Process of Sewage Treatment and Its Main Stages
Human health and environment are mainly suffering from direct disposal of commercial and human effluents into the natural resources with none of the treatment. The sewage treatment is important to scale back the toxicity of sewage and maintain a secure and healthy environment, also as it promotes human welfare.
Sewage Treatment Process
Sewage contains an enormous amount of organic matters which are toxic. Microorganisms are widely utilized in the sewage treatment plant for removing this toxic organic matter. Sewage or wastewater treatment plant consists of two stages:
Primary Treatment
It involves the removal of huge or small sized components within the wastewater through physical processes.
Biological Treatment
The sewage treatment plants are inoculated into Aerobic microorganisms .These organic components of these microbes utilize the sewage and reduce the toxicity which can be measured by BOD (Biological oxygen demand).
After the biological treatment, the sludge is pumped from the treatment plant into an outsized tank. This large tank consists of anaerobic bacteria which cause the digestion of sludge. During digestion, biogas is produced and it is used as an energy source. Hence, Sewage treatment plant design and sewage management play an important role within the maintenance of human welfare.
Energy Generation
Microorganisms which are involved within the production of energy are called microbial fuel cells. Microbial fuel cells are used to generate a variety of energy sources like biogas and electricity. Agricultural waste, manure, and domestic wastes are used as raw materials for the generation of biogas. Biogas generation is completed within the large concrete tank which is named as a biogas plant.
Biomasses (Biowastes) are collected at the biogas plant and therefore the slurry is fed. Biomasses are rich in organic matter. Some of the bacteria inside the biogas plant anaerobically These bacteria can digest the biomasses which are present within the slurry and sewage. During digestion, an enormous amount of mixture of gases is released inside the tank. The mixture of these gases is called biogas. Biogas is removed from the biogas plant through a separate outlet.
Electricity from wastewater can also be generated by Microbial fuel cells. From the wastewater treatment plant microbial fuel cells utilize the organic matter.During digestion, organic matters are converted into the straight molecule and release the CO2 and electrons. Those electrons are absorbed by the electrode and used as the source of electricity.
Odor Control
Odors emitted by sewage treatment are typically a sign of an anaerobic or "septic" condition. Early stages of processing will tend to supply foul-smelling gases, with sulfide being commonest in generating complaints. Carbon reactors, a contact media with bio-slimes, less doses of chlorine, or circulating fluids to biologically capture and metabolize the noxious gases at plants with large processes in urban areas are the processes that are used to fade away the foul odor. Other methods of odor control exist, including addition of iron salts, peroxide , nitrate, etc. to manage hydrogen sulfide levels. High-density solids pumps are used for minimizing the odor by conveying sludge through hermetic closed pipework.
Environmental Aspects
There are many processes that are used in the wastewater treatment plant that are designed to copy the natural treatment processes that occur within the environment, whether that environment may be a natural water body or not. Bacteria within the environment will consume organic contaminants if not overloaded,although this may lead to the reduction of the amount of oxygen within the water and should significantly change the general ecology of the receiving water. Organic contaminants work as a food for the neighbouring bacterial populations and therefore the numbers of disease-causing microorganisms are reduced by natural environmental conditions like predation or exposure to ultraviolet .
Consequently, in cases where the receiving environment provides a high level of dilution, a high degree of wastewater treatment might not be required. However, recent evidence has demonstrated that very low levels of specific contaminants in wastewater, including hormones (from farming and residue from human hormonal contraception methods) and artificial materials such as phthalates that mimic hormones in their action, can have hit or miss adverse impact on the natural biota and potentially on humans if the water is reused for drinking water. As per the law in the US and EU, uncontrolled discharges of wastewater to the environment aren't permitted under law, and strict water quality requirements are to be met, as clean water is essential. A significant threat within the coming decades are going to be the increasing uncontrolled discharges of wastewater within rapidly developing countries.
FAQs on Sewage Treatment in Biology
1. What is sewage treatment?
Sewage treatment is the process of removing physical, chemical, and biological contaminants from wastewater before it is released into the environment. Sewage treatment makes wastewater safe by reducing harmful microorganisms, organic matter, and toxic substances.
- Removes solid waste and suspended particles
- Breaks down organic matter using microorganisms
- Reduces pathogens and harmful chemicals
- Produces treated water that can be safely discharged or reused
2. What are the main stages of sewage treatment?
The three main stages of sewage treatment are primary, secondary, and tertiary treatment. Each stage removes different types of pollutants from wastewater.
- Primary treatment: Physical removal of large solids by screening and sedimentation
- Secondary treatment: Biological breakdown of organic matter by microorganisms
- Tertiary treatment: Advanced purification to remove nutrients, pathogens, and remaining impurities
3. How does primary treatment of sewage work?
Primary treatment works by physically separating large and settleable solids from sewage. It mainly uses mechanical processes to remove suspended particles.
- Screening removes large debris like plastics and rags
- Grit chambers remove sand and small stones
- Sedimentation tanks allow heavier solids to settle as sludge
4. What happens during secondary treatment of sewage?
Secondary treatment uses microorganisms to biologically decompose organic matter in sewage. It is mainly an aerobic process carried out by bacteria.
- Aeration tanks supply oxygen to aerobic bacteria
- Bacteria break down organic pollutants into simpler substances
- Activated sludge settles in a secondary clarifier
5. What is activated sludge in sewage treatment?
Activated sludge is a mixture of wastewater and actively growing aerobic microorganisms used to break down organic pollutants. It is formed during secondary treatment in aeration tanks.
- Contains bacteria, protozoa, and other microbes
- Consumes organic matter as food
- Part of it is recycled to maintain microbial population
6. What is the role of microorganisms in sewage treatment?
Microorganisms play a central role in sewage treatment by decomposing organic waste into simpler, harmless substances. They convert complex organic compounds into carbon dioxide, water, and biomass.
- Aerobic bacteria break down organic matter in the presence of oxygen
- Anaerobic bacteria digest sludge in the absence of oxygen
- Protozoa help control bacterial populations
7. What is tertiary treatment in sewage treatment plants?
Tertiary treatment is the advanced stage of sewage treatment that removes remaining nutrients, pathogens, and fine particles. It improves the quality of treated water for safe discharge or reuse.
- Filtration removes fine suspended solids
- Disinfection using chlorine, ozone, or UV kills pathogens
- Nutrient removal reduces nitrogen and phosphorus levels
8. What is sludge and how is it treated?
Sludge is the semi-solid waste that settles out during sewage treatment processes. It contains organic matter, microorganisms, and inorganic particles.
- Collected from primary and secondary sedimentation tanks
- Treated by anaerobic digestion to reduce volume and pathogens
- May produce biogas (mainly methane) as a byproduct
9. Why is sewage treatment important for the environment?
Sewage treatment is important because it prevents water pollution and protects ecosystems and human health. Untreated sewage can contaminate rivers, lakes, and groundwater.
- Reduces spread of waterborne diseases
- Lowers biological oxygen demand (BOD) in water bodies
- Prevents eutrophication caused by excess nutrients
- Protects aquatic organisms from toxic substances
10. What is the difference between aerobic and anaerobic treatment of sewage?
The main difference between aerobic and anaerobic sewage treatment is the presence or absence of oxygen during microbial breakdown of waste. Both methods use microorganisms but under different conditions.
- Aerobic treatment: Requires oxygen; faster process; used in aeration tanks; produces carbon dioxide and water
- Anaerobic treatment: Occurs without oxygen; slower process; used in sludge digesters; produces methane-rich biogas
