Application of polyaluminium chloride (PAC) in wastewater treatment systems

introduction

Polyaluminum chloride (PAC) is     one of the most widely used chemical reagents in wastewater treatment. Due to its unique properties, it is a suitable alternative to conventional coagulants such as aluminum sulfate. This substance plays an important role in wastewater treatment systems, removing impurities, turbidity, and various pollutants. In this article, we analyze in detail the application, advantages, and mode of action of polyaluminum chloride in wastewater treatment systems.

What is polyaluminium chloride?

Polyaluminum chloride is an inorganic polymer compound with the chemical formula [Al₂(OH)nCl₃₄]. It is available in liquid and powder form. Due to its polymer structure and high electrical charge, this material has the unique ability to coagulate and agglomerate colloidal particles in wastewater.

Mechanism of action of PAHs in wastewater treatment

1. Neutralization of electrical charge

Colloidal particles in wastewater typically carry a negative charge, which causes repulsion between them and stabilizes the suspension. Ascorbic acid, with its high positive charge, neutralizes these negative charges and promotes particle aggregation.

2. Sweep

Large PAH molecules have the ability to absorb and trap small particles, a process called canonical coagulation.

3. Surface adsorption

The polymer structure of PAH allows it to adsorb organic and inorganic pollutants on its surface.

Application of PAC in     wastewater treatment plants

1. Industrial wastewater treatment

• Textile industry: recycling of dyes and organic materials

• Food industry: Declining demand for biochemicals and chemicals

• Chemical industry: heavy metal removal

• Papermaking: Reduction of turbidity and total dissolved solids (TSS)

2. Treatment of municipal wastewater

• Removal of organic substances and suspended matter

• Phosphorus recovery

• Improving filter performance

3. Purification of drinking water

• Reduce turbidity

• Removal of microbial contaminants

• Recovery of organic compounds

4. Private wastewater treatment

• Hospitals: Disposal of medicines and microorganisms

• Laboratories: Reducing chemical pollution

Advantages of using PAH compared to conventional coagulants

1. Increased efficiency     : lower dosage required compared to aluminum sulfate.

2. Wider pH range     : Suitable for use in pH ranges from 5 to 9.

3. Denser clumps     : less sludge formation and better water drainage

4. Shorter mixing time     : higher working speed

5. Reduced chemical consumption     : less need for coagulants.

6. Reduction of dissolved solids     : Less increase in water salinity compared to alum.

7. Increased stability     : The pH value does not need to be constantly adjusted.

8. Lower operating costs     : Even though the unit price is higher, the final cost is lower.

Factors influencing the efficiency   of PAHs     in wastewater treatment

1. Dosage

The ideal PAH dosage depends on the type and concentration of the pollutants and is typically between 5 and 50 ppm.

2. pH value of the wastewater

Although PAC is active over a wide pH range, its optimal effectiveness is achieved at a pH of 6.5 to 8.

3. Mixing time

Generally, fast stirring for 1-3 minutes and slow stirring for 15-30 minutes is recommended.

4. Wastewater temperature

Low temperatures can slow blood clotting . In this case, an increase in the PAC dose may be necessary.

5. Chemical composition of wastewater

The presence of certain ions, such as sulfates, can impair the effectiveness of PAHs.

Use of PAHs in wastewater treatment systems

1. Preparation of the solution     : Normally a 5-10% solution is prepared.

2. Injection     : Injection at a suitable location (usually in front of the quick-mixing tank)

3. Fast mixing     : for even distribution in wastewater

4. Slow mixing     : to form large lumps

5. Sedimentation     : separation of the formed clots.

Calculating the optimal PAC dose

The optimal PAC dose is usually determined using a cupping test:

1. Preparation of identical wastewater samples

2. Addition of various     PAC  doses

3. Mixing and precipitation

4. Measurement of quality parameters (turbidity, dissolved solids, etc.)

5. Choose the dosage that gives the best results with the smallest amount taken.

Comparison of PAH with other coagulants

Safety tips for working with PAC

1. Use personal protective equipment (gloves, goggles)

2. Avoid contact with skin and eyes.

3. Store in     a cool, dry place   .

4. Avoid mixing with incompatible materials.

5. Compliance with the principles of transport safety

The impact of the Common Agricultural Policy on the environment

1. Environmental benefits     :

   • Reducing the use of chemicals

   • Low  sludge formation 

   • Reducing energy consumption

2. Environmental aspects     :

   • Monitoring of aluminum concentration in wastewater

   • Proper management of the  resulting  deposits

   • Prevent unauthorized downloads

Diploma

As an advanced coagulant, polyaluminum chloride has revolutionized wastewater treatment. Its use in wastewater treatment systems is increasing daily due to its high efficiency, flexibility under    diverse    conditions, and cost-effectiveness. By selecting the optimal dosage and application method, the desired wastewater quality can be achieved with minimal operating costs.

Frequently Asked Questions

Question 1     : What is the main difference between PAH and regular alum?
Answer: Compared to aluminum sulfate, PAH has a polymer structure, a higher positive charge, a lower dosage, and a wider pH range.

  Question 2: Is pH adjustment necessary   when using  PACs    ? Answer: Generally, pH adjustment in the range of 6 to 9 is not necessary, but it may be necessary in special cases.

Question 3     : Is PAH suitable for removing heavy metals?
Answer: Yes, PAH is capable of removing many heavy metals through adsorption and precipitation.

Question 4     : How long does PAH last?
Answer: Under suitable conditions, powdered PAH can be stored for up to two years, and liquid PAH up to six months.

Question 5     : Can polyacrylate be combined with other chemicals?
Answer: Yes. In some cases, polyacrylate is used with organic polymers to improve performance. However, combining it with some materials can cause side effects.

Diploma

The use of polyaluminum chloride in     wastewater treatment plants   is an effective, cost-effective, and environmentally friendly solution for complying with wastewater standards. Given the numerous advantages of this material and its ability to solve various treatment problems, it represents an excellent alternative to conventional coagulants. The proper design and use of polyaluminum chloride injection systems significantly improves the efficiency of treatment plants.