Reasons for the increase of PAC dosage

The reasons for the increase of polyaluminum chloride (PAC) dosage can be analyzed from environmental conditions, water quality changes, agent characteristics and operation process. The search information is organized as follows:

1. Influence of environmental factors

Low temperature environment

When the water temperature decreases in winter, the rate of PAC hydrolysis reaction slows down, which makes it difficult to destabilize colloidal particles. Therefore, the dosage should be increased to enhance the electro-neutralization and adsorption effect.

Low temperature will also increase the viscosity of water, weaken the Brownian motion of impurity particles, and affect the formation of flocculation body, so by improving the dose compensation effect.

The pH value versus the alkalinity change

The coagulation effect of PAC is greatly affected by pH value. If the original water pH deviates from the optimal range (5-9), the dosage should be increased to adjust the reaction conditions. For example:

When the raw water and alkali is too low, the PAC neutralization charge should be supplemented;

When the alkali is too high, it is necessary to achieve the net capture and precipitation by increasing the dose.

2. Water quality and pollutant characteristics

Changes in the suspended matter concentration

High turbidity wastewater requires more PAC for electro-neutralization and adsorption bridging. If the concentration of suspended solids suddenly increases (such as in rainy season or industrial load increase), the dosage should be temporarily increased.

Due to the low probability of collision, the flocculation should be strengthened by increasing the dose or cooperating with the coagulant aid (such as PAM).

The types of pollutants are complicated

When treating hydrophilic dyes, emulsified oils or dissolved organic matter, the conventional PAC dosage may be insufficient and the dosage should be increased or replaced with high purity products.

3. Process and operation issues

Mix with insufficient reaction conditions

Insufficient stirring intensity or too short reaction time will lead to insufficient dispersion of PAC, which needs to be compensated by increasing the dosage.

Hydraulic load fluctuation (such as flow impact) may destroy the flocculation balance, so the dosage needs to be adjusted dynamically.

Quality or formulation issues

If the active ingredient of PAC (alumina content) is not up to standard or not completely dissolved (such as agglomeration is not fully stirred), the dose should be increased to achieve the equivalent treatment effect.

4. other factor

The sludge treatment system is overloaded

When the sludge dewatering capacity is insufficient, excessive PAC may lead to the rise and residual turbidity of alum flowers in the sedimentation tank, forming a vicious circle of "continuous dosage to maintain the effect".

Lack of dynamic monitoring and optimization

Without regular small-scale testing or online monitoring, the dosage is added only by experience, which can easily lead to redundant dosage due to water quality fluctuations.

To respond to the proposal

Optimize agent selection: select PAC with high purity and suitable model according to water quality characteristics to reduce invalid addition.

Strengthening process control: determine the optimal dose through beaker test, and adjust the dosage strategy by monitoring parameters such as pH and turbidity in real time.

Equipment maintenance and upgrade: ensure the efficiency of mixing equipment, and add automatic dosing system when necessary for accurate control.