Water temperature has a significant impact on drug consumption, especially in winter when the water temperature is low. Usually, the formation of flocs is slow, and the particles are fine and loose. The main reasons are:
1.The hydrolysis of inorganic salt coagulant is endothermic reaction, and the hydrolysis of low-temperature water coagulant is difficult;
2. The high viscosity of low-temperature water weakens the Brownian motion intensity of impurity particles in the water and reduces the chance of collision, which is not conducive to colloid destabilization and coagulation, but also affects the growth of flocs.
3. When the water temperature is low, the hydration effect of colloidal particles is enhanced, which hinders the coagulation of colloidal particles and also affects the adhesion strength between 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 water will increase, and the corresponding optimal pH value of coagulation will also increase. Therefore, in winter in cold regions, it is difficult to obtain good coagulation effect even if a large amount of coagulant is added.
The pH value of raw water directly affects the hydrolysis reaction of coagulant, that is, when the pH value of raw water is within a certain range, the coagulation effect can be guaranteed. When coagulant is added to the water, the concentration of H+in the water increases due to the hydrolysis of coagulant, which leads to the decrease of pH value of the water and hinders the hydrolysis. To keep the pH value within the optimal range, the water should have enough alkaline substances to neutralize with H+. When the alkalinity of the raw water is insufficient or the coagulant is added excessively, the pH value of the water will drop significantly, which will destroy the coagulation effect.
The size and charge of SS particles in water will affect the coagulation effect. Generally speaking, the particle size is small and uniform, its coagulation effect is poor, the concentration of particles in water is low, and the probability of particle collision is small, which is unfavorable to coagulation; When the turbidity is large, the 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, thus changing the surface characteristics of the original colloidal particles, making the colloidal particles more stable, which will seriously affect the coagulation effect. At this time, oxidant must be added to the water to destroy the role of organic matter and improve the coagulation effect. Soluble salts in water can also affect the coagulation effect. For example, when there is a large amount of calcium and magnesium ions in natural water, it is conducive to coagulation, while a large amount of Cl - is not conducive to coagulation. During the flood season, the high turbidity water containing a large amount of humus is brought into the plant due to the scouring of rainwater, which is the basis for the general increase of chlorine and coagulant dosage.
The basic conditions for colloidal particles to agglomerate are to destabilize colloidal particles and to make the destabilized colloidal particles collide with each other. The function of the coagulant is to destabilize the colloidal particles, while the external hydraulic agitation is to ensure that the colloidal particles can fully contact with the coagulant and make the colloidal particles collide with each other to form flocs. To make the colloidal particles fully contact with the coagulant, the coagulant must be rapidly and evenly dispersed to all parts of the water body after it is put into the water, commonly known as rapid mixing, which requires 10~30 seconds, and no more than 2 minutes at most.
Water volume impact refers to the periodic or non-periodic impact of raw water with large sudden changes. For the urban water consumption of the waterworks and the adjustment of the upstream water consumption all affect the incoming water volume, especially in the summer peak water supply stage, the hourly incoming water volume changes greatly, resulting in frequent adjustment of the dosage of chemicals, and the effect of settling water is not ideal. It is worth noting that this change does not increase nonlinearly. After that, pay attention to observe the alum in the reaction tank to avoid damaging the coagulation effect due to excessive dosage.
In addition to the above factors, there are also some drug saving measures, such as increasing the mixing times of the liquid medicine tank, reducing the precipitation of solid particles of the drug, and stabilizing the drug properties, which can also achieve the goal of saving drug consumption.
1. In order to save costs in the use of polyacrylamide, it is necessary to first select the use model of polyacrylamide. The principle is to select the polyacrylamide with the best effect on wastewater treatment. The expensive polyacrylamide is not necessarily the best, nor should it be cheap, which will lead to poor effect on wastewater treatment, but will increase costs. Select the agent that not only reduces the water content of sludge, but also uses a lower amount of agent per unit. First, flocculating test shall be conducted for the provided reagent samples in the laboratory, and two or three kinds of reagents with good experimental effect shall be selected, and then the machine test shall be conducted respectively to observe the final sludge removal effect, and the final reagent type shall be determined accordingly.
2. Polyacrylamide is generally a solid particle, which needs to be prepared into a certain solubility of water solution, and the concentration is usually between 0.1% and 0.3%. Too thick or too thin will affect the effect, waste chemicals and increase costs,The water for dissolving granular polymer should be clean (such as tap water), not sewage. Normal temperature water is enough, and heating is generally not required. The dissolution is slow when the water temperature is lower than 5 ℃. The dissolution rate is accelerated with the increase of water temperature, but above 40 ℃ will accelerate the degradation of polymer and affect the use effect. Generally, tap water is suitable for preparing polymer solution. Water with strong acid, strong alkali and high salt content is not suitable for preparation.
3. Pay attention to the aging time in the preparation of the agent, so that the agent can be fully dissolved in the water without caking. Otherwise, it will not only cause waste, but also affect the sludge discharge effect. At the same time, it will easily block the filter cloth and pipeline, and cause repeated waste. After the solution is prepared, its storage time is limited. Generally speaking, when the solution concentration is 0.1%, the non-anionic polymer solution shall not exceed one week; Cationic polymer solution shall not exceed one day.
4. After the agent is prepared, during the dosing process, pay attention to the change of mud quality and the effect of mud discharge, and adjust the dosage of the agent timely to achieve a better dosing ratio.
5. The medicine should be stored in a dry warehouse, and the medicine bag should be sealed. During use, use as much as possible. The unused medicine should be sealed to avoid moisture. In the preparation of drugs, it should be noted not to prepare as much as possible. The solution that has been stored for a long time is easy to hydrolyze and can no longer be used.
