8.11 Sewage Treatment

7 min read•january 19, 2023

Riya Patel

AP Environmental Science ♻️

252 resources

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Introduction

Sewage treatment is the process of removing contaminants from wastewater, primarily from household sewage. It includes physical, chemical, and biological processes to remove pollutants and produce an environmentally safe treated wastewater. The final product, called effluent, can be safely released into the environment, such as surface waters or reused for irrigation. The by-products of treatment, such as biosolids, can also be recycled and used as fertilizer.

Primary Sewage Treatment

Primary treatment is the first step in the process of sewage treatment. It involves the physical separation of solid and liquid waste using screens and sedimentation tanks. The goal of primary treatment is to remove large objects and debris, and to settle out heavy particles in the wastewater.

Secondary Sewage Treatment

Secondary treatment is the next step in the process, and involves the use of biological processes to break down the remaining organic matter in the wastewater. This is typically done using microorganisms, such as bacteria, that consume the organic matter and convert it into biomass. Secondary treatment is usually done in aerated lagoons or activated sludge tanks.

Tertiary Sewage Treatment

Tertiary treatment is the final step in the sewage treatment process. It involves the use of physical, chemical, or biological processes to remove remaining pollutants and pathogens from the wastewater. This can include methods such as filtration, disinfection, and nutrient removal. The goal of tertiary treatment is to produce an effluent that is of high enough quality to be safely discharged into the environment or reused for irrigation.

Purpose of Sewage Treatment Plans

The purpose of a sewage treatment plant is to remove pollutants and pathogens from wastewater generated by households, industries and commercial buildings, so that the treated water can be safely released into the environment or reused for irrigation. The main pollutants removed during the treatment process are organic matter, nutrients, pathogens, and other contaminants.

Sewage treatment plants also play an important role in protecting public health by reducing the spread of disease through the removal of pathogens from the wastewater. They also help to protect the environment by preventing pollution of surface waters, groundwater, and coastal areas. Additionally, sewage treatment plants also produce by-products such as biosolids that can be used as fertilizer to improve soil quality.

Moreover, sewage treatment plants also help to conserve water resources by treating and reusing wastewater, which is beneficial in areas where water is scarce. Additionally, they can generate energy through the process of anaerobic digestion of the organic matter present in the wastewater which can be used to power the treatment plant and even provide extra energy to the grid.

Septic Tank

A septic tank is a type of underground wastewater treatment system that is commonly used in areas where there is no connection to a centralized sewage treatment plant. It is essentially a large, underground container that receives and stores wastewater from a building, and allows for the separation and treatment of the waste.

The septic tank is designed to separate solid waste from liquid waste through a process of sedimentation and anaerobic digestion. The solid waste, called sludge, sinks to the bottom of the tank and accumulates over time. The liquid waste, called effluent, flows out of the tank and is typically discharged into a drainage field or leach field, where it is further treated through a process of filtration and bacterial decomposition.

Septic tanks are typically made of concrete, fiberglass, or plastic and are buried underground. They require regular maintenance to ensure they function properly and to prevent the buildup of sludge in the tank. This includes regular pumping of the tank to remove the accumulated sludge, and regular inspections of the tank and drainage field to ensure they are functioning properly.

Proper design, installation and maintenance of septic tanks are important to ensure that they function efficiently and effectively, and to prevent groundwater and surface water pollution.

Where are Septic Tanks Used?

Septic tanks are commonly used in rural areas, suburban areas, and small communities where there is no connection to a centralized sewage treatment plant. Here are a few examples of how septic tanks are used in real life:

Residential homes: Septic tanks are often used in homes that are not connected to a municipal sewer system. The tank receives and treats the waste from the home's plumbing system, and the treated effluent is discharged into a drainage field or leach field.
Small communities: In small towns and rural areas, septic tanks are commonly used to treat the wastewater from multiple homes or businesses. The tanks are typically connected to a common drainage field or leach field.
Recreational areas: Septic tanks are also used in recreational areas, such as campgrounds, RV parks, and cabin communities. The tanks receive and treat the waste from the toilet and shower facilities, and the treated effluent is discharged into a drainage field or leach field.
Commercial properties: Septic tanks can also be used to treat the waste from commercial properties such as small businesses, hotels, and motels. These tanks are typically larger than residential septic tanks to accommodate the greater volume of waste generated by the property.
Remote or off-grid locations: Septic tanks can be used in remote or off-grid locations where there is no access to a centralized sewage treatment system. The tanks are designed to treat the waste generated by the occupants of the location and discharge the treated effluent into the environment.

Groundwater Pollution

Groundwater pollution, also known as groundwater contamination, occurs when pollutants or contaminants enter the groundwater and make it unsafe for human use or the environment. Groundwater is a vital source of drinking water for many communities and is also used for irrigation, industry and other purposes.

There are many sources of groundwater pollution, including agricultural activities, industrial and commercial operations, landfills, and septic systems. Chemicals such as pesticides, fertilizers, oil, gasoline, and industrial chemicals can leach into the groundwater and contaminate it. Additionally, pathogens and microorganisms can also pollute groundwater, making it a health hazard.

Groundwater pollution can have severe and long-lasting effects on the environment and human health. Contaminated groundwater can lead to the destruction of ecosystems, the loss of wildlife habitat, and the contamination of drinking water supplies. In addition, exposure to contaminated groundwater can cause a wide range of health problems, including cancer, birth defects, and neurological damage.

To prevent groundwater pollution, it is essential to properly manage and dispose of hazardous materials and waste, and to implement best management practices for agricultural activities, and industries. Additionally, regular testing and monitoring of groundwater quality is important to detect and address any contamination issues in a timely manner.

Clean Water Act

The Clean Water Act (CWA) is a federal law in the United States that was enacted in 1972 to regulate the discharge of pollutants into the nation's surface waters, including lakes, rivers, streams, wetlands, and coastal areas. The Act's primary goal is to restore and maintain the chemical, physical, and biological integrity of the nation's waters, and to ensure that they are safe for human use and the environment.

The CWA gives the Environmental Protection Agency (EPA) the authority to establish water quality standards for all contaminants in surface waters, and to regulate the discharge of pollutants from point sources, such as municipal and industrial wastewater treatment plants, and nonpoint sources, such as agricultural activities and stormwater runoff.

The CWA also established the National Pollutant Discharge Elimination System (NPDES) permit program, which requires that any discharge of pollutants from a point source into surface waters must have a permit issued by the EPA or an authorized state. The Act also provides for the protection and management of wetlands, and the Clean Water State Revolving Fund, which provides funding for municipalities to improve their wastewater treatment plants.

The Clean Water Act has been successful in improving the quality of surface waters in the United States. However, there are still many challenges ahead, such as addressing nonpoint source pollution, dealing with emerging contaminants, and protecting wetlands and other sensitive aquatic habitats.

The Safe Drinking Water Act

The Safe Drinking Water Act (SDWA) is a federal law in the United States that was enacted in 1974 to protect public health by regulating the nation's public drinking water supply. The Act's goal is to ensure that the drinking water provided by public water systems is safe to drink and meets the standards established by the Environmental Protection Agency (EPA).

The SDWA gives the EPA the authority to set national standards for the quality of drinking water, including standards for contaminants that may be present in drinking water and the treatment technologies that must be used to remove them. The Act also requires public water systems to regularly test and monitor the quality of their drinking water and to provide the results to their customers.

The SDWA also requires the EPA to identify and regulate contaminants that may have an adverse effect on public health. The EPA sets a maximum contaminant level (MCL) for each regulated contaminant, and it is the responsibility of the public water systems to meet these standards.

Additionally, the SDWA also requires public water systems to take steps to protect their sources of drinking water from contamination and to inform their customers of any violations of the standards or any other significant information about their water. The Act also provides funding for states, tribes and local governments to improve their drinking water infrastructure and to ensure access to safe drinking water.

Overall, the Safe Drinking Water Act has been successful in protecting public health by ensuring that the nation's public drinking water is safe to drink, but there is still work to be done to ensure that all Americans have access to safe and clean drinking water.

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