What are the methods to degrade COD?

Degradation methods of COD content in sewage, rivers and other water quality mainly include adsorption method (physical adsorption, chemical adsorption and ion exchange adsorption), water quality coagulation separation method, electrochemical method (bad stability), ozone oxidation method, biological method, etc..

Adsorption method:

The adsorption method is a method of removing COD in wastewater by taking advantage of the large surface area of the adsorbent. The result of adsorption is to make the COD components gather on the surface of the adsorbent and completely separate from the water body. According to the different adsorption mechanisms of adsorbents, adsorption can be divided into physical adsorption, chemical adsorption and ion exchange adsorption.

In the actual adsorption process, one of them is the dominant adsorption, and the other is the cooperative adsorption, and it is difficult to distinguish clearly. The adsorbent is generally made of porous materials, which have a large surface area and can concentrate a lot of organic adsorbates.

At present, the adsorbents used for water treatment include activated carbon, diatomaceous earth, kaolin, activated alumina, zeolite and ion exchange resin. From an economic point of view, in the actual electroplating wastewater treatment, the most widely used activated carbon is inexpensive and easy to recycle.

Inorganic coagulants are used in a relatively large amount in water treatment. In the development of industrialization in recent years, inorganic coagulants have not only greatly increased in output, but also significantly improved in technology, especially in inorganic coagulants. Polymer coagulants. Research on composite coagulants is more popular. Inorganic polymer coagulants can be divided into aluminum salt series and iron salt series according to the composition of metal salts.

The inorganic polymer coagulants commonly used in water treatment at this stage include polyaluminum chloride, polyferric chloride, polyaluminum ferric chloride, polyaluminum ferric silicate and so on. Coagulation tests were carried out on wastewater from steel mills and paper mills using polyaluminum ferric silicate, polyaluminum chloride and polyferric sulfate. The results show that polyaluminum ferric silicate has better effects in removing turbidity and color, and sludge The settling volume is the smallest, the settling time is the shortest, and the speed is the fastest. When the optimum dosage is 2g/L and pH is 7._5, the removal rates of COD, turbidity, chroma and TSS are 43.1%, 94%, 90.7% and 92%, respectively, which are more effective than ordinary aluminum salts in coagulation. more advantage.

Water quality COD biological removal method:

The catalytic oxidation method is an improvement of the traditional oxidation method. A catalyst is introduced into the wastewater treatment, and the catalyst is used to reduce the reaction energy barrier so that the oxidant generates highly oxidizing free radicals and reacts with the pollutants in the wastewater to achieve the purpose of reducing COD. From the perspective of catalytic oxidation reaction conditions, catalytic oxidation methods include photocatalytic oxidation, electrocatalytic oxidation and chemical catalytic oxidation. From the perspective of whether the catalyst and the reactants belong to the same phase, catalysts can be divided into homogeneous and catalysts.

The catalyst is generally a solid catalyst supported on a carrier (porous substance), which is convenient to use and recover and is relatively widely used in the COD treatment of wastewater. The chemical catalytic oxidation method has mild conditions and high COD removal efficiency at normal temperature and pressure and is widely used in the treatment of high COD industrial wastewater such as medicine, chemical industry, and dyestuffs. The effect of ozone catalytic oxidation process on the removal of trace organic pollutants pyrene and fluoranthene in water was investigated.