Most industrial sectors generate wastewater to varying degrees. In today's world of increasingly stringent environmental regulations and water scarcity, 

this wastewater must be treated before discharge or recycling. Statistics show that these wastewater-generating industrial sectors include: mining (coal, 

phosphate, aluminum, iron, potash, copper, gold, borax, etc.), oil extraction, steel, papermaking, food processing (dairy products, meat, starch, sugar 

refining, brewing, potato processing, etc.), oil refining, machinery manufacturing, chemicals, electroplating, pharmaceuticals, ceramics, printing and dyeing,

 power generation, and leather tanning.

Industrial wastewater containing organic matter is often treated using biological methods, employing flocculants to aid sludge dewatering.

When treating industrial wastewater using physicochemical methods, coagulants and flocculants are used to promote the sedimentation of suspended 

impurities in the water. Sometimes, flocculants are also used to aid sludge dewatering.

Because industrial wastewater varies greatly in its sources, chemical composition, and impurity forms, the coagulants/flocculators used to treat it often 

differ as well.

Therefore, for a specific type of industrial wastewater, coagulant and flocculant screening should first be conducted in the laboratory. Then, based on 

practical experience, some general rules can be referenced when selecting flocculants.

Mining: The mining industry consumes large amounts of water for ore washing and flotation to separate useful minerals from gangue. Many minerals, such as 

iron, coal, phosphates, diamonds, zinc, uranium, and sand, are processed using this method.

Flocculants can be used to: separate water from gangue, facilitating water reuse; dewater sludge generated from gangue sedimentation; and separate 

useful minerals suspended in water. Sometimes, metallic minerals need to be dissolved in acids or alkalis during the process. In this case, flocculants are 

used to flocculate and separate undissolved impurities, while the metals are recovered as hydroxides or salts. Nonionic or anionic flocculants are 

commonly used in these processes. Nonionic flocculants are often used in acidic or highly saline solutions.

Papermaking: 

The papermaking industry is one of the largest water-consuming industries and a major consumer of water-soluble polymers. Using polymers can increase

 paper machine production capacity, improve paper quality, reduce water consumption, and mitigate the harmful environmental impact of papermaking.

1. Retention Aid: Adding polymers to the paper machine head helps retain more fillers (titanium dioxide, kaolin, calcium carbonate, etc.) and fibers in the 

paper. The ionicity of the polymer depends on the process characteristics.

2. Filtration Aid: Adding polymers to the wet end of the paper machine increases the filtration rate, thereby increasing the drying speed and increasing 

paper machine output.

3. Recovering paper fibers using medium- to high-cationic polymers.

4. Improving paper dry strength using low-cationic, low-molecular-weight polymers.

5. Temporarily increasing wet strength in the wet end of the paper machine using polymers.

6. Treating process water, wastewater, and sludge in paper mills using polymers.

7. Deinking during waste paper recycling using coagulants followed by high-molecular-weight flocculants.

Textile Industry:

Polymers are used in the textile industry for the following purposes:

1. As a thickener, polymers are added to dyes to give them suitable rheological properties. They have high viscosity at low shear rates, preventing the dye 

from flowing and spreading when stationary. This results in very clear edges on printed patterns; however, at high shear rates, the dye viscosity is very low,

making it easy to process.

2. As a sizing agent, polymers protect yarns, reducing the number of yarn breaks; they also improve the yarn's abrasion resistance during weaving and 

reduce pilling. The sizing agent is weakly bonded to the fabric and only needs to act temporarily.

Petroleum Industry:

Polymers are used in the petroleum industry for the following purposes:

1. Enhanced oil recovery (also known as "tertiary oil recovery"). This involves injecting polymer aqueous solutions into the oil reservoir to displace 

underground crude oil. High molecular weight polymers with strong thickening capabilities are generally required. Polymers with moderate anionicity are 

commonly used.

2. In drilling mud, polymers regulate rheology, reduce water loss, dilute bentonite, and control the swelling of water-sensitive clays. Anionic polymers are 

commonly used. Different molecular weights and anionicities are selected based on their specific applications.

3. Oil well water shut-off and injection well profile control. An aqueous polymer solution is injected into the formation, where a cross-linking reaction occurs,

forming a gel. This reduces the permeability of high-water-cut formations, thereby reducing water production from oil wells or improving the water intake 

profile of injection wells.

4. Treatment of oily wastewater from oil wells. Polymers can assist and accelerate the separation of oil-water mixtures using flotation or centrifugation, 

allowing the purified water to be used for reinjection or discharge.

5. Polymers with moderate anionicity and high molecular weight can reduce the frictional resistance of water flowing in pipelines. Therefore, with the 

pipeline diameter and length remaining constant, adding a small amount of polymer to the water can increase the pipeline's water delivery capacity or 

reduce the power consumption of the drainage pump.