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Sewage and Industrial Wastewater Treatment – Understanding the STP/ETP…

December 29, 2022December 29, 2022
by everflow

What is Wastewater?

Wastewater is a mixture of water and a variety of pollutants, including suspended solids, dissolved organic compounds, nutrients, and microorganisms. Domestic wastewater is typically composed of human waste, food waste, and paper products. Industrial wastewater may include toxic chemicals, heavy metals, oil and grease, and other pollutants.

Suspended solids are the largest component of wastewater and can include anything from toilet paper to food scraps. Dissolved organic compounds, such as detergents, food waste, and solvents, can also be found in wastewater. Heavy metals, salts, and nutrients are also present. Nutrients, such as nitrogen and phosphorus, are the primary sources of energy for microorganisms in wastewater. These microorganisms are responsible for breaking down organic matter, which in turn produces carbon dioxide and other gases. This decomposition is essential for the removal of some pollutants, such as ammonia and phosphorus from wastewater.

Health, Environment, and Social concerns associated with wastewater:

Health: Wastewater contains bacteria, viruses, and parasites that can cause diseases such as cholera, dysentery, hepatitis A, and typhoid. These diseases can spread through contaminated water. Wastewater also contains toxic chemicals, such as lead, arsenic, and mercury, which can cause serious health problems if ingested. Poorly treated wastewater leads to water pollution on its release, creating an even greater risk to public health.
Environment: Wastewater can have a damaging effect on the environment if it is not properly treated or disposed of. Untreated wastewater can pollute drinking water sources and contaminate soil, which can lead to water-borne diseases and the destruction of natural habitats. Wastewater can also cause algal blooms and oxygen depletion in water bodies, which can kill off fish and other aquatic life.
Social: Wastewater can have a significant impact on communities. Poorly treated or disposed wastewater can cause an increase in health risks to local residents. If wastewater is not managed properly, it can create an unpleasant living environment due to odor and the presence of vermin. Furthermore, wastewater has an adverse impact on the local economy, as it can contaminate agricultural land and decrease crop yields.

Precautionary measurements are taken to avoid wastewater-related issues

Precautionary measures are taken because untreated wastewater can cause a variety of negative environmental and health impacts.

To prevent these issues, precautionary measures are taken to ensure that wastewater is collected and disposed of properly. The collection of wastewater is usually done through sewer systems, septic tanks, or catchment basins. These systems allow for the safe collection and transport of wastewater to a treatment facility to remove pollutants and contaminants. Then water is released back into the environment.

Disposal of wastewater is also important in avoiding wastewater-related issues. Depending on the type of wastewater and the level of treatment it has undergone, it can be disposed of in various ways. Treated wastewater may be discharged into a local waterway, sprayed onto land, or recycled for use in industrial processes.

Wastewater collection

Wastewater collection systems typically include a network of pipes, manholes, and other structures such as pumping stations, treatment plants, and storage tanks. The collection systems are responsible for transporting wastewater from residences and businesses to a central drainage system.

Wastewater specific treatment

STP

A sewage treatment plant is a facility where wastewater is processed to remove pollutants and produce a treated effluent that is safe to return to the environment. Treatment processes may include physical, chemical, and biological processes to remove suspended solids, nutrients, and other pollutants. The treated effluent is typically discharged to a receiving water body such as a river, lake, or ocean.

Primary, Secondary, and Tertiary treatment process in STP:

Primary Treatment

It involves the physical removal of solids from wastewater. This is typically accomplished by screening, grit removal, and primary sedimentation. This is usually done by passing wastewater through large screens or grit channels to remove large debris, such as plastic, sticks, and rags. The wastewater is then pumped through a settling tank, which allows suspended solids to settle to the bottom and the clarified water to flow out of the tank. The settled sludge is usually sent to a secondary treatment process, such as anaerobic digestion or activated sludge. Primary treatment involves the addition of a coagulant and aims at removing grits, coarse solids, oil, and grease if any are present.

Secondary Treatment

This process uses bacteria and other microorganisms to break down organic matter from wastewater, such as food waste, soaps, and detergents, and convert it into a form to be released into the environment. The process usually involves aeration and clarification, using tanks, basins, and biological filters.

Membrane bioreactors (MBRs): Another wastewater treatment option is MBRs. These systems use membranes to separate suspended particles from the wastewater and then allow aerobic or anaerobic bacteria to break down the organic material. The end result is a stabilized effluent that meets environmental standards for safe discharge.

Sequential Batch Reactor (SBR): The SBR cycle is composed of several steps: fill, react, settle, decant, and idle. During the reaction stage, the wastewater is aerated and circulated to mix with the microbial population, allowing it to break off the organic matter. In the settling stage, the mixture is settled, allowing lighter biomass and organic matter to rise to the surface and be removed. In the idle phase, the tank is allowed to sit without any aeration or mixing, allowing the biomass to settle and the organisms to rest.

Moving Bed Biofilm Reactor (MBBR): MBBR is a type of wastewater treatment system that uses suspended carriers to provide a large surface area for the attached growth of biofilms. The carriers used in MBBRs provide a large surface area for biofilm growth, which helps to reduce the biomass size required for effective treatment.

Fluidized Bed Bioreactors (FBBR): FBBR is a type of secondary treatment for the removal of organic pollutants from wastewater. This allows microorganisms, such as bacteria and fungi, to colonize the particles and break down the organic pollutants. It is used in conjunction with primary treatment processes to achieve the highest level of pollutant removal possible.

Tertiary Treatment

The tertiary or chemical treatment process of sewage treatment plants typically involves the addition of chemicals such as calcium oxide, sodium hydroxide, and sodium carbonate to the wastewater. This process helps to break down organic matter and remove suspended solids and other contaminants. The process also helps to balance the pH of the water, reduce odors (Activated charcoal), and reduce the level of disease-causing organisms.

Activated charcoal is a carbon filtration that works to remove odor and color by adsorbing and trapping contaminants on the surface of its tiny pores. Activated carbon needs replacement as its capacity to work reduces gradually.

Chlorination: The process involves the addition of chlorine or chlorine-based compounds to the water to kill bacteria and other disease-causing microorganisms. The chlorine kills any disease-causing organisms, which helps to reduce the risk of water-borne diseases.

Ozonation is a form of the advanced oxidation process that produces extremely reactive oxygen species. Ozone is very reactive and readily oxidizes microorganisms, effectively killing them. Ozone oxidizes the cell wall, membrane, and internal components of microorganisms, damaging their structure and function. Ozone also disrupts the microorganism`s metabolic pathways, leading to cell death.

UV treatment – UV water disinfection technique disinfects by penetrating microorganisms and destroying their DNA. Chlorine and other disinfectants can produce toxic disinfection byproducts (THMs or Halo-acetic acids) as well as the dangers that come with their presence on site. Because UV light disinfection is a chemical-free method, it effectively eliminates any concerns about these byproducts.

The important water discharge parameters in STP are biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), and fecal coliform bacteria.

ETP

An effluent treatment plant (ETP) is a facility used to treat wastewater that is produced by industries and other sources. The treated wastewater (or effluent) is then released into the environment, usually a nearby river, lake, or ocean. ETP reduces the number of pollutants in the wastewater to the levels required by national and local environmental regulations.

In comparison with STP, ETP focuses more on reducing the number of chemical pollutants present in wastewater during its secondary treatment process.

Primary, Secondary, and Tertiary treatment process in ETP:

Primary Treatment

The primary treatment process in ETP typically involves the removal of suspended solids, oils, and other physical contaminants from wastewater. Wastewater is Treated by physical processes such as sedimentation, flocculation, clarification, and filtration.

Secondary Treatment

In secondary treatment, industrial effluent processes are modified as per the content and level of certain chemical pollutants. Following some of the industrial wastewater treatment processes will help to understand this concept better.

Oil and petroleum industry:

A vast amount of wastewater is generated from the extraction, refining, and transportation of petroleum products. This contains a variety of contaminants, including oil, grease, heavy metals, and other hazardous substances or pollutants. It helps to reduce the concentration of pollutants and contaminants in the effluent to a level that is safe for discharge into the environment. This is achieved through coagulation, flocculation, and biological treatment. The coagulation/flocculation process involves the addition of a coagulant, such as aluminum hydroxide chloride or aluminum sulfate, to the wastewater to remove suspended solids.

The biological treatment process utilizes microorganisms to break down organic material in the wastewater and reduce the concentration of pollutants. Finally, the N:P ratio is an important parameter for the treatment of oily wastewater by using oil-degrading bacteria. By using these techniques, secondary treatment can effectively reduce the contamination level of effluent and make it suitable for discharge into water bodies.

Example: Microorganisms to remove oil contaminants such as Bacteria, Pseudomonas aeruginosa: P. aeruginosa bacteria are able to break down oil and petroleum products due to their ability to produce enzymes that are specific to hydrocarbons. Pseudomonas bacteria are usually introduced into wastewater as slurry. This slurry is made up of a combination of Pseudomonas bacteria, nutrients, and a carbon source. The carbon source is important because it provides the bacteria with the energy they need to break down the oil and petroleum-based pollutants.

Other common microorganisms used in the oil and petroleum industry for wastewater treatment include bacteria such as Acinetobacter, and Bacillus, and fungi such as Aspergillus and Trichoderma.

Textile industry (Dyes and paints, colorants,):

The main purpose of secondary treatment is to provide BOD removal beyond what is achievable by simple sedimentation. It also removes appreciable amounts of oil and phenol. The dissolved and colloidal organic compounds and color present in wastewater are removed or reduced to stabilize the organic matter. Textile processing effluents are amenable to biological treatments.

Textile waste also contains significant quantities of non-biodegradable chemical polymers. For non-biodegradable pollutants, filtration technologies are utilized in the textile industry to clean wastewater. Traditional membrane processes in textile wastewater treatment include the use of ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. The selection of membrane technologies for textile effluent relies on costs based on the balance between water flux and solute retention. RO also becomes less effective when osmotic pressure, is caused by high salt concentration in the feed wastewater. Becomes too high to obtain a reasonable transmembrane permeate flux without applying excess transmembrane hydraulic pressure.

The membrane filtration system typically consists of a series of membranes with differing pore sizes and compositions that are used to remove particles from the wastewater. The membranes are typically made from polymeric materials such as polyvinylidene fluoride (PVDF), polysulfone, or polypropylene.

Metallurgic, chemical, and Fertilizer industry:

This is usually done through the application of an activated sludge process, trickling filter, rotating biological contactors, and oxidation ponds. The activated sludge process is used to remove organic pollutants from wastewater by using a variety of microorganisms. Trickling filters use a bed of media on which microorganisms grow to degrade the organic pollutants. Rotating biological contactors use a series of rotating plastic disks on which microorganisms grow and degrade organic pollutants. Finally, oxidation ponds are used to provide long-term biological treatment.

Tertiary Treatment

The tertiary treatment or biological treatment process in an ETP is designed to remove organic and inorganic pollutants from wastewater. This process is typically used in applications where the effluent needs to be treated to a high level of purity. The water is then treated with chlorine, ultraviolet light, or ozone to kill any remaining bacteria, viruses, and other pathogens before it is released into the environment. Primary and secondary treatment typically gets wastewater only clean enough to discharge safely into the environment. Tertiary treatment can achieve levels of water purification that make the water safe for reuse in water-intensive processes or even as drinking water.

Tertiary wastewater treatment often works by using a combination of physical and chemical processes to remove harmful microbiological contaminants. The process usually involves filtration followed by additional disinfecting treatment. In some cases, tertiary treatment may also use other specialized treatments like lagoon storage, biological nutrient removal, and nitrogen and phosphorus removal.

Final water disposal activities:

All water either from STP or ETP is finally safely disposed into the environment or reused depending upon the quality of wastewater as follows.

Filters: Tertiary filtration components can contain a few different materials. Sand and activated carbon filters are common, and filters can also contain fine woven cloth. The filters come in a few types, including bag filters, drum filters, and disc filters. Backwash cleans the media components to ensure their continual functioning.

Disinfecting: The process of tertiary disinfection may take a few different forms. Chlorine is one of the most commonly used disinfectants in wastewater treatment. Ultraviolet light is a common disinfectant in tertiary treatment. Ozone is highly reactive and can destroy most microorganisms it comes into contact with.

Discharge: Once the wastewater has undergone tertiary treatment, it is ready for discharge back into the environment. Many municipalities have specific requirements for the discharge of treated water. Tertiary treatment should be sufficient to meet those standards, keep the environment clean and preserve human health, experts say.

Reuse: Many treatment plants use tertiary treatment specifically to make the water safe for human ingestion. Water that has received tertiary treatment is also suitable for numerous operations that require clean water. These include industrial and manufacturing processes, oil and gas extraction and refining, utilities cooling, and agricultural practices like irrigation.

Waste Management

Understanding waste and its possible ways of management

December 2, 2022December 2, 2022
by everflow

Waste and Its Management

What is Waste?

Waste is any material that is discarded or left unused after its initial purpose has been served. It is a major problem in the world today, with large amounts of waste created by human activities. Waste can be found in many forms, including solid, liquid, and gaseous. It can be hazardous or non-hazardous and can come from a variety of sources, such as industrial processes, agriculture, and domestic activities. The improper disposal of waste can have serious environmental and health consequences. Solid waste can contaminate groundwater and soil, while liquid waste can pollute rivers and other bodies of water. In addition, some forms of waste can release toxic substances into the atmosphere, causing air pollution. Waste can also lead to the spread of disease, as some types of waste can be a breeding ground for bacteria and viruses.

The most effective way to address the issue of waste is to reduce, reuse, and recycle. Reducing waste means using less of the resources available and cutting down on the amount of waste produced. Reusing materials instead of buying new products can help reduce the amount of waste produced. Finally, recycling waste can help to reduce the amount of waste that needs to be disposed of, as materials can be processed and reused. Waste is an ever-growing problem that needs to be addressed urgently. By reducing, reusing, and recycling, we can all do our part to help reduce the amount of waste produced.

Classification of Waste

Classification Depending upon the Waste Types:

Solid Waste:

Solid waste is any type of waste material that is discarded after use and cannot be reused or recycled. This type of waste is usually composed of common items such as food scraps, packaging materials, paper and cardboard, and other items that are no longer needed. Solid waste is the most common form of waste and accounts for over two-thirds of all waste produced. Solid waste is a major threat to the environment, as it can contaminate soil and water, pollute the air, and create health risks.

Liquid Waste:

Liquid waste refers to waste materials in liquid forms, such as wastewater, sewage, and industrial effluents. this type of waste can come from a variety of sources, including homes, businesses, and industries. It is generally composed of a mixture of organic and inorganic substances, including oils, grease, detergents, suspended solids, and other contaminants. Liquid waste is considered hazardous when it contains any type of pollutant that can be harmful to humans, animals, and the environment.

Classification Depending upon the Source:

Industrial waste is generated by commercial and industrial processes, such as manufacturing, mining, and energy production.

Municipal waste is generated by households and businesses, including packaging, food waste, and other household items.

Construction and demolition waste is generated from the construction and demolition of buildings and other structures.

Agricultural waste is generated during agricultural practices of growing, harvesting, and recovering food grains. This waste is mostly organic and manageable at the source of its production in many conventional ways.

Depending upon its Management:

Recyclable waste is any material that can be reused or repurposed for another purpose.

Compostable waste is any material that can be broken down into organic matter and used as fertilizer or soil conditioner.

Landfill waste is any material that cannot be recycled or composted and must be disposed of in a landfill.

Classification by the Categories:

Furthermore, all types of waste can be divided into two main categories: hazardous and non-hazardous.

Hazardous waste is any material that is toxic, flammable, corrosive, radioactive, or otherwise dangerous to human health or the environment. Examples of hazardous waste include industrial chemicals, medical waste, electronic waste, etc.

Non-hazardous waste is any material that is not hazardous and poses no risk to human health or the environment. Examples of non-hazardous waste include paper and cardboard, food waste, yard waste, etc.

Waste Management

Waste management is the collection, transport, processing, recycling, or disposal of waste materials, in an effort to reduce their impact on human health and the environment. This includes the management of hazardous or toxic substances, as well as the management of non-hazardous solid and liquid materials. There are different methods and techniques used in waste management, depending on the type of waste and the location where it is generated. For example, in urban areas, municipal waste management programs may involve curbside collection, waste disposal facilities, and recycling centers.

In industrial areas, waste management may involve the use of special containers, incineration, and other types of waste treatment. Waste management in a rural area may involve the use of composting, landfills, and other methods of disposal. In order to reduce the amount of waste that is generated, it is important to develop strategies for reducing, reusing, and recycling materials. This includes encouraging the use of durable goods that can be reused, such as furniture and appliances, and encouraging people to purchase items that are made from recycled materials. It is also important to educate the public about the importance of proper waste disposal, such as avoiding the disposal of hazardous materials and properly disposing of non-hazardous materials.

Finally, it is important to develop and implement effective waste management systems that are tailored to the specific needs of the locality. This may include the development of regulations and laws that govern the disposal of waste, as well as the enforcement of these laws. It is also important to ensure that waste management practices are properly monitored and enforced, in order to ensure that they are effective and safe.

Solid Waste Management:

Solid waste management is the collection, transportation, processing, and disposal of solid waste materials. It is essential to ensure proper waste management to reduce health risks, conserve resources, and protect the environment. The most common methods of solid waste management include recycling, composting, incineration, and landfilling. Each of these methods has its own benefits and drawbacks. Recycling involves reprocessing and reusing discarded materials while composting is the process of breaking down organic materials into a soil-like material. Incineration is a method of burning waste materials to reduce their volume while landfilling involves burying the materials in a designated area.

In addition to these methods, there are several other strategies for managing solid waste. These include source reduction, reuse, and energy recovery. Source reduction involves reducing the amount of waste produced in the first place, while reuse involves finding new uses for existing materials. Energy recovery involves burning waste to create energy. Regardless of the strategy used, it is important to ensure proper solid waste management. This includes establishing regulations and policies that promote proper waste management, as well as educating the public on the importance of waste reduction and recycling. Proper waste management can help to reduce air and water pollution, conserve resources, and reduce the amount of landfill waste. Additionally, proper disposal of solid waste is essential to ensure that it does not end up in landfills or waterways.

Liquid Waste Management:

The management of liquid waste is important in order to protect public health and the environment. Liquid waste must be properly collected, treated, and disposed of in order to reduce potential risks to human health and the environment. Treatment options vary depending on the type and composition of the liquid waste. Common methods of treatment include physical, chemical, and biological processes. The disposal of liquid waste is regulated by local and state laws, which specify the types of waste that must be disposed of in a certain manner and the methods that must be used to do so. In most cases, liquid waste must be disposed of in accordance with federal and state regulations and must be managed in a manner that does not pollute the environment or pose a threat to public health.

Impact of hazardous waste:

The most immediate effect of hazardous waste is the contamination of land, air, and water. Hazardous waste can contain a variety of harmful chemicals that can be released into the environment and can cause a wide range of health problems. Long-term exposure to hazardous waste can lead to cancer, birth defects, and other serious health problems. Hazardous waste can also contaminate nearby groundwater and surface water, creating a risk of contamination for drinking water sources. This can lead to a host of health problems, such as poisoning, gastrointestinal and respiratory illnesses, and even death.

The presence of hazardous waste can also impact the local ecology. It can contaminate soil, killing off beneficial organisms and disrupting the natural balance of the ecosystem. Hazardous waste can leach into rivers and streams, killing off fish and other aquatic life. Additionally, improper handling of hazardous waste can lead to accidental spills, which can have a devastating effect on the environment. Spills can contaminate the soil, water, and air, leading to long-term damage. Overall, hazardous waste can have a devastating effect on human health and the environment. It is important to take steps to ensure that hazardous waste is properly managed and disposed of in order to minimize its potential impacts.

How to Manage Hazardous waste:

Identify Hazards: Identify the type of hazardous waste you are dealing with and its associated risks. This information should be documented and kept on file.

Contain and Label: Contain the hazardous waste in a secure area and use appropriate labels. The labels should specify the type of waste, the quantity, and any safety precautions.

Develop a Management Plan: Develop a plan for the safe storage, transport, and disposal of hazardous waste. Make sure the plan is in compliance with any applicable regulations.

Monitor and Document: Monitor the hazardous waste to ensure it is stored safely and that it is not released into the environment. Document any changes in the hazardous waste and its storage.

Train Employees: Train all employees on the safe handling and disposal of hazardous waste. Make sure they are aware of any safety precautions and regulations.

Dispose of Properly: Dispose of hazardous waste in a way that is safe and compliant with all regulations. This could include recycling, incineration, or other means.

Audit and Review: Perform regular audits and reviews to ensure the hazardous waste is being managed properly. Document any changes or improvements that need to be implemented.

Impact of Non-Hazardous Waste:

Non-hazardous waste, such as plastics, can have a devastating effect on the environment. Plastic consumption has skyrocketed over the past few decades and continues to be a major contributor to pollution. One of the main ways that non-hazardous waste is bad for the environment is through the release of toxins and chemicals. When plastic is not disposed of properly, it can leach toxins into the environment. This can cause soil contamination, air pollution, and water contamination, leading to serious health and environmental issues. Non-hazardous waste can also be bad for the environment when it is not properly recycled or disposed of. When plastic waste is not recycled, it often ends up in landfills or in the ocean, where it can take hundreds of years to decompose. This can cause serious damage to the surrounding environment, leading to water and air pollution, as well as the release of dangerous toxins.

Non-hazardous waste also contributes to global warming. As plastic breaks down, it releases greenhouse gases, which can contribute to the warming of the planet. It can also cause significant damage to local wildlife, as animals can become trapped in the plastic or ingest it, leading to serious health issues. Overall, non-hazardous waste can lead to serious environmental damage if it is not disposed of properly. It can cause air and water pollution, contribute to global warming, and lead to serious health issues for animals and humans alike. To help protect the environment, it is important to make sure that non-hazardous waste is properly recycled or disposed of.

How to manage Non- hazardous Waste:

Reuse: Reuse of non-hazardous waste should be encouraged whenever possible. Items such as paper, cardboard, plastic, aluminum, glass, and other materials can be recycled or reused in new products.

Reduce: Minimizing the amount of non-hazardous waste generated is one of the best strategies for managing it. This can be done by reducing the number of products purchased, reusing items, and avoiding single-use items.

Recycle: Recycling non-hazardous waste is one of the best ways to manage it. Recycling not only helps reduce waste but also conserves resources and energy.

Compost: Composting non-hazardous waste helps create a nutrient-rich soil amendment that can be used in gardens and landscaping.

Donate: Donating non-hazardous waste to organizations such as Goodwill and the Salvation Army can help reduce waste and provide a valuable service to the community.

Dispose of: When non-hazardous waste cannot be recycled or reused, it should be disposed of properly. This can include taking it to a landfill or hazardous waste facility.

Future of waste management:

With technological advancements in waste collection, sorting, and disposal, all the processes can be managed with advanced instruments and robotics. Some of the futuristic solutions for waste management are smart waste bins, plasma gasification, pneumatic waste collection, fleet management systems, al waste sorting. These all options can help to make waste management sustainable and environmentally friendly but, the infrastructure required to produce and implement these technologies need to be developed.