Compact integrated electrochemical wastewater treatment system with electroflotation and coagulation

Abstract

The present invention introduces a compact, prefabricated wastewater treatment unit that integrates electrocoagulation, electrooxidation, and electroflotation into a single system. This unit is specifically designed for rapid deployment and efficient removal of various pollutants from industrial, municipal, or emergency wastewater streams. It operates solely using an electrical power source, without requiring the continuous addition of external chemical coagulants, making it practical and sustainable for remote or crisis-affected areas. The treatment process occurs in three main chambers.

Description

[0001] Compact Integrated Electrochemical Wastewater Treatment System with Electroflotation and Coagulation Field of the Invention The present invention relates to wastewater treatment technologies. More specifically, it concerns a compact, prefabricated treatment unit that uses electrochemical oxidation, electrocoagulation, and electroflotation for the rapid and efficient removal of organic and inorganic contaminants. This system is designed for both industrial and municipal wastewater treatment, with particular application in emergencies, such as natural disasters, where traditional treatment infrastructure is damaged or unavailable. Background of the Invention Conventional wastewater treatment methods require specialized operators, complex equipment, and the continuous addition of chemical coagulants and disinfectants (1, 2). These processes are often time-consuming and costly, and they are not well-suited for rapid deployment. During natural disasters such as floods and earthquakes, damaged water and sewage infrastructure can lead to outbreaks of waterborne diseases, posing a significant threat to public health (3). Therefore, there is a clear need for portable, rapidly deployable treatment systems that can operate without the need for large quantities of chemicals or complex mechanical equipment. Electrochemical treatment systems have emerged as promising alternatives (4). These systems generate coagulants and oxidants in situ using electricity, which simplifies operation and eliminates the need for external chemical dosing (5). However, existing systems are often too large, energy-inefficient, or incapable of handling both dissolved and suspended contaminants simultaneously. The present invention addresses these shortcomings by integrating electrocoagulation, electrochemical oxidation, and electroflotation into a single, compact, prefabricated unit. Electrochemical methods have also been effectively used in many studies to remove pollutants from wastewater (6). In this method, by placing several electrodes with specific materials and contact surfaces in the wastewater and connecting them to an electrical source with a specific voltage and amperage, it is possible to remove organic pollutants (7). In electrochemical methods, in addition to dissolved organic compounds, suspended particles, color, and harmful bacteria are also removed from the wastewater (8). Typically, three types of electrodes—graphite, iron, and aluminum—are used for electrochemical treatment. The use of iron and aluminum electrodes, in addition to directly oxidizing organic compounds, can lead to the release of iron or trivalent aluminum ions into the wastewater (9). These ions have coagulating properties and can neutralize the surface charge of non-settleable suspended (colloidal) particles in water, creating conditions for them to connect to each other and form large flocs (10). Part of these flocs usually settle, and another part floats on the water's surface. Therefore, it becomes possible to separate them from the water. Thus, electrochemical methods can easily remove both dissolved organic compounds and suspended compounds from wastewater (11). These methods are usually simple and inexpensive. However, they are generally used alongside other treatment methods to have the greatest impact. Sometimes, a combination of the above methods is considered in industries for complete treatment. Although wastewater treatment methods have been used in various ways as mentioned above, by combining and arranging them in a specific order, a powerful treatment plant can be designed to treat various types of industrial wastewater. Various ways for oxidizing organic materials by electrochemical methods have been suggested, the most important of which are: (a) direct oxidation on the anode, (b) indirect oxidation with hydroxyl radicals (·OH) on the anode (inert), (c) Electro-Fenton and cathodic Fenton, (d) indirect oxidation with active chlorine in the presence of chloride, (e) sulfate electrolysis and production of sulfate radicals (Sulfate Radical Pathway), (f) other indirect oxidation pathways (anodic ozonation, peroxynitrate, etc.), and (g) cathodic reduction (cathode catalysts and reductive decomposition). The sacrificial electrode can be iron or aluminum. If the sacrificial electrode is aluminum, according to Equation 11, Al³⁺ ions are released into the aqueous environment, and if the sacrificial electrode is iron, Fe²⁺ and Fe³⁺ ions are released into the aqueous environment. Using the following equations, one can calculate how many moles of metal ions can be released into the water per mole of the electrode.^^^^^^^^ → ^^^^^^^^3+ + 3^^^^− (^^^^^^^^.11)^^^^^^^^ → ^^^^^^^^2+ + 2^^^^− (^^^^^^^^.12)Al³⁺ and Fe³⁺ ions are hydrolyzed in water according to Equations 13 and 14. The solid metal hydroxides (Al(OH)₃ or Fe(OH)₃) form flocs that trap colloids and suspended solids (12). In the design, pH balance and alkalinity must be considered because the hydrolysis process is pH-dependent.^^^^^^^^3+ + 3^^^^2^^^^ → ^^^^^^^^(^^^^^^^^)3 (^^^^) + 3^^^^+ (^^^^^^^^.13)^^^^^^^^3+ + 3^^^^2^^^^ → ^^^^^^^^(^^^^^^^^)3 (^^^^) + 3^^^^+ (^^^^^^^^.14)One of the important reactions in electrochemical treatment is the cathodic reduction of oxygen to hydrogen peroxide, which acts as a precursor for the electro- Fenton process (see Equation 15) (13).^^^^2 + 2^^^^+ + 2^^^^− → ^^^^2^^^^2 (^^^^^^^^.15)This reaction is used to produce hydrogen peroxide on-site. When it is combined with Fe²⁺ ions, hydroxyl radicals are generated (according to the subsequent reaction).^^^^^^^^2+ + ^^^^2^^^^2 → ^^^^^^^^3++.^^^^^^^^ + ^^^^^^^^− (^^^^^^^^.16)The hydroxyl radical (·OH) is a very strong oxidant (14). It attacks resistant organic compounds and mineralizes them. In the electro-Fenton process, the Fe²⁺ ion is electrochemically regenerated at the cathode (15). Another phenomenon is the direct production of the ·OH radical on passive anodes, which can also occur during the electrochemical treatment of wastewater. The oxidation of water on the surface of a 'passive' anode occurs according to the following equation.^^^^2^^^^ →.^^^^^^^^ + ^^^^+ + ^^^^− (^^^^^^^^.17)^^^^^^^^+.^^^^^^^^ →.^^^^ + ^^^^2^^^^ → ^^^^^^^^2 + ^^^^2^^^^ (^^^^^^^^.18)Boron-doped diamond (BDD) and some metallic oxide anodes enhance this indirect oxidation pathway (16, 17). This method is suitable for deep mineralization. Using Faraday's law, the mass of dissolved metal or the number of moles of species produced can be calculated. To calculate the number of moles of metal released into the water due to the electrolysis process (n), Equation 19 is used, and to determine the mass of metal released by the electrolysis process (m), Equation 20 is used. (^^^^^^^^.19) ^^^^ =^^^^^^^^^^^^ ^^^^^^^^(^^^^^^^^.20)In these equations, I is current (Ampere), t is time (seconds), z is the number of electrons transferred per metal atom (3 for Al³⁺ and 2 for Fe²⁺), F is Faraday's constant (approximately 96485 C·mol⁻¹), and M is the molar mass (grams per mole). These equations are used to determine the size of the electrodes and estimate the required electrical charge to produce the target coagulant dose. Equation 21 can also be used to determine the input electric current to the electrodes. Where j is the current density (Ampere per square meter), I is the current (Ampere), and A is the anode surface area (square meter). The treatment rate and electrode dissolution rate increase proportionally with the current density. Therefore, j should be chosen to balance the production speed and the useful life of the electrode. When chloride ions (Cl⁻) are present in the environment, during electrochemical reactions, these ions are first converted to molecular chlorine (Cl₂) (Equation 22), and then hydrolyzed in water to produce HOCl / OCl⁻ (Equation 23). This process is called the indirect chlorination pathway.2^^^^^^^^− → ^^^^^^^^2 + 2^^^^− (^^^^^^^^.22)^^^^^^^^2 + ^^^^ ^^^^ ↔ ^^^^^^^^^^^^^^^^ + ^^^^+2 + ^^^^^^^^− (^^^^^^^^.23)The HOCl / OCl⁻ ions are oxidants that remove organic materials, but they can form chlorinated by-products (18). If the feedstock contains chloride, this issue must be considered. The production of sulfate radicals through anodic persulfate is another oxidation pathway that occurs during the electrochemical treatment of wastewater (see Equations 24 and 25). The sulfate radical (^^^^^^^^4.−) is a strong oxidant used for breaking down resistant organic compounds. This pathway can be utilized in advanced electrochemical oxidation. Reviewing various oxidation methods, especially when combined with electrochemical processes, shows that an efficient system can be achieved for removing persistent pollutants from industrial wastewater. Such an approach not only enhances the quality of the effluent but also enables the reuse of water. Electrochemical treatment systems provide a unique advantage by combining oxidation, coagulation, and flotation in a single process (19). These systems can simultaneously remove dissolved organic matter, suspended solids, and harmful microorganisms without the continuous addition of external chemicals. Furthermore, they are flexible and can be adapted to different wastewater types, making them suitable for both industrial and emergency applications. By integrating these capabilities into a compact and prefabricated unit, wastewater can be treated quickly and effectively, even in remote locations or during disasters where conventional treatment plants are unavailable. Summary of the Invention The present invention introduces a compact, prefabricated wastewater treatment unit that integrates electrocoagulation, electrooxidation, and electroflotation into a single system. This unit is specifically designed for rapid deployment and efficient removal of various pollutants from industrial, municipal, or emergency wastewater streams. It operates solely using an electrical power source, without requiring the continuous addition of external chemical coagulants, making it practical and sustainable for remote or crisis-affected areas. The treatment process occurs in three main chambers. In the first chamber, wastewater passes through iron or aluminum electrodes, which act as sacrificial anodes to release Fe³⁺ or Al³⁺ ions. These ions destabilize colloidal particles and promote the formation of flocs, enabling effective aggregation of both settleable and non-settleable suspended solids. At the same time, multiple electrochemical reactions take place, including direct oxidation, hydroxyl radical generation, electro-Fenton reactions, active chlorine oxidation (in the presence of chlorides), sulfate radical formation, and cathodic reduction. These processes work together to degrade dissolved organic contaminants, improving overall water quality. The second chamber focuses on electroflotation, where water electrolysis produces fine hydrogen and oxygen microbubbles. These bubbles attach to the flocculated particles, lifting them to the surface of the water. A mechanical skimming device then transfers the floating solids into the third chamber, where they are collected and stored as sludge for removal. The system’s compact design allows it to be factory-built and easily transported to the site of need. Once installed, it can begin treating wastewater almost immediately, making it ideal for emergency applications, such as natural disasters or industrial accidents. The unit is engineered to run on low-voltage direct current (≤ 40 V), ensuring safety and energy efficiency. Its modular nature allows for scalability, as multiple units can be connected in parallel or series to meet different treatment capacities. This integration of electrochemical processes into a single prefabricated unit addresses critical challenges in modern wastewater management by combining high efficiency, operational simplicity, and portability. Description • Power Requirements: Operates on low-voltage DC power (≤ 40 V) for safety. • Electrode Materials: Iron or aluminum electrodes function as sacrificial anodes releasing Fe³⁺ or Al³⁺ ions. • Oxidation Pathways: Hydroxyl radicals (·OH), active chlorine, and sulfate radicals achieve mineralization of resistant organics. • Electroflotation: Micro-bubbles reduce sludge density, improving solid– liquid separation efficiency. • Compact Design: Entire system is housed in a prefabricated modular container, reducing installation time and cost. The invention provides a modular wastewater treatment unit capable of simultaneously removing colloidal, suspended, and dissolved contaminants using only an electrical power supply. The system is factory-built, easy to transport, and quick to install, making it suitable for emergency response and remote locations. Wastewater treatment is a complex process that traditionally requires specialists and various chemicals, such as coagulants, making the construction and commissioning of treatment plants time-consuming. This creates a need for compact, rapidly deployable treatment systems. Prefabricated wastewater treatment packages meet this need, as they are factory-built, easily transported, and can be operational shortly after installation. They are particularly valuable in emergencies—such as floods or earthquakes—where damaged infrastructure threatens public health by risking waterborne disease outbreaks. An effective example is an integrated package combining electrochemical treatment and electroflotation, which requires only an electrical power source to operate. This system consists of three key sections (as shown in Figure 1). In the first section, wastewater passes through iron or aluminum electrodes, releasing trivalent metal ions (Fe³⁺ or Al³⁺) that act as coagulants. These ions cluster suspended particles (including settleable and colloidal solids) into larger flocs, increasing their weight and improving their separation. Simultaneously, the electric current enables multiple pollutant-removal pathways: (a) direct oxidation at the anode, (b) indirect oxidation via hydroxyl radicals, (c) Electro-Fenton and cathodic Fenton processes, (d) indirect oxidation using active chlorine (if chloride is present), (e) sulfate electrolysis generating sulfate radicals, and (f) cathodic reduction—all contributing to the degradation of dissolved organic contaminants. The wastewater then flows into the second chamber, which contains additional electrodes. Here, along with continued electrochemical reactions, water electrolysis produces fine bubbles of oxygen and hydrogen. These bubbles attach to suspended particles, carrying them to the water’s surface. A mechanical paddle skims these floated solids into a third compartment. The treated wastewater is discharged from the outlet of the second chamber. Finally, in the third section, a pump removes the accumulated floating sludge from the water surface, completing the treatment process.

[0002] Brief Description of Drawings [Fig 1]: Schematic diagram of the integrated electrochemical-electroflotation wastewater treatment unit

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Claims

Claims 1.- A prefabricated wastewater treatment unit integrating electrochemical coagulation, electrooxidation, and electroflotation, comprising: (A) a first chamber with iron or aluminum electrodes for releasing Fe³⁺ or Al³⁺ coagulant ions and for performing electrochemical oxidation reactions, (B) a second chamber with electrodes generating fine gas bubbles via electrolysis for flotation of suspended solids, (C) a third chamber for collection and removal of floated sludge, wherein the system operates solely using an external electrical power source without continuous addition of chemical coagulants. 2.- The system of claim 1, wherein multiple oxidation pathways including direct anodic oxidation, hydroxyl radical oxidation, active chlorine oxidation, sulfate radical oxidation, and electro-Fenton reactions occur simultaneously in the first chamber. 3.- The system of claim 1, wherein hydroxyl radicals (·OH) are generated in- situ on the electrode surface or through Fenton reactions to mineralize refractory organic contaminants. 4.- The system of claim 1, wherein the electroflotation section utilizes hydrogen and oxygen micro-bubbles produced via water electrolysis to lift coagulated solids to the water surface for mechanical skimming. 5.- The system of claim 1 is compact, transportable, and rapidly deployable, enabling immediate wastewater treatment in emergency scenarios such as floods, earthquakes, or industrial accidents. 6.- The system of claim 1 operates on low-voltage direct current (≤ 40 V) for safety and energy efficiency. 7.- The system of claim 1 is configured for scalable treatment capacity by connecting multiple modular units in parallel or series.

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