The dosage of flocculant is too large, there may be several reasons!

The factors that affect the coagulation effect (agent dosage) in water treatment are relatively complex, including water temperature, pH value and alkalinity, the nature and concentration of impurities in the water, external water conservancy conditions, etc. Just a few of the main factors are outlined below.

1. The influence of water temperature

Water temperature has a significant impact on chemical consumption, especially low water temperature in winter. Generally, 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 low-temperature water coagulants;

② The viscosity of low-temperature water is high, which weakens the intensity of Brownian motion of impurity particles in the water and reduces the chance of collision, which is not conducive to the destabilization and cohesion of colloids and also affects the growth of flocs.

③When the water temperature is low, the hydration of colloidal particles is enhanced, hindering colloid aggregation and affecting the adhesion strength between colloidal particles.

④Water 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 good coagulation effect even if a large amount of coagulant is added.

2. The influence of pH value and alkalinity

The pH value is an indicator of whether water is acidic or alkaline, which is an indicator of the concentration of H+ in the water. The pH value of the raw water directly affects the hydrolysis reaction of the coagulant, that is, the coagulation effect can be guaranteed only when the pH value of the raw water is within a certain range. When coagulant is added to water, the H+ concentration in the water increases due to hydrolysis of the coagulant, which causes the pH value of the water to decrease and hinders the progress of hydrolysis. 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 amount of alkalinity (usually HCO3-), which can neutralize the H+ produced during the hydrolysis 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 excessively, the pH value of the water will drop significantly, destroying the coagulation effect.

3. Influence of the nature and concentration of impurities in water

The size and chargeability of SS particles in water will affect the coagulation effect. Generally speaking, if the particle size is small and uniform, the coagulation effect is poor, the particle concentration in the water is low, and the probability of particle collision is small, which is detrimental to coagulation; when the turbidity is large, in order to destabilize the colloid in the water, the required chemical consumption is will be greatly increased. When there is a large amount of organic matter in the water, it can be adsorbed by the clay particles, thus changing the surface characteristics of the original colloidal particles and making the colloidal particles more stable, which will seriously affect the coagulation effect. At this time, oxidants must be added to the water to destroy the effect of the organic matter , improve the coagulation effect. Soluble salts in water can also affect the coagulation effect. For example, when there are a large amount of calcium and magnesium ions in natural water, it is beneficial to coagulation, while a large amount of Cl- is not conducive to coagulation. During the flood season, high turbidity water containing a large amount of humus enters the plant due to rainwater erosion. This is why the commonly used method of increasing the dosage of chlorine and coagulant beforehand is based on this.

4. Influence of external water conservancy conditions

The basic conditions for the agglomeration of colloidal particles are, first, to destabilize the colloidal particles, and second, to cause the destabilized colloidal particles to collide with each other. The main function of the coagulant is to destabilize the colloidal particles, while external hydraulic agitation ensures that the colloidal particles can fully contact the coagulant, causing the colloidal particles to collide with each other to form flocs. To fully contact the colloidal particles with the coagulant, the coagulant must be quickly and evenly dispersed into all parts of the water body after it is put into the water. This is commonly known as rapid mixing, which requires within 10 to 30 seconds and no more than 2 minutes at most.

5. Influence of water volume impact load

Water volume shock refers to the periodic or non-periodic water volume shock of raw water that changes suddenly and greatly. Adjustments to urban water consumption and upstream water volume in waterworks will affect the amount of water entering the plant. Especially during the peak water supply period in summer, the amount of water entering the plant changes greatly, resulting in frequent adjustments to the dosage of chemicals, and the effect of post-sinking water is not very satisfactory. It is worth noting that this change does not rise linearly. Afterwards, attention should be paid to observing the alum flowers in the reaction tank to avoid excessive dosage and destroying the coagulation effect.

6. Flocculant medication saving measures

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

① If you want to save costs when using polyacrylamide, you first need to choose the type of polyacrylamide to use. The principle is to choose the polyacrylamide with the best effect in treating wastewater. Expensive ones are not necessarily the best, and don’t try to be cheap. Poor wastewater treatment effect will increase costs. Select chemicals that not only reduce the moisture content of sludge but also lower the unit dosage of chemicals. First, conduct a flocculation experiment on the provided pharmaceutical samples in the laboratory, select two to three pharmaceuticals with good experimental results, and conduct on-machine experiments respectively to observe their final mud-out effect, and determine the final pharmaceutical variety accordingly.

②Polyacrylamide is generally solid particles. It needs to be prepared into an aqueous solution with a certain solubility. The concentration is usually between 0.1% and 0.3%. Too thick or too thin will affect the effect, waste chemicals, increase costs, and dissolve granular polymers. The water should be clean (such as tap water), not sewage. Normal temperature water is enough and generally does not need to be heated. Dissolution is very slow when the water temperature is lower than 5℃. Increasing the water temperature will speed up the dissolution rate, but above 40℃ will accelerate the degradation of the polymer and affect the use effect. Generally, tap water is suitable for preparing polymer solutions. Water with strong acid, strong alkali and high salt content is not suitable for preparation.

③Be sure to pay attention to the dissolution time when preparing the agent, so that the agent is fully dissolved in the water and does not agglomerate. Otherwise, it will not only cause waste, but also affect the mud removal effect. At the same time, it will easily cause blockage of the filter cloth and tube, creating repeated waste. Once the solution is prepared, its storage time is very limited. Generally speaking, when the solution concentration is 0.1%, the non- and anionic polymer solution should not be used for more than one week; the cationic polymer solution should be used for no more than one day.

④After the agent is prepared, during the dosing process, attention should be paid to the changes in the mud quality and the effect of the mud out, and the dosage of the agent should be adjusted in a timely manner to achieve a better dosage ratio.

⑤Medicines should be stored in a dry warehouse, and the medicine bags should be sealed. During use, use as much as possible, and unused medicines should be sealed to avoid moisture. When preparing pharmaceuticals, care should be taken not to prepare too much. Pharmaceutical solutions that have been left for a long time are prone to hydrolysis and cannot be used anymore.