What is PAC?
PAC is a common flocculating agent in sewage treatment, and its full name is poly aluminium chloride. The Chinese name is polyaluminum chloride, also known as water purification agent.
It is widely used in tap water treatment, industrial sewage treatment, municipal sewage treatment and circulating water purification.
What are the “features” of the PAC?
Due to the different production processes and raw materials of PAC products, it becomes “each with its own characteristics”, which is embodied in the following six types:
White:
It is a newly developed new water purification material, which is specialized in food, drinking water, urban water supply, paper making, medicine, cosmetics, daily chemical industry, etc., with very high purity and highest price.
Light yellow:
Second only to white PAC, mainly used for drinking water treatment, in which the content limit of heavy metals is relatively strict, good flocculation effect, high efficiency and stability in purification, less dosage, low cost, is a special water treatment flocculant for major water plants.
Golden yellow:
It is currently the most widely used in the market. Whether it is industrial water supply, industrial wastewater, industrial water recycling and municipal sewage treatment, it is the best choice.
Brown and coffee:
The color is darker than golden yellow because the iron content is higher than other polyaluminum chloride product lines.
It is powerful for low temperature, low turbidity and high algae sewage, mainly used for drinking water, urban water supply, industrial water purification, etc.
These three types of products are produced according to the special requirements of customers.
How to play the “special effects”?
The water purification process of polyaluminum chloride can be divided into three stages: coagulation stage, flocculation stage and sedimentation stage.
1.Coagulation stage
In PAC when the water is injected into the coagulation vessel and the raw water is coagulated rapidly, fine alum flowers will be formed in a very short time. At this time, the water body becomes more turbid, which requires the water flow to generate fierce turbulence.
2.Flocculation stage
The flocculation stage is a process in which alum flowers grow and become coarse, which requires proper turbulence degree and sufficient residence time (10~15min). At the later stage, a large number of alum flowers can be observed to gather and slowly sink, forming a clear layer on the surface.
3. Settling stage
It is the process of flocculation sedimentation in the sedimentation tank, and the water flow is required to be slow. In order to improve the efficiency, inclined pipe or plate settler is generally used.
A large number of coarse alum flowers are blocked by the inclined pipe (plate) wall and deposited at the bottom of the pool. The upper water is clarified water, and the remaining alum flowers with small particle size and small density gradually drop. On one side, they continue to collide with each other, and the residual turbidity remains basically unchanged in the later period.
How is PAC saved for use?
1. The polyaluminum chloride shall be kept in a dry, moisture-proof and heat-proof place (< 80℃ do not damage the package, and the product can be stored for a long time).
The effective storage period of liquid product is half a year, and the effective storage period of solid product is two years. The solid product can still be used after being wet.
2. Polyaluminum chloride products must be dissolved before use, and the dissolution equipment and dosing facilities shall be made of corrosion-resistant materials.
