In embodiments where growth of archaea is desired, carbon dioxide supplementation may be especially advantageous. Moreover, in embodiments where growth of archaea is desired, the addition of various yeast strains may be advantageous as well to provide supplemental carbon dioxide. Various yeast strains produce carbon dioxide as a byproduct of metabolism, which may provide an in situ renewable source of carbon dioxide. However, enrichment of the reaction media may proceed by any other suitable method, now known or developed in the future. 
     Bio-oxidation rates are subject, in part, to the rate limiting conditions described herein, such as, for example, oxygen mass transfer and sulfur substrate availability. In addition, induction times for bio-oxidizing activity, growth cycles, biocide activities, bacteria variability, and the like, as well as economic considerations, all affect the rates and duration of bio-oxidation in accordance with various embodiments of the present invention. 
     Still referring to  FIG. 2 , in an exemplary embodiment, bacteria  302 , water  304 , and nutrients  306  may be mixed within bioreactor  310  by an agitator to form effluent solution  212 . Air source  308  provides compressed air to the bioreactor  310  to further agitate effluent solution  212  and provide bacteria  302  with oxygen to further enable the growth of bacteria  302 . 
     In an exemplary embodiment, hot liquid  312  may be introduced into the bioreactor utilizing heat exchanger  330  and a pump. The hot liquid  312  may be in any form that provides heat to bioreactor  310 . Hot liquid  312  is introduced into bioreactor  310  to encourage population growth of bacteria  302  contained therein. 
     Effluent solution  212  passes from bioreactor  310  to effluent holding tank  320 . Effluent holding tank  320  may comprise air source  314 , to further agitate effluent solution  212  and/or provide bacteria  302  in effluent solution  212  with oxygen. Effluent solution  212  is applied to agglomerated ore  208  to form augmented ore  214 . As discussed herein, in an aspect of the present invention, agglomerated ore  208  is transported to heap  230  via a conveyor belt and effluent solution  212  is applied to agglomerated ore  208  during transportation to form augmented ore  214 . Further, effluent solution  212  can be applied to agglomerated ore  208  in an irrigation solution utilizing low pressure spray nozzles to form augmented ore  214 . 
     In an exemplary embodiment, effluent solution  212  is at least one of an effluent from a bioreactor and a raffinate. In an aspect of this exemplary embodiment, effluent solution  212  is only a raffinate. 
     Referring now to  FIGS. 1 and 2 , in an exemplary embodiment, augmented ore  214  is formed into heap  230 . Although any means of heap construction may be used, conveyor belt stacking minimizes compaction of augmented ore  214  within heap  230 . Minimizing compaction in the stacking of heap  230  can allow oxygen and/or nutrients greater access to bacteria  302  throughout heap  230 , which allows uniform leaching of heap  230  and improves metal recovery from heap  230 . Other means of stacking such as end dumping with a dozer or top dumping can lead to regions of reduced fluid flow within heap  230  due to increased compaction and degradation of augmented ore  214 . 
     In various embodiments, augmented ore  214  may be placed on a lined leach pad or impermeable geologic formation via conveyor stacking, truck dumping, loader-assisted stacking, and/or a combination thereof. The height of heap  230  may range from about 5 meters to about 100 meters, depending upon various factors. In an aspect of the present invention, augmented ore  214  can be layered on top of an existing heap, a partially formed heap, a depleted heap, portions thereof, or combinations thereof. 
     In accordance with an exemplary embodiment, heap  230  may be further augmented via stream  216  after formation. In accordance with an exemplary embodiment, nutrients such as pyrite, ammonia, ammonium containing materials (such as ammonium sulphate and/or ammonium nitrate), and potassium phosphate may optionally be added to heap  230  via stream  216 . Further, in accordance with an exemplary embodiment, heap  230  may be further augmented by applying raffinate to heap  230  via stream  216 , as will be further discussed below. Stream  216  can be raffinate, raffinate and nutrients, raffinate and acid, or raffinate and bacteria or combinations thereof. Stream  216  can comprise a bacteria concentration significantly below that of effluent solution  212 . Accordingly in various embodiments, heap  230  yields metal-bearing solution  218 . 
     Now with reference to  FIG. 3 , a bio-augmentation leaching process  200  is illustrated according to various embodiments of the present invention. A portion of metal-bearing solution  218 , indicated as pregnant leach stream (“PLS”)  228 , can be directed to bio-augmentation  220 . PLS  228  contains at least a portion of bacteria  302 . Diverting a portion of metal-bearing solution  218 , such as PLS  228 , may be advantageous because conditioning  416  may comprise a process that kills bacteria or otherwise renders bacteria less effective. Moreover, use of PLS  228  in bio-augmentation  220  may be advantageous since it may contain a distribution of strains of bacteria  302  which are effective in leaching. As shown in  FIGS. 8 and 10 , PLS  228  may be processed to enhance bacteria  302 . 
     PLS  228  can be combined with effluent solution  212  or can be applied separately to agglomerated ore  208 . Furthermore, PLS  228  can provide a source of at least one of acid and water. In accordance with one aspect of the present invention, depending on the process and/or apparatus used in conditioning  416 , it may be advantageous to direct PLS  228  from conditioning  416  to bio-augmentation  220 . For example, overflow from a solid-liquid phase separation unit or similar apparatus employed in conditioning  416  may be directed to bio-augmentation  220  for use in further inoculating agglomerated ore  208  with bacteria  302 . Diverting PLS  228  to, for example, bio-augmentation, preserves the bacteria present in PLS  228 , which may otherwise be destroyed if subjected to conditioning  416 . 
     PLS  228  and effluent solution  212  may be applied to agglomerated ore  208 , individually or in any combination using any means described herein, known to those skilled in the art, or hereafter devised. For example, the combination of PLS  228  and effluent solution  212  may be applied to agglomerated ore  208  moving on a conveyor by use of irrigation employing, for example, sprayer nozzles above the conveyor. In another example, PLS  228  and effluent solution  212  may be applied to agglomerated ore  208  in series. In this regard, PLS  228  may be applied before effluent solution  212  is applied. The application of PLS  228  to agglomerated ore  208  on a first section of a conveyor adds a portion of bacteria and acid to begin bio-augmentation  220  and may increase the effectiveness of effluent solution  212  which is applied to agglomerated ore  208  on a second section of the conveyor. However, effluent solution  212  may be applied before PLS  228 . The application of effluent solution  212  to agglomerated ore  208  on a first section of a conveyor inoculates agglomerated ore  208  to begin bio-augmentation  220  and PLS  228  can be applied on a second section of the conveyor to ensure that effluent solution  212  does not evaporate during transportation to the heap  230 . 
     The Examples set forth herein are illustrative of conventional heap leaching techniques and various aspects of certain preferred embodiments of the present invention. The process conditions and parameters reflected therein are intended to exemplify various aspects of the invention, and are not intended to limit the scope of the claimed invention. 
     As discussed above, conventional heap leaching techniques are unsatisfactory in a number of ways. The first two examples listed below, Examples 1 and 2, contain test data from conventional heap leaching techniques. The second two examples listed below, Examples 3 and 4, contain test data from bio-augmentation heap leaching techniques of the present invention. 
     EXAMPLE 1 
     An example of a heap leaching technique employs the introduction of a suitable bacterial strain into the process, generally via a raffinate, during an agglomeration step. Specifically, a heap leach test was performed utilizing a raffinate in the agglomeration step and a raffinate in the irrigation solution. The results of such test indicated by reference numeral  1  in  FIG. 4 . 
     EXAMPLE 2 
     An example of a heap leaching technique employs the introduction of a suitable bacterial strain into the process, generally during an agglomeration step. Specifically, a heap leach test was performed utilizing raffinate at 0.50% bacteria in the agglomeration step and a raffinate in the irrigation solution. The results of such test indicated by reference numeral  2  in  FIG. 4 . 
     EXAMPLE 3 
     An example of a bio-augmentation heap leach employs the introduction of bacteria in the irrigation solution. Specifically, a heap leach test was performed utilizing raffinate in the agglomeration step and a raffinate at 0.01% bacteria in the irrigation solution. The irrigation solution of Example 3 was continuously applied. The results of such test indicated by reference numeral  3  in  FIG. 4 . 
     EXAMPLE 4 
     An example of a bio-augmentation heap leach employs the introduction of bacteria in the irrigation solution. Specifically, a heap leach test was performed utilizing raffinate and 5 kg/t acid in the agglomeration step and a raffinate at 1.00% bacteria in the irrigation solution. The irrigation solution of Example 4 was applied for 2 days. The results of such test indicated by reference numeral  4  in  FIG. 4 . 
     As illustrated in  FIG. 4 , the copper recovery is greater in Examples 3 and 4 employing exemplary embodiments of the present invention than in conventional heap leaching techniques described in Examples 1 and 2. 
     For ease of discussion, the description of various exemplary embodiments of the present invention herein generally focuses on the recovery of desired metal values from chalcopyrite-containing ore or concentrate; however, any suitable metal bearing material may be utilized. In accordance with an exemplary embodiment, metal values from the metal-bearing product stream are removed during an electrowinning step, either with or without a solution conditioning step such as solvent extraction or ion exchange, to yield a pure, cathode copper product or a copper powder product. 
     Referring now to  FIG. 5 , metal recovery process  400  may be any process for recovering copper and/or other metal values, and may include any number of preparatory or conditioning steps. For example, metal-bearing solution  218  may be prepared and conditioned for metal recovery through one or more chemical and/or physical processing steps. Metal-bearing solution  218  from bio-augmentation heap leaching process  200  may be conditioned to adjust the composition, component concentrations, solids content, volume, temperature, pressure, and/or other physical and/or chemical parameters to desired values and thus to form a suitable metal-bearing solution. Generally, a properly conditioned metal-bearing solution  218  will contain a relatively high concentration of soluble copper in, for example, an acid sulfate solution, and preferably will contain few impurities. In accordance with one aspect of an exemplary embodiment of the invention, however, impurities in the conditioned metal-bearing solution ultimately may be decreased through the use of a separate solvent/solution extraction stage, as discussed herein. Moreover, the conditions of metal-bearing solution  218  preferably are kept substantially constant to enhance the quality and uniformity of the copper product ultimately recovered. 
     Referring to  FIGS. 1-3 and 5 , in accordance with various aspects of the present invention, a metal-bearing material  202  is provided for processing in accordance with metal recovery process  400 . Metal-bearing material  202  may be an ore, a concentrate, or any other material from which metal values may be recovered, as discussed herein. Metal values such as, for example but not limited to, copper, gold, silver, platinum group metals, nickel, cobalt, molybdenum, rhenium, uranium, rare earth metals, and the like, may be recovered from metal-bearing material  202  in accordance with various embodiments of the present invention. Various aspects and embodiments of the present invention, however, prove especially advantageous in connection with the recovery of copper from copper sulfide concentrates and/or ores, such as, for example, chalcopyrite (CuFeS 2 ), chalcocite (Cu 2 S), bornite (Cu 5 FeS 4 ), covellite (CuS), enargite (Cu 3 AsS 4 ), digenite (Cu 9 S 5 ), and/or mixtures thereof. Thus, in various embodiments, metal-bearing material  202  is a copper ore or concentrate, and in an exemplary embodiment, metal-bearing material  202  is a copper sulfide ore or concentrate. 
     With reference to  FIG. 5 , metal recovery process  400  is illustrated according to various embodiments of the present invention. Metal recovery process  400  comprises leach process  200 , conditioning  416 , and metal-recovery  418 . In various embodiments, leach process  200  can be any method, process, or system as presented herein that enables a metal value to be leached from a metal-bearing material. 
     In accordance with various embodiment of the present invention, leach process  200  comprises a bio-augmentation heap leaching process. In accordance with an exemplary embodiment, the bio-augmentation heap leaching process can comprise providing an metal-bearing material  202  or ore, agglomerating the metal-bearing material  202  or ore, adding bacteria to the agglomerated ore  208  to form augmented ore  214 , forming heap  230  with augmented ore  214 , and may further include augmenting heap  230  to produce metal-bearing solution  218 , as discussed herein. 
     In various embodiments, leaching  200  provides metal bearing solution  218  for conditioning  416 . In various embodiments, conditioning  416  can be for example, but is not limited to, a solid liquid phase separation step, a pH adjustment step, a dilution step, a concentration step, a metal precipitation step, a filtration step, a settling step, a temperature adjustment step, a solution/solvent extraction step, an ion exchange step, a chemical adjustment step, a purification step, a precipitation step, and the like, as well as, combinations thereof. In an exemplary embodiment in which conditioning produces a solid product by, for example, selective precipitation, conditioning  416  can include a solid liquid phase separation step configured to yield metal rich solution  417  and a metal bearing solid. In various embodiments, such as, for example, when a precipitate is formed, the conditioning  416  may include a solid-liquid phase separation. In an exemplary embodiment, conditioning  416  includes a settling/filtration step. In various embodiments, conditioning  416  produces metal-rich solution  417 . 
     In various embodiments, metal-rich solution  417  may be subjected to metal recovery  418  to yield metal value  440 . In exemplary embodiments, metal recovery  418  can comprise electrowinning metal-rich solution  417  to yield recovered metal value  440  as a cathode. In one exemplary embodiment, metal recovery  418  may be configured to employ conventional electrowinning processes and include a solvent extraction step, an ion exchange step, an ion selective membrane, a solution recirculation step, and/or a concentration step. In one preferred embodiment, metal recovery  418  may be configured to subject metal-rich solution  417  to a solvent extraction step to yield a rich electrolyte solution, which may be subject to an electrowinning circuit to recover a desired metal value  440 . In another exemplary embodiment, metal recovery  418  may be configured to employ direct electrowinning processes without the use of a solvent extraction step, an ion exchange step, an ion selective membrane, a solution recirculation step, and/or a concentration step. In another preferred embodiment, metal recovery  418  may be configured to feed metal-rich solution  417  directly into an electrowinning circuit to recover a desired metal value  440 . In an especially preferred embodiment, metal value  440  is copper. 
     With further reference to  FIG. 5 , metal-rich solution  417  may be suitably treated in metal-recovery  418  to advantageously enable the recovery of a metal value  440 , such as, for example, a copper value. In one exemplary embodiment, metal-recovery  418  comprises direct electrowinning (DEW). In another exemplary embodiment, metal-recovery  418  comprises solvent extraction and electrowinning (SX/EW). In another exemplary embodiment, metal-recovery  418  is configured to produce a copper powder. 
     As discussed above, it has been found that the cultivation of a bacterial colony that has been exposed to a leaching operation tends to improve leaching and ultimately metal recovery. While not intending to be bound or limited to any particular theory or methodology, it is theorized that such methodologies enable the selective pressure of a leaching operation to be harnessed so that the most effective bacterial strains increase in concentration in a given media volume. The cultivation of a bacterial colony may include the supplementing (also referred to as fortifying) the bacterial colony with one or more nutrients. For example, a bacterial colony may be fortified with ammonia (and other nitrogen containing materials), phosphate, potassium, and magnesium. In various embodiments, these nutrient constituents may be introduced in any suitable media, including a Modified Kelly&#39;s Media (MKM), in the following concentrations comprising:
         (NH 4 ) 2 SO 4  (0.4 g/L+/−0.2 g/L)   K 2 HPO 4  (0.04 g/L+/−0.02 g/L)   MgSO 4  7H 2 O (0.4 g/L+/−0.2 g/L)       

     In various embodiments, nutrient constituents may be introduced in a RMKM matrix comprising a blend of 50 percent water and 50 percent raffinate plus ammonium sulphate and potassium phosphate. RMKM media may have a concentration of ammonium sulphate of about 0.01 g/L to about 0.08 g/L, and preferably a concentration of about 0.04 g/L. RMKM media may have a concentration of potassium phosphate of about 0.01 g/L to about 0.08 g/L, and preferably a concentration of about 0.04 g/L. 
     In various embodiments, ambient air may also be used to fortify the reaction media. 
     For example, carbon existing as carbon dioxide in ambient air may be utilized for energy conversion and cell growth. Preferably, carbon dioxide levels in ambient air delivered into solution will be approximately 7.5%. Enriched air containing different concentrations of carbon dioxide may also be used. Other forms of enriched air may also be used in accordance with the present invention, including, for example, enriched nitrogen and enriched oxygen air. However, enrichment of the media may proceed by any other suitable method, now known or developed in the future. 
     In various embodiments, a bacterial colony that has been exposed to a leaching operation may be fortified with nutrients and returned (e.g., recycled) into a bio-augmentation and/or heap leaching operation. In such embodiments, the bacterial colony is kept separate from the bioreactor system, which is discussed above and shown in an exemplary embodiment in  FIG. 2 . Accordingly, in such embodiments, the bacterial colony that has been exposed to a leaching operation is mixed with the bacterial colonies from the bioreactor system upon introduction into the bio-augmentation step. In various embodiments, as leaching time increases, less bacteria from the bioreactor may be needed and, in various embodiments, the bioreactor system may be deactivated from time to time or for extended periods of time. 
     With reference to  FIG. 6 , exemplary method  600  is illustrated. Exemplary method  600  illustrates many of the same features as in  FIG. 3  and such features are labeled in like manner. A portion of metal bearing solution  218  may be diverted to bio-augmentation  220  via fortified pregnant leach stream  628  (“fPLS  628 ”). fPLS  628  may be fortified using nutrients  650 . Nutrients  650  may comprise one or more nutrients described herein or hereinafter discovered to be useful in bacterial cultivation. For example, nutrients  650  may comprise ammonia (and other nitrogen containing materials), phosphate, potassium, magnesium air, and/or air enriched with carbon dioxide and/or nitrogen. Nutrients  650  may be added to fPLS  628  by any suitable manner. For example, nutrients  650  may be mixed with an aqueous solution and added to fPLS  628 . Addition in this matter may ensure that nutrients  650  are well blended into liquid media prior to introduction into fPLS  628 . Nutrients  650  may be bubbled through fPLS  628  in embodiments where nutrients  650  comprise gaseous nutrients. Nutrients  650  may be introduced as solid species into fPLS  628 . Nutrients  650  may foster the growth of bacteria in fPLS  628 . 
     With reference to  FIG. 9 , exemplary method  900  is illustrated. Exemplary method  900  illustrates many of the same features as in  FIG. 2  and such features are labeled in like manner. A portion of metal bearing solution  218  may be diverted via feed pregnant leach stream  902  (“feedPLS  902 ”). feedPLS  902  may be sent to a growth area, such as pond  904 . Pond  904  may comprise a pond, tank, vat, pool, or other growth area that is capable of retaining and holding feedPLS  902 . A growth area provides a place for a medium containing a bacterial colony, such as in feedPLS  902 , to grow, amplifying the number of bacteria in the bacterial colony. 
     The micro-organisms in the liquid media of pond  904  may be fortified by adding nutrients, such as the nutrients discussed above, which may be added via nutrient input  906 . The nutrients added via nutrient input  906  may comprise one or more nutrients described herein or hereinafter discovered to be useful in bacterial cultivation. For example, the nutrients added via nutrient input  906  may comprise ammonia (and other nitrogen containing materials), phosphate, potassium, magnesium air, and/or air enriched with carbon dioxide and/or nitrogen. The nutrients added via nutrient input  906  may be added to pond  904  by any suitable manner. For example, nutrients may be mixed with an aqueous solution and added to pond  904  through nutrient input  906 . Addition in this matter may ensure that the nutrients are well blended into liquid media prior to introduction into pond  904 . The nutrients added via nutrient input  906  may be bubbled into pond  904  in embodiments where nutrients comprise gaseous nutrients. Nutrients may be introduced as solid species into pond  904  via nutrient input  906 . Nutrients added via nutrient input  906  may foster the growth of micro-organisms in pond  904 . 
     The environmental conditions of pond  904  may be controlled to promote micro-organisms growth. For example, temperature may be controlled. Tarps, shades, or the like may be used to control exposure to direct sunlight. Pond  904  may be agitated using a mechanical agitating device. For example, a mechanical device may be used to stir the liquid contained in pond  904  or, in various embodiments, circulate the liquid contained in pond  904  in a bottom to top manner. 
     Bio-augmentation  220  may receive fortified liquid medium  908  from pond  904 . Fortified liquid medium  908  comprises micro-organisms from pond  904  that has been fortified with nutrients. Thus, fortified liquid medium  908  may contain a higher concentration of micro-organisms than feedPLS  902 . Moreover, fortified liquid medium  908  may comprise micro-organisms that are well suited for use in leaching due to the selective pressure exerted in heap  230 . 
     With reference to  FIG. 10 , exemplary method  1000  is illustrated. Exemplary method  1000  illustrates many of the same features as in  FIG. 9  and such features are labeled in like manner. A portion of metal bearing solution  218  may be diverted via feed pregnant leach stream  902  (“feedPLS  902 ”). feedPLS  902  may be sent to a growth area, such as second heap leaching operation  1002 . Second heap leaching operation  1002  may comprise a heap leaching operation capable of receiving feedPLS  902 . 
     Second heap leaching operation  1002  may be fortified with nutrients, such as the nutrients discussed above, which may be added via nutrient input  1004 . The nutrients added via nutrient input  1004  may comprise one or more nutrients described herein or hereinafter discovered to be useful in micro-organism cultivation. For example, the nutrients added via nutrient input  1004  may comprise ammonia (and other nitrogen containing materials), phosphate, potassium, magnesium air, and/or air enriched with carbon dioxide and/or nitrogen. The nutrients added via nutrient input  1004  may be added to second heap leaching operation  1002  by any suitable manner. For example, nutrients may be mixed with an aqueous solution and added to second heap leaching operation  1002  through nutrient input  1004 . Addition in this matter may ensure that the nutrients are well blended into liquid media prior to introduction into second heap leaching operation  1002 . The nutrients added via nutrient input  1004  may be bubbled into second heap leaching operation  1002  in embodiments where nutrients comprise gaseous nutrients. Nutrients may be introduced as solid species into pond second heap leaching operation  1002  via nutrient input  1004 . Nutrients added via nutrient input  1004  may foster the growth of micro-organisms in second heap leaching operation  1002  and may aid in the leaching process of second heap leaching operation  1002 . 
     The environmental conditions of second heap leaching operation  1002  may be controlled to promote micro-organism growth. For example, temperature may be controlled. Tarps, shades, or the like may be used to control exposure to direct sunlight. Second heap leaching operation  1002  may be agitated using a mechanical agitating device. 
     Bio-augmentation  220  may receive fortified liquid medium  1006  from second heap leaching operation  1002 . Fortified liquid medium  1006  comprises micro-organisms from second heap leaching operation  1002  that have been fortified with nutrients. Thus, fortified liquid medium  1006  may contain a higher concentration of micro-organisms than feedPLS  902 . Moreover, fortified liquid medium  1006  may comprise micro-organisms that are well suited for use in leaching due to the selective pressure exerted in heap  230 . 
     In various embodiments, a bacterial colony that has been exposed to a leaching operation may be combined with the bacterial colony of a bioreactor system. In such embodiments, the bacterial colony that has been exposed to a leaching operation is mixed with the bacteria from the bioreactor system, for example the bioreactor system discussed above and shown in an exemplary embodiment in  FIG. 2 . In various embodiments, a bacterial colony that has been exposed to a leaching operation may undergo treatment to make the liquid media carrying the bacterial colony more suitable for placement into a bioreactor. 
     With reference to  FIG. 7 , exemplary method  700  is illustrated. Exemplary method  700  illustrates many of the same features as in  FIG. 2  and such features are labeled in like manner. A portion of metal bearing solution  218  may be diverted via return pregnant leach stream  702  (“rPLS  702 ”). rPLS  702  may be conducted into bioreactor  310  directly. In this manner, a bacterial colony that has been exposed to a leaching operation (i.e., the bacteria contained within rPLS  702 ) may be combined with the bacterial colony of bioreactor  310 . As described above, bioreactor  310  may comprise a source of bacteria  302 , a source of water  304 , a source of nutrients  306 , and a source of air  308 . Bioreactor  310  may further contain an agitator, which may be utilized to mix the ingredients within bioreactor  310 . Heat exchanger  330  may be coupled with bioreactor  310  to circulate hot liquid  312 . In various embodiments, rPLS  702  may be conducted directly into effluent holding tank  320 . 
     With reference to  FIG. 8 , exemplary method  800  is illustrated. Exemplary method  800  illustrates many of the same features as in  FIG. 2  and such features are labeled in like manner. A portion of metal bearing solution  218  may be diverted via raw leach stream  802  (“rawPLS  802 ”). rawPLS  802  may comprise comprises water, acid, copper ions, other metal ions or contaminants, and a bacterial colony. The concentration, pH, or other features of rawPLS  802  may not be suitable for direct introduction into bioreactor  310 . Thus, rawPLS  802  may be processed in pretreatment  806  to render rawPLS  802  more suitable for bioreactor  310 . 
     As discussed above, rawPLS  802  may not be suitable for direct introduction into bioreactor  310  due to pH, the presence of contaminants, excessive water content, or a concentration of bacteria that is too low. Thus, pretreatment  806  may comprise one or more steps to make rawPLS  802  more suitable for introduction into bioreactor  310 . Preferably, pretreatment  806  is conducted in a manner that kills, destroys, or otherwise loses or incapacitates as small a portion of the bacteria in rawPLS  802  as possible, though in various embodiments larger portions of bacteria in rawPLS  802  may be lost. 
     Pretreatment  806  may comprise a pH adjustment step, a precipitation step, a solid liquid phase separation step, a dilution step, a concentration step, an ion exchange step, a filtering step, a settling step, and the like, as well as combinations thereof. For example, pretreatment  806  may comprise adding materials, such as a base, to raise the pH of the rawPLS  802  and/or adding water to dilute the acid. Also for example, water may be removed from rawPLS  802  in pretreatment  806 , which would raise the concentration of bacteria in rawPLS  802 . Also for example, pretreatment  806  may comprise adjusting temperature of rawPLS  802  to better match the temperature of bioreactor  310 . In addition, metal ions may be precipitated in pretreatment  806  to prevent their entry into bioreactor  310 . These operations, and the like, may performed in alone or in any combination to prepare rawPLS  802  for introduction into bioreactor  310 . 
     Bioreactor  310  may receive pretreated metal-bearing solution  804 , which is discharged from pretreatment  806 . Pretreated metal-bearing solution  804  may be in a state that is suitable for introduction into bioreactor  310 . For example, pretreated metal-bearing solution  804  may have a similar pH, bacterial concentration, and temperature as the medium within bioreactor  310 . 
     As described above, bioreactor  310  may comprise a source of bacteria  302 , a source of water  304 , a source of nutrients  306 , and a source of air  308 . Bioreactor  310  may further contain an agitator, which may be utilized to mix the ingredients within bioreactor  310 . Heat exchanger  330  may be coupled with bioreactor  310  to circulate hot liquid  312 . The bacteria from pretreated metal-bearing solution  804  are thus fortified in bioreactor  310 . 
     As discussed above, the present invention includes a heap leaching process utilizing bio-augmentation to improve the efficiency of metal extraction operations. The present invention has been described with reference to various exemplary embodiments. However, many changes, combinations, and modifications may be made to the exemplary embodiments without departing from the scope of the present invention. For example, the various components may be implemented in alternate ways. These alternatives can be suitably selected depending upon the particular application or in consideration of any number of factors associated with the operation of the system. In addition, the techniques described herein may be extended or modified for use with other metal extraction processes. These and other changes or modifications are intended to be included within the scope of the present claims. 
     The present invention has been described above with reference to a number of exemplary embodiments. It should be appreciated that the particular embodiments shown and described herein are illustrative of the invention and are not intended to limit in any way the scope of the invention as set forth in the claims. Those skilled in the art having read this disclosure will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present invention. For example, various aspects and embodiments of this invention may be applied to recovery of metals other than copper, such as nickel, zinc, cobalt, and others. Although certain preferred aspects of the invention are described herein in terms of exemplary embodiments, such aspects of the invention may be achieved through any number of suitable means now known or hereafter devised. Accordingly, these and other changes or modifications are intended to be included within the scope of the present invention. 
     It is believed that the disclosure set forth above encompasses at least one distinct invention with independent utility. While the invention has been disclosed in the exemplary forms, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Equivalent changes, modifications and variations of various embodiments, materials, compositions and methods may be made within the scope of the present invention, with substantially similar results. The subject matter of the inventions includes all novel and non-obvious combinations and sub combinations of the various elements, features, functions and/or properties disclosed herein. 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element or combination of elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of any or all the claims or the invention. Many changes and modifications within the scope of the instant invention may be made without departing from the spirit thereof, and the invention includes all such modifications. Corresponding structures, materials, acts, and equivalents of all elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claim elements as specifically claimed. The scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given above.