What is the Role of Water Clarifiers in Enhancing Water Treatment?

Wastewater treatment is crucial in safeguarding public health and the environment. Wastewater purification not only removes pollutants or contaminants, but also leads to its recycling and reuse, reduced solid waste, reduced energy consumption, and more. Today, different equipment used for wastewater treatment this includes clarifier tanks. Wastewater clarifiers are vital in transforming murky, contaminated water into clean and environmentally safe water that can be reused or safely disposed. Is that all? Obviously not. Are you intrigued to know more about wastewater clarifiers? This post discusses how to improve efficiency with the use of clarifier in water treatment? This post answers these questions in detail. Stay tuned.

A Quick Introduction to Clarifiers

Wastewater clarifiers are popularly called sedimentation tanks or settlers. Being one of the primary units of wastewater treatment plants, they are used to separate impurities and solid particles from the wastewater through gravitational settling. Today, wastewater clarifiers are available in various designs such as rectangular or circular tanks. Additionally, most clarifiers may come with different mechanisms like scrapers or inclined parts to enhance their performance.

Role of Clarifies in the Wastewater Treatment

Here are some pointers that describes primary function of clarifiers in detail.

  • Separate Solids: Wastewater contains a diverse range of contaminants, pollutants, substances, and suspended solids including organic matter, debris, and other particulate materials. Clarifiers make a significant difference as they use gravity to settle these impurities at the bottom of the tank. This helps create clear liquid on the top.
  • Improve Water Clarity: By removing harmful contamination, clarifiers significantly improve the quality of water. This transparent liquid layer is called clarified effluent, which undergoes several processes before it is discharged into receiving waters.
  • Sludge Collection: In addition to the wastewater clarification, they facilitate the collection of settled solids or contaminants that form a sludge later at the bottom tank. This sludge can be treated separately and removed periodically.
  • Reduce Biological Load: Removing solids from wastewater also reduces the biological load on downstream treatment processes. This is beneficial for other subsequent treatments as they can operate efficiently.

Why Use Clarifiers for Water Treatment?

There are countless benefits of using clarifiers for wastewater treatment. Here are some important ones. 

  • The first and foremost important benefit of using clarifiers for wastewater treatment is they improve water quality. They remove solids and other harmful pollutants, making the treated water safe for discharge into the environment or reuse. 
  • The removal of solids and particulate matter by clarifiers can help reduce the load on downstream treatment processes, such as filters and disinfection systems. This can increase equipment life and lower maintenance requirements.
  • Clarifiers reduce the need for chemical coagulants and flocculants and also minimize the energy required for the subsequent processes. This leads to huge cost savings, which can be diverted towards business segments.
  • Meeting regulatory standards is the fundamental requirement for any wastewater treatment process. These standards help in protecting human health and the environment. Clarifiers help ensure compliance with discharge limits and environmental regulations.
  • These clarifiers also help reduce Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in wastewater. They are critical indicators of water pollution. 
  • Another great benefit of clarifiers is their flexibility. Today, they are available in different sizes and designs. This makes them adaptable to various wastewater treatment needs. 

Classification of Water Clarifiers

Here are two broad categories of water classifiers.

Primary Clarifiers in Wastewater Treatment – Introduction and Function

They are the most crucial and integral components of wastewater treatment plants. They serve the initial stage in the process, and their primary function is to separate heavy solids and large particles by allowing gravity to facilitate settling. When the wastewater passes through the clarifiers, these solids settle to the bottom, while lighter materials like oil and grease rise to the surface and are skimmed off. This whole process helps reduce the concentration of suspended solids while improving the water quality. Additionally, they help in stabilizing hydraulic fluctuations in the influent flow. This ensures a consistent flow into subsequent treatment processes. These clarifiers set the stage for further treatment to meet environmental discharge standards and regulations.

Secondary Clarifiers in Wastewater Treatment – Introduction and Function

They are circular or rectangular tanks designed to remove solids and impurities that have yet to be completely settled during the primary treatment phase. These clarifiers allow microorganisms to settle under the influence of gravity. Water velocity decreases as the wastewater passes through the clarifiers, allowing the heavier solid particles to settle into the bottom of the tank. The removed solids are collected and further processed for reuse or recycling. Compared to primary clarifiers, they are crucial in achieving the desired water quality standards ensuring environment-friendly wastewater treatment. This makes them a critical element in the overall treatment process.

Types of Water Treatment Plant Clarifiers 

Different types of clarifiers are used in water treatment plants. Here are some important ones based on their shape or specific attributes.

  • High-Rate Clarifiers: Compared to primary clarifiers, these clarifiers can handle a huge water flow in a smaller space. High-rate clarifiers use inclined tubes or plates to increase the settling rate of particles. This makes them more efficient in terms of capacity and space. 
  • Circular Clarifiers: They are commonly used in primary and secondary treatment processes. These clarifiers use mechanical or hydraulic mechanisms to assist in the settling and removing solids.
  • Mechanical Clarifiers: These clarifiers are often used in large water treatment plants. They use mechanical mechanisms to agitate the water or sludge for settling. Additionally, they may have scrapers, rotating arms, or other mechanisms to remove solids. 
  • Rectangular Clarifiers: These clarifiers are used in case of space constraints or if a specific configuration is required. As the name implies, they are designed with a rectangular basin shape, and can be equipped with mechanical scrapers to improve the settling process.
  • Lamella Clarifiers: These clarifiers are effective in removing small particles from water. They are widely preferred in water treatment plants with space constraints. They create a large settling area with plates or tubes within a compact space.
  • Cross-Flow Clarifiers: These clarifiers enhance the settling process by utilizing the horizontal flow of water. They are effective for high solids water concentrations. 

Key Components of Wastewater Clarifiers

The components of wastewater clarifiers vary based on the specific design and type. However, here are some fundamental components:

  • Inlet: This is the point from where the untreated wastewater enters the clarifiers. Also called an influent, it may feature grates or screens to remove impurities and prevent equipment damage.
  • Inlet Distribution System: It distributes the influent across the clarifier to ensure efficient settling.
  • Clarifier Basin: It is the primary component of the clarifier. It offers adequate space for wastewater to settle and separate into layers, with solids and particles settling to the bottom and clean water rising to the top.
  • Settling Zone: This is the most crucial area within clarifiers, where gravity causes heavy particles to settle down. Depending on the clarifier design, this often includes inclined tubes, lamella settlers, and more.
  • Sludge Collection System: This is mainly used to collect and transport the settled solids to specific points. This can be done using several equipment, such as sludge rakes or scrapers.
  • Effluent Launder: This collects the clean water from the upper layer and directs it towards the outlet for further treatment or discharge.
  • Effluent Outlet: The clean water exits the clarifier through this outlet for additional treatment or discharge into the environment.
  • Scum Removal System: Most times, a scum layer may form at the top due to lighter solids and fats. This system is used to skim off and remove the scum layer.
  • Overflow Weirs: These weirs control the water level in the clarifier basin. Also, they ensure that only clean water flows out while preventing the escape of settled solids.
  • Controls and Instrumentation: They monitor and regulate the clarifier’s operations while ensuring optimal performance.

Factors Influencing the Design of Wastewater Clarifiers

Wastewater clarifier design involves several factors to ensure effective operations. Here are some important ones:

  • Flow Rate and Hydraulic Loading: The amount of wastewater entering the clarifiers per unit and the flow distribution are vital aspects to consider. This is important to ensure even settling and prevent short circuiting.
  • Settling Characteristics of Solids: The size, density, and settling velocity of solids play a key role in the clarifier design. In-depth knowledge and understanding of these characteristics help determine the required retention time and tank dimensions.
  • Retention Time: The clarifiers should offer sufficient retention time for solids. The retention time depends on many factors such as the settling characteristics of the solids, the effluent quality, and more.  
  • Clarifier Geometry: The shape and size of the clarifiers are essential factors. The most common designs include circular, rectangular, and inclined plate clarifiers. The choice of clarifier design depends on various factors such as solids loading, available space, and settling characteristics of the water or fluids in the application.
  • Overflow and Underflow Rates: These are the most important parameters in the design and operation of wastewater clarifiers. They refer to the water flow exiting as clarified effluent, and the concentrated sludge that settles at the bottom. They must be controlled to optimize the separation and carryover of solids. 
  • Inlet and Outlet Configurations: The performance of clarifiers mainly depends on the location and design of influent and effluent channels. 
  • Sludge Density and Concentration: The size and capacity of sludge removal equipment are influenced by the concentration of the settled sludge.
  • Maintenance and Access: Easy equipment access and periodic inspection are important to ensure long life and operational efficiency.
  • Temperature and Environmental Conditions: Temperature variations and other environmental fluctuations can massively influence the clarifier’s performance.

Essential Wastewater Clarifier Maintenance Tips

Regular inspection and maintenance of clarifiers is crucial for their reliability and long-term efficiency. The following are some important tips to keep clarifiers in good working conditions.

  • The first and foremost important thing is to visually inspect the clarifiers and their components. This helps you identify signs of wear, corrosion, and damage.
  • Most clarifiers feature moving parts like the drive mechanism. Thus, they should be lubricated as per the manufacturer’s recommendation to prevent excessive wear and reduce friction.
  • Perform regular sludge removal to prevent excessive accumulation. This mainly depends on the clarifier design and sludge accumulation rates.
  • Monitor the effluent quality to ensure it meets the required regulatory standards.
  • Keep safety protocol in mind when working with clarifiers. Provide personal protective equipment (PPE) to operators, and ensure they are neatly trained in safety procedures.
  • Clean baffles and wires to maintain proper flow distribution and minimize short circuiting possibilities.
  • In-stock essential spare parts for components such as motors, seals, and bearings to minimize downtime.
  • Consult wastewater treatment specialists if any major damage is identified.

Do you still want to know more about clarifiers? If yes, the next part of this blog series will be uploaded soon. This part highlights the design, components, and maintenance of clarifiers. Meanwhile, you can browse HPI Processes, to understand the types of industrial parts and equipment they offer. If you require clarifiers for water treatment, it is always a good practice to consult a prominent industry expert such as HPI Processes, Inc. With vast years of experience and market presence, the company is committed to bringing environmental-friendly yet cost-effective solutions to fulfill several processing line needs. Having known all these aspects about wastewater clarifiers, you may still be eager to know more about them. Stay tuned to read the next part of this blog to learn more.