The Solution of Papermaking Wastewater Treatment Process

papermaking wastewater is an important factor in polluting water sources, and it is also a kind of industrial pollution source. Therefore, it is particularly important to realize the cleaning and resource utilization of the papermaking production process.

Before understanding the treatment process of papermaking wastewater, we first need to understand the source and characteristics of papermaking wastewater, and then we can better manage the efficiency of papermaking wastewater.

What is the source of papermaking wastewater:

◆ Fiber separation during pulping, dilution, pressing, drying pulp and other processes during bleaching and papermaking to remove sewage with high concentrations of pollutants such as a large number of fibers, inorganic salts and pigments, namely black water

◆ During the washing and bleaching process, a large amount of mid-stage water containing high concentrations of lignin, cellulose and resinate and other difficult biodegradable components is produced.

◆ The sewage discharged from the paper machine contains a lot of fibers, fillers and sizing materials, that is, white water

What are the characteristics of papermaking wastewater:

◆ papermaking wastewater contains high COD and suspended solids (SS) content and serious chromaticity.

◆ The concentration of SS and COD in papermaking wastewater is relatively high, and COD is composed of two parts: insoluble COD and soluble COD. Usually, insoluble COD accounts for most of the total amount of COD. Part of the insoluble COD is removed at the same time.

How we treat papermaking wastewater:

Therefore, the main problem to be solved in waste papermaking wastewater treatment is to remove SS and COD.

The BOD5 value in waste paper and papermaking sewage is relatively low, and the ratio of BOD5 to COD is generally 0.15 to 0.25, and the biodegradability is poor. The coagulation treatment method can only remove part of BOD5, and the removal of most of the BOD5 should mainly be solved by biochemical methods.

1. air flotation or sedimentation method

air flotation and sedimentation are both physical and chemical treatment methods, which are used for small and medium-sized waste paper and papermaking enterprises that discharge a large amount of sewage per ton of paper and have a low concentration.

Its typical treatment process is as follows: sewage → screen → sump → air flotation or sedimentation → discharge

2. Combination of physicochemical and biochemical treatment

For large and medium-sized waste paper and papermaking enterprises with low sewage discharge per ton of paper and high COD content in sewage, biochemical treatment should be followed after primary physical and chemical treatment, so that the treated effluent finally meets the requirements of discharge standards.

The typical process flow of the physicochemical plus biochemical treatment method is as follows:

Sewage → screen → adjustment → sedimentation or air flotation → A/O or contact oxidation → secondary sedimentation tank → discharge

3. Treatment and application of paper sludge

• recycled pulp

1. The recovered pulp can be reused for papermaking or sold as a raw material for low-grade paper, resulting in direct economic benefits;

2. Reduce the sewage treatment load and reduce the consumption of chemicals.

3. Common equipment mechanical bar screen

• sludge dewatering

After the sewage is treated by physicochemical and biological methods, a large amount of sludge will be produced, which needs to be dewatered.

Common equipment plate and frame filter press, belt filter press,screw press sludge dewatering machine.

In determining the overall process plan of a specific sewage treatment facility, the following principles are followed:

1. Strong adaptability to changes in water quality and stable operation

2. Capital construction investment and operating costs should be reduced to save floor space and reduce energy consumption

3. It should be easy to operate, flexible to operate and easy to manage

4. The adverse impact on the surrounding environment should be minimized

5. It should be easy to realize automatic control and improve the level of operation management

BIOETP provide service for  ETP/STP designing, equipment manufacturing, plant installation, operation training and maintenance service. also provide solutions and equipments for almost all kinds of sludge dewatering treatment. also provide smell control solutions and smell control plant and related equipmentsfor APIs industry and feed processing industry. 

So, if you have any ETP/STP , sludge dewatering , smell control requirement aroused, please feel free to contact BIOETP. You can find our contact on BIOETP official website www.bioetp.com.