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Papermaking wastewater is a kind of difficult-to-treat wastewater, and it will produce papermaking black liquor. The black liquor contains lignin, cellulose, volatile organic acids, etc. It has odor and strong pollution. Because the physical and chemical method has the advantages of fast treatment and good treatment effect, it is widely used in the advanced treatment of papermaking wastewater. The commonly used physical and chemical methods include: advanced oxidation method, flocculation precipitation method, membrane separation method, adsorption method, etc.
1. Advanced oxidation method
Advanced Oxidation Processes (AOPs for short), also known as deep oxidation technology, is a new technology developed in the 1980s for the treatment of refractory organic pollutants. Under the action of oxidant, electricity, sound, light irradiation, catalyst, etc., it has extremely strong oxidation ability (its potential is 2.80V, second only to fluorine 2.87V [-OH] and then through the addition of [-OH] and organic compounds The formation, replacement, electron transfer, bond breaking, ring opening and other functions make the refractory macromolecular organic matter in the wastewater oxidatively degrade into low-toxic or non-toxic small molecular substances, and even directly decompose into CO: and H: O The purpose of harming.
The technology has the advantages of fast reaction speed, high processing efficiency, complete destruction of toxic pollutants, no secondary pollution, wide application range, easy operation, etc., and is widely used in toxic and difficult to degrade industrial wastewater such as pharmaceuticals, fine chemicals, printing and dyeing In the treatment of organic wastewater, etc., it has gradually become a hot spot in the research of refractory wastewater treatment.
According to the way of generating free radicals and the reaction conditions, it can be divided into Fenton oxidation method, supercritical water oxidation method, photocatalytic oxidation method, ultrasonic oxidation method, electrocatalytic oxidation method, ozone oxidation method and wet oxidation method.
2. Flocculation and precipitation method
The flocculation precipitation method is a method of removing polymerized pollutants suspended and colloidal in water through a series of actions by a polymerization product formed by a flocculant. For the three-stage treatment of pulp and paper wastewater, this method has been widely used. Under optimal operating conditions, flocculation-electric flotation is used to continuously treat papermaking wastewater. The CODcr of wastewater can be reduced from 1416mg / L to 48.9mg / L.
3. Membrane separation method
The membrane separation method uses a special semi-permeable membrane to separate the solute and the solvent, so that a certain solute in the solution on one side permeates through the membrane or the solvent, so as to achieve the purpose of separating the solvent.
The traditional two-phase anaerobic process (BS) and membrane separation technology combined system (MBS) is used to treat papermaking black liquor configuration wastewater. The results show that the system COD removal rate can reach 73.1, higher than the BS system (48.6%) It is superior to the BS system in terms of anaerobic sludge activity and operating stability; when the COD load is 6kg- (m3-d) -1, the MBS acidification rate is 20.1%, and the acidification level is 7.5%, which is slightly better than the BS system (respectively 7.0% and 5.0%).
4. Chemical method
The chemical method is a professional agent that achieves the reduction of pollutant indicators by adding specific chemical agents. The agent has environmental removal products with high removal rate, fast reaction speed, small dosage, easy addition, convenient use and no secondary pollution. After the end is added, it can be directly discharged.