Instructions for wastewater treatment using physicochemical methods

1. The necessity of physicochemical methods in wastewater treatment

Physicochemical methods are an important part of the wastewater treatment process. They include the following aspects:

Removing mechanical impurities:

Before wastewater is treated by chemical or biological methods, mechanical impurities such as sludge particles, algae, leaves and other impurities need to be removed. Methods such as filters, screens and slow flow (sedimentation) help to remove these impurities.

Create favourable conditions for chemical processing:

Physicochemical methods such as chemical precipitation, flocculation and coagulation help to facilitate chemical reactions. By removing larger dirt particles and impurities in wastewater, chemical reactions can proceed more efficiently and produce larger agglomerated residues.

Increase biological process efficiency:

In biological wastewater treatment, removing impurities and dissolved organic matter from wastewater is important. These impurities and organic substances can reduce the efficiency of biological processes by inhibiting the activity of bacteria or microorganisms present in the treatment tank.

Prevent clogging and equipment damage:

If wastewater contains many impurities, they can clog sewer pipes and other wastewater treatment equipment. Fluid obstruction can also harm wastewater treatment equipment and reduce their performance.

Ensuring aesthetics:

Treating wastewater by physical and chemical methods can make wastewater more transparent, free from suspended impurities and unpleasant odors. 

Meet environmental standards and regulations:

Environmental standards and wastewater quality regulations often require the removal of impurities and pollutants before releasing the wastewater into the environment. Physicochemical methods help to meet these requirements and to ensure compliance with legal regulations.

2. Physicochemical methods in wastewater treatment

Physicochemical methods in wastewater treatment are the process of using chemical reactions to remove or reduce pollutants in wastewater. There are many different physicochemical methods used to treat wastewater, depending on the nature of the wastewater and the treatment objectives. Here are some popular physicochemical methods:

- Floculation and Coagulation: In this method, chemicals such as zinc chloride, aluminum chloride are added to wastewater to create small crystals (floc) from dirty particles. These crystals then form larger clumps that are easily separated from the water.

Oxidation and Reduction: This method uses an oxidizer such as chlorine, ozone or peroxide to convert organic substances or toxic compounds into less toxic substances. At the same time, the reduction process can also be used to reduce heavy metal ions.

Chemical Precipitation: Using chemical compounds to form insoluble precipitates in wastewater, removing heavy metal ions or difficult-to-treat organic substances.

- Ion Exchange: Resin beads containing ions act as an exchanger, holding ions present in wastewater and replacing them with non-toxic ions.

- Using bacteria or microorganisms (Biological Treatment): Biological processes such as bacterial anaerobic treatment, anaerobic sludge treatment and biological filtration rely on microbial activity to destroy or convert organic substances and toxic compounds.

- Using activated carbon (Activated Carbon Adsorption): Activated carbon adsorb organic substances and other organic compounds from wastewater using membranes and membrane methods (Membrane Processes). It includes processes such as basic filtration, nanofiltration, reverse omosis filtration and super omosis filtration to separate the particles, organic substances and ions from wastewater.

- Using ultraviolet rays (Ultraviolet Disinfection): Ultraviolet rays kill bacteria and microorganisms in wastewater.

- Using antibiotic agents (Advanced Oxidation Processes - AOPs): These processes use a combination of strong oxidation and optical reactions to destroy toxic substances in wastewater.

Each method has its own advantages and limitations, and the choice of physicochemical method depends on the nature of the wastewater as well as the specific treatment goals.

3. Advantages and disadvantages of physicochemical methods in wastewater treatment

Physicochemical methods in wastewater treatment have their own advantages and disadvantages. Here are some advantages and disadvantages of the physicochemical method:

Advantages:

- No use of chemicals: One of the main advantage of the physicochemical method is that it doesn’t need any chemicals. This can help to reduce the risk of environmental pollution from chemical disposal after treatment.

- Safe and environmentally friendly: Because chemicals aren’t used, physicochemical methods are often safer and do not cause any major negative impact on the environment.

- Ability to separate small particles: Physicochemical methods are often effective in removing small suspended particles and in creating cleaner water.

- Does not create byproducts: Compared to chemical methods, physicochemical methods are less likely to create unwanted byproducts or toxic byproducts during the processing.

Disadvantages:

- Low efficiency for some types of pollutants: Physicochemical methods are often ineffective in removing dissolved organic substances or heavy metal ions, which requires combination with other methods.

- Complex technical process: Separating small particles in wastewater through physicochemical methods can require complex equipment and elaborate processes to ensure effectiveness.

- Potential for suspended particle pollution: In some cases, the process of creating suspended particles can create a risk of environmental pollution if not properly handled or removed.

- Need to be maintained and operated periodically: Machinery and equipment used in physical and chemical methods need to be maintained and operated periodically to ensure effectiveness.

The physicochemical method has many advantages, especially in terms of safety and environmental friendliness. However, it also has disadvantages and limitations that need to be carefully considered.

4. Practical application of physicochemical methods in wastewater treatment

 Physicochemical methods have wide applications in wastewater treatment in many different fields. Below are some of the main areas where physicochemical methods are used in wastewater treatment:

- Industrial wastewater treatment: Manufacturing industries often generate wastewater containing organic substances, organic compounds, heavy metals and other toxic substances. Physicochemical methods such as membrane filtration, activated carbon adsorption and chemical precipitation can be used to remove or reduce these substances.

- Urban wastewater treatment: Wastewater from cities contains many organic substances, bacteria and other substances. Membrane filtration, bacterial gas treatment, and the use of ultraviolet rays can help to eliminate pathogens and to create safe wastewater before being discharged into the environment.

- Agricultural wastewater treatment: Wastewater from agricultural activities often contains fertilizers, pesticides and organic substances from the livestock process. Physicochemical methods such as chemical precipitation and membrane filtration can be used to reduce pollution from agricultural wastewater.

- Petroleum and oil exploitation wastewater treatment: Oil and energy exploitation activities often create wastewater containing oil, organic compounds and heavy metals. Physicochemical methods such as activated carbon adsorption and precipitation processes can be used to treat this wastewater.

- Application in waste treatment: Waste treatment processes, such as biological decomposition, create wastewater containing organic substances and other organic compounds. Physicochemical methods such as anaerobic sludge treatment and the use of ultraviolet rays can be applied to produce clean wastewater from this process.

Thus, physicochemical methods have important applications in many different areas of wastewater treatment to remove or reduce pollutants and create environmentally safe wastewater.

5. Differences between chemical methods and physicochemical methods in wastewater treatment

Physical and chemical methods are both important methods in wastewater treatment to remove or reduce pollutants in the wastewater. However, there are some differences in how they work and in their scope of application. The differences between these two methods are listed below:

1. Physical Treatment:

- How it works: Physicochemical methods focus on changing the physical properties of the particles, organic matter or other pollutants in the wastewater but without changing its molecular structure or chemical quality. These methods often rely on separation based on gravity, particle size, or different properties of the substances present in the wastewater.

For example: Physicochemical methods include basic filtration (such as sand or rock filtration), nanofiltration, reverse osmosis filtration, super osmosis filtration, the use of membranes and membrane methods to separate particles and organic substances and the use of activated carbon to adsorb substances.

- Scope of application: Physicochemical methods are often effective in separating suspended particles, bacteria, dissolved organic matter and some ions from wastewater.

2. Chemical Treatment:

- How it works: Chemical methods rely on the use of chemicals to act on pollutants in wastewater, usually through chemical reactions such as redox or chemical precipitation and changes in the molecular structure of compounds.

For example: Chemical methods include coagulation and flocculation (precipitation and flocculation), oxidation with substances such as chlorine, ozone, peroxide, the use of bacteria or microorganisms to treat the wastewater (treatment bacteria) and the use of antibiotics (Advanced Oxidation Processes - AOPs) to decompose toxic substances.

- Scope of application: Chemical methods are often used to reduce the concentration of organic substances, bacteria, viruses, heavy metal ions and other pollutants in the wastewater.

Physicochemical methods focus on changing the physical properties of substances in wastewater to separate them, while chemical methods create chemical reactions in order to transform and remove pollutants.

Treating wastewater with physical and chemical methods combined with other treatment methods will bring the highest efficiency in the wastewater treatment process. Depending on the conditions and characteristics of the wastewater source, the appropriate method will be selected to achieve the best efficiency. With 10 years of experience in the field of consulting and designing wastewater treatment systems , FEC Environment will support and assist the customers to achieve the highest efficiency in the process of operating wastewater treatment systems.