The wastewater generated by the paper industry is characterized by a wide variety of types, large water volume, and high organic pollutant content, making it one of the difficult industrial wastewater to treat. The wastewater comes from various processes of pulp and paper making, with different physical properties and concentrations of organic pollutants. Effective treatment processes are determined based on the characteristics of the wastewater. Currently, the main methods used for treating wastewater in the paper industry include sedimentation, air flotation, adsorption, membrane separation, aerobic and anaerobic biological treatment methods, as well as several process combination treatment methods. Regardless of the method used, wastewater needs to be pre treated. Pre treatment is mainly aimed at improving wastewater quality to meet the inlet requirements of various processes, enhancing the overall effectiveness of wastewater treatment, and ensuring the stability of the entire treatment system. Therefore, pretreatment plays a very important role in wastewater treatment in the paper industry.

The pretreatment of wastewater in the paper industry can be divided into in plant pretreatment and out of plant pretreatment. In plant pretreatment mainly involves the recovery of pulp from white water, often using filtration, air flotation, etc. for recycling and utilization, which can avoid a large amount of pulp entering the wastewater treatment system. This not only improves the yield of pulp but also saves the cost of wastewater treatment; Off site pretreatment is mainly aimed at ensuring that the wastewater entering the physical, chemical, biochemical and other treatment systems can meet the process requirements to the greatest extent possible, and enable the system to operate stably.

The pre-treatment process mainly consists of grilles, screens, fiber recovery systems, regulating water volume and quality, and other process components. Different pretreatment methods can be adopted according to the water quality of different paper industry wastewater to remove some pollutants, improve wastewater quality, and achieve the best treatment effect of the entire wastewater treatment system.