Tertiary treatment of wastewater is a process that removes the remaining contaminants in the wastewater that have not been removed by primary and secondary treatment. Tertiary treatment is the final stage of treatment in wastewater treatment plants (WWTPs), and it is essential to remove the remaining pollutants from the wastewater before it is discharged into the environment. Tertiary treatment is necessary because the effluent from secondary treatment may still contain high levels of nutrients, organic compounds, and other pollutants that could be harmful to the environment and human health.
This article will discuss the various methods of tertiary treatment, their benefits, and their limitations.
Methods of Tertiary Treatment
Filtration
Filtration is a process that involves passing wastewater through a filter medium, such as sand, activated carbon, or a membrane. The filter medium removes suspended solids, bacteria, viruses, and other contaminants from the water. Filtration is an effective method of tertiary treatment and is commonly used in conjunction with other treatment processes, such as disinfection, to produce high-quality effluent.
There are several types of filtration processes, including:
a) Rapid Sand Filtration
Rapid sand filtration is a process in which wastewater is passed through a bed of sand at a high flow rate. The sand removes suspended solids and organic matter from the water. Rapid sand filtration is commonly used in WWTPs as a tertiary treatment process.
b) Activated Carbon Filtration
Activated carbon filtration involves passing wastewater through a bed of activated carbon. Activated carbon is a porous material that has a high surface area, which allows it to absorb contaminants from the water. Activated carbon filtration is an effective method of removing organic compounds, such as pesticides, from wastewater.
c) Membrane Filtration
Membrane filtration involves passing wastewater through a membrane that has tiny pores. The membrane acts as a physical barrier that separates the contaminants from the water. Membrane filtration is an effective method of removing bacteria, viruses, and other pathogens from wastewater.
Disinfection
Disinfection is a process that involves killing or inactivating bacteria, viruses, and other pathogens in wastewater. Disinfection is essential to prevent the spread of waterborne diseases and to protect the environment.
There are several disinfection methods, including:
a) Chlorination
Chlorination involves adding chlorine to wastewater to kill bacteria and other pathogens. Chlorine is a powerful disinfectant that is commonly used in WWTPs. However, chlorination can produce harmful by-products, such as trihalomethanes (THMs), which can be harmful to human health.
b) UV Disinfection
UV disinfection involves exposing wastewater to ultraviolet (UV) light, which kills bacteria and other pathogens. UV disinfection is a safe and effective method of disinfection that does not produce harmful by-products.
c) Ozonation
Ozonation involves adding ozone to wastewater to kill bacteria and other pathogens. Ozone is a powerful oxidizing agent that can destroy organic compounds, such as pesticides and pharmaceuticals, in wastewater. Ozonation is an effective method of disinfection, but it can be expensive.
Advanced Oxidation Processes (AOPs)
Advanced oxidation processes (AOPs) are a group of processes that involve the generation of highly reactive oxidizing agents, such as hydroxyl radicals, to degrade organic compounds in wastewater. AOPs are effective in removing persistent organic pollutants (POPs) and other recalcitrant compounds from wastewater.
There are several AOPs, including:
a) Fenton’s Reagent
Fenton’s reagent involves adding hydrogen peroxide and iron to wastewater to generate hydroxyl radicals. Hydroxyl radicals are highly reactive and can destroy organic compounds in wastewater.
b) Photocatalysis
Photocatalysis involves using a catalyst, such as titanium dioxide, to activate the degradation of organic compounds in wastewater under the presence of UV light. Photocatalysis is an effective method of removing organic compounds, such as pharmaceuticals, from wastewater.
c) Electrochemical Oxidation
Electrochemical oxidation involves applying an electrical current to wastewater to generate oxidizing agents, such as hydroxyl radicals, to degrade organic compounds. Electrochemical oxidation is an effective method of removing persistent organic pollutants (POPs) from wastewater.
Benefits of Tertiary Treatment
The benefits of tertiary treatment of wastewater are numerous, and they include:
- Improved Water Quality
Tertiary treatment removes the remaining contaminants in the wastewater, producing high-quality effluent that can be safely discharged into the environment or reused for non-potable applications, such as irrigation.
- Protection of Public Health
Tertiary treatment removes bacteria, viruses, and other pathogens from wastewater, preventing the spread of waterborne diseases and protecting public health.
- Protection of the Environment
Tertiary treatment removes nutrients, organic compounds, and other pollutants from wastewater, preventing eutrophication of water bodies and protecting the environment.
- Compliance with Regulations
Tertiary treatment is necessary to comply with regulations that govern the discharge of wastewater into the environment. Failure to comply with these regulations can result in fines and penalties.
Limitations of Tertiary Treatment
The limitations of tertiary treatment of wastewater include:
- High Cost
Tertiary treatment is generally more expensive than primary and secondary treatment, mainly due to the cost of equipment and chemicals required for the treatment processes.
- Energy Intensive
Some tertiary treatment processes, such as AOPs, are energy-intensive, requiring significant amounts of electricity to operate.
- Generation of Sludge and Chemical By-Products
Tertiary treatment processes, such as filtration and AOPs, generate sludge and chemical by-products that must be properly disposed of to prevent environmental contamination.
- Maintenance Requirements
Tertiary treatment equipment requires regular maintenance to ensure proper operation, which can be time-consuming and costly.
Conclusion
Tertiary treatment of wastewater is an essential process in WWTPs that removes the remaining contaminants in the wastewater before it is discharged into the environment. Tertiary treatment methods include filtration, disinfection, and advanced oxidation processes (AOPs), each with its benefits and limitations. The benefits of tertiary treatment include improved water quality, protection of public health and the environment, and compliance with regulations. The limitations of tertiary treatment include high cost, energy intensity, generation of sludge and chemical by-products, and maintenance requirements. Overall, tertiary treatment of wastewater is necessary to protect public health and the environment and ensure compliance with regulations governing the discharge of wastewater into the environment.
FAQs
What is the tertiary treatment of wastewater?
Tertiary treatment is the final stage of wastewater treatment that removes remaining contaminants from the water to produce high-quality effluent that can be safely discharged into the environment or reused.
What are the methods of tertiary treatment of wastewater?
The methods of tertiary treatment include filtration, disinfection, and advanced oxidation processes (AOPs).
What are the benefits of tertiary treatment of wastewater?
The benefits of tertiary treatment include improved water quality, protection of public health and the environment, and compliance with regulations.
What are the limitations of tertiary treatment of wastewater?
The limitations of tertiary treatment include high cost, energy intensity, generation of sludge and chemical by-products, and maintenance requirements.
Why is tertiary treatment of wastewater important?
Tertiary treatment is important because it removes the remaining contaminants in the wastewater, preventing the spread of waterborne diseases, protecting the environment, and ensuring compliance with regulations.
Read Also:
An Overview of Wastewater Treatment
Preliminary Treatment of Wastewater
