Abstract:
A method and system for treating waste water from hydraulic fracturing is disclosed. The treatment includes removing the sand, suspending the inorganic metals and impurities, using flocculation to engulf the impurities, and separating the impurities from the water, resulting in pure water that can be reused in the process.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 61/777,983 which was filed on Mar. 12, 2013. The entire content of that application is incorporated hereinto by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to methods and devices that are useful for filtration and chemical treatment of waste water. It finds particular application in hydraulic fracturing processes, and will be described with particular reference thereto. However, it is to be appreciated that the present disclosure is also amenable to other like applications. 
         [0003]    Generally, hydraulic fracturing waste water is composed of 85% water, 10% sand, and 5% chemicals. The 5% of chemicals in the hydraulic fracturing waste water can contain a wide range of possible different compounds, such as inorganic salts and flocculants, organic chemicals, and biocides. 
         [0004]    There are currently several methods available for the treatment of waste water. Examples are removal of solids by gravitation, coagulation (which depends on the electric charge among particles), and flocculation (which does not depend on the electric charge among particles). 
       BRIEF DESCRIPTION 
       [0005]    The present disclosure provides method for filtering and treating waste water to obtain pure water that can be reused. 
         [0006]    These and other non-limiting characteristics of the disclosure are more particularly disclosed below 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The following is a brief description of the drawing, which is presented for the purposes of illustrating the disclosure set forth herein and not for the purposes of limiting the same 
           [0008]      FIG. 1  is an illustration of an exemplary filtration and treatment method and system used for the treatment of waste water. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    A more complete understanding of the processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the existing art and/or the present development, and are, therefore, not intended to indicate relative size and dimensions of the assemblies or components thereof. 
         [0010]    Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function. 
         [0011]    The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). When used with a specific value, it should also be considered as disclosing that value. For example, the term “about 2” also discloses the value “2” and the term “from about 2 to about 4” also discloses the range “from 2 to 4.” 
         [0012]    Disclosed in various embodiments are devices and methods for filtering and chemically treating waste water using flocculation. This can be applied to treating waste water that is created during, for example, a hydraulic fracturing process. More details of the methods and systems follow with reference to  FIG. 1 . The methods can be generally divided into three (3) phases. The system includes a water flowpath and multiple solids flowpaths. 
         [0013]    Initially, waste water from waste water source  101  is piped through waste water basin inlet  111  into waste water basin  110 . Water source  101  can be a well from a hydraulic fracturing process. The waste water from the hydraulic fracturing process is generally a combination of sand, inorganic salts and flocculants, organic chemical and biocides. Generally, hydraulic fracturing water is composed of 85% water, 10% sand, and 5% chemicals. The chemicals in the hydraulic fracturing water can contain a wide range of possible different compounds. The volume of the waste water basin  110  can be altered as desired. 
         [0014]    Biocides and bactericides may optionally be added to waste water basin  110  to treat the waste water. The biocides and bactericides may be used to kill microorganisms including, but not limited to, slime forming bacteria and algae, as well as sulfate reducing bacteria. They can also prevent algae growth in the waste water basin  110 . The basin can be used to provide storage, generate enough head to run the system, etc. 
         [0015]    Phase 1 encompasses the removal of solids from the waste water. The waste water exits waste water basin  110  through outlet  112  and enters the centrifuge  120  through inlet  121 . Rinse water  125  is also pumped into centrifuge  120  through rinse inlet  123 . The waste water and rinse water are centrifuged to ensure complete precipitation and removal of the solids in the waste water. These solids include sand. The solids removed in centrifuge  120  exit through centrifuge solids outlet  124 , and the waste water exits through water outlet  122 . The solids may then be recycled back to the well for reuse in the fracking process. 
         [0016]    Optionally, a separation tank  130  can be included in the system wherein the waste water and any remaining solids may be decanted to remove the final solids. The separation tank receives water from the centrifuge through inlet  131 , and water exits through outlet  132 . 
         [0017]    Phase 2 encompasses the chemical treatment of the waste water. The waste water can be provided from centrifuge  120  through centrifuge water outlet  122 , or from the separation tank  130  through separation tank outlet  132 . The waste water enters the acidification tank  140  through inlet  141 . In acidification tank  140 , inorganic metals and impurities are dissolved. Exemplary impurities include various minerals. 
         [0018]    An acid source  145  provides acid that is used to lower the pH of the waste water in the acidification tank through inlet  143 . A mineral acid, like sulfuric acid (H 2 SO 4 ) or hydrochloric acid (HCl), can be used. A pH of about 1 to about 2 is needed to ensure all impurities and inorganic metals are dissolved. 
         [0019]    The waste water then leaves acidification tank  140  through outlet  142  and enters chemical suspension tank  150  through inlet  151 . In the chemical suspension tank a base is added to the waste water from base source  155  through inlet  153 . The base can be sodium hydroxide (NaOH), potassium hydroxide (KOH), or calcium hydroxide (Ca(OH) 2 ). The base is added in an amount sufficient to raise the pH of the waste water up to about 14. This causes the inorganic metals and impurities to be suspended. 
         [0020]    After the inorganic metals and impurities are suspended, the waste water leaves chemical suspension tank  150  through outlet  152  and enters polymer treatment tank  160  through inlet  161 . In polymer treatment tank  160  the waste water is treated with a flocculant from flocculant source  165  entering through inlet  163 . 
         [0021]    Different types of flocculants, inorganic and organic, can be utilized in the filtration and chemical treatment of waste water. Inorganic flocculants include salts of multivalent metals, such as aluminum and iron. When salts of multivalent metals are used in filtration and treatment of waste water, they are used at very high levels. This can lead to large sludge deposits, which can be affected by pH changes. Organic flocculants are typically polymeric in nature. When organic flocculants are used in the filtration and treatment of waste water, they are used at very low levels. The polymeric flocculants can be synthetic or natural water-miscible polymers. The polymer used may be natural or synthetic. The polymer may be cationic, nonionic, anionic, or amphoteric. 
         [0022]    Desirably, a natural polymer is used as the flocculant to remove the suspended impurities and inorganic metals. Preferably the polymer will be natural and biodegradable, not synthetic. Examples of a natural biodegradable polymer include polysaccharides, which are starchy in nature. When the waste water is treated with the polymers, the polymers will establish flocculants. The flocculants will engulf or capture the impurities and the inorganic metals, making their separation possible. 
         [0023]    Phase 3 encompasses the filtering the waste water. After the waste water is treated with a flocculant, it exits polymer treatment tank  160  through outlet  162 . The waste water enters filtration system  170  through inlet  171 . In filtration system  170 , the waste water and the impurities are filtered to separate the pure water from sludge. The sludge contains all the organic and inorganic impurities. The sludge leaves filtration system  170  through solids outlet  174 . The filtered water leaves filtration system  170  through outlet  172 . Filtered water is thus obtained. 
         [0024]    The sludge enters incinerator  180  through sludge inlet  181  and is incinerated. The incinerated sludge fumes may exit the incinerator throough outlet  182  be fed into a fume treatment or neutralization basin  185  through inlet  186  to prevent the fumes from going into the atmosphere. The neutralization basin  185  may contain a 20% potassium hydroxide solution that neutralizes pollutants in the fumes. The fumes then exit the basin. 
         [0025]    Optionally, the filtered water can be filtered a second time in reverse osmosis filtration system  175  before being pumped into treated water basin  190  if high quality water is desired. The water enters the reverse osmosis system through inlet  176  and exits through outlet  177 . 
         [0026]    The filtered water will be pumped into treated water basin  190  through inlet  191  from filtration system  170 , or from reverse osmosis filtration system  175  if included. 
         [0027]    The filtered water in treated water basin  190  may optionally be recycled from treated water basin  190  through outlet  192 . In a hydraulic filtration system, the filtered water can be recycled back to the well through outlet  192 . 
         [0028]    The present disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.