Dosing ratio of industrial polyaluminum chloride
Release time: 2025-08-20
The following is a professional analysis of the dosage ratio of industrial grade polyaluminum chloride (PAC) in the treatment of industrial sewage, comprehensive technical specifications and practical application points:
I. Characteristics and basis of polyaluminum chloride addition
Product classification and selection
Solid PAC: The content of alumina (Al₂O₃) should be ≥28% (national standard GB/T 22627-2022), and the dissolution ratio is usually 1:9~1:15 (by weight ratio) (that is, 1 part PAC plus 9~15 parts water), which is prepared into a 5%~10% solution for addition. The concentration below 1% is easy to hydrolyze and fail, while the concentration above 10% is easy to cause waste.
Liquid PAC: the content of alumina is more than 10%, which can be directly added, but the transportation and storage cost is high, so it is suitable for nearby sewage treatment scenarios.
Core influencing factors
The water quality characteristics (turbidity, pH, type of pollutants) determine the actual amount, and the best ratio should be determined through a small test.
Temperature and pH value: in low temperature or low pH water quality, high concentration of PAC may lead to decreased effect due to rapid hydrolysis.
2. Method for determining the dosage ratio
(1) Pilot test steps (key links)
Configuration of reference solution:
We weighed 3g of solid PAC, added 50ml of water to dissolve it, and made up to 100ml to prepare a 3% solution (weight ratio).
Gradient test:
Six groups of equal amount of sewage samples were taken and PAC solution was added in different doses (e.g., 10~50mg/L). After stirring, the formation speed of alum, sedimentation effect and residual turbidity were observed.
Optimizing and adjusting:
If the sedimentation tank has little alum flowers and high residual turbidity, the dosage should be increased; if the alum flowers are large and upturned, the dosage should be reduced.
(2) Production and distribution standards
Dissolution: Solid PAC should be dissolved with tap water or well water, and stirred for at least 5 minutes until no particles are present.
Concentration of added substances:
General sewage: 5%~8% solution (that is, 50~80g PAC/liter of water);
High turbidity wastewater (e.g., metallurgy, paper making): can be increased to 10% solution.
3. Add the dosage ratio by industry
According to the type of water quality and pollution load, the consumption in typical industrial scenarios is as follows (unit: kg PAC/ 1000 tons of sewage):
trade | Dosage range | special requirements |
Low turbidity industrial water | 2.5~25 | Add after dilution at 1:3 |
sanitary waste | 15~50 | It is often used in combination with polyacrylamide (PAM) |
paper waste | 50~300 | When the turbidity is high, the upper limit is taken and the precipitation process is combined |
Dyeing/bleaching wastewater | 100~300 | It needs to be decolored and can be combined with a special decolorant |
electroplating effluent | 20~100 | Focus on removing heavy metals and control pH 5~9 |
Metallurgical/coal washing wastewater | 20~150 | The sedimentation speed is high and the stirring should be strengthened |
Note: The above data are industry experience values, and the actual water quality testing and small test should be used.
IV. Key points and common problems
Avoid excessive dosage:
Excess will lead to a surge in sludge quantity, increase in treatment cost, and limited removal effect on dissolved organic matter (such as COD).
Collaborative processing technology:
It is recommended to use the combined process of PAC and PAM for refractory wastewater (e.g., printing and dyeing, coking): first add PAC coagulation, and then use 0.1%~0.3% PAM solution to assist coagulation.
Precise concentration control:
The alumina content of liquid PAC should be tested regularly to prevent the degradation of effective components during storage.
V. CONCLUSIONS
The dosage ratio of industrial PAC should follow the principle of "small-scale optimization, classified regulation and dynamic adjustment":
Basic ratio: solid PAC is dissolved in 1:9~1:15, and the dosage concentration is 5%~10%;
Industry adaptation: the dosage should be selected according to the pollutant load. For high concentration wastewater (such as paper making and printing), it should be increased to 100~300kg/ thousand ton water;
Risk control: It is strictly prohibited to use wastewater to dissolve PAC to avoid secondary pollution of heavy metals.
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