Waste Water Treatment by Sewage Treatment Plants-A Review

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Waste Water Treatment by Sewage Treatment Plants-A Review

Debargha Banerjee

Assistant Professor Civil Engineering Department

JIS College of Engineering Kalyani,India

Debasish Das

Assistant Professor Civil Engineering Department

JIS College of Engineering Kalyani, India

Uddipta Ghosh

Assistant Professor Civil Engineering Department

JIS College of Engineering Kalyani, India

Nawshad Hossain

UG student

Mechanical Engineering Department JIS College of Engineering

Kalyani, India

Amena Khatun

UG student

Civil Engineering Department JIS College of Engineering Kalyani, India

Abstract: The concomitant impact of agricultural development, industrialisation, and urbanisation are causing serious water shortages in the majority of river basins. State- owned sewage treatment plants (STP) for municipal waste water, as well as common effluent treatment plants for treating wastewater from all major industries, are not performing according to norms. The effluent from treatment plants is frequently unfit for human consumption, and waste water reuse is generally limited to agricultural and industrial uses. Only a few studies have been published on the treatment of waste water in industry, particularly in relation to the establishment of sewage treatment plants (STP) systems. Another advantage of water is that it can be recycled and reused.The entire waste water treatment sector can be split into four categories: chemical, physical, biological, and mathematical.


For all life on Earth, water is one of the most important natural resources. Water availability and quality have long played a key role in defining not only where people may live, but also how happy they can be. The country's total utilisable water supply is estimated to be around 1123 BCM (690 BCM from surface and 433 BCM from ground), accounting for only 28% of total water derived. from precipitation. Irrigation accounts for around 85% (688 BCM) of total water use, which is expected to rise to 1072 BCM by 2050. Groundwater is a major source of irrigation. The amount of water consumed by a family or a country is referred to as "water use."

The following categories are used to categorise water use: Fresh water for motels, hotels, restaurants, office buildings, other commercial facilities, and civilian and military institutions is used commercially.

For most individuals, domestic water use is the most important daily usage of water. Domestic use water includes water used in the home on a daily basis for things like drinking, food preparation, bathing, washing clothing

and dishes, flushing toilets, and watering lawns and gardens.

For processing, cleaning, transportation, dilution, and cooling in manufacturing plants, industrial water is an important resource. Steel, chemical, paper, and petroleum refining are some of the most water-intensive industries. Industries frequently reuse the same water for several purposes.

Water artificially applied to farm, orchard, pasture, and horticultural crops, as well as water used to irrigate pastures, for frost and freeze protection, chemical application, crop cooling, harvesting, and salt leaching from the crop root zone, is referred to as irrigation water use.

Water is used in the mining industry to extract naturally occurring minerals, solids like coal and ores, liquids like crude petroleum, and gases like natural gas. Quarrying, milling (such as crushing, screening, washing, and flotation), and other mining processes fall into this category. About 32% of the water utilised in mining is saline.

Water withdrawn by public and private water suppliers, such as county and municipal water works, and distributed to customers for domestic, commercial, and industrial purposes is referred to as public supply water. In 1995, nearly 225 million people, or 84 percent of the country's population, relied on water given by public water suppliers.[1]

The following home activities are examples of wastewater sources:

  • Human excreta (faeces, urine, blood, and other biological fluids) are frequently mixed with used toilet paper or wet wipes; if collected from flush toilets, this is known as blackwater.

  • Greywater, also known as washing water (personal hygiene, clothes, floors, dishes, autos, etc.)[2]

    Industrial wastewater is created by the following activities:

  • Industrial site drainage (silt, sand, alkali, oil, chemical wastes); (biocides, heat, slimes, silt)

  • Water used in industrial processing.

  • Organic or biodegradable waste, such as that generated by hospitals, abattoirs, creameries, and food processors.

  • Acid and alkali waste with extreme pH. Toxic waste from metal plating, cyanide manufacturing, and other processes.


    Environmental Impact Assessment (EIA):

    Environmental Impact Assessment (EIA) is a method of assessing the possible environmental consequences of a proposed project or development, taking into account interconnected socioeconomic, cultural, and human-health consequences, both positive and negative. Environmental Impact Assessment (EIA) is a methodology used by the United Nations Environment Programme (UNEP) to determine the environmental, social, and economic implications of a project prior to making a decision. Its goal is to predict environmental implications early in the project planning and design process, as well as to develop solutions to mitigate negative effects. [4]

    Projects are shaped to fit the local environment, and predictions and options are presented to decision-makers. EIA can provide both environmental and economic benefits, such as reduced project implementation and design costs and time, avoided treatment, clean-up expenses, and the effects of laws and regulations.[5]

    Goal and main motive of EIA:

    The objective of EIA is

    I To determine, forecast, and assess the economic, environmental, and social effects of development operations.

    1. To give decision-makers with knowledge on the environmental effects, and

    2. to encourage ecologically sound and sustainable development by identifying appropriate alternatives and mitigation measures.

    ETP and STP are two different types of waste water treatment systems.

    The following are some of the most common types of wastewater treatment processes:

    Effluent Treatment Plants (ETPs) (ETP) Sewage Treatment Plants (STPs) (STP)

    1. Effluent Treatment Plants (Common and Combined) (CETP)

      Every year, 1.8 million people are expected to die as a result of waterborne illnesses. Inadequate sanitation is responsible for a significant portion of these deaths.

      Wastewater treatment is a critical endeavour that must be prioritised for the sake of society and our future. Wastewater treatment is the process of removing

      contaminants from wastewater and home sewage to create a waste stream or solid waste that can be discharged or reused. [6]


      Sewage treatment is the process of eliminating toxins from residential and municipal wastewater, which primarily consists of residential sewage with some industrial effluent thrown in for good measure. To remove impurities and generate treated wastewater (or treated effluent) that is safe to release into the environment, physical, chemical, and biological techniques are used. Sewage sludge is a semi- solid waste or slurry that is produced as a by-product of sewage treatment. Before it can be disposed of or applied to the land, the sludge must be treated further. Wastewater treatment is another term for sewage treatment. The latter, on the other hand, is a broader phrase that can refer to both domestic and industrial wastewater.In most cities, the sewer system will also transport a percentage of industrial wastewater to the sewage treatment plant, which has typically been pre-treated at the factory to reduce pollutant load. If the sewer system is a combined sewer, storm water will be carried to the sewage treatment plant as well. Sewage is transported by sewerage, which includes drains, pipework, and pumps that transport sewage to the treatment plant's input.[7]

      Necessity ofSTP:

  • The major function of sewage treatment plants is to filter sewage water that comes from the domestic, commercial, and industrial sectors.

  • Treatment of sewage water has become critical because it prevents the spread of infections and illnesses caused by sewage water.

  • It aids society in keeping the environment and water clean.

  • The primary, secondary, and tertiary stages of sewage treatment facilities are the three stages of these plants.

  • The contaminants that are easier to remove from the wastewater are removed in the primary stage. Oils, grease, and fats are examples of compounds that can be easily removed.

    The biological pollutants in wastewater are removed in the secondary stage.[8]

    Treatment Levels and different types of Mechanism of STP

    • Primary treatment

    • Secondary treatment

    • Tertiary treatment

    • Fourth Treatment

Primary treatment:

Sewage runs through massive tanks known as "pre-settling basins," "primary sedimentation tanks," or "primary clarifiers" during the primary sedimentation stage. Sludge settles in the tanks, while grease and oils rise to the surface

and are scraped away. Mechanically driven scrapers in primary settling tanks continuously move the collected sludge towards a hopper in the tank's base, where it is pumped to sludge treatment facilities. Saponification can occasionally be achieved by recovering grease and oil from floating materials (soap making).

Secondary treatment:

It is intended to significantly reduce the biological content of sewage originating from human waste, food waste, soaps, and detergents. The bulk of municipal plants use aerobic biological methods to handle settled sewage liquor. The biota requires both oxygen and food to function properly. Biodegradable soluble organic pollutants (e.g. sugars, lipids, organic short-chain carbon molecules) are consumed by bacteria and protozoa, which bind most of the less soluble components into the filter. Biodegradable soluble organic pollutants (e.g. sugars, lipids, organic short-chain carbon molecules) are consumed by bacteria and protozoa, which bind most of the less soluble components into the filter. Fixed-film and suspended- growth secondary treatment systems are the two types. Moving bed biofilm reactors (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) systems have evolved from the fixed-film basis. The footprint of an MBBR system is often smaller than that of a suspended-growth system. Moving bed biofilm reactors (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) systems have evolved from the fixed-film basis. The footprint of an MBBR system is often smaller than that of a suspended- growth system. Activated sludge, in which the biomass is mixed with the sewage, is one type of suspended-growth system that can be operated in a smaller space than trickling filters that treat the same volume of water. Fixed- film systems, on the other hand, are better suited to handle large changes in biological material and can remove organic material and suspended particles at higher rates than suspended growth systems. A secondary clarifier is used to settle out and separate biological filter material generated in the secondary treatment bioreactor in some secondary treatment processes.

Tertiary treatment:

The goal of tertiary treatment is to offer a final treatment stage for the effluent before it is discharged into the receiving environment (sea, river, lake, wet lands, ground, etc.). At every treatment plant, more than one tertiary treatment technique may be applied. When disinfection is used, it is always the last step. It's sometimes referred to as "effluent polishing."

Fourth treatment stage:

Pharmaceuticals, ingredients in household chemicals, chemicals used in small businesses or industries, environmental persistent pharmaceutical pollutants (EPPP), and pesticides may not be eliminated in the traditional treatment process (primary, secondary, or tertiary treatment), resulting in water pollution. Despite the modest quantities of those chemicals and their breakdown products, aquatic creatures may be harmed. Compounds with endocrine disruptive effects, toxic compounds, and

substances that promote the development of bacterial resistance have all been identified as "toxicologically relevant" in medications. They primarily belong to the EPPP group. Micropollutants are being eliminated via a fourth treatment stage during sewage treatment in Germany, Switzerland, Sweden, and the Netherlands, with tests underway in numerous more countries. The activated carbon filters that absorb the micro contaminants are the most common of these process processes. The use of advanced oxidation with ozone followed by granular activated carbon (GAC) as a cost-effective treatment for pharmaceutical residues has been recommended. A combination of ultrafiltration and GAC has been suggested for a complete removal of microplastic. The usage of enzymes such as the enzyme is also being looked into. The utilization of secreting fungus cultivated at a wastewater treatment plant to digest micro pollutants while also providing enzymes at a cathode of a microbial bio fuel cell is a novel concept that could provide an energy-efficient treatment of micro pollutants. The ability of microbial bio fuel cells to handle organic materials in wastewater is being researched.

"Source control" techniques, such as improvements in medication development or more responsible medication handling, are also being investigated to limit pharmaceuticals in water bodies.[9]


The lack of treatment is at the root of the problems related with wastewater reuse. The problem is to identify low-cost, low-tech, user-friendly solutions that, on the one hand, do not jeopardize our significant wastewater-dependent livelihoods while, on the other hand, safeguard our priceless natural resources from degradation.Constructed wetlands are increasingly acknowledged as an effective wastewater treatment technology. Constructed wetlands use less material and energy than conventional treatment systems, are simple to run, have no sludge disposal issues, and can be maintained by unskilled workers. Furthermore, because these systems are powered by natural energy such as sun, wind, microorganisms, plants, and animals, they have cheaper construction, maintenance, and operation costs. As a result, policy decisions and coherent programmes encompassing low-cost decentralized waste water treatment technologies, bio-filters, efficient microbial strains, organic / inorganic amendments, appropriate crops/cropping systems, and cultivation appear to be required for planned, strategic, safe, and sustainable wastewater use.


    1. https://www.cdc.gov/healthywater/other/index.html#:~:text=Wate r%20can%20be%20used%20for,agriculture%2C%20industry%2 C%20and%20electricity.

    2. https://en.wikipedia.org/wiki/Wastewater

    3. https://www.micronicsinc.com/filtration-news/what-is-industrial- wastewater/

    4. https://en.wikipedia.org/wiki/Wastewater_treatment#:~:text=Wast ewater%20treatment%20is%20a%20process,purposes%20(called


    5. https://ww.drishtiias.com/to-the-points/paper3/environmental- impact-assessment- 1#:~:text=Environmental%20Impact%20Assessment%20(EIA)% 20is,impacts%2C%20both%20beneficial%20and%20adverse.

    6. https://www.biologydiscussion.com/environment/environmental- impact-assessment-eia-definition-process-and-importance/16777

    7. Sewage Treatment Plant (STP)

    8. https://www.marineinsight.com/tech/sewage-treatment-plant/

    9. https://www.britannica.com/technology/wastewater- treatment/Primary-treatment

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