Abstract:
A chemical-free and no-microbe method for pre-treating a broad range of waste waters is presented. The said method involves electrocoagulation (EC) operated in synchronization with electrolytic ozone (EO 3 ). In the combinatory method, each technique not only applies its own treatments, they also create synergistic effects from real-time reactions among the reagents generated by electrolysis. Two refractory waste waters, seawater and tannery effluent, are tested by the combinatory method, EC+EO 3 , to assess the viability of the said method. Without adjustment, each of the said waste waters is remedied by EC+EO 3  from its raw state to a clean condition more effectively and more economically than that can be delivered by the respective prevailing processes of pretreatment for each of the said waste waters.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a combination of two electrochemical techniques into a multi-effects method for pre-treating miscellaneous wastewaters. More specifically, the invention relates to electrocoagulation (EC) and electrolytic ozone (EO 3 ) working simultaneously for quick abatement of the major pollution indices including COD, coloration, TSS, TOC, heavy metals, microorganisms and TDS of the treated waters without using chemicals and/or microbes. 
     2. Background of the Related Art 
     Water is vital to the survival of all life on the earth. Regardless of the water sources, water often requires some form of purification before use. Purification of water, or water treatment, is determined by the goals of end-use, such as, irrigation, aquatic cultivation, industrial production, or human consumption. Water can always be treated to the desired level of purity but, at a cost. When deciding a water-treatment protocol, one needs to consider the following factors: capital cost, power consumption, maintenance, throughput, foot-print area, secondary pollution, as well as post-treatment cost. Practically, capital cost and energy consumption are two most essential factors. 
     Seawater covers about 71% of the earth&#39;s surface, and it is the most abundant source of water. When water becomes scarce, people frequently look to the sea or ocean for water. Nevertheless, seawater is a complex waste water with average salinity of about 30 to 38 parts per thousand (ppt), or 30,000 to 38,000 parts per million (ppm), or 3.0 to 3.8%. The salinity of water is also referred as total dissolved solids (TDS) which is associated with water conductivity. In the 10 principal inorganic salts of seawater, the leading 2 ions are Cl −  (55.04%) and Na +  (30.61%), followed by SO 4   2− , Mg 2+ , Ca 2+ , K + , HCO 3   − , Br − , BO 3   3−  and Sr 2+  to constitute 99% of the seawater salinity collectively. Besides the normal organic matter (NOM), seawater contains other organic materials depending on the estuary where seawater is taken for desalination. Distillation and reverse osmosis (RO) are the two most popular techniques for desalination around the world. For protecting boilers, heat exchangers and RO membranes from fouling by the inorganic salts and organic matters in seawater, various antiscalants or scale inhibitors, inorganic acids/bases, coagulants/precipitation agents and oxidants are employed for pre-treating the seawater as taught in U.S. Pat. No. 4,713,195; U.S. Pat. No. 7,862,727; and U.S. Pat. No. 7,931,809, as well as in Ning et al., Desalination and Water Treatment, Volume 9, pp 92-95 (2009), just to name a few. Distillation and RO are energy-thirst techniques, while distillation spends energy on heating seawater, RO consumes energy in the form of high pressure to extract freshwater out of seawater. In addition to power consumption, the use of chemicals and polymers in the pretreatments not only escalates the operation cost, but it also add burden to environment and post-treatments. Especially, RO expels treated water more polluted than the feed water to the sea, which causes severe damage to the ecology of discharge area. 
     Leather tanning is a centuries-old industry which provides materials for making shoes, furs/clothing, furniture, gloves, bags and belts. Leather is made from raw hide or skin, a byproduct of the meat industry, requiring an intensive use of water in many mechanical and chemical processing steps. For processing 850 Kg raw hide, it generally consumes 25-50 m 3  of water and 150 Kg chemicals resulting in 250 Kg finished leather with 25-50 m 3  waste water and 600 Kg solid wastes. Apparently, there are 150 Kg chemicals and 600 Kg solids dissolved or dispersed in the effluent needed to be removed prior to the discharge or re-use of the water. Although modern tannery fabrication techniques have significantly reduced the usage of water and metal, the tannery effluent is still a highly contaminated and hard-to-treat waste. Virtually all tannery effluents are black in color filled with fat, oil, grease (FOG), high SS (suspended solids, up to 3,000 ppm), high sulfide (strong foul smell), high COD (chemical oxygen demands, up to 50,000 ppm), high TKN (total Kjeldahl Nitrogen) and high TDS (up to 90 ppt). The pretreatment of tannery effluent includes flotation of FOG by dissolved air for skimming, and oxidation of sulfides by liming and aeration as taught in U.S. Pat. No. 4,913,826; U.S. Pat. No. 5,472,619, U.S. Pat. No. 6,649,067 and U.S. Pat. No. 7,670,493. In the pretreatment, a huge amount of power is spent on driving pumps, blowers, mixers and dryers (dehydrators). Furthermore, the process employs several large pools for outdoor exposure and flotation, which is space demanding and lack of sanitation. In the following primary and secondary treatments of tannery effluent, precipitation agents, coagulants and bacteria are extensively applied resulting in secondary pollution and high cost for handling the sludge produced. 
     Seawater and tannery effluent serve as two stubborn liquids for proving the principle and performance of the combinatory technique, EC+EO 3 , as a viable pretreatment method for remedying waste waters. The instant invention will present data on treating seawater and a tannery effluent by EC+EO 3  using only electricity. As no chemical or microbe is involved in the treatments, the sludge formed in treating each of the said waste waters is a useful resource, an added value to the treatments by EC+EO 3 . The EC+EO 3  treatment is also fast, energy effective and pollution free. 
     SUMMARY OF THE INVENTION 
     Seawater and tannery effluent serve as two stubborn liquids for proving the principle and performance of the combinatory technique, EC+EO 3 , as a viable pretreatment method for remedying waste waters. The instant invention will present data on treating seawater and a tannery effluent by EC+EO 3  using only electricity. As no chemical or microbe is involved in the treatments, the sludge formed in treating each of the said waste waters is a useful resource, an added value to the treatments by EC+EO 3 . The EC+EO 3  treatment is also fast, energy effective and pollution free. 
     The present invention combines the EC treatment with real-time supply of ozone from EO 3  as a pretreatment method for miscellaneous waste waters. In some cases, the combinatory method, EC+EO 3 , is the only technique needed for treating some waste waters to the desired level of purity. EC and EO 3  use electrolysis of metal and water, respectively, on different electrodes and cell configuration at different power rates for water treatment. Thus, the reactors of EC and EO 3  are two independent systems involving in-situ generation of active reagents, metal ions from EC whereas gases and radicals from EO 3 , for in-situ eradication of contaminants in the water treated. Working alone, EC and EO 3  can only decontaminate waters to a certain degree of purity at a period of time. However, when the metal ions of EC meet the gases and radicals of EO 3  in real-time rate, the resulted agents can impart EC+EO 3  treating capability and treating capacity at several orders of those delivered by EC or EO 3 . It is the first objective of the present invention to offer EC+EO 3  as a viable alternative to the prevailing pretreatment methods that depend heavily on chemicals and microbes wherein large foot-print and lengthy treatment are required. 
     Generally, iron (Fe) and aluminum (Al) are the two most common metals used as the sacrificial anode for EC, and the cathode can also be Fe or Al. In other words, EC may use either different metals or same kind of metals for its anode and cathode. Regardless of the electrode material, EC can be driven on direct current (DC) or alternating current (AC). When an AC power is employed, the electrodes of EC reactor will take turns to serve as the sacrificial anode to provide the metal ions or cations for coagulation, and all electrodes may be consumed evenly. On the other hand, if EC is operated on a DC power, the electrodes can be arranged in bipolar configuration using Fe and Al in an alternating order. Thence, both cations of Fe and Al can be present to handle wastewaters with wide ranges of chemistry. Ozone can enhance the treating power of aluminum ion (Al 3+ ), and ferrous ion (Fe 2+ ) as well. Furthermore, in the presence of O 3 , Fe 2+  can be oxidized quickly to ferric ion (Fe 3+ ), hydroxyl radical (.OH), ferrate (FeO 4   2− ) and ferryl species [Fe(IV)O] 2+ . Both of the latter two ions, Fe(IV/VI), are highly unstable and soon they will return to the stable states of Fe ions, Fe(II/III). It is the fast reduction of Fe(IV/VI) making them as oxidants more potent than O 3 , and the ions also impart EC+EO 3  3 to 5 orders of magnitude faster than EC or EO 3  working alone on reducing SS/coloration/COD/BOD/S 2− /TKN/TDS . . . etc of waste waters. For achieving the synergistic effects, the concentration of O 3  provided to the EC+EO 3  treatment should be at least 20 times of that of Fe 2+ . The desirable dosage of O 3  can be easily managed by adjusting the operation power of EO 3 . 
     Different from the conventional generation of O 3  by corona discharge and other electrolytic ozone designs, EO 3  of the present invention has the following uniqueness and advantages: 
     1. No ion-exchange membrane is required, 
     2. Any water including waste waters may serve as the source of ozone, 
     3. No hazardous or precious metal in the catalyst of ozone anode, 
     4. Low operation voltages (24 V DC or lower), 
     5. Throughput of ozone is proportional to the power densities applied, and 
     6. Large operation current needs are fulfilled by supercapacitors. 
     The key to the success of EO 3  of the present invention is the catalyst of ozone anode. A publicized recipe of ozone-formation catalyst is re-formulated, which is assisted with a proprietary fabrication-protocol developed in-house, to fit the needs of the present invention. 
     In the integration of EC and EO 3  treatments, the natures of waste waters will decide the operation modes of EC+EO 3 . As some contaminants may adhere or deposit on the ozone anode causing permanent damages to the catalyst, the O 3  gas is withdrawn from EO 3  reactor into the EC chamber for treating waste waters containing such contaminants. Due to the close proximity of two reactors, the delivery of ozone is so prompt and continuous that the formation of aforementioned synergistic effects is as effective as the electrodes of EC and EO 3  being disposed in a same container. In another mode of EC+EO 3  treatment, the intake waste water is first treated in the EC chamber, after filtration, the EC-treated water is flown into the EO 3  reactor for direct reactions with gases, radicals and electrodes therein. At the mean time, the ozone gas is drawn to the upstream EC chamber for forming the synergistic effects. For the water used to produce O 3  gas in the EO 3  reactor is the intake waste water itself, the EC+EO 3  system is self-contained. 
     Another objective of the present invention is to offer an effective way for handling the sludge formed in the EC+EO 3  treatment, namely, the separation of sludge from purified water and the disposal of sludge. In the pretreatment of seawater by EC+EO 3 , there is magnetite (Fe 3 O 4 ) formed in the sludge with other metals, notably, magnesium (Mg) and calcium (Ca), which take 3.69% and 1.16%, respectively, of the inorganic salt present in seawater. By means of the ferromagnetism of magnetite, the sludge can be easily separated from the treated seawater using a magnetic field, for example, a permanent magnet or an electromagnet. After drying the sludge cake at low temperatures, the solid becomes an ore that contains a high concentration of Mg ready for recycling. The recovery of Mg from the sludge of EC+EO 3  treatment is similar to the industrial extraction of Mg from seawater but easier, moreover, the sludge may allow the retrieval of Ca, lithium (Li) and manganese (Mn) as well. In the EC+EO 3  treatment of tannery effluent, the sludge, a mixture of organic materials and iron oxides, can be adsorbed on a carrier like diatomite or low-cost activated carbon for easy separation from the purified water, and, the filtered solids can be easily dehydrated into an odorless and nourishing organic-fertilizer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is best understood by reference to the embodiments described in the subsequent sections accompanied with the following drawings. 
         FIG. 1  is a schematic diagram of an EC reactor with four electrodes arranged in bipolar configuration and injection of ozone bubbles through a diffuser according to a preferred embodiment of the invention. 
         FIG. 2  is a schematic diagram of an independent EO 3  reactor equipped with a circulation of water as the source of ozone and an evaluation system for transferring ozone gas to a point of use according to a preferred embodiment of the invention. 
         FIG. 3  is an injection mode of EC+EO 3  treatment wherein ozone gas is drawn form EO 3  reactor into EC chamber for generating synergistic effects to expedite the treatment of waste waters. 
         FIG. 4  is a self-contained mode of EC+EO 3  treatment wherein waste water is first treated by EC to become an internal and incessant supply of water for producing ozone gas in EO 3  reactor. 
         FIG. 5  is a schematic diagram of a series-mode of EC+EO 3  technique according to an embodiment of the invention. 
         FIG. 6  is a schematic diagram of a parallel mode of EC+EO 3  technique according to an embodiment of the invention. 
         FIG. 7  is a flow process of a prior treatment for tannery waste water that employs chemicals and microbes. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention presents an innovative method by combining the reagents of electrocoagulation (EC) and electrolytic ozone (EO 3 ) into a multi-effects means, or EC+EO 3 , as a pretreatment or the major treatment for miscellaneous waste waters. The novel method involves EC operated in synchronization with ozone produced by EO 3 . As ozone meets the cations of EC, more potent reactants will be generated leading to an expedite eradication of contaminants in waste waters. To understand the present invention and its merits, introductions of EC and EO 3  are given as follows 
     Electrocoagulation (EC) 
     EC is a 100+ years old (since 1906) technique for water treatment. The practice of EC is very straightforward: by sticking two electrodes into a waste water followed by applying a DC or AC voltage to the electrodes, the electrode receiving positive volt will be dissociated into cations initiating coagulation or precipitation of suspended and dissolved solids in the water. Because EC generates only the cation required for treatments without anion, it is cleaner and more economic than the conventional chemical method. Furthermore, EC electrodes also provide direct oxidation-reduction to the contaminants, which are not available in chemical treatment. As shown in Table 1, EC is capable of removing a significant amount of inorganic, organic, and microbial pollutants. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Decontamination Capabilities of EC 
               
             
          
           
               
                 Removal 
                   
               
               
                 Rtes (%) 
                 Contaminants 
               
               
                   
               
               
                 96-99+ 
                 Al, Ag, Am, Ba, Cd, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, 
               
               
                   
                 Ra, Si, U, Zn, Bacterium, Total Coliform, 
               
               
                   
                 Coloration, Petroleum Hydrocarbons, Pesticides, 
               
               
                   
                 Phosphates, TSS 
               
               
                 90-95 
                 As, CN − , F − , N, Pb, V 
               
               
                 70-80 
                 B, Co, Mo 
               
               
                 60-69 
                 NH 4   + , Hg 
               
               
                 20-59 
                 K, Se 
               
               
                  0-19 
                 Na, Cr −   
               
               
                   
               
             
          
         
       
     
     The performance of EC treatment is profoundly affected by the anode material. In practice, the composition of waste water will decide which metal is most suitable as the anode. For example, aluminum (Al) should be the anode for treating the wastewaters from food plants and kitchens, and iron (Fe) is the choice of anode on handling textile and tannery waste waters. Salts of Al and Fe, for example, alum [KAl(SO 4 ) 2 ] and ferric chloride (FeCl 3 ), are frequently used chemicals in the conventional water treatments. Henceforth, Al and Fe have become two of the most popular anodes for EC. After an anode material is chosen for treating a specific type of waste water, the EC system may need abrupt adjustments of the pH of intake water, reactor configuration, electrode areas, electrode gaps, power rates and water flow rates to cope with the sudden variation of waste water. The aforementioned variation of effluent may be due to changes in temperature, water usage, reactant dosage or reaction time at the production line. It needs to design the EC system in a high capability so that it can handle any unusual variation in effluent to maintain the system&#39;s designed performance, and to operate the system without the need of chemical including pH adjustment. 
       FIG. 1  shows a preferred embodiment of EC reactor  10  of the instant invention. There are 4 electrodes, A to D, arranged in bipolar configuration in the EC vessel  102 . Among the 4 metallic electrodes, A and C are iron or stainless steel, B and D are aluminum. All electrodes are rectangle plates disposed at a constant gap, such as 5 cm. Only electrodes A and D are connected to the positive and negative pole, respectively, of an outer power supply  104 . Through the electric conductivity of water, electrodes B and C will become bipolar electrodes, that is, one side of each electrode carries positive polarity and the other side is negative. During the EC treatment, waste water enters the vessel at the bottom portion, and it exits from the upper section of vessel. While the water is in the EC vessel  102 , diffuser  100  delivers ozone gas, which is produced in a nearby EO 3  reactor  10  (also not shown in  FIG. 1 ). Heavier sludge  130  will settle at the tapered bottom of EC vessel  102  for discharge, yet, there are more particles flowing with water out of the vessel. If a DC voltage is applied across the electrodes A and D, electrode A and the positive sides of electrodes B and C will proceed the cation formation as described in Equations 1 and 2:
 
Fe→Fe 2+ +2 e   −   (1)
 
Al→Al 3+ +3 e   −   (2)
 
When an AC power is employed, all 4 electrodes will contribute to reactions 1 and 2. The theoretical production of Fe 2+  and Al 3+  can be calculated from Faraday&#39;s 2nd law in Equation 3:
 
Metal ion generated(mg/sec)= IM/Fne   − ·(1000 mg/g)  (3)
 
Where I is the EC operation current in Amps (coulomb/sec), M is the atomic weight of Fe (55.85 g/mole) or Al (26.98 g/mole), F is the Faraday constant (96,485 coulomb/mole), and ne −  is the number of electron transferred in the reactions (2 for Fe, 3 for Al). On the other hand, the reaction at the cathode is the electrolysis of water as shown in Equation 4:
 
2H 2 O+2 e   − →H 2 ↑+OH −   (4)
 
Both of H 2  produced and O 3  injected will cause turbulence in the EC vessel  102  imparting the following benefits: uniform treatment of water, inhibition of sludge deposition on electrodes, and flotation of froth that is formed by the suspended contaminants and coagulants from reactions 1 and 2. By combining Eq 4 with Eq 1 &amp; 2, respectively, the complete reduction-oxidation or redox of Fe and Al in EC treatment can be expressed as Eq 5 and 6, respectively:
 
4Fe+10H 2 O+O 2 →4Fe(OH) 3(s) ↓+4H 2 ↑  (5)
 
3Al+8H 2 O→Al(OH) 2(s) ↓+2Al(OH) 3(s) ↓+4H 2 ↑  (6)
 
Equations (5) and (6) have simplified the electrochemical reactions Fe and Al in water. Depending on the pH of water, Fe 2+  can form a family of iron oxides, or iron corrosion products, including magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH), goethite (α-FeOOH) and green rust [Fe II   4 Fe III   2 (OH).12SO 4 .8H 2 O]. Similarly, Al 3+  can react with OH −  and form Al(OH) 2+ , Al 2 (OH) 2   4+ , Al 6 (OH) 15   3+ , Al 13 (OH) 24   2+ , Al(H 2 O) 6   3+ , Al(H 2 O) 6 OH 2+  and Al(H 2 O) 4 (OH) 2   + . All foregoing compounds and precipitates of Equations (5) and (6) will enhance the efficiency of EC treatment.
 
     Electrolytic Ozone (EO 3 ) 
     EO 3  has been used for water treatment since 1840. Its history is longer than EC&#39;s. Similar to EC, EO 3  also requires at least two electrodes to serve as anode and cathode. Nevertheless, the electrodes of EO 3  can only be used in the mono polar configuration. Furthermore, the anode has to be always connected to the positive pole of a DC power supply. The reason that the anode of EO 3  must be charged a positive power is a reduction-sensitive catalyst coated on the EO 3  anode. Had the anode been misconnected, the catalyst coated thereon would be forever ruined. In the electrolysis of water, oxygen gas will be formed at anode and hydrogen gas at cathode as depicted in Equations (7) and (8):
 
Anode reaction: 2H 2 O→O 2 ↑+4H + +4 e   −  E°=1.23V  (7)
 
Cathode reaction: 2H 2 O+2 e   − H 2 ↑+OH − E°=0.0 V  (8)
 
Where E° is the standard electrode potential required for the evolution of the corresponding gas. If ozone is desired, it needs a higher E° for electrolyzing water as shown in Equation 9:
 
Anode reaction: 2H 2 O→O 3 ↑+6H + +6 e   − E°=1.60V  (9)
 
Using an anode material that has an oxygen-evolution-potential, or oxygen overpotential, higher than the E° of Eq 9, to electrolyze water, O 3  will be co-produced with O 2  on the anode. Although a number of precious metals, such as, platinum (Pt), palladium (Pd), gold (Au), and several carbonaceous materials, for example, glassy carbon, graphite and boron doped diamond (BDD), possess high oxygen overpotential, they produce insufficient ozone for water treatment, and their cost is too high to be viable. The practical catalyst for ozone generation via the electrolysis of water may be found in a group of metal oxides including β-form lead oxide (β-PbO 2 ), iridium oxide (IrO 2 ) and doped tin oxide (SnO 2 ).
 
     As disclosed in U.S. Pat. No. 4,839,007 issued to Kötz et al., the O 2  overpotential of Pt anode is 1.55V. Under the same test condition, antimony doped tin oxide (Sb 2 O 5 —SnO 2 ) has an O 2  overpotential from 1.75 to 1.97 V, and the O 2  overpotential of β-PbO 2  is 1.75V. Obviously, SnO 2  is a better candidate as O 3 -formation catalyst than β-PbO 2  for the sakes of high reactivity and low toxicity, and SnO 2  is preferred over IrO 2  on the cost-basis alone. It is known that a dopant like F, Cl, Sb, Mo, W, Nb, Ta or a combination of the above can impart SnO 2  conductive. Moreover, addition of a second dopant, like, Fe, Co, Ni, Cu, Rh, Ru or Pd, to Sb 2 O 5 —SnO 2  may enhance the catalytic activity of tin oxide. Ni is selected as the second dopant by Wang et al. in J. Electrochem. Soc.,  Volume  152(11), pp D197-D200 (2005) for making doped tin oxide for O 3 -generation. Wang et al also claim that the atomic ratio of three metals in Sb—Ni-doped tin oxide (Sb,Ni—SnO 2 ) should be Sn:Sb:Ni=1000:16:2 using water-soluble tin compound, namely, tin chloride (SnCl 4 .4H 2 O), as the precursor of tin oxide. The exact formulation of Wang et al is fully adopted by Christensen et al in U.S. Pat. No. 7,985,327. However, to extend the life time of Sb—Ni-doped tin oxide (Sb,Ni—SnO 2 ) catalyst, also to increase the efficiency of EO 3  cell, patent &#39;327 has taught the following modifications:
         Add an inter layer of Sn/Sb at 100:10 between Ti substrate and the catalyst.   Add a third dopant, gold (Au) or lead (Pb) to Sb,Ni—SnO 2 .   Insert an ion-exchange membrane between the anode and cathode.       

     While the inclusion of expensive Au and vulnerable membrane in EO 3  will increase the capital cost along with a shorter service life for EO 3  cell, Pb is an environmental hazard banned from drinking water. Moreover, the membrane prevents the EO 3  cell from contacting contaminated waters for direct treatment. Referring to the article of Wang et al as a reference, the instant invention has conducted drastically different alterations as follows:
         1) The precursor of tin oxide is switched from tin chloride (SnCl 4 .4H 2 O) to a tin carboxylate compound. The elimination of chloride (Cl − ) can prevent Cl −  corrosion to the catalyst film, as well as the formation of HCl fume during the fabrication of catalyst film.   2) The atomic ratio of Sn:Sb:Ni is changed from 1000:16:2 to a range from 800:20:2 to 500:20:2. Relative to Sn, the contents of Sb and Ni are significantly increased for extending the life time of Sb,Ni—SnO 2  catalyst, which is measured by the catalytic activity.   3) The life time of Sb,Ni—SnO 2  catalyst is further prolonged by a meticulous control on the preparation of the catalyst-forming solution, as well as on the fabrication protocol that involves a plural number of coating-drying-sintering cycles under a temperature program.   4) Using stainless steel as cathode (Pt is used as cathode by Wang et al) to couple with the anode made of Sb,Ni—SnO 2  on titanium (Ti/Sb,Ni—SnO 2 ) without membranes inserted between the anodes and cathodes.   5) EO 3  is a water-treatment technique of low operation-voltage (24 volt or lower) and high operation-current (2 mA/cm 2  or higher). As a large area of electrodes is required for desalination and treatments of industrial wastes, these operations require a huge amount of current. The needs of large current are fulfilled by supercapacitors, which is first proposed in the U.S. Pat. No. 6,984,295 issued to the first inventor of the instant invention. By means of the power-amplification of supercapacitors, DC power supplies of low power-rates can be employed for a large EO 3  system to reduce the capital cost. The supercapacitor suitable for EO 3  application should have a working voltage of 30V with capacitance at 20 F (farad) or higher.       

       FIG. 2  shows a preferred embodiment of the EO 3  generator  20  of the instant invention. There are 3 zones of operation in the sustainable reactor of O 3 -generation of  FIG. 2 . The first zone is comprised of EO 3  vessel  220  and water reservoir  222  that supplies the precursor of O 3 . Inside the EO 3  vessel, there is a stack of electrodes containing 3 anodes, represented by  233  in slanted bars, and 4 cathodes, represented by  235  in clear long bars. For the best results, each anode  233  is sandwiched by two cathodes  235  at a fixed distance from 0.8 to 1.0 mm provided by non-conductive spacers wherein the whole parallel pack is secured by bolts and screws designated as  237 . All electrodes are rectangular plates with a plural number of perforated holes in preferred patterns thereon (not shown in  FIG. 2 ). All anodic plates are combined electrically in a pack for connecting to the positive pole of an outer DC power supply, and all cathodic plates are linked in the same way for linking to the negative pole of the same power supply. As the electrode assembly of EO 3  is virtually open, the anodic gases, O 2 /O 3 , and cathodic gas, H 2 , can fully mix and react, which has no detrimental effect to the performance of EO 3 . Tap water or other fresh water is circulated between EO 3  vessel  220  and water reservoir  222  via the return conduit  224 . The aforementioned electrode gases and water vapor can be withdrawn from the top of EO 3  vessel to any point of use (POU) by a vacuum pump  260 . The vacuum pump  260  and its accessories constitute the second operation zone of  FIG. 2 . Actually, O 3  is directly formed in micro sizes in water, but they are depicted in large circles represented by  250  for clarity. The dissolution of O 3  in water is dependent of the water temperature, the lower the temperature the more the gas will be in water. In any event, only 0.3% of O 3  produced by EO 3  will dissolve in water and the rest will remain in gaseous state. The vacuum pumping  260  is doing more than just the delivery of O 3  to a POU, it also inhibits the build up of calcium carbonate (CaCO 3 ) on the cathodes and bubble deposition on electrodes. With the coverage of the scale on cathodes, EO 3  will lose its performance eventually. Also, the cumulation of gas bubbles on the electrode surface is detrimental to both anodes and cathodes. 
     As seen in  FIG. 2 , block  240  in dotted square is the third operation zone for providing the DC power needed for O 3  generation. Depending on the designed power-rates, block  240  may contain one or a bank of supercapacitors  242 , circuit C 1  for controlling the charge-discharge of supercapacitors, and a DC power source  244 , for example, batteries, solar/wind energies, fuel calls, generators or city grids, for charging supercapacitors. By the commands of circuit C 1 , power source  244  can apply a pre-determined low-current to charge the supercapacitor  242 . Then, the capacitors can amplify the charging currents into larger currents for delivery to anodes and cathodes of EO 3  to produce O 3  as planned. Through the adjustments of total electrode area submerged in water, the power rates of supercapacitor, and the discharge frequency of supercapacitor, the throughput of ozone, measured in g/hour or Kg/hour, can be custom-made to meet all application needs. Our in-house studies show: when the EO 3  electrodes receive a power density of 0.1 W/cm 2  (10V×10 mA/cm 2 ), O 3  throughput is measured as 0.4 mg O 3 /cm 2 ·min. Based on the foregoing throughput, the EO 3  system can be designed accordingly. The supercapacitor bank for the system can be built based a unit capacitor with an electric specification of 30V/20 F. 
     Combinatory Treatment EC+EO 3    
     As the anodes of EC are consumable, they can be disposed in any waste waters for direct treatment. Nevertheless, the EC cell as  FIG. 1  can provide two types of cation to increase the treating capability of EC, it is still limited by reaction rates. In the chemical coagulation using ferrous chloride (FeCl 2 ) as the coagulant, when hydrogen peroxide (H 2 O 2 ) is added, hydroxide radical (.OH) will be formed by the reaction between peroxide and Fe 2+  as described in Equation 10:
 
Fe 2+ +H 2 O 2 →Fe 3+ +.OH+OH −   (10)
 
The .OH radical is more potent than Fe 3+  that the treatment with H 2 O 2 , also known as the Fenton&#39;s reaction, is faster than Fe 3+  working alone. Since O 3  is an oxidant more powerful than H 2 O 2 , the combination of O 3  and coagulants generated by EC should perform better than either EC-only or the Fenton reaction. The forgoing logic is validated in the instant invention, and the performance of EC+EO 3  is shown in treating seawater and tannery effluent.
 
       FIG. 3  shows a preferred embodiment of injection mode  30  for applying the EC+EO 3  treatment. In  FIG. 3 , EO 3  vessel  312  is an unit designated specifically for generating O 3  (the power supply is not shown in  FIG. 3 ) using tap water or other freshwater stored in reservoir  310  wherein water is circulated between the generator and the reservoir by water pump P 1 . In order to prevent the precursor of O 3  from over-heating, reservoir  310  is made of metal for heat dissipation, and a water-level monitor is installed in the reservoir  310  to ensure that the amount and temperature of water are adequate. Same as  FIG. 2 , there is also a vacuum pump P 2  in  FIG. 3  for transferring O 3  gas to EC vessel  322 . Waste water designated as  301  is pumped by pump P 3  into EC vessel  322  from an inlet located at a lower portion of vessel. The valve above the intake pump of water  301  is provided for batch-wise or continuous treatment of waste water  301 . There are 4 electrode plates, 2 each for Fe and Al, arranged in bipolar configuration and alternating order (same as  FIG. 1 ) at 5 cm or larger separation. During the EC+EO 3  treatment, heavier sludge will settle at the bottom of EC vessel  322  for removal from discharge port  373 . Lighter sludge and froth will flow with water and they exit the EC vessel from outlet  320  to retention tank  351 . There is a magnetic field provided by a permanent magnet M or electromagnet M under the retention tank to attract and to hold the ferromagnetic sludge. With the assistance of magnetic separation, the clarified supertanant is drawn from outlet  330  (pump is not shown in  FIG. 3 ) into filter F, such as, microfilter or ultrafilter, for further purification. After filtration, the clean water is released from outlet  340  and saved in storage tank S. O 3  produced by corona discharge is compared with O 3  from EO 3  on practicing the EC+EO 3  treatment, the results are similar except the latter is more effective. Because of the close proximity to EC reactor and difference of the efficiency of O 3  generation (4% in corona discharge vs 30% in EO 3 ), EO 3  outperforms the corona discharge in water treatment. 
     The EC+EO 3  treatment via injection mode as  FIG. 3  is applied to waste waters containing pollutants that may permanently adhere to anode or damage Sb,Ni—SnO 2  catalyst, for example, petroleum oil, grease, varnish, high level of Cl − , strong acids and string bases. When the aforementioned contaminants are first eradicated by EC to an acceptable level, the treated water can then be treated by EO 3  in tandem with EC as shown in  FIG. 4 . Therefore,  FIG. 4  represents the self-contained mode  40  of EC+EO 3  treatment, wherein the precursor of O 3  is produced internally and constantly. Same as the injection mode, waste water  401  is fed by a pump (not shown in  FIG. 4 ) through a valve, which decides batch-wise or continuous treatment, into the EC vessel  422  for treatment. Sludge generated in the EC vessel  422  will be either precipitated and discharged through the valve under the vessel, or retained by a magnetic field M followed by filtration in filter F and discharge from the valve under the filter. After electrocoagulation and filtration, the treated water is pumped by pump P 4  into EO 3  vessel  410  for ozonation by a stack of 2 anodes and 3 cathodes, as well as for O 3  generation. Once purified water is delivered from the first EC treatment to EO 3 , O 3  can be evacuated back to EC reactor to start the EC+EO 3  treatment, and thereby the EC+EO 3  treated water becomes easier target for the immediate ozonation. After the direct ozonation, if water is determined to meet the goal (online monitor is not shown in  FIG. 4 ), it will be released from outlet  420  and saved in storage tank S for use. Otherwise, water will be turned to EC vessel  410  via conduit  405  for repeated EC+EO 3  treatment and ozonation. 
     Each of EC and EO 3  has its unique actions on treating waters. Basically, EC treatment mainly involves physical reactions, while EO 3  treatment is purely the oxidative reactions of O 3 . Although EC can decontaminate waters faster than EO 3 , yet, EO 3  can purify water to a cleaner state than EC. The power of EO 3  comes from the multiple derivatives of O 3 . As the anodic gases, O 3 /O 2 , and the cathodic gas, H 2 , are not separated in the instant invention, O 3  can react with H 2  to form hydrogen peroxide (H 2 O 2 ). Moreover, singlet oxygen or nascent oxygen, &lt;O&gt;, and a number of radicals can be formed in the reactions of O 3  with water as grossly described in Equation 11:
 
O 3 →O 2 +&lt;O&gt;
 
2O 3 +2H 2 →2H 2 O 2 +O 2  
 
O 3 +H 2 O→2.OH+O 2  
 
O 3 +H 2 O 2 →.OH+.O 2 H+O 2  
 
O 3 +.O 2 H→.O 3 H+O 2   (11)
 
The nascent oxygen, &lt;O&gt;, and free radicals, particularly, .OH, are more highly oxidizing than O 3 , and they can decompose refractory compounds and oxidize virtually all residual organics completely to CO 2  and H 2 O. Except Au, Pt, Pd and Ir, O 3  can oxidize metals to metal oxides in their highest oxidation state. By means of the oxidation, some metal ions become precipitate, such as, Mn 2+  to MnO 2  for easy separation from water. An interesting reaction is the formation of CaO or quicklime by O 3 , which is converted to hydrated lime [Ca(OH) 2 ] by water dissolution, known as slaking, as described in Equations 12 and 13, respectively:
 
Ca 2+ +&lt;O→CaO  (12)
 
CaO+H 2 O→Ca(OH) 2 +heat  (13)
 
Once lime, Ca(OH) 2 , is present in water, it will begin the softening of water by removing the hardness, such as, MgCl 2 , CaCl 2  and MgSO 4 , etc. While tap water is used as the precursor of O 3  in the instant invention, TDS of ozonated water dropped from 150 ppm to under 80 ppm, which is considered as soft water. Water softening by EO 3  is cleaner than liming for EO 3  gives no solids and twice amount sludge of lime applied is produced in chemical treatment, also, EO 3  is more environment friendly than ion exchange, as EO 3  is zero discharge and ion exchange releases excessive sodium ions (Na + ) into the sewerage systems.
 
     Equations (5) and (6) show that Fe(OH) 3  and Al(OH) 3  are the coagulants from using Fe and Al as EC anodes, respectively, for water treatment. Both coagulants are so highly charged precipitates that they can neutralize the negative charge carried by colloidal particles in water. Through the fast charge neutralization, that is, a physical reaction known as coagulation, and other types of bonding including hydrogen bonding, the coagulated solids can agglomerate into flocs. As flocs further grow, they will adsorb more recently coagulated particles and colloids in water. Eventually, the growth of floc, also known as flocculation, will cease as the floc is condensed into a mass heavier than the lifting buoyancy of water. By then, flocs become sludge that can be settled down by gravity. Since the molecular weight of Fe(OH) 3  is larger than that of Al(OH) 3 , Fe is a generally preferred anode material for EC than Al. Regardless of the source of ozone, when O 3  is introduced into the EC reactor that provides both Al 3+  and Fe 2+ , the following synergistic reactions will occur as shown by Equations 14, 15 and 16:
 
Al 3+ +&lt;O&gt;→Al 2 O 3   (14)
 
2Fe(OH) 3 +O 3 +4OH − 2FeO 4   2− +5H 2 O  (15)
 
Fe 2+ +O 3 →[Fe(IV)O] 2+ +O 2   (16)
 
     In Equation 15, the product alumina (Al 2 O 3 ) can serve as a binder that can bind coagulants and colloids of water into a compact and strong sludge. On the other hand, Fe(VI) and Fe (IV) formed in Eq (15) and (16), respectively, are oxidants of several-order more potent than O 3  and they are capable of eradicating organic contaminants, heavy metals and microbes several-order faster than EC or EO 3  working alone. The addition of the synergistic reactions, Equations 14-16, to the EC reactions, Equations 5 and 6, as well as to the EO 3  reactions, Equations 11-13, imparts the EC+EO 3  treatment a high capability and a high capacity for handling a broad range of waste waters. Not only can this technique treat miscellaneous waters filled with contaminants in various natures, it can also handle all challenges of fluctuation in the pollution level without compromise. Two refractory waste waters, seawater and tannery effluent, are treated by EC+EO 3 , respectively, to show the “proof of principle” and “proof of performance” of EC+EO 3  from using simplified EC reactor and EO 3  generator in the following examples. 
     Two Modes of Combinatory Treatment 
     Depending on the nature of intake water or liquids, the treatment using EC+EO 3  technique can be conducted in two modes. Please refer to  FIG. 5 .  FIG. 5  is a schematic diagram of a series-mode  50  of EC+EO 3  technique according to an embodiment of the invention. In  FIG. 5 , waste waters to be treated do not contain contaminants harmful to the catalyst-coated anode of EO 3 , the EO 3  reactor is in series with the EC reactor. At step CS 1  of the series-mode  50 , waste water is withdrawn by a water pump into the EC reactor wherein water-borne contaminants subjected to electrolysis and coagulation at step CS 2 . Sludge formed in the EC reactor is paramagnetic, thus, it is either settled to the bottom of reactor by gravity, or retained by a magnetic field provided by an electromagnet device. After most sludge is removed, the electrolyzed water is filtered at step CS  3  using micro-filtration or ultra-filtration, depending on the particle size. At step CS 4 , the water is judged on its solid content. If the water contains solids more than a predetermined level, it is returned to steps CS 2  and CS 3  for further treatment via line  53 . Water in low-solid-content is flown to the EO 3  reactor for ozonation at step CS 5 . When a clarified water is present in EO 3  reactor, the reactor will constantly generate ozone gas. Using a vacuum pump or Venturi tube, the O 3  gas will be evacuated, via line  52 , into the EC reactor forming the potent Fe(IV/VI) ions leading to expedited oxidation of contaminants. After EO 3 , the disinfected water is decided at step CS 6  on its cleanliness, for repeated series treatments of CS 2 , CS 3  and CS 5  via line  51 , or for storage at step CS 7 . Then, the clean water is used at step CS 8 . Steps CS 2  and CS 3  may involve the discharge of sludge to post treatment at step CS 9 . Because of its dryness, sludge formed in the combinatory treatment is facilely converted to solids of value in the post treatment. 
     On the other hand, if the liquids for the combinatory treatment belong to the following categories:
         Seawater or high salty (TDS&gt;3,000 ppm) brine,   Petroleum, fat, oil, grease (FOG). lacquer, tar,   Organic solvents or organic mixtures of low water content (&lt;5% by weight),   Strong acids and bases in high concentration (&gt;30% by weight),
 
the aforementioned liquids are then treated by a parallel mode  60  wherein the EO 3  reactor is in parallel with the EC reactor as shown in  FIG. 6 .  FIG. 6  is a schematic diagram of the parallel mode  60  of EC+EO 3  technique according to another embodiment of the invention. In the parallel mode  60 , O 3  gas is formed in EO 3  reactor at step CP 3  without exposing the anodes to harmful pollutants for long service life. A fresh water  600 , such as, tap water, is circulated in lines  620  and  640  as the precursor of ozone. Using a vacuum pump or Venturi tube, O 3  gas is evacuated, via line  604 , into the EC reactor. By a water pump, a contaminated liquid, whether aqueous or non-aqueous, is flown from step CP 1  into EC reactor for the combinatory treatment at step CP 2 . In the combo treatment, a paramagnetic sludge is formed in a quantity decided by the EC power and O 3  gas dosing. Most of the sludge is found in the EC reactor and a magnetic separator of step CP 3 , and the rest is present at step CP 4 , micro- or ultra-filtration. Sludge is collected for post treatment at step CP 9  into recyclable solids. After the combo treatment. CP 2 , and filtration, CP 3 - 4 , the water is examined at step CP 5  on its cleanliness, for repeated treatments of CP 2 -CP 4  via line  601 , or for storage at step CP 6 . Then, at step CP 7 , the clean liquid is used for production or other purpose.
       

     Example 1 
     Without adjustment, raw seawaters taken from Taiwan Strait are treated by the EC+EO 3  method in parallel mode  60  using a system as depicted in  FIG. 6 . Followings are the dimensions of EC reactor and EO 3  generator along with their respective electrode packs: 
     EC Reactor 
     
         
         Housing: Cylindrical plastic tube of 17 cm inner diameter and 50 cm in height. It can contain 9 liters (9 L) water for treatment. Seawater is circulated between the EC vessel and an open bucket of 20 L volume for the EC+EO 3  treatment. 
         Electrode: 2 Fe plates and 2 Al plates, each at 11.5 cm wide, 27 cm long and 0.1 cm thick, in bipolar configuration as described in  FIG. 1 . However, the polarities of the two outer electrodes, Fe and Al, are switched as indicated in Table 2.
       The electrode stack is disposed 3 cm above water to protect the electrode leads from corrosion.   
     
         DC Power Supply: 100V/60 A.
 
EO 3  Generator
 
         Housing: Same as the EC reactor. The generator uses a close container that holds 20 L tap water for O 3  formation. A pump is employed to circulate tap water between O 3  generator and water reservoir. 
         Electrode: The electrode stack consists of 5 home-made Ti/Sb,Ni—SnO 2  anodes sandwiched by 6 stainless cathodes, wherein each electrode is a plate of 7.5 cm wide×25 cm long×0.1 cm thick, in mono-polar configuration as described in  FIG. 2 . However, supercapacitor is not employed for the operation current of Exp 1 is well within the current range of DC power supply used. The electrode stack is disposed 2 cm above water to protect the electrode leads from corrosion. 
         Vacuum pump: It provides a vacuum of 50 cm Hg (9.67 psi) for withdrawing O 3  gas from EO 3  generator to EC reactor. 
         DC Power Supply: 30V/200 A.
 
Test Method
 
       
    
     Since the fundamental of the EC+EO 3  method is established, only the levels of operation voltage of EC and EO 3 , water flow rate in EC reactor and the treatment time of EC+EO 3  need to be determined. Three levels of DC volts are chosen for driving EC and EO 3 , that is, 10-20-30 V for EC and 5-7-10 V for EO 3 . In each voltage selected for EC operation, only one trial uses Al electrode (electrode D of  FIG. 1 ) as anode, the other two use Fe electrode (electrode A of  FIG. 1 ) as anode. 
     Based on three variables, they are: EC/EO 3  voltage, water flow-rate and treatment time, and 3 levels for each variable, an orthogoal array known as Latin Square 9, L 9 , developed by Genichi Taguchi, is employed for examining the performance of each parameter set used by EC+EO 3  to treat seawaters. The TDS values of seawaters before and after the EC+EO 3  treatment are measured for assessing the treatment effects of EC+EO 3  under each set of operation parameters. The results are listed in Table 2. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Seawater Pretreated by EC + EO 3   
               
             
          
           
               
                   
                 Raw 
                 EC 
                 EO 3   
                   
                 Treated Water 
               
             
          
           
               
                 # 
                 TDS 
                 A 
                 V 
                 I 
                 V 
                 I 
                 FR 
                 TT 
                 TDS 
                 ΔTDS 
               
               
                   
               
             
          
           
               
                 1 
                 30.7 
                 Fe 
                 10 
                 11.8/ 
                 5 
                 4.2/ 
                 5 
                 10 
                 30.4 
                 −0.3 
               
               
                   
                   
                   
                   
                 13.4 
                   
                 3.7 
               
               
                 2 
                 29.8 
                 Al 
                 10 
                 13.9/15.4 
                 7 
                 8.4/ 
                 10 
                 20 
                 29.3 
                 −0.5 
               
               
                   
                   
                   
                   
                   
                   
                 17.3 
               
               
                 3 
                 17.3 
                 Fe 
                 10 
                 10.2/ 
                 10 
                 16.1/ 
                 20 
                 30 
                 18.3 
                 −1.0 
               
               
                   
                   
                   
                   
                 11.4 
                   
                 14.4 
               
               
                 4 
                 30.0 
                 Al 
                 20 
                 32.5/ 
                 10 
                 15.1/ 
                 5 
                 20 
                 30.4 
                 +0.4 
               
               
                   
                   
                   
                   
                 40.9 
                   
                 13.5 
               
               
                 5 
                 29.1 
                 Fe 
                 20 
                 27.9/ 
                 5 
                 4.1/ 
                 10 
                 30 
                 27.0 
                 −2.1 
               
               
                   
                   
                   
                   
                 39.3 
                   
                 13.8 
               
               
                 5′ 
                 17.6 
                 Fe 
                 20 
                 26.7/ 
                 5 
                 3.6/ 
                 10 
                 30 
                 15.4 
                 −2.2 
               
               
                   
                   
                   
                   
                 38.5 
                   
                 12.2 
               
               
                 6 
                 18.7 
                 Al 
                 20 
                 23.8/ 
                 7 
                 8.6/ 
                 20 
                 10 
                 19.1 
                 +0.4 
               
               
                   
                   
                   
                   
                 26.6 
                   
                 7.5 
               
               
                 7 
                 30.0 
                 Fe 
                 30 
                 45/ 
                 7 
                 8.2/ 
                 5 
                 15 
                 30.5 
                 +0.5 
               
               
                   
                   
                   
                   
                 60+ 
                   
                 7.2 
               
               
                 8 
                 21.9 
                 Al 
                 30 
                 31.8/ 
                 10 
                 14.3/ 
                 10 
                 10 
                 20.8 
                 −1.1 
               
               
                   
                   
                   
                   
                 53.4 
                   
                 13.7 
               
               
                 9 
                 18.0 
                 Fe 
                 30 
                 32.6/ 
                 5 
                 3.8/ 
                 20 
                 20 
                 19.5 
                 +1.5 
               
               
                   
                   
                   
                   
                 55.3 
                   
                 3.6 
               
               
                   
               
               
                 Legends in Table 2: 
               
               
                 TDS = total dissolved solids of seawater in ppt (parts per thousand). 
               
               
                 ΔTDS = TDS difference of seawater before and after treatment in ppt. 
               
               
                 A = Anode of EC. 
               
               
                 V = operation voltage of EC and EO 3  in Volt. 
               
               
                 I = operation current of EC and EO 3  in Ampere. Two values are recorded for each operation voltage of EC and EO 3  at the start and end of treatment. 
               
               
                 FR = water flow rate in L/min. 
               
               
                 TT = EC + EO 3  treatment time in minute. 
               
             
          
         
       
     
     In Table 2, seawaters with TDS higher than 29 ppt are raw, others were treated once or more times by the combinatory method prior to the test of Table 2. Regardless of raw or treated seawaters, they receive no chemical or adjustment before the EC+EO 3  treatment. In other words, all seawaters in Table 2 are subjected to the EC+EO 3  treatment and filtration only. Test #5 shows high ΔTDS value, which is confirmed in test #5′ under the same parameter set. The reason that test #5 and #5′ producing the highest ΔTDS values is that they are operated with the best combination of Fe 2+ /Al 3+  and O 3  dose. If Fe 2+ /Al 3+  are over produced and O 3  is insufficient, the seawater will show a higher TDS value than that before the EC+EO 3  treatment as seen in #9 in Table 2. 
     In Table 2, the EC+EO 3  treatment is operated in constant-voltage mode, whereas the operation currents increase with the increase of conductivity or TDS of seawater. When the operation current exceeds the current limit of power supply as in test #7 of Table 2, the operation voltage will fall from the preset level to lower voltages, such as, 30V to 25V (not listed in test #7). Using a DC power supply of constant-current type, or supercapacitor as a barrier for preventing the power supply from the interference of seawater conductivity, EC treatment can work under high voltage and low current. High volt/low ampere is a desirable operation set for the EC+EO 3  treatment. When supercapacitor is used to isolate the power supply from seawater, the capacitor should have a working voltage of 100V with capacitance of 10 F. Because the EC system in Example 1 is open to atmosphere, O 3  can escape freely. As a consequence, the EC+EO 3  treatment requires at least 10-minute treatment time to reduce the TDS of just 20 L seawater by 1.0 ppt. If the utilization efficiency of O 3  is improved, the EC+EO 3  treatment should attain a higher TDS reduction on more volume of seawater in a shorter time than those shown in Table 2. Nevertheless, Table 2 indicates that the EC+EO 3  pretreatment is capable of cutting the TDS of raw seawater in half without the use of chemicals or microbes. Pretreatment of seawater by any prevailing technique never reports 50% reduction of TDS. 
     In addition to the significant reduction of TDS of seawater, sludge produced in the EC+EO 3  treatment is not only easy to be separated from water, but it is also a valuable resource for retrieving minerals entrapped. As taught in the U.S. Pat. No. 6,190,566 issued to Tsouris et al, a high-purity magnetite (Fe 3 O 4 ) particles is produced via EC treatment of a brine. Magnetite, Fe(II,III), and hematite (Fe 2 O 3 ), the two major iron oxides, along with iron oxyhydroxides and other metal ions present in seawater compose the sludge of EC+EO 3  treatment. It is magnetite and hematite that impart sludge ferromagnetic property. Hence, the sludge can be easily and quickly retained by a magnetic field generated by a permanent magnet or an electromagnet for separation from the treated water. After most sludge is held by the magnet, filtration of the residual solids in seawater is less demanding to a filter, such as, micro-filtration. Moreover, wet sludge from the magnetic separation is easy to form a dense cake on a dewatering device, like, press filter. Subsequently, the sludge cake can be dehydrated at a mild condition, for example, 300° C. at ambient for two hours, into dry particles. Depending on the location of seawater, the sintered sludge may contain a high concentration of magnesium (Mg), calcium (Ca), potassium (K), lithium (Li) or precious metals. The aforementioned metals can be easily recovered from their concentrated states. Using EC+EO 3  for the pretreatment of seawater, the resulted sludge is a valuable material, a value added to desalination. 
     Example 2 
     A black, messy and strongly foul tannery effluent is treated by the EC+EO 3  method in parallel mode  60  of  FIG. 6  as Example 1, except the cylindrical EC vessel is directly used as a close reactor for treating 9 L waste water per batch. Only two stages of EC+EO 3  treatment using the parameter set of #5 in Table 2 are applied to the tannery effluent for quick assessment of feasibility:
     Stage 1 2-hour EC+EO 3  treatment followed by activated-carbon adsorption and filtration   Stage 2 1-hour EC+EO 3  treatment using a system as shown in  FIG. 4  followed by filtration
 
Table 3 lists the results of 2-stage treatment.
   

     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Treatment of a Tannery Effluent by EC + EO 3   
               
             
          
           
               
                   
                 Indices 
                 Raw 
                 1st Stage 
                 2nd Stage 
               
               
                   
                   
               
             
          
           
               
                   
                 BOD (mg/L) 
                 2625 
                 1249 
                 45 
               
               
                   
                 COD (mg/L) 
                 5689 
                 2623 
                 582 
               
               
                   
                 TSS(mg/L) 
                 2578 
                 210 
                 32 
               
               
                   
                 TDS (mg/L) 
                 17,000 
                 14,900 
                 12,700 
               
               
                   
                 NH 3 —N (mg/L) 
                 246 
                 153 
                 66 
               
               
                   
                 Cr 6+  (mg/L) 
                 3 
                 1.2 
                 0.3 
               
               
                   
                 pH 
                 6.1 
                 7.6 
                 8.3 
               
               
                   
                 Coloring 
                 Black 
                 Clear→light 
                 Crystal 
               
               
                   
                   
                   
                 brown 
                 Clear 
               
               
                   
                   
               
             
          
         
       
     
     Because the goal of Example 2 is a feasibility investigation of remedying a tannery effluent by EC+EO 3 , thus, the process parameters of the EC+EO 3  technique are not optimized. Nevertheless, comparing to a prior treatment of tannery waste water as shown in  FIG. 7 , the EC+EO 3  treatment is clearly more effective and more economic in terms of: facility footprint, processing procedures, chemicals and microbes usage, and power consumption (a lot of power is consumed at aeration of  FIG. 7 ). Moreover, the sludge of  FIG. 7  is contaminated with the chemicals applied, yet the sludge produced in the EC+EO 3  treatment is a mixture of iron oxides, carbon, as well as biological and organic materials. The latter is easy to dehydrate into odorless and nourishing fertilizer. Virtually, there is no disposal cost on handling sludge produced in the EC+EO 3  treatment of tannery effluent. On the contrary, sludge of the EC+EO 3  treatment is a valuable byproduct. Except TDS, Table 3 indicates that the EC+EO 3  technique has the capability of becoming a clean, economic and complete solution for the remediation of tannery effluent. 
     At the first stage of EC+EO 3  treatment, the filtrate was clear originally, but it turned into light brown after sitting a few days. The foregoing discoloration could be due to that an ingredient of the partially treated waster is sensitive to air or light. Apparently, the discoloring component is eliminated at the second stage of EC+EO 3  treatment as the filtrate remains crystal clear indefinitely. Assuming an equal opportunity for Fe 2+  and Al 3+  to be formed in the EC reactor, also based on average EC current of 33.6 A, the theoretical production of Fe 2+  and Al 3+  can be calculated via Equation 3 as follows:
 
Fe 2+  formed=33.6×55.85×1000/96485×2=9.72 mg/sec
 
Al 3+  formed=33.6×26.98×1000/96485×3=3.13 mg/sec
 
Similarly, the total anode area of EO 3  submerged in water is 1725 cm 2  [(7.5 cm×23 cm)/side×10 sides]. Based on the ozone throughput of 0.4 mg/cm 2 ·min, the theoretical production of O 3  is 690 mg/min. In every minute process of EC+EO 3  treatment, the dose of O 3  is merely 1.18 times of the formation of Fe 2+ , which is far below the required threshold of 20 times. By increasing the O 3  throughput in conjunction with the reduction of EC current for creating the desired O 3 /Fe 2+  ratio, a faster and more thorough treatment on the tannery effluent than the results of Table 3 will then be delivered by the EC+EO 3  treatment.
 
     CONCLUSION 
     The invention has combined two independent electrochemical techniques for water treatment, namely, EC and EO 3 , into an innovative method, EC+EO 3 . Particularly, when Fe 2+  from EC reacts with O 3  from EO 3 , several powerful oxidants including .OH, FeO 4   2−  and [Fe(IV)O] 2+  will be generated. The aforementioned oxidants are several-order more reactive than the reagents produced in EC, EO 3  or EC/EO 3  connected in-tandem. By means of the synergistic effects, the EC+EO 3  method can treat a broader range of waste waters at larger water volume than EC and EO 3  working alone. In the present invention, the “proof of principle” and “proof of performance” of the EC+EO 3  technique on treating seawater and tannery effluent have been validated. Actually, in-house studies have discovered that the EC+EO 3  treatment is also applicable to effluents from the following industries, such as, food, textile, paper, dairy, meat, metal, mining, petroleum, pharmaceuticals, plastics, chemicals, semiconductor and plating. In all treatments, the EC+EO 3  method offers the benefits of pollution free, high throughput (fast treatment), small footprint, low operation cost, low disposal cost and no waste. In many cases, sludge produced in the EC+EO 3  treatments is a useful resource.