The development process and background of industrial wastewater treatment

Analysis of domestic and foreign sewage treatment development history, combined with China's development status of the 18th National Congress report pointed out: construction of ecological civilization, chemical enterprises towards green development, efficient development, low-carbon development direction transformation. Increase the intensity and requirements of pollution control and sewage treatment, and actively study and innovate to make our country have their own sewage treatment technology while constantly absorbing advanced technology of foreign sewage treatment. In the second half of 2015, the benefits of regional chemical enterprises began to decline, due to the national environmental protection policy strict requirements of enterprises to increase investment in environmental protection, overcapacity, sales decline, and higher prices of many reasons, the speed of industrial development has been affected to varying degrees. In the initial stage of transformation, the phenomenon of industrial development fluctuations is normal, we must adhere to the transformation. Continuous improvement.

2. Research status of industrial wastewater treatment

2.1 Process and principle of wastewater pretreatment The process treatment before biochemical treatment is called pretreatment. The biochemical system runs smoothly and the investment cost and operation cost are relatively small. However, it is not possible to treat wastewater by biochemical treatment alone, because industrial wastewater contains some active substances that can damage the ecosystem: Microorganisms and fungi have the presence of inhibiting and destructive substances, so in order to ensure the healthy operation of the biochemical system, a series of pretreatment must be carried out before the sewage enters the physicochemical section to adjust the biodegradability of the water quality and ensure the healthy operation of biochemical treatment.

There are two specific purposes of pretreatment: first, the organic or inorganic substances contained in the wastewater that have an impact on the active substances of the sludge in the biochemical tank are separated and removed to a certain extent or transformed into other harmless forms to protect the growth environment of the active substances of the sludge; The second is to reduce the chroma, salinity and suspended particles of the water before the biochemical section, adjust the COD load, and reduce the operating pressure of the biochemical section. Impurities in wastewater can be divided into suspended matter, colloids and dissolved matter according to particle size, and other large particles with particle size greater than 100 μm generally will naturally precipitate or separate from the water body. Colloids and fine particles and suspended matter need condensation, flocculation and coagulation methods to convert small particles into large particles, precipitate and separate from the water body.

1.1.1 Coagulation method and flocculation method Add coagulation agents containing positive ions or groups in wastewater. Using the principle of electrostatic induction, when adding a large number of positive ions or groups into colloids, a large number of positive ions will form a large number of colloidal particles between colloidal particles to coagulate and adsorb together to form macromolecular groups. It is easy to separate from the water body to achieve the purpose of water purification. The most used coagulants are aluminum sulfate, ferrous sulfate, alum, ferric chloride and so on. Flocculation method is the use of polymer coagulant in sewage to form a linear polymer polymer, polymer structure between the particles adsorption combination to form a relatively stable bridging effect, in this subunit between the continuous formation of bridging accumulation, condensation polymer material continues to grow, and finally reached saturation to form large particles of flocculant condensation together. Commonly used flocculants are polyacrylamide (PAM), polyiron (PE) and so on.

1.1.2 Coagulation method As the name suggests, the coagulation method is a method that combines coagulation and flocculation. Coagulation method is often applied in the process of industrial sewage pretreatment, the basic process is roughly the first to add coagulant (alum, ferrous sulfate and other agents) to the sewage, eliminate the electrostatic repulsion between colloidal particles, and then add flocculant (PAM, PE and other agents), so that the radius of the particles in the water increases, forming precipitation.

1.1.3 After the removal and treatment of sewage impurity particles into the iron carbon micro-electrolysis section Iron carbon treatment method is also called iron carbon micro-electrolysis method or iron carbon internal electrolysis method. Iron carbon micro-electrolysis uses the REDOX reaction of Fe2 + /Fe3 + in iron carbon micro-electrolysis. Iron carbon micro-electrolysis will form countless tiny units of iron carbon galvanic cells. The activity of active electrons is generated, which promotes the reactivity of organic matter in the sewage, makes the toxic and unsaturated substances in the sewage decompose and transform into other forms, reduces the load of chemical oxygen demand COD and biological oxygen demand BOD5, and lays the foundation for the normal operation of the subsequent treatment section. Iron carbon micro-electrolysis is an important means of industrial wastewater treatment. The iron carbon method has a remarkable effect on the treatment of industrial wastewater with toxic and high COD concentration. The reaction principle of the iron-carbon method is recognized as follows: under acidic conditions, iron-carbon fillers are added to water, forming a galvanic reaction between iron and carbon, forming a local unit of a large number of micro-current reaction areas, and promoting the reduction and oxidation of inorganic substances in sewage under the action of micro-current. The treatment effect of iron carbon micro-electrolysis is good in the actual sewage treatment, and the treatment effect has been recognized. The shortcomings of iron carbon method analysis: ① the price of iron carbon filler is not cheap, in the acidic conditions are decomposed, part of the incomplete reaction of iron filings and carbon will remain in the water, increasing the amount of sewage solid waste, blocking the instrument pipeline; ② Iron forms black iron sulfide in sulfur-containing wastewater under acidic conditions, which increases the color of the water, and a large number of iron ions enter the water to increase the salt content of the water.