Introduction of wastewater treatment technology of Shandong Everbright Technology Development Co., LTD

Shandong Everbright Technology Development Co., Ltd. is located in Dongping County Industrial Park at the foot of Mount Tai and by the side of Dongping Lake, mainly engaged in the research and development, production and sales of cellulose ether, starch ether and medicinal excipients. The company was established in September 2009, wholly owned by Shandong Everbright Group, covers an area of 330 mu, with a total investment of 560 million yuan, construction of plants and other facilities of 60,000 square meters.

Our company hydroxypropyl methyl cellulose (HPMC) project adopts the "slurry method" production process, which is the non-ionic cellulose mixed ether obtained from refined cotton in inert solvent through the process of alkalization, etherification, neutralization and washing. The main raw materials are refined cotton, caustic soda, toluene, isopropyl alcohol, methyl chloride, propylene oxide and so on.

The refined cotton is crushed and alkalized with concentrated alkali to obtain uniform alkalization alkali cellulose. The alkali cellulose is etherized with the etherizing agent propylene oxide and methyl chloride in the inert solvent containing low concentration lye at low temperature and high temperature respectively, and then hydroxypropyl methyl cellulose is made through the process of dissolving, washing, drying, grinding, mixing, packaging and so on. Industrial grade HPMC, pharmaceutical food grade HPMC production process is roughly the same, mainly the selection of raw materials and washing and so on slightly different.

The main pollution producing link of hydroxypropyl methyl cellulose in the process of production is the dissolving wastewater in the process of solvent recovery. The wastewater produced by washing and separation contains salts, toluene, isopropyl alcohol, propylene oxide, chloromethane, etc. In addition, there are drainage of vacuum system, flushing wastewater of workshop floor and equipment, acid and alkali wastewater discharged from soft water station, sewage discharged from circulating water system, and domestic wastewater produced by office and life.

Production process wastewater CODcr is about 30,000-40000mg /L; BOD5 ≤1000mg/L, the sewage is discharged 24 hours, the discharge is uneven.

According to the characteristics of sewage generation, a sewage treatment station of 700m3/d is designed in the project, in which the regulating pool is enlarged to 1500m3. It also acts as an accident pool and is linked with a special accident pool to ensure that nothing goes wrong.

According to the nature of sewage, the comprehensive disposal scheme of sewage separation and quality treatment is adopted. Among them, the first four items of sewage enter into the pretreatment system of the sewage treatment station. After the pretreatment removes cellulose, benzene chain break and dechlorination, and improves the biodegradability of the sewage, they enter into the biochemical comprehensive treatment unit of the sewage treatment station together with domestic sewage. After reaching the standard of entering the county sewage treatment station, the sewage discharged from the discharge tank and circulating cooling water is mixed into the sewage network of the park.

The sewage treatment process of sewage treatment station is as follows:

A. Wastewater treatment unit

The pretreatment of wastewater is one of the key factors for the effective operation of the whole system. There are many kinds of production wastewater with complex composition, some of which contain high salt content and poor biochemical properties, and some of which contain toxic substances, which can inhibit or poison the growth of microorganisms. Therefore, it is necessary to remove or destroy as much as possible before biological treatment process, so as to ensure the normal operation of biochemical treatment process and have a high removal rate. Pretreatment can maximize the removal of macromolecular organic matter, toxic substances, suspended small particles and other biodegradable substances.

① Neutralization sedimentation tank

The main function of the neutralization sedimentation tank is to adjust the pH value and precipitate the sewage at the same time to achieve the effect of removing SS in the sewage and the purpose of reducing COD.

② Microelectrolytic reactor

Using the principle of electrochemistry, using the special shape three-dimensional electrode technology, through the liquid phase and gas phase electrode reaction, under the catalytic action of liquid phase anode dissolving fresh particles, the gas phase anode products play a selective oxidation role, destroy the structure of polymer compounds, remove the hair group, and complete a series of processes such as oxidation, reduction, adsorption, coagulation. After treatment by this device, COD and chroma can be significantly reduced, and BOD5 can be significantly increased, so that the subsequent biochemical treatment can be carried out smoothly.

(3) Efficient coagulation sedimentation tank

In the efficient coagulation sedimentation tank, the fine suspended matter in the wastewater will undergo coagulation reaction with the added coagulant and gradually form a larger floc. The floc generated by the coagulation reaction will be precipitated and separated by the rectification system and inclined plate precipitation, so that a large amount of suspended matter and part of COD in the wastewater will be removed from the water and the wastewater will be partially purified. Applying the theory of shallow sedimentation, the clarification is divided into many shallow sedimentation tanks, such as increasing the sedimentation area and shortening the sedimentation time; In the reaction tank, the principles of compression diffusion layer and adsorption bridging are used to make the suspended substances in water destabilize, condense into large particles, and improve the precipitation effect. Ring gap drainage to ensure smooth drainage. The residence time of wastewater in the high efficiency coagulation sedimentation tank is 6 hours.

④ Dissolved gas floating

Main functions: To remove the residual suspended matter in the coagulation tank, reduce the pollution to the catalytic oxidation device packing, to ensure the efficient and stable operation of the catalytic oxidation tower.

Part of the treated wastewater circulates into the dissolved air tank, and under the state of pressurized air, the air is supraturated and dissolved, and then mixed with the raw water added with flocculant at the entrance of the air floating tank. As the pressure decreases, the supraturated air is released and forms tiny bubbles, which quickly adhere to the suspended matter and lift it to the surface of the air floating tank. This creates an easily removed sludge floating layer, and heavier solids deposited on the bottom of the pool are also removed.

(5) photochemical catalytic oxidation

Photochemical catalytic oxidation is mainly the use of light and strong oxidant and catalyst together produced strong comprehensive oxidation to oxidize and decompose organic matter and inorganic matter in wastewater, to achieve the purpose of purifying water quality. The main principle is to use metal ions as the catalyst of hydrogen peroxide, supplemented by ultraviolet radiation, the reaction process produces hydrogen and oxygen free radicals, greatly improving the efficiency of oxidation reaction. By adding low dose oxidant to control the degree of oxidation, so that organic matter in wastewater partial oxidation, coupling or polymerization, the formation of molecular weight is not too large intermediate products, so as to change their solubility and coagulation precipitation, and then through adsorption to remove it. Compared with deep oxidation, this method can greatly save the amount of oxidant and reduce the total cost of wastewater treatment. Photocatalytic oxidation has a good effect on the removal of hydrocarbons, halides, carboxylic acids, surfactants, dyes, nitrogen-containing organic matter and organophosphorus insecticides in water.

B. Biochemical treatment process unit

① hydrolytic acidification

Before entering anaerobic treatment, hydrolysis treatment has dual functions. One is to conduct biological pretreatment of wastewater, improve its biochemical properties, and adsorb and degrade part of organic matter; The second is to digest the sludge of the system.

② Upflow anaerobic sludge reactor

The advanced UASB structure in China is adopted to give full play to the role of anaerobic bacteria. In the first stage, the refractory macromolecules are hydrolyzed into small biochemical molecules, part of the chrominosity is removed, and converted into organic acids under the action of acid-producing bacteria. In the second stage, methanogenic stage, methanogenic bacteria metabolize methanogenic gas using the small molecules of organic acids produced in the first stage.

③ Strengthen the SBR pool

The enhanced SBR reactor is divided into three zones: the bioselective zone, the facultative zone and the main reaction zone. The biological selection zone was set at the front of the SBR reaction tank and operated under anaerobic or facultative conditions. The facultative zone not only serves as a biological selection zone to assist anaerobic or facultative operation, but also plays a buffer role in the change of inlet water quality and quantity, and also has the effect of enhancing denitrification. Batch reactor has stronger impact load resistance and better treatment effect than continuous flow reactor.

④ Biochar filter

The SBR system drains water into the biochar filter to further remove organic matter and ammonia nitrogen in the wastewater to ensure that the effluent meets the standard requirements.

④ sludge thickening

The remaining sludge is discharged by the float into the sludge enrichment tank, where the sludge is concentrated. After the enrichment, the sludge volume is reduced by half.