Paper is a widely used consumable in daily life, which has spurred the development of paper mills. However, paper mills discharge a large amount of wastewater during manufacturing. Paper wastewater belongs to the category of difficult to solve wastewater, and it produces paper black liquor, which contains lignin, fibers, volatile organic compounds, etc. It has a strong odor and pollution. The papermaking industry uses wood, wheat straw, reeds, shredded cloth, etc. as raw materials, and separates cellulose through high-temperature and high-pressure cooking to make paper pulp. During the production process, the non fibrous portion of the discharged raw materials becomes papermaking black liquid. Black liquor contains lignin, fibers, volatile organic compounds, etc. It has an unpleasant odor and strong pollution.

The composition of pulp and paper wastewater is very complex, and its composition depends not only on the method of paper pulp, but also on various factors such as the type of commodity and raw material used. The suspended substances in the wastewater of the papermaking industry mainly come from the tree roots, grass shavings, sediment in the material preparation section, as well as the furnace ash, slag discharged with the water, fibers and fillers lost in various processes of pulp and paper making; The main source of BOD in wastewater comes from the pulping and cooking process, such as glycogen, aldehydes, organic compounds, etc. generated by fiber decomposition. In chemical pulp, BOD5 in cooking wastewater accounts for more than 80%; The COD and coloring substances in wastewater mainly come from lignin and derivatives in the pulp and cooking process; The harmful substances in wastewater mainly include crude sulfate soap in cooking wastewater, organic fluorides in bleaching wastewater, as well as small amounts of mercury, phenols, etc. However, these harmful substances are usually very low in content. The toxicity and "three effects" of organic fluorides in bleaching wastewater have caused increasing concern in developed countries. Below, the editor will tell you about the treatment methods for paper mill wastewater. Let's learn together.

Physical and chemical methods for treating papermaking wastewater: In the advanced treatment of papermaking wastewater, physical and chemical methods have advantages such as fast remediation and good solution effects,

The commonly used methods include advanced oxidation method, flocculation precipitation method, membrane separation method, adsorption method, etc.

1. Advanced oxidation method for papermaking wastewater treatment

Also known as deep oxidation technology, under the influence of oxidants, electricity, sound, light irradiation, catalysts, etc., the oxidation ability is generated to interact with organic matter, such as addition, substitution, electron transfer, bond breaking, ring opening, etc., which oxidizes and degrades difficult to degrade macromolecular organic matter in wastewater into slightly toxic or non-toxic small molecule substances, and even directly decomposes into CO: and H: O, achieving the effect of harmless treatment.

The characteristic of this technology is that it has the advantages of fast reaction speed, high efficiency in solving problems, damage to toxic pollutants, no secondary pollution, wide applicability, and easy to use;

Widely used in the treatment of harmful and difficult to degrade industrial wastewater such as pharmaceutical, biochemical, printing and dyeing organic wastewater, it has gradually become a hot research topic in the solution of difficult to degrade wastewater.

2. Flocculation precipitation method for treating papermaking wastewater

It is a aggregation product formed by coagulants, which removes large molecular weight pollutants floating and gelatinous in water through a series of effects. This method has been widely used for the tertiary treatment of pulp and paper wastewater. In the operating environment, continuous treatment of papermaking wastewater using flocculation electro flotation can reduce the CODcr of the wastewater from 1416mg/L to 48.9mg/L.

3. Membrane separation method for papermaking wastewater treatment

Membrane separation method uses a special semi permeable membrane to separate solutes and solvents, allowing a certain solute in one side of the solution to penetrate through the membrane or solvent, thereby achieving the effect of separating solvents.

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