Patent Publication Number: US-2015060282-A1

Title: Water treatment and reuse system

Description:
RELATED APPLICATIONS 
     This non-provisional application is a continuation of U.S. patent application Ser. No. 12/796,523 filed on Jun. 8, 2010, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the field of water treatment systems, and more particularly, to systems and methods for filtering wastewater. 
     BACKGROUND 
     Oil production industries are consistently forced to deal with water challenges that result from drilling processes. During a drilling process, an oil/water mixture is pumped from the ground, which is referred to as production water or wastewater. The wastewater coming from the ground could be 95% water and 5% oil by volume. The wastewater may also include traces of heavy metals and other contaminants. Before the wastewater can be safely disposed of or reused, the contaminants need to be removed. Thus, oil companies have the challenge of removing contaminants and safely disposing of the wastewater. Other companies in other industries face similar problems of having to safely dispose of wastewater. 
     One common way of treating wastewater is through a reverse osmosis filtering process. Unfortunately, the reverse osmosis filtering process is expensive and can be relatively slow especially when the oil content in the wastewater is high. Another common way of treating the wastewater is through a distillation process. Again, the distillation process is expensive and time consuming. Yet another way of treating the wastewater is through a chemical processes. The chemical processes are again expensive, and further processes are needed to return the wastewater to a safe level. 
     Thus, there is a need in the art for improved filtering systems so that wastewater can be safely and reliably processed. 
     SUMMARY 
     Embodiments described herein provide improved systems for filtering wastewater. The filtering systems include a first filtering stage that uses electrocoagulation (EC) to separate suspended particles from the wastewater. The filtering systems also include a second filtering stage that uses mechanical filtering to remove suspended particles that remain to produce filtered water that is free or substantially free from suspended particles. This multi-stage filtering process effectively filters wastewater in a cost-effective manner while allowing for high through-put levels. 
     One embodiment comprises a water filtering system comprising a first filtering stage and a second filtering stage. The first filtering stage receives a flow of wastewater, and uses electrocoagulation to separate suspended particles from the wastewater and produce filtered wastewater. The second filtering stage receives the filtered wastewater from the first filtering stage, and uses mechanical filtering to remove suspended particles from the filtered wastewater and produce filtered water that is free or substantially free from suspended particles. 
     In another embodiment, the water filtering system includes a third filtering stage that receives the filtered water from the second filtering stage, and removes dissolved particles from the filtered water to produce filtered water that is free or substantially free from dissolved particles. 
     In another embodiment, the water filtering system includes a pre-filtering stage that removes hydrocarbons from the flow of wastewater before the wastewater is fed to the first filtering stage. 
     Other exemplary embodiments may be described below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings. 
         FIG. 1  illustrates a water filtering system in an exemplary embodiment. 
         FIG. 2  illustrates another water filtering system in an exemplary embodiment. 
         FIG. 3  illustrates yet another water filtering system in an exemplary embodiment. 
         FIG. 4  illustrates one exemplary implementation of the water filtering system shown in  FIG. 1 . 
         FIG. 5  illustrates a detailed exemplary implementation of a water filtering system. 
         FIG. 6  is a flow chart illustrating a method of filtering wastewater in an exemplary embodiment. 
         FIG. 7  is a flow chart illustrating another method of filtering wastewater in an exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The figures and the following description illustrate specific exemplary embodiments of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope of the invention. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the invention is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. 
       FIG. 1  illustrates a water filtering system  100  in an exemplary embodiment. Water filtering system  100  includes multiple stages for filtering wastewater (also referred to as production water). One example of the wastewater is produced during oil drilling processes. Water filtering system  100  includes a first filtering stage  110  and a second filtering stage  120 . A filtering stage refers to a phase or part of an overall filtering process where one or more systems operate to filter wastewater. 
     When in operation, first filtering stage  110  receives a flow of wastewater  102 . First filtering stage  110  uses electrocoagulation (EC) to separate suspended particles from the wastewater  102  and produce filtered wastewater  104 . Second filtering stage  120  receives the filtered wastewater  104  from first filtering stage  110 . Second filtering stage  120  uses mechanical filtering (e.g., one or more mechanical filters) to separate out or remove suspended particles from the filtered wastewater  104  that may remain, and produce filtered water  106  that is free or substantially free from suspended particles. The filtered water  106  may still have some suspended particles, but the number of particles (in parts per million) have been reduced to a level that is considered safe for disposal or reuse. This multi-stage filtering process removes polymers, paraffin, heavy metals, or other contaminating particles from the wastewater  102 , which results in water that may be disposed of or reused safely. 
       FIG. 2  illustrates another water filtering system  200  in an exemplary embodiment. Water filtering system  200  is similar to the system  100  in  FIG. 1 , but additionally includes a third filtering stage  230 . Third filtering stage  230  receives the filtered water  106  from second filtering stage  120 . Third filtering stage  230  then separates out or removes dissolved particles from the filtered water  106  of second filtering stage  120  to produce filtered water  208  that is free or substantially free from dissolved particles. Third filtering stage  230  may comprise a reverse osmosis system, a desalinization system, or another type of filtering system. The filtered water  208  may still have some dissolved particles, but the number of particles (in parts per million) have been reduced to a level that is considered safe for reuse or disposal. 
       FIG. 3  illustrates yet another water filtering system  300  in an exemplary embodiment. Water filtering system  300  is similar to the system  100  in  FIG. 1 , but additionally includes a pre-filtering stage  340 . Pre-filtering stage  340  receives the flow of wastewater  102  before the wastewater  102  reaches first filtering stage  110 . Pre-filtering stage  340  operates to separate out or remove oil and other hydrocarbons from the wastewater  102  to produce wastewater  102 ′ that is substantially free from hydrocarbons. Pre-filtering stage  340  may include an oil separator, an oil skimmer, a MyCelx® filter, and/or other types of filters. The flow of wastewater  102 ′ is then fed to first filtering stage  110 . 
     Although not shown in  FIG. 3 , third filtering stage  230  as shown in  FIG. 2  may be implemented along with pre-filtering stage  340  as shown in  FIG. 3 . Also, although oil separation is shown in pre-filtering stage  340 , the process of oil separation may be performed after first filtering stage  110  or after second filtering stage  120 . 
       FIG. 4  illustrates one exemplary implementation of the water filtering system  100  shown in  FIG. 1 . Water filtering system  100  may be configured in a different manner in other embodiments, as this is just one example. In this embodiment, first filtering stage  110  includes an electrocoagulation (EC) system  412  connected to a plurality of settling tanks  414 - 416 . EC system  412  comprises any system that uses electrocoagulation to separate suspended particles from a liquid. One example of EC system  412  is a system produced by Powell Water Systems, Inc. Settling tanks  414 - 416  comprise any type of tank that is able to store water. Tanks  414 - 416  are referred to as settling tanks because as the wastewater sits in the tank after the electrocoagulation process, particles in the wastewater release from the liquid and settle to the bottom of the tank. Any desired type, size, and number of tanks may be used for settling tanks  414 - 416 . 
     When in operation, EC system  412  receives the flow of wastewater  102 . As illustrated by the arrows in  FIG. 4 , the wastewater  102  flows up through the EC system  412  and out of its top. EC system  412  includes pairs of conductive metal plates, which act as sacrificial electrodes (one as an anode and one as a cathode). As the wastewater  102  flows through EC system  412 , a potential is placed across the electrodes which injects a current through the wastewater  102 . The positive side undergoes anodic reactions while the negative side undergoes cathodic reactions. Consumable metal plates, such as iron or aluminum, are usually used as sacrificial electrodes to continuously produce ions in the wastewater  102 . Ions (e.g., heavy metals) and colloids (organic and inorganic) are mostly held in the wastewater  102  by electrical charges. The released ions neutralize the charges on the particles in the wastewater  102  and thereby initiate coagulation. As a result, the reactive and excited state causes the contaminant particles to be released from the wastewater  102 . 
     The wastewater  102  from EC system  412  is gravity-fed to settling tanks  414 - 416  where the wastewater  102  is temporarily stored. As the wastewater  102  sits in settling tanks  414 - 416 , the neutralized particles in the wastewater  102  separate from the wastewater  102  and fall to the bottom of settling tanks  414 - 416 . The particles that are released from the wastewater  102  form a slurry of solids on the bottom of settling tanks  414 - 416 , while the filtered water  104  remains as a liquid on top of the slurry. 
     Settling tanks  414 - 416  may be filled one at a time. For example, after settling tank  414  has been filled, wastewater  102  from EC system  412  may be fed to settling tank  415  while the wastewater  102  in settling tank  414  is allowed to sit. Similarly, after settling tank  415  has been filled, wastewater  102  from EC system  412  may be fed to settling tank  416  while the wastewater  102  in settling tanks  414 - 415  is allowed to sit. When settling tank  416  is being filled or about to be filled, the filtered wastewater  104  from settling tank  414  may be fed to second filtered stage  120  so that the liquid in setting tank  414  is emptied. When settling tank  414  is emptied, the filtered wastewater  104  from settling tank  415  may be fed to second filtered stage  120  so that the liquid in setting tank  415  is emptied. Settling tanks  414 - 416  may be used in this manner to receive wastewater  102  from EC system  412  and feed filtered wastewater  104  to second filtering stage  120 . 
     In another embodiment, settling tanks  414 - 416  may be connected in series so that filtered wastewater  104  from settling tank  414  may be fed to settling tank  415  where particles may be allowed to further separate from the wastewater  102 . Filtered wastewater  104  from settling tank  415  may be fed to settling tank  416  where particles may again be allowed to further separate from the wastewater  102 . The filtered wastewater  104  from settling tank  416  may then be fed to second filtered stage  120 . 
     The filtered wastewater  104  sitting in one or more of settling tanks  414 - 416  is subsequently fed to second filtering stage  120 . Second filtering stage  120  includes one or more mechanical filters  422 . For example, mechanical filters  422  may comprise multiple filters having a desired pore size for the particles to be filtered, such as a 0.5 micron pore size, a 0.1 micron pore size, etc. Alternatively, mechanical filters  422  may comprise step-down filters where each successive filter in series has a smaller pore size. Within second filtering stage  120 , the filtered wastewater  104  is passed through mechanical filters  422  and produces filtered water  106  that is free or substantially free from suspended particles. The filtered water  106  may still have some suspended particles, but the number of particles (in parts per million) have been reduced to a level that is considered safe for reuse or disposal. 
       FIG. 5  illustrates a detailed exemplary implementation of a water filtering system  500 . The scope of the invention is not limited to this embodiment, as the detail provided in the filtering stages in this embodiment is for the purpose of example. Water filtering system  500  includes first filtering stage  110  and second filtering stage  120  as illustrated in  FIG. 4 . In addition to the first and second filtering stages  110  and  120 , water filtering system  500  includes third filtering stage  230 , pre-filtering stage  340 , and a filter press  550 . In this embodiment, third filtering stage  230  includes a reverse osmosis (RO) filter  532 . Pre-filtering stage  340  includes an oil separator  542  and one or more MyCelx® filters  544 . Oil separator  542  may comprise a flow-through separator or an oil skimmer. 
     When in operation, the wastewater  102  is first passed through pre-filtering stage  340 . Thus, the flow of wastewater  102  enters oil separator  542  where oil separator  542  operates to remove oil and other hydrocarbons from the wastewater  102 . The wastewater  102  is then passed through one or more MyCelx® filters  544 , which acts to remove remaining hydrocarbons from the wastewater  102  that was not removed by oil separator  542 . The flow of wastewater  102 ′ that leaves pre-filtering stage  340  should thus be free or substantially free of oil and other hydrocarbons. 
     The flow of wastewater  102 ′ then enters first filtering stage  110  where EC system  412  receives the flow of wastewater  102 ′. As the wastewater  102 ′ flows up through EC system  412  and out its top, EC system  412  neutralizes the charges of the particles in the wastewater  102 ′ through electrolysis. The wastewater  102 ′ from EC system  412  is gravity-fed to settling tanks  414 - 416  where the wastewater  102 ′ is temporarily stored. As the wastewater  102 ′ sits in settling tanks  414 - 416 , the neutralized particles in the wastewater  102 ′ separate from the wastewater  102 ′ and fall to the bottom of settling tanks  414 - 416 . The particles that are released from the wastewater form a slurry on the bottom of settling tanks  414 - 416 , while the filtered water  104  remains on top of the slurry. 
     The filtered wastewater  104  sitting in settling tanks  414 - 416  is subsequently fed to second filtering stage  120 . Within second filtering stage  120 , the filtered wastewater  104  is passed through one or more mechanical filters  422 . In this example, the filtered wastewater  104  is passed through mechanical filters  422  having a 0.1 micron pore size. Mechanical filters  422  remove particles that are still suspended within the filtered wastewater  104  to produce filtered water  106  that is free or substantially free from suspended particles. 
     The filtered water  106  from second filtering stage  120  is subsequently fed to third filtering stage  230 . Within third filtering stage  230 , the filtered water  106  is passed through reverse osmosis filter  532 . Reverse osmosis filter  532  acts to remove particles that are dissolved in the filtered water  106  and produce filtered water  508  that is free or substantially free from dissolved particles. For example, reverse osmosis filter  532  may remove sodium, chlorides, or other particles that are dissolved in the filtered water  106 . The filtered water  508 , at this point, should be considered safe for disposal or reuse. 
     The slurry that forms on the bottom of settling tanks  414 - 416  is also processed by water filtering system  500  in the following way. As is illustrated in  FIG. 5 , the filtered wastewater  102 ′ that is fed into settling tanks  414 - 416  separates into a liquid and a slurry as the neutralized particles fall to the bottom of settling tanks  414 - 416 . The liquid stored in settling tanks  414 - 416  is the filtered wastewater  104  that is fed to second filtering stage  120 . The slurry is fed from the bottom of settling tanks  414 - 416  to filter press  550 . Filter press  550  squeezes the remaining liquid out of the slurry. The liquid that is squeezed out of the slurry is fed back to EC system  412  of first filtering stage  110  to be processed again. The solid material remaining from filter press  550  may be disposed of in any desired manner, such as a landfill. 
     Water filtering system  500  as described above advantageously produces clean water (filtered water  508 ) that may be disposed of safely by simply dumping it onto the ground or into a water system, such as a pond. The filtered water  508  may also be reused in some manner because most or all of the contaminants in the water have been removed. Not only is water filtering system  500  effective in removing contaminants, it can reach through-puts of 1000 gallons per minute, 2000 gallons per minute, or more which allows system  500  to filter large quantities of wastewater. Also, the cost of filtering the wastewater using system  500  is lower than other filtering methods. 
     In addition to the systems above, embodiments herein may be described as methods of filtering wastewater.  FIGS. 6-7  illustrate some of the filtering methods provided herein. 
       FIG. 6  is a flow chart illustrating a method  600  of filtering wastewater in an exemplary embodiment. The steps of method  600  may be performed in the systems described above. The steps of the flow charts described herein are not all inclusive and may include other steps not shown. 
     In step  602 , an electrocoagulation (EC) process is performed on a flow of wastewater to separate suspended particles from the wastewater to produce filtered wastewater. The EC process may include passing the wastewater through an EC system to neutralize the charges of the particles in the wastewater. The EC process may further include feeding (such as by using gravity) the wastewater from the EC system to one or more settling tanks where the wastewater is temporarily stored. As the wastewater sits in the settling tanks, the neutralized particles in the wastewater separate from the wastewater and fall to the bottom of the settling tanks. The particles that are released from the wastewater form a slurry on the bottom of the settling tanks, while the filtered wastewater remains on top of the slurry. 
     In step  604 , the filtered wastewater from step  602  is passed through one or more mechanical filters to separate out or remove suspended particles from the filtered wastewater and produce filtered water that is free or substantially free from suspended particles. The mechanical filters may have any desired pore size, such as 0.1 microns. 
     Step  606  is an optional step that may be performed on the filtered water produced in step  604 . Step  606  comprises passing the filtered water through a reverse osmosis filter or another type of filter to remove dissolved particles from the filtered water and produce filtered water that is free or substantially free from dissolved particles. 
       FIG. 7  is a flow chart illustrating another method  700  of filtering wastewater in an exemplary embodiment. The embodiment in  FIG. 7  is similar to the one shown in  FIG. 6 , but includes an optional pre-filtering step. Thus, before the wastewater is processed using electrocoagulation, an oil separation process is performed on the flow of wastewater to separate out or remove oil or other hydrocarbons from the wastewater in step  702 . The oil separation process may include passing the wastewater through an oil separator or an oil skimmer and/or passing the wastewater through one or more MyCelx® filters. After the oil separation process, the EC process in step  602  may be performed on the wastewater that is free or substantially free from hydrocarbons. 
     Although not specifically spelled out, additional details of the methods of filtering wastewater may be gleaned from the description above regarding the filtering systems. 
     Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.