The development process and background of industrial wastewater treatment

1.1.4 Neutralization of pH Industrial wastewater generally uses sodium hydroxide and sulfuric acid to regulate pH.

1.1.5 Fenton oxidation wastewater flows into Fenton reaction, and hydrogen peroxide H2O2 is added. H2O2 and Fe2 + brought by electrolytic reaction form strong oxidizing Fenton reagent, which can produce ·OH radical with strong oxidizing ability. Under catalysis, The free radical can destroy the polymer aromatic ring, which is difficult to be removed by biochemical removal, so as to degrade and remove. The biodegradability of wastewater is greatly improved, and the B /C ratio is increased. In addition to the above process, the pretreatment of wastewater also includes membrane separation, air flotation, filtration, disinfection ion exchange and adsorption and other physical and chemical sections. According to the actual situation of factory sewage, different process requirements are selected for wastewater pretreatment.

1.1 Biochemical Treatment process and Principle of Industrial wastewater At present, most industrial wastewater treatment is bioactivated sludge process. The use of biological activated sludge process has evolved A large number of treatment techniques, industrial park secondary sewage treatment plants commonly used treatment processes are: A /O phosphorus removal process, A /O nitrogen removal process, AB process, A2 /O phosphorus removal and nitrogen removal process, UASB process, oxidation ditch series process. The different distribution and combination of treatment facilities make the processing focus and operation debugging of different treatment processes different. With the continuous development and progress of sewage treatment has been formed: A /O process, UASB process, ion exchange resin, reverse osmosis water treatment technology, biofilm method and other typical biochemical treatment processes. The following will be an in-depth introduction to these several widely used processing processes.

2.2.1 A /O(A2 /O) process A /O is the abbreviation of Anoxic /Oxic(anaerobic/aerobic) or Anerabic /Oxic(anaerobic/aerobic) technology, which is an important treatment process for the biological treatment of sewage to remove phosphorus and nitrogen. In the process of biological nitrogen removal, as denitrifying bacteria are anaerobic bacteria, they need a large amount of carbon sources to maintain metabolism and achieve denitrification process. However, after the aerobic nitrification reaction, the concentration of organic matter (carbon source) in polluted water is low, which cannot provide sufficient demand for denitrification. In the traditional biological dephosphorization and nitrogen removal section, methanol is added in front of the anoxic unit to supplement the content of organic carbon sources. The anaerobic section is placed before the aerobic section, and the organic matter contained in the water is used as the carbon source. This method is called pre-denitrification process. Nitrate and nitrite are introduced into the anoxic reaction section through the mixed liquid reflux.

AB process AB process is a new two-stage biological treatment process, that is, adsorption biodegradation method for short. AB process is A high-load method and two stages of activated sludge method combined treatment method, A, B two sections are strictly separated, so that different characteristics of bacteria are separated, played a complementary, complementary role. Therefore, AB process has higher removal rates of BOD5, COD, SS, TP and ammonia nitrogen than traditional activated sludge process. However, the AB process cannot achieve the effect of deep phosphorus and nitrogen removal, because the limit of phosphorus and nitrogen removal is restricted, and there are still a large number of nutrients in the sewage, which is easy to lead to eutrophication of the water body. Principle: The main role of AB process in the removal of pollutants in sewage is reflected in the adsorption flocculation effect of section A. The sewage is directly connected to Section A through the pipeline, and the suspended matter in the wastewater is mixed with bacteria to form A copolymer with relatively stable structure, and at the same time, it provides abundant microorganisms for Section A. It increases the growth rate of the microbial community in section A under sewage treatment, shortens the microbial metabolic cycle, and decomposes a large number of viscous substances. This part of viscous substances interacts with suspended substances, large particles and free bacteria in the wastewater to form adsorption condensation, produce flocculant groups, and finally separate from the water through screen or precipitation. Stage B is similar to the ordinary activated sludge process.

2.2.3 UASB process The Chinese name of UASB is upflow anaerobic sludge bed, which includes the double-sided characteristics of anaerobic activated sludge method and anaerobic filtration method. Born in 1971 in Henan Agricultural University, researchers used the difference in the nature of substances with different densities under the action of gravity to create a three-phase separator, which created favorable conditions for the advent and upgrade of upflow anaerobic sludge beds. The UASB process has the advantages of simple structure, low operation, maintenance and operation difficulty, and is suitable for different kinds of industrial sewage treatment requirements. After long-term development and innovation, it has mature technical support and has been widely promoted and used. Principle: The composition of UASB is divided into sludge reaction zone, gas-liquid-solid three-phase separation and gas chamber. There is a large amount of anaerobic active sludge at the bottom of the reactor tower. Due to the condensation and suspension of this part of sludge, a suspended layer of sludge in good condition is formed at the bottom of the anaerobic tower. In the suspended state, the metabolism of microorganisms, bacteria and fungi is active. When the waste water enters from the bottom of the anaerobic tower, the organic matter will be fully catabolized by the active sludge components into biogas and produce bubbles. The bubbles continue to merge and float up under the action of water pressure, driving part of the sludge to float up into the three-phase separator on the upper part of the anaerobic tower, and the gas burst from the water surface into the biogas processing unit, where it is collected and derived from the UASB reaction tower. The other part of the floating sludge mixture enters the three-phase separator area, and the solid-liquid-gas mixture in the region is formed into large particle groups through the flocculation and coagulation of chemicals added in the three-phase separator. The density becomes larger and sinks to the bottom to continue to participate in the biochemical reaction of the activated sludge at the bottom. The metabolites of the activated sludge substances will continue to separate the sludge bed from the water outlet with the buoyancy. It is collected outside the tower and then processed into solid waste by a mud press.