Question

List three pollutants that can be removed by a sewage treatment plant.

Short answer

Organic pollutants, inorganic pollutants, and pathogens.

Step-by-step solution

Understanding Sewage Treatment

A sewage treatment plant processes wastewater to remove contaminants and make it safe to release into the environment or use for other purposes. It uses various physical, chemical, and biological processes to achieve this.

Identify Organic Pollutants

One of the main goals of sewage treatment is to remove organic pollutants. Organic pollutants include substances like human waste, food waste, and plant materials. Biological treatment processes in sewage plants break down these pollutants into simpler, less harmful substances.

Identify Inorganic Pollutants

Inorganic pollutants such as heavy metals, nitrogen compounds, and phosphorus are also targeted in sewage treatment. Chemical processes like precipitation and advanced filtration methods are commonly used to remove these inorganic substances from wastewater.

Identify Pathogens

Pathogens, including bacteria, viruses, and parasites, are disease-causing microorganisms that can be present in sewage. Sewage treatment plants use disinfection methods, such as chlorination or UV treatment, to eliminate these pathogens and ensure the treated water is safe.

Key concepts

Organic Pollutants

When we talk about organic pollutants in sewage treatment, we refer to substances that primarily originate from living organisms. These pollutants can range from human waste and discarded food to remnants of plant materials. The treatment plant employs biological processes to degrade these materials.

• Biological Treatment: This method leverages helpful microorganisms to decompose organic pollutants. Here, bacteria and other microbes feed on waste, breaking it down into simpler, benign substances like carbon dioxide and water.
• Biodegradability: Organic pollutants are often biodegradable, meaning microorganisms can naturally decompose them over time. This makes them relatively easier to handle in sewage treatment.
• Reduction of BOD: A key target in treating organic pollutants is reducing BOD or Biological Oxygen Demand. BOD indicates the amount of oxygen needed by microorganisms to decompose organic matter in water, and effective sewage treatment aims to significantly lower this demand.

It's important to manage organic pollutants properly to prevent issues such as oxygen depletion in natural water bodies, which can harm aquatic life.

Inorganic Pollutants

In sewage treatment, inorganic pollutants present a different challenge compared to organic ones. These include a variety of substances like heavy metals and nutrients such as nitrogen and phosphorus. These materials are not biodegradable and often require more complex treatment processes.

• Types of Inorganic Pollutants: Common constituents include heavy metals like lead, mercury, and cadmium, which are toxic even in small amounts. Nutrients such as nitrates and phosphates are also managed to prevent problems like algal blooms in water bodies.
• Chemical Processes for Removal: Inorganic pollutants are often removed through chemical reactions. For instance, precipitation can convert dissolved metals into solid forms that are easier to filter out. Ion exchange and membrane filtration are also effective in targeting these pollutants.
• Environmental Impact: If not properly managed, inorganic pollutants can cause long-lasting harm to ecosystems. Heavy metal accumulation can poison aquatic life, while excess nutrients can disrupt water chemistry.

Treating inorganic pollutants is vital to protect water quality and maintain ecological balance.

Pathogens Removal

Pathogens are microscopic organisms that cause diseases, including bacteria, viruses, and parasites found in sewage. Their removal is a crucial step in ensuring water is safe for discharge or reuse. Several methods are employed to eliminate these pathogens.

• Disinfection Techniques: Two common methods are chlorination and UV irradiation. Chlorination uses chlorine to kill pathogens, while UV treatment uses ultraviolet light to inactivate microorganisms.
• Microbiological Safety: Ensuring the treated water is free from harmful microbes is vital to prevent public health issues. Effective pathogen removal reduces risks of waterborne diseases.
• Natural Treatment Systems: Some facilities employ natural systems, like constructed wetlands, which utilize plants and natural bacteria to break down pathogens.

Through comprehensive pathogen removal processes, sewage treatment plants ensure that the water released back into the environment or reused for various applications is safe and hygienic.