Grit chambers are effective in removing heavier particles, they are not designed to remove smaller particles or dissolved contaminants. These finer particles are typically addressed through other treatment processes such as sedimentation basins, biological reactors, and chemical treatment units. The combination of various treatment processes ensures that wastewater is treated to meet the required environmental standards before it is released back into the environment or reused.
Types of Grit Chamber in Wastewater Treatment -Working Principles and Uses
Grit chamber is an essential component in wastewater treatment plant that help remove heavy particles and debris from wastewater before it enters in the treatment plant. They are typically the first stage of treatment and are designed to trap and remove grit such as sand, gravel and other heavy solids which can cause damage to downstream equipment. In this post, we will explore the different types of grit chamber in wastewater treatment plant, working principle and use of grit chamber in Sewage treatment plant.
Types of Grit Chambers in Wastewater Treatment
The main types of grit chambers in wastewater treatment plant are vortex grit chambers, aerated grit chambers and horizontal grit chambers. See the sub-types of each in following:
1. Vortex Grit Chamber
- Conventional Vortex Grit Chamber
- Forced Vortex Grit Chamber
- High-Efficiency Vortex Grit Chamber
2. Aerated Grit Chamber
- Circular Tank Grit Chamber
- Rectangular Tank Grit Chamber
- Aerated Grit Chamber with Baffles
3. Horizontal Flow Grit Chamber
- Rectangular Grit Chamber
- Circular Grit Chamber
- Aerated Horizontal Flow Grit Chamber
1. Vortex Grit Chamber
Vortex grit chambers use centrifugal force to separate grit from wastewater. In this design, the wastewater is introduced tangentially into a circular chamber, creating a vortex that causes heavier particles to settle to the bottom of the chamber. The separated grit is then removed by a screw conveyor or similar mechanism and wastewater is passed for next stage in wastewater treatment plant.
1.1 Conventional Vortex Grit Chamber
This is the simplest and most common type of vortex grit chamber. It consists of a circular or rectangular chamber that creates a vortex through tangential inflow. The centrifugal force generated by the vortex causes heavier grit to settle to the bottom of the chamber, where it is removed by a screw conveyor or similar mechanism.
1.2 Forced Vortex Grit Chamber
This type of chamber uses an external motor or pump to force water into the chamber at a high velocity. This creates a stronger vortex that can remove smaller and lighter particles than a conventional vortex grit chamber. The separated grit is then removed by a screw conveyor or similar mechanism.
1.3 High-Efficiency Vortex Grit Chamber
This is designed to improve the efficiency of conventional vortex grit chambers by reducing the size of the chamber and increasing the velocity of the inflow. This creates a stronger vortex that can remove finer grit particles. The separated grit is then removed by a screw conveyor or similar mechanism.
2. Aerated Grit Chamber
Aerated grit chambers use aeration to float lighter organic matter and allow heavier grit to settle to the bottom of the chamber. In this design, air is introduced into the wastewater, which causes the organic matter to float to the top, where it can be skimmed off. The grit then settles to the bottom and is removed by a screw conveyor or similar mechanism.
2.1 Circular Tank Grit Chamber
This subtype is a circular tank that uses aeration to create a vertical flow pattern that separates organic matter from grit. The organic matter floats to the surface, where it can be skimmed off, and the grit settles to the bottom of the tank, where it is removed by a screw conveyor or similar mechanism.
2.2 Rectangular Tank Grit Chamber
This subtype is a rectangular tank that uses aeration to create a horizontal flow pattern that separates organic matter from grit. The organic matter floats to the surface, where it can be skimmed off, and the grit settles to the bottom of the tank, where it is removed by a screw conveyor or similar mechanism.
2.3 Aerated Grit Chamber with Baffles
This subtype uses aeration and baffles to create a horizontal flow pattern that separates organic matter from grit. The baffles create a zigzag flow path that allows for better separation of the grit from the organic matter. The grit settles to the bottom of the tank, where it is removed by a screw conveyor or similar mechanism.
3. Horizontal Flow Grit Chamber
Horizontal flow grit chambers are designed to allow wastewater to flow horizontally through a chamber, which slows down the velocity of the water and allows heavier particles to settle at the bottom of the grit chamber. The grit is then removed by a screw conveyor or similar mechanism and the water goes for next process in waste water treatment plant.
3.1 Rectangular Grit Chamber
This is a rectangular tank that uses a horizontal flow pattern to separate grit from wastewater. The grit settles in the bottom of the chamber and it is removed by a screw conveyor or similar mechanism.
3.2 Circular Grit Chamber
This is a circular tank that uses a horizontal flow pattern to separate grit from the wastewater. The grit settles in the bottom in the chamber and it is removed by a screw conveyor or similar mechanism.
3.3 Aerated Horizontal Flow Grit Chamber
This uses aeration to create turbulence and trap grit in chamber. As wastewater flows through the grit chamber, fine bubbles are introduced to create a gentle mixing action causing the grit to settle out of the water. The aerated grit chamber is designed to achieve high grit removal efficiency while minimizing organic matter removal.
Working Principle of Grit Chamber in Wastewater Treatment
A grit chamber is a primary treatment unit in wastewater treatment plants designed to remove heavy and coarse particles, collectively referred to as "grit," from the incoming wastewater. Grit includes materials such as sand, gravel, broken glass, and other dense solids that can settle in the wastewater due to their weight. The main purpose of a grit chamber is to prevent these abrasive and heavy particles from causing damage to downstream equipment, such as pumps, pipes, and settling tanks, which could lead to operational problems and increased maintenance costs. See the below steps of the working principle of grit chamber.
Wastewater Inflow
Raw wastewater from various sources enters the wastewater treatment plant and is directed towards the grit chamber. At this stage, the wastewater may contain a wide range of solid particles, including grit.
Reduced Flow Velocity
The velocity of the incoming wastewater is deliberately reduced as it enters the grit chamber. This reduction in flow velocity allows the heavier grit particles to settle and separate from the liquid. The slower flow prevents the grit from being carried further downstream in the treatment process.
Settling Zone
Within the grit chamber, there is a settling zone where the wastewater flow becomes quiescent. This calm environment allows the grit particles to gradually settle to the bottom of the chamber due to their greater density. As the particles settle, they accumulate in the bottom of the chamber.
Grit Removal
Once the grit particles have settled to the bottom, mechanical equipment or systems are used to remove them. Common methods of grit removal include:
Grit Removal System
This system typically consists of a chain or bucket mechanism that collects and lifts the settled grit from the bottom of the chamber. The collected grit is then transported and discharged into appropriate containers for further processing or disposal.
Grit Pump
In some cases, a specialized grit pump may be used to remove the settled grit from the bottom of the chamber. The pump helps lift the grit-laden slurry and send it to a grit classifier for further separation and dewatering.
Wastewater Outlet
After the grit removal process, the wastewater continues its flow through the treatment process, which may involve various additional treatment steps such as screening, sedimentation, biological treatment, and disinfection to further purify the water before its discharge or reuse.
Uses of Grit Chamber in Sewage Treatment Plant
The grit chamber is designed to enhance the efficiency of the treatment process in sewage treatment plant and prevents damage to downstream equipment and reduces overall operating cost of the operation.
A grit chamber, also known as a grit chamber tank or detritus tank, is an essential component of a sewage treatment plant's preliminary treatment process. Its primary function is to remove heavy inorganic particles, such as sand, gravel, stones, and other coarse materials, from the wastewater before it enters further treatment processes. See the below the key uses and benefits of a grit chamber in a sewage treatment plant:
Grit Removal
Grit chambers are designed to separate and remove coarse and heavy particles that could cause abrasion, clogging, or damage to downstream equipment and processes. These particles often settle at the bottom of the chamber due to their weight.
Protection of Equipment
By removing abrasive materials, grit chambers help prevent wear and tear on pumps, valves, and other mechanical components downstream in the treatment process. This extends the lifespan of the equipment and reduces maintenance requirements.
Prevention of Clogging
Inorganic particles like sand and gravel can cause blockages and clogs in pipes, channels, and treatment units. Grit chambers prevent these particles from entering the system and causing operational issues.
Maintenance of Flow
Removing large and heavy particles from the wastewater stream ensures a consistent and even flow rate throughout the treatment process. This prevents uneven distribution of pollutants and improves the efficiency of subsequent treatment steps.
Minimization of Settling Tanks Maintenance
Grit that enters settling tanks can settle at the bottom and reduce their effective volume, requiring more frequent maintenance. By removing grit in the preliminary stage, the load on settling tanks is reduced.
Improved Treatment Efficiency
Removing grit from the wastewater stream allows downstream treatment processes, such as biological treatment and sedimentation, to work more effectively. Grit can interfere with these processes and reduce their efficiency.
Reduction of Odors
Grit chambers can help remove larger debris that might contribute to odor issues in the treatment plant. This contributes to a more pleasant working environment for plant operators.
Protection of Ecosystems
In cases where treated effluent is discharged into natural water bodies, removing grit prevents the introduction of solid particles that could harm aquatic ecosystems and disrupt their balance.
Compliance with Regulations
Many environmental regulations mandate the use of grit chambers as part of preliminary treatment processes to ensure that wastewater discharged into water bodies meets specific quality standards.
Grit chambers are available in various designs, such as vortex-type and rectangular-type chambers, and their effectiveness depends on factors like flow rate, particle size distribution, and the design of the chamber. Proper maintenance of the grit chamber is crucial to ensure its efficient operation, as accumulated grit should be periodically removed to prevent the chamber from becoming less effective over time.
