Phosphating wastewater treatment process

Posted by Kuajing Plus on September 26th, 2021

Phosphating wastewater is the pretreatment of metal surface treatment, generally including degreasing and rust removal, surface conditioning, and phosphating passivation.

Phosphating wastewater treatment process description:

1. Chemical removal of zinc

Chemical methods for removing zinc include the sulfide method and alkali method coagulation precipitation.

2. Phosphorus removal by chemical precipitation by the lime method

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Adding lime milk clarified liquid and adjusting the pH value to 10~11, most of the phosphate in the wastewater can be precipitated and removed. The lime milk also neutralizes while removing phosphorus.

3. Phosphorus removal and oil removal by coagulation air flotation

The addition of flocculant makes the residual phosphorus in the wastewater and other pollutants undergo a coagulation reaction, and the flocs produced are attached to the air floatation method to produce a large number of fine bubbles, and the bubble buoyancy is used to bring them out of the water. At the same time as dephosphorization, it can also absorb and remove oil droplets. The bubble rises fast, and the operation is safe and reliable. It is an economical and practical deoiling technology.

4. Activated carbon adsorption phosphorus removal

Activated carbon is the most commonly used adsorbent in water treatment. It has good adsorption performance and chemical stability is not easy to break and has low airflow resistance. The commonly used ones are powder and granular. The process utilizes the huge specific surface area of activated carbon to fully adsorb trace residual phosphorus and other pollutants in wastewater.

5. Stirring and mixing device

Both the primary and secondary reactors are equipped with stirring devices. The stirring speed in the tank is gradually reduced by using a pulley or a reducer to meet the needs of stirring and mixing at different stages in the entire reaction process, making the reaction more thorough and more conducive to the subsequent precipitation Process. The pipeline mixer in the process makes the neutralization reaction easier when adding H2SO4, and can make the effluent pH value fully meet the standard.

6. Discharge mud by gravity or water pressure

The sludge or scum produced in the primary and secondary reactors and air flotation tanks in the system are regularly discharged into the sludge thickening tank by gravity or hydraulic pressure to be concentrated and then transported to landfill after natural drying. The clear liquid is returned to the conditioning tank for physical and chemical treatment.

7. Backwashing and desorption

Both the silica sand filter and the activated carbon adsorber in the system need to be backwashed regularly to prevent clogging, and the wastewater produced by them is returned to the regulating tank. In addition, in order to regenerate the activated carbon, a high-temperature heating regeneration method is used to activate, and water vapor is used to desorb the granular carbon in the activated carbon filter to ensure the normal adsorption effect.