Types of Waste Water and How They Impact the Environment
It is a type of water which is contaminated by human use like washing of clothes, industrial discharge, commercial as well as agricultural activities. As all these contaminating sources disturb the quality of water which leads to contamination of water. Contamination also depends on various sources or products such as domestic wastewater, municipal wastewater i.e sewage and industrial waste of chimanies. Wastewater mainly contains physical, chemical and biological pollutants. We can purify this contaminated water by various methods, there are so many power plants which do purification processes.
Effects of Contaminant on Quality of Water:
There are various harmful result noticed due to contamination of water, some of them are listed below:
Loss of Aquatic Organisms: Aquatic organisms are harmed due to contaminated water. As discharges and runoff of harmful contaminants like pesticides into waterways can be lethal to aquatic life, causing death of fishes, prawns, etc.
Loss of Local Invertebrate Species: As these small invertebrates are food for fishes and other aquatic organisms. Death of these invertebrates lead to starvation for those aquatic organisms who are dependent on them for food and they start migrating to other water bodies exposing them to greater risk and stress.
Decrease in Biochemical Oxygen Demand(BOD): Due to waste or harmful contaminants they use up natural oxygen present in the water body. Excess nutrients can also lead to algal blooms and oxygen is used up when the algae die and decompose. Decrease in available oxygen causes difficulty in breathing to aquatic organisms.
Contaminant increases turbidity and decreases water clarity of water thus making water murky. So this aquatic organism is not able to find their prey and detect predators.
Contaminated water causes internal damage to aquatic organisms as they reduce the reproductive ability of aquatic organisms, decrease in immunity, causes disorder in the central nervous system, etc.
Types of Water Pollution Depending on Different Source:
Surface Water Pollution: This type of pollution includes pollution in rivers, lakes and oceans. Here water sources are contaminated by various means like industrial waste, release of sewage waste, etc.
Marine Pollution: one of the common ways by which contaminants enter the sea are rivers. Here directly discharging sewage and industrial waste into the ocean causes pollution into oceans. Plastic debris can absorb toxic chemicals from ocean pollution, potentially poisoning any creature that eats it.
Groundwater Pollution: Use of pesticides and insecticides causes contamination of groundwater. Groundwater pollution is directly connected to soil pollution.
Wastewater Management:
Wastewater treatment is a several step process and by going through these process we purify contaminant water:
Steps performed during purification of contaminated water:
Wastewater Collection
Screening
Primary Treatment
Secondary Treatment
Final Treatment
Wastewater Collection:
Very first step in the purification process is collection of water in a storing tank which further goes through various filtration steps.
Screening:
This is the very first step of water treatment. In this process large objects are removed from wastewater and then moved into the grit and sand removal tank, where they are further treated.
Primary Treatment:
After going through screening water is taken to primary treatment where all organic waste present in water is removed and this process is done by pouring the wastewater into a big tank where solid matthew style down at the base.
The settled solids, after primary treatment, are called the sludge. This sludge is decomposed by bacteria and the gas emitted by this decomposition is known as biogas, which can be used as a fuel or can be used to generate electricity.
Secondary Treatment:
After primary treatment water is passed to an aeration tank where air is tapped into water to increase the growth of aerobic bacteria in the water. These bacteria break down small particles of sludge that are not broken during primary treatment. These broken slugs are known as activated sludge. These activated sludge contain air in them.
Final Treatment:
This activated sludge is passed through a bed of sand drying machine where the sludge is dried up and from the water is filtered out. This water is filtered and then released into the river.
How to Control Water Pollution:
There are several way to prevent water pollution, some of them are below:
Industrial Wastewater Treatment:
As industrial waste is discharged into water bodies which causes contamination of water.
So by using pre-treatment plants for reducing harmful chemicals present in industrial waste, this process will decrease contamination of water.
Agriculture Wastewater Treatment:
By reducing use of pesticides and weedicides we can reduce underground water pollution. As these chemicals contaminantes water which causes various health related issues.
Municipal Wastewater Treatment:
Instead of discharging sewage waste directly into water bodies treat it in separate sewage treatment plants to reduce water pollution.
FAQs on Waste Water Story: Understanding Water Pollution
1. What is wastewater and what are its main sources?
Wastewater is any water that has been contaminated by human activities. It is also commonly known as sewage. The main sources of wastewater include:
- Domestic: Water from homes, including toilets, sinks, showers, and laundry.
- Industrial: Waste from factories, manufacturing plants, and food processing units, which often contains harmful chemicals.
- Agricultural: Runoff from farms that may carry pesticides, herbicides, and fertilisers.
- Stormwater: Rainwater that flows over roofs, roads, and other surfaces, picking up pollutants along the way.
2. What are the common types of contaminants found in wastewater?
Wastewater contains a complex mixture of contaminants that can be broadly classified into several types:
- Organic Impurities: These include human faeces, animal waste, food scraps, and detergents.
- Inorganic Impurities: These consist of nitrates, phosphates, and heavy metals like mercury and lead.
- Nutrients: Phosphorus and nitrogen from fertilisers and human waste act as nutrients.
- Microbes: Harmful microorganisms such as bacteria (like those causing cholera and typhoid) and protozoa (causing dysentery) are present.
- Suspended Solids: Materials like sand, silt, and grit are also found in wastewater.
3. How do the contaminants in untreated wastewater harm rivers and aquatic life?
Releasing untreated wastewater directly into water bodies has severe consequences. The excess nutrients like nitrogen and phosphorus cause an explosive growth of algae, a process called eutrophication. When these algae die, bacteria decompose them, consuming large amounts of dissolved oxygen in the water. This depletion of oxygen suffocates and kills fish and other aquatic animals. Furthermore, toxic chemicals and heavy metals poison the water, making it unsuitable for both aquatic life and human use.
4. What is the difference between sewers and a sewerage system?
Sewers are the individual underground pipes that carry wastewater from its source, like homes and industries. A sewerage system is the entire network of these interconnected sewers. It acts like a transport system, collecting wastewater from various points and carrying it to a central location, the Wastewater Treatment Plant (WWTP), for purification.
5. Can you explain the main steps of cleaning water at a Wastewater Treatment Plant (WWTP)?
The purification of wastewater at a WWTP typically involves three main stages as per the 2025-26 CBSE syllabus:
- Primary Treatment: This is a physical process. First, wastewater passes through bar screens to remove large objects like plastic bottles and rags. Then, it goes into a grit and sand removal tank. Finally, the water is left in a large sedimentation tank where solid faeces, called sludge, settle at the bottom.
- Secondary Treatment: This is a biological process. Air is pumped into the clarified water to help aerobic bacteria grow. These bacteria consume the remaining organic waste.
- Tertiary/Final Treatment: The treated water is disinfected using chemicals like chlorine or by using ultraviolet (UV) light to kill any remaining disease-causing microbes before it is released into a water body.
6. Why is it important to use both physical and biological processes to treat wastewater?
It is crucial to use both physical and biological processes because they target different types of pollutants. Physical processes, like screening and sedimentation, are effective at removing large, visible solids and suspended particles. However, they cannot remove dissolved organic matter or microscopic germs. This is where biological processes are essential. They use living microorganisms (bacteria) to break down these dissolved organic impurities, effectively 'eating' the waste and cleaning the water on a microscopic level.
7. What is sludge, and how is it treated and used?
Sludge is the semi-solid organic matter that settles at the bottom of sedimentation tanks during primary wastewater treatment. This sludge is transferred to a separate tank called a digester. Here, anaerobic bacteria (bacteria that don't need oxygen) decompose it. This process produces biogas, which is a valuable fuel that can be used to generate electricity. After digestion, the remaining dried sludge can be used as organic manure or fertiliser, as it is rich in nutrients.
8. Besides large treatment plants, what are some alternative methods for sewage disposal and in what situations are they useful?
For areas without a centralised sewerage system, alternative on-site disposal methods are used. Two important examples are:
- Septic Tanks: These are underground tanks suitable for individual houses, hospitals, or clusters of homes. They collect sewage and allow solids to settle and decompose anaerobically. They are useful in rural or suburban areas where connecting to a main sewer line is not feasible.
- Composting Toilets: These are 'dry' toilets that treat human waste with minimal or no water. They use biological processes to decompose waste into compost. These are particularly useful in regions with severe water scarcity or in eco-sensitive areas.
9. What simple housekeeping practices can a student adopt to help reduce water pollution?
Every individual can contribute to reducing water pollution through better habits. For example, you should never pour cooking oil, fats, or grease down the drain as they can harden and block pipes. Similarly, solid wastes like tea leaves, cotton, soft toys, and sanitary towels should be thrown in the dustbin, not flushed. Using natural or biodegradable cleaning products instead of harsh chemicals also helps reduce the load of pollutants in the wastewater.
10. What is the fundamental link between poor sanitation and the spread of water-borne diseases?
The fundamental link is contamination. Poor sanitation means human excreta and wastewater are not disposed of safely. These wastes contain harmful pathogens (disease-causing germs). When this untreated waste contaminates drinking water sources, like wells or rivers, or the soil where food is grown, these pathogens can easily enter the human body. This leads to the spread of dangerous water-borne diseases such as cholera, typhoid, dysentery, and hepatitis.
