Affect the coagulation effect (dosage of reagents) in water treatment are relatively complex, including water temperature, pH value and alkalinity, the nature and concentration of impurities in water, external water conditions, etc. The following only briefly describes a few major factors.

1、Effect of water temperature

Water temperature has a significant impact on drug consumption, especially in winter when the water temperature is low. Usually, flocs form slowly, and the particles are small and loose. The main reasons are:
1. The hydrolysis of inorganic salt coagulants is an endothermic reaction, and it is difficult to hydrolyze coagulants in low-temperature water;
2. The viscosity of low-temperature water is high, which weakens the Brownian motion intensity of impurity particles in the water and reduces the chance of collision, which is not conducive to the destabilization and coagulation of colloids, and also affects the growth of flocs.

3. When the water temperature is low, the hydration of the colloidal particles is enhanced, which hinders the aggregation of the colloids and also affects the adhesion strength between the colloidal particles.
4. The water temperature is related to the pH value of the water. When the water temperature is low, the pH value of the water increases, and the corresponding optimal pH value for coagulation will also increase. Therefore, in winter in cold areas, it is difficult to obtain a good coagulation effect even if a large amount of coagulant is added.

2. Effect of pH and alkalinity

The pH value of raw water directly affects the hydrolysis reaction of coagulant, that is, the coagulation effect can only be guaranteed when the pH value of raw water is within a certain range.

When coagulant is added to water, the H+ concentration in the water increases due to the hydrolysis of the coagulant, which causes the pH value of the water to decrease, hindering the hydrolysis process.

To keep the pH value within the optimal range, there should be enough alkaline substances in the water to neutralize H+. Natural water contains a certain alkalinity (usually HCO3-), which can neutralize the H+ produced by the hydrolysis process of the coagulant and has a buffering effect on the pH value. When the alkalinity of the raw water is insufficient or the coagulant is added in excess, the pH value of the water will drop significantly, destroying the coagulation effect.

3. The influence of the nature and concentration of impurities in water

The size and charge of SS particles in water will affect the coagulation effect. Generally speaking, the coagulation effect is poor when the particle size is small and uniform, and the particle concentration in water is low and the probability of particle collision is small, which is not conducive to coagulation; when the turbidity is very large, the required drug consumption will be greatly increased in order to destabilize the colloid in the water.

When there is a large amount of organic matter in the water, it can be adsorbed by clay particles, thereby changing the surface properties of the original colloid particles and making the colloid particles more stable, which will seriously affect the coagulation effect. At this time, oxidants must be added to the water to destroy the effects of organic matter and improve the coagulation effect.

Soluble salts in water can also affect the coagulation effect. For example, when there are a lot of calcium and magnesium ions in natural water, it is conducive to coagulation, while a lot of Cl- is not conducive to coagulation. During the flood season, due to the erosion of rainwater, high turbidity water containing a lot of humus enters the plant. The general method of increasing the amount of pre-chlorination and coagulant addition is based on this.

4. Influence of external water conditions

The basic conditions for the aggregation of colloidal particles are, first, destabilization of the colloidal particles and, second, collision of the destabilized colloidal particles with each other. The main function of the coagulant is to destabilize the colloidal particles, while the external hydraulic agitation ensures that the colloidal particles can fully contact with the coagulant, so that the colloidal particles collide with each other to form flocs.

In order to ensure full contact between the colloidal particles and the coagulant, the coagulant must be quickly and evenly dispersed to all parts of the water body after being added to the water. This is commonly known as rapid mixing and is required to be within 10 to 30 seconds and no more than 2 minutes.

5、Impact of water shock load

Water volume shock refers to the periodic or non-periodic, sudden and large changes in raw water volume shock. For water plants, the city's water consumption and upstream water volume adjustments affect the water volume entering the plant, especially during the peak water supply period in summer. The water volume entering the plant changes greatly, resulting in frequent adjustments to the dosage of the reagents, and the water effect after settling is not very ideal.

It is worth noting that this change is not a linear increase. You should pay attention to the alum bloom in the reaction tank to avoid excessive dosage that will destroy the coagulation effect.

In addition to the above-mentioned influencing factors, there are also some measures to save medicine, such as increasing the number of stirring times of the medicine liquid pool, reducing the precipitation of solid particles in the medicine, and stabilizing the medicine properties, which can also achieve the purpose of saving medicine consumption.