Unit : 9

 Solid computations

 Solid Production and Characteristics

 Minimization of Residuals Generation 

Recovery of Treatment Chemicals

 Residuals Conveyance 

 Management of Sludges & Liquid Residuals

 Disposal of Specific Residuals 


Solid Computations : 

Solid computations for a water treatment plant would include calculations for the following:

Flow Rate: The volume of water that needs to be treated and the rate at which it needs to be processed. This is important for determining the sizing and capacity of equipment, such as pumps and filters. 

Chemical Dosage: The amount of chemicals, such as coagulants and disinfectants, that need to be added to the water at each stage of treatment. This is important for ensuring that the water is effectively treated and that the chemicals are used efficiently.  

Sludge volume: The volume of solids that are removed from the water during treatment and need to be disposed of. This is important for determining the capacity of sludge storage and treatment facilities.  

Hydraulic Loading: The flow rate and pressure of water at each stage of treatment. This is important for ensuring that the water is moving through the treatment process efficiently and that equipment is not overworked.  

Water Quality: The concentration of specific contaminants in the water before and after treatment. This is important for ensuring that the water meets regulatory standards and is safe for distribution to customers.

These calculations are typically done using information from water quality tests, equipment specifications, and local regulations. It is important to note that these calculations should be reviewed and verified by a professional engineer to ensure that the water treatment plant is designed and operated safely and effectively. 

Solid Production and Characteristics : 

Solid production in a water treatment plant refers to the amount of solids (such as sediment or sludge) that are removed from the water during the treatment process. These solids are typically composed of inorganic and organic matter, including minerals, microorganisms, and other particles.

The characteristics of the solids produced in a water treatment plant can vary depending on the source of the water being treated and the specific treatment processes used. Some common characteristics include:

Size: The size of the solids can range from small particles to large clumps. Smaller particles are typically removed through processes such as filtration or sedimentation, while larger clumps are removed through processes such as coagulation and flocculation.

Density: The density of the solids can range from low (such as microorganisms) to high (such as minerals).

Moisture content: The moisture content of the solids can vary depending on the treatment process. For example, solids removed through sedimentation may have a high moisture content, while those removed through filtration may have a lower moisture content.

Organic content: The organic content of the solids can vary depending on the source of the water being treated. Solids from surface water sources may have a higher organic content, while those from ground water sources may have a lower organic content.

It is important to properly handle and dispose of the solids produced in a water treatment plant to ensure that they do not negatively impact the environment or public health. This often includes dewatering the solids, which is the process of removing as much water as possible from the solids to reduce the volume and weight, making them more manageable and less costly to transport and dispose of. 

Minimization of Residuals Generation : 

Minimizing the generation of residuals (also known as waste or by-products) in a water treatment plant is an important consideration in the design and operation of the facility. Residuals can include both solid and liquid waste, and can have a negative impact on the environment and on the cost of operating the treatment plant.

Some strategies for minimizing the generation of residuals in a water treatment plant include:

Using A Multi-barrier Approach: This involves using a combination of different treatment processes to remove contaminants from the water, rather than relying on a single process. This can help to reduce the amount of solids and chemicals that need to be removed from the water.

Optimizing Chemical Dosage: By carefully controlling the amount of chemicals used in the treatment process, it is possible to minimize the amount of chemicals that need to be removed from the water and the amount of solids that are produced.

Reusing and Recycling: Some residuals, such as sludge, can be treated and reused as fertilizer, soil conditioner, fuel, or other beneficial products.

using advanced technologies: Some new technologies like membrane filtration, ozone, and UV-light can help to reduce the amount of solids and chemicals that need to be removed from the water.

Implementing good housekeeping practices:

Simple actions like regular cleaning, maintenance and monitoring of the equipment, storage and handling of the chemicals can help to minimize the generation of residuals.

It is important to note that the specific strategies for minimizing residuals will vary depending on the source of the water being treated, the specific contaminants that need to be removed, and the regulations and standards that must be met. Consultation with a professional engineer would be necessary to design a cost-effective and environmentally friendly water treatment plant. 

Recovery of Treatment Chemicals : 

Recovery of treatment chemicals in a water treatment plant refers to the process of reusing or recycling chemicals that have been added to the water during the treatment process. This can help to reduce the cost of operating the treatment plant and also minimize the environmental impact of the treatment process.

Some common methods for recovering treatment chemicals include:

Chemical precipitation: This involves adding a chemical to the water to cause dissolved chemicals to precipitate out of the water. The precipitate can then be removed and the dissolved chemical can be recovered and reused.

Ion exchange: This involves passing the water through a resin or other material that can remove ions from the water. The ions can then be recovered and reused.

Reverse osmosis: This involves passing the water through a membrane that can remove dissolved chemicals from the water. The chemicals can then be recovered and reused.

Evaporation: This involves evaporating the water from the chemical solution to recover the chemical.

Incineration: This involves burning the solids or sludge that contain the chemical to recover the chemical.

It is important to note that recovery of treatment chemicals is not always possible or practical, depending on the chemical and the specific treatment process used. Additionally, the recovery methods should be evaluated in terms of their energy consumption, chemical consumption, and waste generation. 

The chemical recovery process should also be comply with the regulations and standards to ensure the safety of the environment and public health.Consultation with a professional engineer would be necessary to design a chemical recovery process that is cost-effective and environmentally friendly. 

Residuals Conveyance : 

Residuals conveyance in a water treatment plant refers to the process of transporting and disposing of the solids and liquids that are removed from the water during the treatment process. This can include sludge, scum, and other waste materials that are generated by the treatment process.

Some common methods for conveying residuals in a water treatment plant include:

Pumps: Pumps can be used to move sludge and other residuals through pipes or hoses to a storage or treatment facility.

Conveyors: Conveyors, such as belt conveyors or screw conveyors, can be used to move solids from one location to another within the treatment plant.

Trucks: Residuals can be loaded into trucks and transported off-site for disposal or treatment.

Sludge Lagoons: Residuals can be stored in a lagoon or pond where they can be treated or allowed to decompose before being disposed of.

It is important to note that the method of residuals conveyance will depend on the type and amount of residuals, local regulations, and available disposal options. Additionally, the residuals conveyance system should be designed and operated to minimize the environmental impact, ensure safety, and comply with regulations and standards. 

Residuals should be handled in a way that minimizes odors and the risk of spills, leakage or leaching, and also protect the public health and the environment. Consultation with a professional engineer would be necessary to design a residuals conveyance system that is cost-effective and environmentally friendly.

Management of Sludges & Liquid Residuals : 

The management of sludges and liquid residuals in a water treatment plant is an important consideration in the design and operation of the facility. These residuals can have a negative impact on the environment and on the cost of operating the treatment plant if not handled properly.

Sludges are the solid residuals generated by the treatment process, and their management includes methods like:

Dewatering: Dewatering is the process of removing as much water as possible from the sludge to reduce the volume and weight, making it more manageable and less costly to transport and dispose of. Common dewatering methods include belt filter presses, centrifuges, and lagoons. 

Stabilization: Sludges that are not going to be disposed of immediately can be stabilized to reduce the potential for odors and pathogens. Stabilization can be achieved through chemical, biological, or physical methods.  

Disposal: Sludges can be disposed of by landfilling, incineration, or by using them as a soil conditioner, fertilizer, or fuel. 

Liquid residuals are the liquid waste generated by the treatment process, and their management includes methods like:

Treatment: The liquid residuals can be treated to remove pollutants and contaminants before being released to the environment. Methods like pH adjustment, chemical precipitation, adsorption, membrane filtration, biological treatment, and oxidation are used to treat liquid residuals.  

Disposal: The treated liquid residuals can be disposed of by releasing them to a surface water body, injecting them into the ground, or evaporating them.  

It is important to note that the management of sludges and liquid residuals will depend on the type and amount of residuals, local regulations, and available disposal options. Additionally, the management system should be designed and operated to minimize the environmental impact, ensure safety, and comply with regulations and standards. Consultation with a professional engineer would be necessary to design a management system that is cost-effective and environmentally friendly. 

Disposal of Specific Residuals : 

The disposal of specific residuals in a water treatment plant will depend on the type of residuals and the regulations and standards that must be met. Some common methods of disposal for specific types of residuals include:

Biosolids: Biosolids are the solid residuals generated by biological treatment processes, such as activated sludge. They can be stabilized and used as a soil conditioner or fertilizer, if they meet the regulations and standards for pathogen and heavy metal content.

Sludge: Sludge is the solid residual generated by other treatment processes, such as sedimentation or filtration. It can be dewatered and disposed of by landfilling, incineration or used as a soil conditioner, fertilizer, or fuel.

Chemical Residuals: Chemical residuals are the liquid or solid waste generated by the addition of chemicals during the treatment process. They can be treated or neutralized before disposal.

Oil and Grease: Oil and grease can be removed from wastewater using a process called gravity separation, or by using chemicals or biological methods. The separated oil and grease can be recycled or disposed of in an appropriate manner.

Heavy Metals: Heavy metals can be removed from wastewater using chemical precipitation, ion exchange, or adsorption. The removed metals can be recycled or disposed of in an appropriate manner.

It is important to note that disposal methods must comply with local and national regulations. Some of the regulations include: the Resource Conservation and Recovery Act (RCRA), the Clean Water Act (CWA), and the Clean Air Act (CAA). Consultation with a professional engineer would be necessary to design a disposal system that is cost-effective, environmentally friendly and comply with regulations and standards.