Papermaking wastewater is one of the main industrial pollution sources.
Straw and wood pulp are often used as raw materials in papermaking industry, Papermaking wastewater is a kind of industrial wastewater which is difficult to be treated because of its complex composition and poor biodegradability. The production of pulping and papermaking generally consists of pulping, pulp washing, bleaching and papermaking.
Papermaking is a kind of high organic wastewater with high concentration, high suspended matter content, and refractory to biodegradation. The wastewater produced in papermaking industry has many kinds, large amount of water and high content of organic pollutants, which is one of the industrial wastewater that is difficult to be treated.
Wastewater comes from every process of pulping and papermaking. Its physical properties and concentration of organic pollutants are different. According to the characteristics of wastewater, an effective treatment process is determined.
At present, the main methods of wastewater treatment in papermaking industry are sedimentation, air flotation, adsorption, membrane separation, aerobic, anaerobic and other treatment methods, as well as several combined treatment methods.
Our factory mainly produces wedge wire screen filter element and applies it to the sewage treatment equipment of paper mill.
The selection of wastewater process in papermaking industry
The selection of process plan plays the most important role in the construction of wastewater treatment facilities, ensuring the treatment effect of treatment facilities and reducing the operation cost. Therefore, it is necessary to select the feasible and reasonable treatment process technology in combination with the design scale, wastewater quality characteristics and local actual conditions and requirements, and select the best overall engineering after comprehensive technical and economic analysis Art scheme and implementation mode.
In the determination of the overall process plan of wastewater treatment facilities, the following principles shall be followed:
- The selected process must be advanced and mature in technology, strong in adaptability to water quality change, stable in operation, and able to ensure that the effluent quality can meet the requirements of the factory use standard and the national wastewater discharge standard.
- The selected process shall reduce capital construction investment and operation cost, save floor space and reduce energy consumption.
- The selected process shall be easy to operate, operate flexibly and manage. According to the water quality and quantity, the process operation parameters and operation can be adjusted properly.
- The selected process shall be easy to realize automatic control and improve the operation management level.
- The selected process shall minimize the adverse impact on the surrounding environment (odor, noise, mist, etc.)
Pretreatment of wastewater treatment in papermaking industry
No matter what method is adopted, the waste water needs to be pretreated. The main purpose of pretreatment is to improve the quality of waste water, so as to meet the inflow requirements of each process, improve the overall effect of waste water treatment, and ensure the stability of the whole treatment system, therefore, pretreatment plays an important role in the wastewater treatment of papermaking industry.
The pretreatment of papermaking industrial wastewater can be divided into in plant pretreatment and out of plant pretreatment. In plant pretreatment is mainly to recycle the pulp in white water, often using filtration, air flotation, etc.
Pretreatment process mainly includes: grid, screen (wedge wire screen), fiber recovery system, regulating water quantity and quality, etc.
According to different water quality of papermaking industry wastewater, different pretreatment methods can be adopted to remove some pollutants and improve wastewater quality, so as to achieve the best treatment effect of the whole wastewater treatment system.
Grid, screen (wedge wire screen, rotary drum screen)
Because the paper industry wastewater often contains bark, wood chips, plastics, pulp fiber chips and other small suspended solids, for example, the wastewater discharged by the wood mill in the preparation process often contains bark, wood chips and so on, a lot of white water will be produced in the process of papermaking, such as papermaking and so on.
These substances will cause damage to the water pump and affect the main treatment process. In particular, the water distribution system of UASB, hydrolytic acidification and other processes in biological treatment is seriously blocked. Therefore, before entering the water pump and main treatment system, it is required to intercept it, set grid to intercept large suspended solids and screen to intercept small suspended solids.
The Johnson screen grid is generally used in the treatment of paper-making wastewater with large amount of water. Due to the large amount of wastewater and many kinds of suspended solids, the grid can effectively intercept the larger suspended solids, high processing capacity, not easy to block.
The rotary drum screen is usually used in the small amount of water and the waste water contains a lot of fine suspended matters such as pulp, At the same time, it can also remove the floating matter of large particles, and the removal rate of suspended matter and large particles can reach more than 90%.
Fiber recovery system
There are a lot of pulp fibers in the papermaking wastewater. If the pulp fibers are not recycled, a lot of pulp will enter the wastewater treatment system, which will seriously affect the treatment effect of the wastewater treatment system and cause pulp waste.
Screen filtration mainly includes: gravity gravity self flow screen filtration, ordinary rotary filter, tangential unidirectional flow rotary filter, bidirectional flow rotary filter, etc.
In this process, Johnson screen is the best choice of filter element.