Paper wastewater treatment

In the process of papermaking, not only do we use a lot of raw materials, but we also 

have a high dependence on water resources. As a result, the paper mill will discharge 

a large amount of wastewater. If not treated in a timely manner, it not only wastes 

water resources but also pollutes the environment.

（1） What types of wastewater are present in papermaking wastewater?

Papermaking wastewater is not only a large amount of industrial wastewater, but also 

contains different types of wastewater, which makes it difficult to treat. 

At the same time, different treatment methods need to be adopted according to the 

water quality of different wastewater.

① Steaming wastewater refers to the wastewater discharged after the cooking of raw 

materials, which contains a large amount of lignin, carbon oxides and derivatives, volatile 

organic compounds such as methanol, and inorganic substances such as alkali and carbonate 

sulfate. The solution color is red or black. Therefore, these wastewater have the characteristics 

of complex composition, poor biodegradability, and high concentration.

② Paper making wastewater mainly contains small fibers, which are white in color. Its organic 

concentration is relatively low and contains many degradable substances. It is generally used 

for reuse and is a relatively easy to treat wastewater in papermaking.

③ Bleach wastewater contains a large amount of organic chlorinated compounds, which are 

highly toxic and difficult to degrade by microorganisms, making treatment challenging.

There are many other types of wastewater, and during the treatment process, we use corresponding 

pretreatment methods based on water quality, water quantity, and other factors, We then use biological 

methods to remove organic matter from the wastewater, and finally achieve standard discharge of 

papermaking wastewater through deep treatment.

（2） What are the treatment methods for papermaking wastewater?

Proper pretreatment of papermaking wastewater is a prerequisite for 

ensuring the effectiveness of biochemical treatment. Pre treatment methods 

include air flotation, oxidation, membrane separation, etc.

The air flotation method is a commonly used method to remove suspended solids 

and organic matter from papermaking wastewater. The principle is that when air is 

introduced into the water, it can generate small bubbles. In order to allow the alum 

flowers formed by small suspended solids in the water to adhere to the air bubbles, a 

coagulant needs to be added to the wastewater. In this way, the so-called floating slag 

is the suspended solids that float up with the bubbles, which can effectively recover 

suspended solids in the water and improve water quality.

Oxidation method can improve the biodegradability of papermaking wastewater and 

remove organic matter from the wastewater. Among them, Fenton oxidation method is 

a commonly used oxidation method. The principle is that H2O2 generates hydroxyl radicals (· OH)

 with strong oxidation ability under the catalytic action of Fe2+, which accelerates the oxidation of 

organic pollutants and further converts organic molecules into small molecules such as CO2 and H2O.

Biological treatment utilizes the metabolic function of microorganisms to degrade and convert dissolved

 and colloidal organic pollutants in wastewater into harmless and stable substances, thereby purifying the wastewater.

Generally, anaerobic biological treatment and aerobic biological treatment are required. 

① Anaerobic method is a method of treating wastewater through anaerobic microbial degradation and metabolism 

under anaerobic conditions, including UASB reactor, IC reactor, EGSB reactor, etc. 

② Aerobic treatment is a method of utilizing aerobic microorganisms to degrade and metabolize wastewater und aerobic conditions. Common aerobic treatment methods include biological contact oxidation, biological fluidized bed, SBR, and others.

Papermaking wastewater is the most obvious problem - high pollution. Compared to ordinary industrial 

wastewater, its concentration is higher, and its internal chemical composition is very complex, making degradation difficult. 

Currently, the main treatment measure for this type of wastewater is the combination technology method, which achieves 

standard discharge of wastewater through a combination of physical and chemical treatment and biochemical treatment. 

In the future, there will be more utilization of papermaking wastewater to achieve recycling, so membrane separation and 

other technologies will also be indispensable.