1. Source and nature of wastewater

Because the papermaking wastewater itself is very complex, it is a kind of industrial wastewater that is difficult to handle. Papermaking wastewater mainly comes from the two production processes of pulping and papermaking in the paper industry. Pulping is to separate the fibers in the plant raw material, make a slurry, and then bleach, this process will produce a large amount of papermaking wastewater; papermaking is to dilute, shape, press, and dry the slurry to make paper, this The process is also prone to papermaking wastewater. The main waste water produced in the pulp process is black liquor and red liquor, and the main paper produced is white water.

2. Harm of papermaking wastewater

Papermaking wastewater is very harmful, especially black water, which contains more than 90% of the total discharge of paper industry. Because of its large alkalinity, deep color, heavy odor, foam, and a large amount of consumption. Dissolved oxygen in water, if discharged without treatment, will seriously pollute the water source, causing harm to the environment and human health. The most serious environmental pollution in the middle section is the chlorine-containing wastewater generated during the bleaching process. In addition, the bleaching waste liquid contains toxic dioxins, which are extremely toxic, and poses a serious threat to the ecological environment and human health.

3, the main pollutants

COD, chroma, SS, etc.

4, the processing method

(1) Treatment process

At present, the treatment method mainly uses a materialized + biochemical treatment mode.

(2) Processing

1 After the wastewater enters the wastewater treatment system, it first removes the large debris through the trash rack, enters the grid pool and enters the concrete pool;

2 by adding polyaluminum chloride or polyacrylamide to produce a coagulation reaction;

3 After entering the air flotation, remove SS and some BOD and COD from the wastewater;

4 The air floats out into the two-stage biochemistry of anaerobic and aerobic, and removes most of the BOD and COD in the water;

5 After the secondary sedimentation tank, the COD and color of the wastewater will not meet the national emission standards, and the chemical coagulation will be used to strengthen the wastewater to meet the discharge standards.

(3) Treatment of medicaments

High-efficiency decolorizing agent: used for the decolorization of wastewater after pulp wastewater.

Flocculation decolorant: It has a good treatment effect on wastewater with medium chroma and low concentration of COD.

Polyaluminium chloride: used for flocculation precipitation before biochemistry and clarification of biochemical effluent.

Aluminum sulfate: used for the treatment of red or black liquor.

Complex base: adjust the pH value and improve the coagulation effect.

Sulfuric acid: Neutralization reaction of alkaline wastewater.

Sodium hydroxide: adjust the pH value, neutralize the acidic wastewater, and improve the reaction effect of the coagulant.

Polyacrylamide: used for the recovery of white water fibers, flocculation of coagulation tanks, and flocculation of sludge dewatering.