- Explain, with the aid of a sketch, how an Aerobic Sewage Treatment plant operates.(10)
Aerobic Sewage Treatment plant operates
An Aerobic Sewage Treatment Plant utilizes oxygen and the action of aerobic microorganisms (primarily bacteria) to break down and remove organic pollutants from wastewater. It typically involves several stages that work in conjunction to achieve effective treatment.
1. Aerobic Wastewater Treatment – Veolia Water Technologies UK
2. Understanding Wastewater: How Does a Sewage Treatment Plant Work? – DomBor Valve
Operational Stages:
- Preliminary Treatment:
- Screening and Grit Removal: The incoming wastewater first passes through screens or bar racks to remove large debris like trash, plastics, and grit. This prevents damage to equipment and improves the efficiency of subsequent treatment processes. 1. Sewage Treatment Plant Process STP – Perfect Pollucon Services www.ppsthane.com2. Bar Screens and Grit Removal in Sewage Treatment Plants – Netsol Water www.netsolwater.com
- Primary Treatment:
- Sedimentation: The wastewater then flows into a primary sedimentation tank (clarifier), where the flow is slowed down, allowing heavier suspended solids to settle at the bottom as primary sludge. The clarified water, now with a significant portion of solids removed, moves on to secondary treatment. 1. Wastewater treatment – Sedimentation, Filtration, Clarification | Britannica www.britannica.com2. Common Problems with Aerobic Wastewater Treatment Systems and How to Avoid Them samcotech.com
- Secondary Treatment (Aerobic Process):
- Aeration Tank: This is the heart of the biological treatment. The clarified water from the primary clarifier is mixed with activated sludge, a rich culture of aerobic microorganisms. Air or oxygen is continuously supplied through diffusers or surface aerators to promote the growth and activity of these bacteria. The bacteria consume and break down the organic matter in the wastewater, converting it into carbon dioxide, water, and more biomass (new bacterial cells). 1. Activated-sludge method | Biological Process, Aerobic Bacteria, Wastewater Treatment www.britannica.com2. Why is Aeration Important for Wastewater Treatment? – OxyMem www.oxymem.com3. Decoding Aerobic Treatment: Organic Matter to Clean Water genesiswatertech.com
- Secondary Clarifier: The aerated mixture then flows into the secondary clarifier, where the activated sludge settles at the bottom due to gravity. The clarified water at the top, now with significantly reduced organic matter and suspended solids, is either discharged or undergoes further treatment (tertiary treatment) depending on the required effluent quality. 1. Activated sludge – Wikipedia en.wikipedia.org
- Tertiary Treatment (Optional):
- Filtration: Additional filtration processes, like sand filters or membrane filtration, may be employed to further remove suspended solids and other fine particles from the treated effluent.
- Nutrient Removal: Processes like biological nutrient removal or chemical precipitation can be used to remove nitrogen and phosphorus from the effluent, preventing eutrophication (excessive nutrient enrichment) in receiving water bodies. 1. Nutrient Removal and Recovery from Municipal Wastewater – MDPI www.mdpi.com
- Disinfection: The final treated effluent is disinfected, usually with chlorine or UV light, to kill or inactivate any remaining pathogens before discharge. 1. Aerobic treatment system – Wikipedia en.wikipedia.org
- Sludge Treatment:
- Thickening: The settled sludge from both primary and secondary clarifiers is collected and thickened to reduce its volume and facilitate further treatment.
- Anaerobic Digestion: The thickened sludge is then transferred to an anaerobic digester, a sealed tank where anaerobic bacteria decompose the organic matter in the absence of oxygen. This process further reduces sludge volume, stabilizes it, and produces biogas (primarily methane), which can be used as a renewable energy source.
- Dewatering: The digested sludge is dewatered to remove excess water, making it easier to handle and dispose of.
- Disposal or Reuse: The final dewatered sludge can be disposed of in landfills or, if suitable, used as fertilizer or soil conditioner. 1. Sewage sludge treatment – Wikipedia en.wikipedia.org
Key Processes in Aerobic Treatment:
- Aerobic Degradation: Aerobic bacteria in the aeration tank utilize oxygen to break down organic matter. 1. Why is Aeration Important for Wastewater Treatment? – OxyMem www.oxymem.com
- Floc Formation: Bacteria form flocs, which help in the removal of suspended solids and other pollutants. 1. Healthy Bacteria Are Vital to Wastewater Treatment – Probiotic Solutions® probiotic.com
- Sedimentation: Flocs and solids settle in clarifiers, separating them from the treated water. 1. What are the three stages of wastewater treatment? – Smart Water Magazine smartwatermagazine.com
Advantages of Aerobic Treatment:
- Effective removal of organic matter and suspended solids, leading to high treatment efficiency 1. What is Aerobic Wastewater Treatment? watertreatmentservices.co.uk
- Relatively stable and easy to operate compared to anaerobic processes
- Can achieve high levels of treatment, suitable for various discharge standards
- Odor control: Aerobic conditions minimize the production of foul-smelling gases
Disadvantages:
- Energy-intensive due to the need for aeration and mixing
- Generates a considerable amount of sludge that requires further treatment and disposal 1. Sewage treatment – Wikipedia en.wikipedia.org
By effectively utilizing the metabolic activities of aerobic microorganisms, these treatment plants significantly reduce pollutants and pathogens in wastewater, protecting both human health and the environment.