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KR-20260065307-A - MODIFIED BREAK POINT CHLORINATION PROCESS FOR CHEMICAL OXIDATION TREATMENT OF PLATING WASTEWATER

KR20260065307AKR 20260065307 AKR20260065307 AKR 20260065307AKR-20260065307-A

Abstract

The present invention relates to a method for chemically oxidizing plating wastewater using a modified breakthrough point chlorination process. The present invention comprises: a primary oxidation step of forming primary treated water by injecting sodium hypochlorite into plating wastewater that has undergone primary chemical treatment processes such as reduction and coagulation reactions, while maintaining the redox potential at 850 to 900 mV, thereby primary oxidizing multiple pollutants including heavy metal-ammonia complex compounds, phosphorus compounds combined with said complex compounds, cyanide compounds, and organic matter; a secondary oxidation step of forming secondary treated water by injecting sodium hypochlorite into said primary treated water while maintaining the redox potential at 850 to 900 mV, thereby secondary oxidizing said multiple pollutants; a hydroxide reaction step of forming tertiary treated water by injecting sodium hydroxide into said secondary treated water to coagulate heavy metals and phosphate ions separated from said complex compounds to form hydroxide precipitates; and a coagulation step of forming quaternary treated water by injecting a polymer coagulant into said tertiary treated water to form multiple pollutant aggregates. The technical gist of the invention is to include: a residual chlorine removal step of injecting sodium sulfite into the above-mentioned 4th-grade treated water to form a 5th-grade treated water from which residual chlorine has been removed; and a solid-liquid separation step of separating the above-mentioned 5th-grade treated water from solid.

Inventors

  • 최병중
  • 김백규
  • 공명준
  • 임성진

Assignees

  • 부산장림표면처리사업협동조합

Dates

Publication Date
20260508
Application Date
20241101

Claims (5)

  1. A primary oxidation step of forming primary treated water by injecting sodium hypochlorite into plating wastewater that has undergone chemical pretreatment, while maintaining the redox potential at 850 to 900 mV, to primarily oxidize multiple pollutants including heavy metal-ammonia complexes, phosphorus compounds combined with said complexes, cyanide compounds, and organic matter; A secondary oxidation step of forming secondary treated water by injecting sodium hypochlorite into the primary treated water to maintain the redox potential at 850 to 900 mV while secondary oxidizing the multiple pollutants; A hydroxide reaction step of forming a tertiary treated water by injecting an alkali metal or alkaline earth metal containing a hydroxide group into the secondary treated water to aggregate heavy metals and phosphate ions separated from the complex compound to form a hydroxide precipitate; A coagulation step of forming a quaternary treated water by injecting a polymer coagulant into the above tertiary treated water to form a multi-pollutant aggregate; A residual chlorine removal step of injecting sodium sulfite into the above-mentioned 4th treated water to form 5th treated water from which residual chlorine has been removed; and A method for chemically oxidizing plating wastewater using a modified breakthrough point chlorine treatment process, characterized by including a solid-liquid separation step for separating solids and liquids from the above-mentioned fifth treated water.
  2. In Article 1, The above first oxidation step is, A chemical oxidation treatment method for plating wastewater using a modified breakthrough point chlorination process, characterized by injecting sodium hydroxide to maintain a pH of 6.5 to 8.0.
  3. In Article 1, The period between the above secondary oxidation step and the above hydroxide reaction step is, A method for chemically oxidizing plating wastewater using a modified breakthrough point chlorination process, characterized by further including an oxidation reaction retention step of receiving the secondary treated water and securing a retention time for the oxidation of residual cyanide of the cyanide compound.
  4. In Paragraph 3, Between the oxidation reaction retention step and the hydroxide reaction step, A method for chemical oxidation treatment of plating wastewater using a modified breakthrough point chlorination process, characterized by further including an oxidation power monitoring step of monitoring whether the redox potential of 850 mV or higher and pH 6.5 to 7 are maintained for the secondary treated water.
  5. In Article 1, The above secondary oxidation step is, A chemical oxidation treatment method for plating wastewater using a modified breakthrough point chlorination process, characterized by further injecting sulfuric acid into the primary treated water.

Description

Method for Chemical Oxidation Treatment of Plating Wastewater Using a Modified Break Point Chlorination Process The present invention relates to a method for chemically oxidizing plating wastewater using a modified breakthrough point chlorination process. Korea's plating industry has developed alongside the growth of the automobile, shipbuilding, electronics, and machinery industries, and plays an important role as one of the foundational industries. According to industry-specific data from the Ministry of Environment's Environmental Statistics Portal, as of 2021, approximately 42,637 m³ of plating wastewater is generated daily, and there are about 1,864 plating wastewater discharge facilities in the country. Plating wastewater contains heavy metals such as copper, nickel, chromium, zinc, and iron, as well as cyanide, and in particular, contains large amounts of harmful substances and non-biodegradable organic substances that are detrimental to the human body. In plating wastewater, cyanide and heavy metals can combine through complex chemical reactions to form complex compounds. Additionally, when ammonia ( NH₃ ) and nickel ions ( Ni²⁺ ) combine, complex compounds such as hexaammine nickel(II) ions exist. Furthermore, non-biodegradable phosphates generated during the electroless plating process are also difficult to treat and are important substances that must be treated in plating wastewater. Currently, oxidation methods used for plating wastewater treatment include Fenton oxidation, ozone oxidation, and Break Point Chlorination (BPC). Fenton oxidation is a representative advanced oxidation treatment method that oxidizes and decomposes oxidized substances by generating hydroxyl radicals with strong oxidizing power. It involves adding hydrogen peroxide and divalent iron ions, which act as catalysts, to generate hydroxyl radicals as reaction products, thereby removing recalcitrant organic pollutants and treating bound pollutants in plating wastewater. However, this method requires reacting the iron ions (catalyst) with the hydrogen peroxide (oxidizing agent) in an acidic environment with a pH of 2 to 4 to generate hydroxyl radicals. This necessitates precise pH management and generates excessive sludge, while also causing high corrosiveness and scale formation. Furthermore, hydrogen peroxide content exceeding 6% is a toxic substance requiring high management, whereas concentrations below this level present a significant economic burden due to high unit costs. Ozone oxidation is an oxidation process utilizing ozone ( O₃ ). Ozone reacts with water to generate hydroxyl radicals and hydroxide ions, and these generated hydroxyl radicals oxidize and decompose recalcitrant organic and inorganic pollutants. However, due to the nature of ozone generators that produce electrical discharge (corona discharge) using oxygen or air, they require high energy, which is a disadvantage as they result in high installation and operating costs. Such high energy costs make them unsuitable for large-scale wastewater treatment facilities. In particular, because ozone itself is toxic, it can pose a risk to workers and the working environment. Additionally, ozone oxidation has the disadvantage of requiring additional management processes due to the possibility of incomplete oxidation and its susceptibility to pH and temperature. Breakpoint chlorination is a process that involves injecting chlorine to react with ammonia nitrogen ( NH₃ -N) within Total Nitrogen (TN), a water pollutant, to generate combined residual chlorine. This chlorine is then oxidized and removed into harmless nitrogen gas, while the residual chlorine provides a sterilization effect. During this process, sodium hypochlorite (NaOCl) dissociates into hypochlorous acid (HOCl). This hypochlorous acid reacts with oxidizable substances, such as organic matter and ammonia, consuming chlorine to form chloramines. Ultimately, the breakthrough point is reached, allowing pollutants to decompose while residual chlorine remains to exert a sterilization effect. However, conventional breakthrough point chlorination processes have often caused problems involving complex treatment procedures, high chemical usage, and sludge generation. Therefore, there is a practical need for a method that can efficiently solve problems such as complex treatment procedures, excessive generation of solid-liquid sludge, and high chemical costs in the plating wastewater treatment process, thereby treating ammoniacal nitrogen, heavy metal complex compounds, and non-biodegradable organic substances contained in plating wastewater while simultaneously minimizing environmental impact and economic burden. Figure 1 is a process flow diagram showing the chemical oxidation treatment method of plating wastewater using the modified breakthrough point chlorine treatment process of the present invention in steps. The present invention is susceptible to various modifications and may have various embodiments, and s