Application fields of water treatment agents

Its application fields include industrial water, municipal / drinking water treatment, wastewater treatment and seawater desalination.

In the field of industrial water, it is mainly used in industrial circulating water treatment and industrial boiler water treatment. The chemicals used in industrial circulating water treatment mainly include scale inhibitor, corrosion inhibitor, bactericide and algicide, cleaning agent, pre film agent, etc. The common methods of industrial boiler water treatment include outside boiler water treatment and inside boiler water treatment. The main chemicals used are: corrosion and scale inhibitor, deoxidizer, feed water alkali reducer, ion exchanger, regeneration agent, softener, alkalinity regulator, scale remover, etc. The water treatment agents involved in municipal / drinking water treatment generally include: bactericide, algaecide, flocculant, corrosion inhibitor, etc. The water treatment agents involved in wastewater treatment generally include flocculant, sludge dehydrating agent, defoamer, chelating agent, decolorizing agent, etc. The main technologies of seawater desalination include distillation and membrane. The membrane is easy to be blocked in use, so it is necessary to add scale inhibitor, detergent, flocculant, scale inhibitor and dispersant in water. The distillation method is easy to produce boiler scale and reduce the evaporation efficiency. Polyphosphate, organic phosphoric acid and phosphonic polycarboxylic acid can be added to the raw water to soften the water quality, chelate calcium, magnesium ions and other metal ions to make it difficult to precipitate and prevent the formation of scale.

02

Types of water treatment chemicals

Water treatment agents include flocculant, corrosion inhibitor, scale inhibitor, biocide, lax agent, cleaning agent, premembrane agent, defoamer, decolorizer, chelator, Deoxidizer and ion exchange resin.

one

About flocculant

As long as you remember three points, the first point is that flocculant is mainly used to strengthen solid-liquid separation in the field of sewage treatment. The second point is that coagulant aid can be used to enhance the flocculation effect. The third point is that flocculant is the cheapest and most efficient method of phosphorus removal.

two

About coagulant aid

As long as two points are kept in mind, the first point is that the function of coagulant aid is to adjust or improve the coagulation conditions; the second point is that it can increase the particle size, density and firmness of alum.

three

Corrosion and scale inhibitor

As the name suggests, corrosion and scale inhibitor is a kind of water treatment agent to alleviate the scaling and corrosion of circulating water equipment such as boiler. The agent is composed of alkaline substance and organic compound, and corrosion inhibitor is added to prevent the heating surface from being corroded. The alkaline substance in the reagent reacts with calcium and magnesium salts in the water to form water slag in the boiler through chemical reaction. After precipitation, it is discharged out of the boiler through the blowdown function, so as to reduce the concentration of calcium and magnesium ions in the water and prevent the boiler from scaling.

four

Cleaning agent

Cleaning agent is a kind of volatile solvent which can dissolve the penetrant. It is used to remove the excess penetrant on the surface of the inspected workpiece. Some cleaning agents are specially designed to remove metal hydroxides, calcium carbonate and other similar fouling on the surface of polyamide, polysulfone and membrane components. Before using the cleaning agent, check the cleaning tank, pipeline and security filter, and install a new filter element.

five

bactericide

Bactericide is mainly a kind of medicine to eliminate bacteria, microorganisms and other harmful bacteria. In the world, it is usually used as a general term for the control of various pathogenic microorganisms.

Common technologies:

1) Sterilization, disinfection: water disinfection methods can be divided into chemical and physical two. Physical disinfection methods include heating method, ultraviolet method and ultrasonic method; chemical methods include chlorination method, ozone method, heavy metal ion method and other oxidant methods.

2) Magnetization: the treatment of water by magnetic field effect is called magnetization of water.

3) Precision filtration technology: the microporous filter element and membrane made of special materials are used to intercept the particles and bacteria in the water by using their uniform pore size, so that they cannot be removed and intercepted through the filter element and membrane. Precision filtration can filter micro (μ m) or nano (nm) particles and bacteria. It is also widely used in the advanced treatment of water.

4) Ultrafiltration technology: ultrafiltration is a membrane separation technology. Under a certain pressure (0.07-0.7mpa, up to 1.05mpa), water flows on the membrane surface. Water, dissolved salt and other electrolytes are tiny particles that can penetrate the ultrafiltration membrane, while particles and colloidal substances with large molecular weight are blocked by the ultrafiltration membrane, so that some particles in water can be separated. The pore size of ultrafiltration membrane is determined by the retention test of a certain molecular weight material, and expressed by the value of molecular weight.

5) Ozone: it is a kind of blue gas with special fishy smell at room temperature, and its molecular formula is O3. Ozone has strong oxidizability. Ozone can oxidize and denaturate the protein of bacteria and fungi, and make the electrolyte lose its function. It can kill bacterial propagules and spores, viruses and fungi, and can destroy botulinum toxin. It can remove and kill toxic substances and bacteria in air, water and food, and can remove peculiar smell. It is widely used in disinfection, sterilization and other processes of food production.

In the process of disinfection and sterilization, ozone only produces non-toxic oxides, and the excess ozone is finally reduced to oxygen. There is no residue on the disinfected articles, so it can be directly used for food disinfection and sterilization.

6) Ion exchange: the so-called ion exchange is the equal charge reaction between ions in water and ions on ion exchange resin. Taking the reaction process of H + cation exchange resin HR and Na + in water as an example: HR + Na + = Na + + H +. It can be seen from the above formula: in the ion exchange reaction, the cation in water (such as Na) is transferred to the resin, and an exchangeable h on the ion exchange resin is transferred to the water. The process of Na transfer from water to resin is ion replacement. The process of H exchange from resin to water is called dissociation process. Therefore, as a result of the process of dissociation and displacement, Na and H exchange positions. This change is called ion exchange.

7) Ultraviolet: when the mercury lamp is ignited, it can emit ultraviolet light with wavelength of 1400nm-4900nm (1nm = 10-10m), which can penetrate the cell wall of bacteria, kill microorganisms and achieve the purpose of disinfection and sterilization. The ultraviolet wavelength is about 2600nm.

Ultraviolet disinfection is mainly used in the treatment of small amount of drinking water. It is characterized by: strong killing ability, short contact time; simple equipment, convenient operation and management, colorless, tasteless water after treatment, no harm of poisoning; it will not increase chloride ion like chlorine gas.

8) Adsorption water purification technology: mainly refers to activated carbon and other substances with adsorption capacity adsorption technology. Here is a brief introduction of some characteristics of activated carbon: activated carbon is widely used in the purification, dehydrogenation, deodorization and deodorization of drinking water, food industry, chemical industry, electric power and other industrial water. In general, it can remove 63% - 86% colloidal matter; about 50% iron; and 47% - 60% organic matter.

03

Common water treatment chemicals

one

Polyaluminum chloride

Polyaluminum chloride is a kind of inorganic polymer coagulant. Due to the bridging effect of hydroxyl ion and the polymerization of multivalent anions, it is a kind of inorganic polymer water treatment agent with large molecular weight and high charge.

characteristic:

1) The floc has the advantages of fast forming, good activity and filtration.

2) It is not necessary to add alkaline additives. If deliquescence occurs, the effect will not change.

3) It has wide pH value, strong adaptability and wide application.

4) The treated water has less salt.

5) It can remove water pollution caused by heavy metals and radioactive substances.

6) High effective ingredients, easy to store and transport.

effect:

1) Strong electric neutralization of colloidal substances in water.

2) The hydrolysate has excellent bridging adsorption to suspended solids in water.

3) Selective adsorption of soluble substances.

Application:

1) Urban water supply and drainage purification: River water, reservoir water, groundwater.

2) Industrial water purification.

3) Urban sewage treatment.

4) Recovery of useful substances in industrial wastewater and waste residue, promotion of the settlement of pulverized coal in coal washing wastewater, and recovery of starch in starch manufacturing industry.

5) Various industrial wastewater treatment: printing and dyeing wastewater, leather wastewater, fluoride wastewater, heavy metal wastewater, oily wastewater, papermaking wastewater, coal washing wastewater, mining wastewater, brewing wastewater, metallurgical wastewater, meat processing wastewater, sewage treatment.

6) Paper sizing

7) Sugar refining

8) Casting molding

9) Crease proof fabric

10) Catalyst carrier

11) Pharmaceutical refining

12) Quick setting of cement

13) Cosmetic raw materials

two

Polyferric sulfate

The morphology of PFS is light yellow amorphous powder solid, easily soluble in water, 10% (weight) water solution is reddish brown transparent solution, hygroscopic. Polyferric sulfate is widely used in the purification of drinking water, industrial water, various industrial wastewater, urban sewage, sludge dewatering and so on.

Compared with other inorganic flocculants, PFS has the following characteristics

1) New type, high quality and high efficiency ferric salt inorganic polymer flocculant;

2) It has excellent coagulation performance, dense alum and fast settling speed;

3) No harmful substances such as aluminum, chlorine and heavy metal ions, no water phase transfer of iron ions, non-toxic, harmless, safe and reliable;

4) It can remove turbidity, decolorization, deoiling, dehydration, bacteria, odor, algae, COD, BOD and heavy metal ions;

5) The pH range of the water body is 4-11, and the optimum pH range is 6-9. After purification, the pH value and total alkalinity of the raw water change little, and the corrosion to the treatment equipment is small;

6) The results show that the purification effect is remarkable for micro polluted, algae containing, low temperature and low turbidity raw water, especially for high turbidity raw water;

7) The dosage is small, the cost is low, and the treatment cost can be saved by 20% - 50%.

three

polyacrylamide

Polyacrylamide (PAM) is a water-soluble polymer, insoluble in most organic solvents, with good flocculation, which can reduce the friction resistance between liquids. According to the ionic characteristics, it can be divided into four types: non-ionic, anionic, cationic and amphoteric.

Precautions for use of cationic polyacrylamide:

1) Floccule size: too small floccule will affect the drainage speed, too large floccule will make floccule restrict more water and reduce the degree of mud biscuit. The molecular weight of polyacrylamide can adjust the size of flocs.

2) Sludge characteristics: first, understand the source, characteristics, composition and proportion of sludge. According to different properties, sludge can be divided into organic and inorganic sludge. Cationic polyacrylamide is used to treat organic sludge, while anionic polyacrylamide flocculant is used to treat inorganic sludge. Cationic polyacrylamide is used when the alkalinity is very strong, and anionic polyacrylamide is not suitable when the acidity is very strong. When the solid content is high, the dosage of polyacrylamide is usually large.

3) Floc strength: floc should be stable and not broken under shear. Improving the molecular weight of polyacrylamide or selecting the appropriate molecular structure is helpful to improve the stability of flocs.

4) Ionic degree of polyacrylamide: for dewatered sludge, flocculants with different ionic degrees can be used. After small-scale test, the best polyacrylamide can be selected. In this way, the best flocculant effect can be obtained, and the dosage can be minimized to save cost.

5) The dissolving of polyacrylamide: good dissolving ability can give full play to flocculation. Sometimes need to speed up the dissolution rate, then consider the concentration of polyacrylamide solution.

Application scope:

1) It can be used as retention aid and reinforcing agent in papermaking process.

2) It is used as coagulant aid, flocculant and sludge dehydrating agent in water treatment.

3) In oil drilling and production, it is used as precipitation agent and oil displacement agent.

4) PAM is also widely used in thickening, colloid stabilization, drag reduction, adhesion, film-forming, biomedical materials and so on.

four

Inorganic flocculant aluminum sulfate

The suitable pH range is related to the hardness of raw water. The suitable pH is 5-6.6 for soft water treatment, 6.6-7.2 for medium hard water treatment and 7.2-7.8 for high hard water treatment. The water temperature range of aluminum sulfate is 20oC ~ 40oC, and the coagulation effect is very poor when the temperature is lower than 10oC. Aluminum sulfate is less corrosive and easy to use, but the hydrolysis reaction is slow and needs to consume a certain amount of alkali.

five

Inorganic flocculant ferric chloride

Inorganic flocculant ferric oxide is another common inorganic low molecular coagulant. The product has black brown crystal of solid and high concentration of liquid. It has the advantages of easy to dissolve in water, large and heavy alum, good sedimentation performance and wide adaptability to temperature, water quality and pH. The suitable pH range of ferric chloride is 9-11, the floc density is high, it is easy to precipitate, and the effect is still good at low temperature or high turbidity. The solid ferric chloride has strong water absorption, strong corrosiveness and easy to corrode the equipment. It has high anti-corrosion requirements for dissolving and dosing equipment, pungent odor and poor operating conditions.