I: Introduction

Papermaking wastewater treatment equipment refers to the treatment method for wastewater generated by the papermaking industry. Papermaking wastewater mainly comes from the two production processes of pulping and papermaking in the papermaking industry. Pulping and papermaking both discharge a large amount of wastewater; the wastewater generated by pulping is seriously polluted. The wastewater discharged during pulp washing is dark brown and is called black water. The concentration of pollutants in black water is very high, with a BOD of up to 5-40g/L, and contains a large amount of fiber, inorganic salts and pigments. The wastewater discharged from the bleaching process also contains a large amount of acid and alkali substances. The wastewater discharged from the papermaking machine is called white water, which contains a large amount of fiber and fillers and rubber added during the production process.

II. Papermaking wastewater treatment methods

Papermaking wastewater pretreatment: The pretreatment process mainly consists of grids, screens, fiber recovery systems, and processes to adjust water volume and water quality. Different pretreatment methods can be adopted according to the different water quality of papermaking industrial wastewater to remove some pollutants, improve the water quality of wastewater, and achieve the treatment effect of the entire wastewater treatment system.

Main treatment methods for papermaking wastewater: The SS and COD concentrations of wastepaper wastewater are relatively high. COD is composed of insoluble COD and soluble COD. Usually, insoluble COD accounts for the majority of the total COD composition. When SS is removed from the wastewater, most of the insoluble COD is removed at the same time. The BOD5 value in wastepaper wastewater is relatively low, and the ratio of BOD5 to COD is generally 0.15-0.25, with poor biodegradability. Coagulation treatment can only remove part of BOD5, and the removal of most of BOD5 should mainly be solved by biochemical methods. (1) Adopt flotation or sedimentation methods. By adding coagulants, most of the SS can be removed, and most of the insoluble COD and part of the soluble COD and BOD5 can be removed at the same time. Its typical treatment process is as follows: Sewage→Screen→Collection Tank→Floatation or Sedimentation→Discharge Floatation and sedimentation are both physical and chemical treatment methods. The treatment effect is related to the selected equipment, process parameters, coagulants, etc. Its COD removal rate is generally higher than the COD removal rate of pulping middle water, usually reaching 70% to 85%. For small and medium-sized waste paper papermaking enterprises with a discharge volume of more than 150m3 per ton of paper and low concentration, the effluent water quality indicators can reach or approach the discharge standards through flotation or sedimentation treatment.

Characteristics of papermaking wastewater treatment equipment 1. The papermaking wastewater treatment equipment is made of carbon steel anti-corrosion treatment or stainless steel components and assembled on site. It is light in weight, easy to transport and install; 2. It adopts glass fiber reinforced plastic, carbon steel and stainless steel anti-corrosion structure, which has excellent characteristics such as corrosion resistance and anti-aging, and has a service life of more than 60 years; 3. It is placed below the surface. The surface above the papermaking wastewater treatment equipment can be used as greening or other land, and there is no need to build houses, heat and insulate. The system integration is realized to the maximum extent, reducing the floor space; 4. No noise, no odor, and reducing secondary pollution; 5. It is not limited by the amount of papermaking wastewater, flexible and can be used alone or in combination. 6. The entire papermaking wastewater equipment treatment system is equipped with a PLC fully automatic electrical control system and an equipment fault alarm system. It is safe and reliable in operation. It generally does not require special management. It only needs to maintain and maintain the papermaking wastewater treatment equipment in a timely manner, and the management cost is small.