Sources of Domestic Wastewater

Domestic wastewater originates from various human-related activities within residential areas and includes:

  1. Residential Areas:

    2. Homes and households contribute significantly to domestic wastewater through activities such as:

    • Sanitary wastewater from toilets, baths, showers, sinks, and laundry.
    • Greywater from kitchen activities, washing dishes, and food disposal.
  2. Commercial Establishments:

    3. Commercial spaces, including offices, shops, and small-scale businesses, produce wastewater from:

    • Sanitary facilities similar to those in residential areas.
    • Commercial activities like cleaning, food preparation, and product manufacturing.
  3. Institutional Facilities:

    4. Schools, hospitals, prisons, and other institutions generate wastewater from:

    • Sanitary fixtures, kitchens, laundry, and medical facilities.
    • Specialized activities such as research labs or healthcare-related procedures.
  4. Public Facilities:

    5. Public spaces and recreational facilities contribute to wastewater through:

    • Public toilets, parks, recreational areas, and swimming pools.
    • Street cleaning, municipal wash-downs, and stormwater runoff.
  5. Others:

    6. Additionally, domestic wastewater sources may include:

    • Septic tanks, where not connected to a centralized sewer system.
    • Illicit connections, such as improper stormwater drainage into sanitary sewers.
    • Infiltration and inflow from groundwater or rainwater entering the sewer system.

Characteristics of Domestic Wastewater:

Domestic wastewater typically contains a mix of organic matter, suspended solids, nutrients, pathogens, detergents, and chemicals, varying in concentration based on the source and activities in the area.

Understanding the diverse sources of domestic wastewater aids in designing effective treatment processes tailored to handle the specific characteristics and volumes of wastewater produced from different sources.

Block Diagram of Conventional Sewage Treatment Plant

[Primary Settling Tank] -> [Aeration Tank] -> [Secondary Settling Tank] -> [Disinfection] -> [Effluent]

Explanation with Labels:

1. Primary Settling Tank:

This is the initial stage where raw sewage enters the treatment plant. In this tank, large solids settle to the bottom as primary sludge while floating materials like oils and grease are skimmed off the surface.

2. Aeration Tank:

After primary treatment, the settled sewage moves to the aeration tank. Here, biological processes occur as microorganisms break down organic matter present in the sewage, aided by aeration to provide oxygen for microbial activity.

3. Secondary Settling Tank:

The sewage from the aeration tank moves to the secondary settling tank where the remaining suspended solids, including microorganisms, settle at the bottom as activated sludge. Clearer water rises to the surface.

4. Disinfection:

The effluent from the secondary settling tank undergoes disinfection to kill harmful pathogens and bacteria. This can be achieved through processes like chlorination, UV treatment, or other disinfection methods.

5. Effluent:

The treated water, now considered effluent, is discharged into receiving water bodies or subjected to further treatment based on regulatory standards and specific plant requirements.

Difference between Industrial Wastewater and Municipal Wastewater
Aspect Industrial Wastewater Municipal Wastewater
Origin: Generated from industrial processes and activities in manufacturing facilities, factories, and industrial plants. Originates from residential, commercial, and public sources in urban or rural areas.
Composition: Varies widely based on the industry; may contain specific pollutants related to manufacturing processes (e.g., heavy metals, chemicals). Contains a mix of organic and inorganic pollutants from households, commercial establishments, and public spaces.
Volume: Volume fluctuates based on industrial production levels and processes; can be intermittent or continuous. Volume is relatively consistent, influenced by population density, urbanization, and water use patterns.
Treatment Requirements: Often requires specialized treatment due to unique contaminants; treatment may be tailored to the specific industry. Generally undergoes conventional treatment processes such as sedimentation, biological treatment, and disinfection.
Regulatory Standards: Subject to industry-specific regulations; may need to comply with discharge limits set by environmental authorities. Regulated by environmental agencies with standards set for parameters such as BOD, COD, and pathogen levels.
Point of Generation: Generated at specific points within industrial facilities where production processes occur. Originates from distributed sources such as households, commercial buildings, and public infrastructure.
Characteristics: Can be highly variable and complex, depending on the industrial sector; may contain toxic substances. Varies based on the nature of human activities; can contain household chemicals, nutrients, and pathogens.
Operational Problems of Primary Treatment Units

(1) Screens:

Screens in wastewater treatment plants are prone to several operational issues:

  • Clogging: Screens can easily become clogged by debris, fibrous materials, grease, or large objects present in the influent wastewater, reducing their efficiency in removing solids.
  • Mechanical Failures: Problems such as screen breakage, jamming, or malfunctioning of the rakes or mechanisms can occur, leading to interruptions in the screening process.
  • Inadequate Cleaning: Insufficient cleaning of screens can result in buildup and accumulation of solids, decreasing their effectiveness and potentially causing odors or blockages in downstream processes.

(2) Grit Chamber:

Grit chambers encounter specific operational challenges:

  • Accumulation of Grit: Improper design or inadequate maintenance may lead to excessive grit accumulation, reducing the efficiency of downstream equipment and causing wear and damage to pumps and pipelines.
  • Inefficient Grit Removal: Inadequate settling time or improper flow distribution can result in insufficient removal of grit particles, leading to their carryover into subsequent treatment units.
  • Poor Cleaning Mechanisms: Ineffective or insufficient cleaning mechanisms within the grit chamber may cause sediment buildup, reducing the chamber's capacity and overall efficiency.

(3) Equalization Tank:

Operational issues in equalization tanks can include:

  • Short-Circuiting: Poor tank design or hydraulic inefficiencies can lead to short-circuiting, causing unequal distribution and mixing of wastewater within the tank, affecting the intended equalization process.
  • Stratification: Inadequate mixing can result in stratification, where different layers of wastewater with varying characteristics remain separated, reducing the effectiveness of equalization.
  • Ineffective Volume Control: Inaccurate volume control or improper sizing may result in overflow or underflow situations, leading to inefficiencies in treatment processes downstream.

Addressing these operational problems through proper maintenance, regular inspections, and appropriate design considerations is crucial to ensure the effective performance of primary treatment units in wastewater treatment plants.

Operational Phases of Sequential Batch Reactor (SBR)

Phases:

  1. Fill Phase:
    • The reactor is filled with influent wastewater.
    • Minimal or no aeration/mixing occurs during this phase.
  2. React Phase:
    • Aeration and mixing are activated to facilitate biological treatment.
    • Microorganisms metabolize organic matter in the wastewater.
  3. Settle Phase:
    • Aeration/mixing stops, allowing solids to settle at the bottom.
    • Clear water rises to the top, separating from settled sludge.
  4. Decant Phase:
    • Clear, treated water is carefully decanted or withdrawn from the top of the reactor.
    • Effluent is removed, leaving settled solids behind.
  5. Idle Phase:
    • The reactor remains idle, allowing any remaining sludge to settle further.
    • Prepares for the start of the next cycle.

Sketch (Not Visible Here):

  • The sketch typically shows a rectangular or cylindrical tank.
  • It illustrates the different phases: filling of wastewater, aeration and mixing during treatment, settling of solids, decanting of treated water, and idle periods between cycles.

The Sequential Batch Reactor (SBR) operates through these distinct phases within a single reactor, enabling batch-wise treatment of wastewater with careful control over aeration, mixing, settling, and decanting stages to achieve effective treatment outcomes.

What is Grit? Significance of Grit Chamber

Grit:

Grit refers to heavy, inorganic particles present in wastewater, primarily composed of sand, gravel, cinders, eggshells, and other abrasive materials. These particles have a higher specific gravity compared to organic matter, making them settle more rapidly in aqueous environments.

Significance of Grit Chamber:

A Grit Chamber in wastewater treatment serves several crucial purposes:

  1. Removal of Grit:

    The chamber effectively removes grit particles from wastewater, preventing abrasion and wear in downstream equipment such as pumps, pipes, and valves. If left untreated, grit can cause damage and operational issues in treatment units.

  2. Protection of Equipment:

    By removing abrasive grit, the chamber protects mechanical equipment from damage, extending their lifespan and reducing maintenance costs. It helps prevent clogging, erosion, and wear in pumps and other components.

  3. Prevention of Settling in Tanks:

    Grit chambers prevent the settling of abrasive particles in other treatment units, ensuring proper functioning of settling tanks and preventing sedimentation issues.

  4. Enhanced Treatment Efficiency:

    By removing grit, the chamber improves the overall efficiency of subsequent treatment processes, allowing for better performance of biological treatment units and reducing the load on downstream treatment stages.

  5. Improvement of Effluent Quality:

    Reducing the presence of grit in the wastewater contributes to producing cleaner effluent, meeting environmental standards and regulatory requirements for discharged water quality.

Overall, the Grit Chamber plays a critical role in maintaining the effectiveness of wastewater treatment processes by removing abrasive, heavy particles that can cause damage, operational issues, and decreased efficiency in downstream equipment and treatment units.

Parameters in Wastewater Treatment Design
  1. SOR (Surface Overflow Rate):

    2. SOR refers to the rate at which wastewater flows over the surface area of a settling tank or clarifier. It's calculated by dividing the flow rate of wastewater by the surface area of the tank.

    Importance in Design:

    SOR determines the efficiency of solid-liquid separation within the tank. Properly designing for an optimal SOR helps ensure adequate settling of suspended solids, facilitating efficient removal and clearer effluent.

  2. WOR (Weir Overflow Rate):

    3. WOR represents the rate at which clarified water overflows the weirs in a settling tank, calculated by dividing the flow rate of clarified water by the total length of weirs.

    Importance in Design:

    WOR influences the effectiveness of separating the clarified water from settled solids. Proper design to maintain an appropriate WOR ensures sufficient retention time for settling and prevents carryover of solids in the effluent.

  3. Detention Time:

    4. Detention Time is the duration wastewater remains in a specific treatment unit, calculated by dividing the volume of the unit by the influent flow rate.

    Importance in Design:

    Detention Time determines the contact time between wastewater and treatment processes. Adequate detention time is crucial for achieving desired treatment goals, such as biological degradation or settling of solids, ensuring effective treatment.

These parameters play critical roles in the design and operation of wastewater treatment units, influencing the efficiency of solid-liquid separation, the effectiveness of clarifiers, and the overall treatment performance.

Significance of Equalization Tank in Industrial Wastewater Treatment

An equalization tank in an industrial wastewater treatment plant serves several important functions:

  1. Flow Smoothing:

    It helps in leveling out variations in the flow rate and characteristics of incoming wastewater, which can fluctuate significantly in industrial settings due to production cycles or batch processes. By equalizing flow rates, it prevents shock loads and excessive strain on downstream treatment units.

  2. Chemical and pH Balancing:

    Industrial wastewater often contains varying chemical compositions and pH levels based on different production processes. The equalization tank allows for blending and mixing of wastewater streams to achieve a more uniform and stable composition, facilitating more effective treatment downstream.

  3. Temperature Equalization:

    In certain industries, wastewater temperatures can fluctuate widely due to manufacturing processes. The equalization tank helps in balancing and normalizing these temperature variations, preventing thermal shocks to biological treatment systems and ensuring optimal microbial activity.

  4. Reducing Peaks and Load Variability:

    By reducing high peaks in flow rate or pollutant loadings, the equalization tank helps in managing the load on subsequent treatment units. This assists in achieving more consistent treatment performance and avoids overwhelming treatment processes during peak production periods.

  5. Optimizing Treatment Efficiency:

    The equalization tank enhances the overall efficiency of the treatment plant by providing a buffer and allowing the treatment process to operate more uniformly, enabling the downstream units to work at their optimum design capacities.

In summary, the equalization tank plays a crucial role in managing and balancing the incoming industrial wastewater, enabling a more stable and consistent flow and composition for downstream treatment processes. It ensures smoother operation, better treatment efficiency, and protects treatment units from potential shock loads, ultimately aiding in the effective treatment of industrial effluents.

Foaming as an Operational Problem in Activated Sludge Process

Foaming is a common operational issue encountered in the Activated Sludge Process, characterized by the formation of excessive foam on the surface of aeration tanks or secondary clarifiers. It arises due to various factors:

  • Microbial Imbalance: Changes in the microbial population or composition, such as an overgrowth of filamentous bacteria, can contribute to foam formation.
  • High Organic Loading: Excessive organic loading or sudden increases in influent organic matter can lead to foam production.
  • Surfactants and Chemicals: Presence of certain surfactants or chemicals in the influent can cause foam formation due to their surface-active properties.
  • Process Upsets: Operational upsets, fluctuations in pH, temperature, or nutrient imbalances, can also trigger foaming.
Overcoming Foaming in Activated Sludge Process

Addressing and mitigating foaming issues involves several strategies:

  1. Foam Control Agents:

    Use of chemical additives or anti-foaming agents to control foam formation. These agents disrupt the foam structure, reducing surface tension and preventing foam buildup.

  2. Process Optimization:

    Optimize operational parameters such as aeration, mixing, and sludge retention time to maintain stable conditions, promoting the growth of desirable microbial populations and suppressing filamentous bacteria.

  3. Biomass Management:

    Regularly monitor and control the biomass within the system. Implement proper sludge wasting techniques to prevent excessive biomass buildup, which can contribute to foam formation.

  4. Improved Nutrient Control:

    Ensure proper nutrient balance within the system, particularly nitrogen and phosphorus, to support healthy microbial activity and prevent excessive foam formation.

  5. Operational Monitoring:

    Implement frequent monitoring and process control measures to detect and address any potential causes of foaming promptly.

Implementing a combination of these strategies tailored to the specific conditions and causes of foaming in the Activated Sludge Process helps mitigate foam formation, ensuring stable and efficient operation of the wastewater treatment plant.

Bulking of Sludge: Causes and Solutions

Bulking of sludge is a common operational problem in wastewater treatment plants, characterized by poor settling of activated sludge, resulting in a high volume of solids escaping into the treated effluent. It occurs due to various factors:

  • Filamentous Bacteria: Overgrowth of filamentous bacteria in the activated sludge, resulting in the formation of long, stringy structures that impede settling.
  • Nutrient Imbalance: Imbalances in nutrients, especially excessive levels of certain nutrients like nitrogen or phosphorus, can lead to bulking.
  • Low Dissolved Oxygen (DO): Inadequate aeration or low DO levels in the aeration tank can favor the growth of filamentous bacteria and contribute to bulking.
  • High Organic Loading: Sudden increases in organic loading can overwhelm the treatment system, causing sludge bulking.
  • Temperature and pH: Extreme temperature variations or pH fluctuations beyond optimal ranges can also trigger sludge bulking.
Overcoming Bulking of Sludge

To address and mitigate bulking problems, the following solutions and strategies can be implemented:

  1. Identify and Control Filamentous Bacteria:

    Implement microscopic analysis to identify specific filamentous bacteria causing bulking. Adjust treatment processes to discourage their growth through changes in aeration, mixing, or nutrient control.

  2. Nutrient Management:

    Ensure balanced nutrient levels in the system by optimizing the dosage of nitrogen and phosphorus. Adjusting nutrient ratios can help control microbial growth and prevent bulking.

  3. Optimize Aeration:

    Ensure adequate and uniform aeration in the activated sludge tank to maintain optimal dissolved oxygen levels, discouraging filamentous growth and promoting healthy microbial activity.

  4. Gradual Load Adjustment:

    Avoid sudden increases in organic loading by implementing gradual changes in influent flow rates or pollutant loadings, preventing shocks to the treatment system.

  5. Temperature and pH Control:

    Maintain stable temperature and pH conditions within optimal ranges to avoid extremes that can trigger sludge bulking. Control pH levels through buffering and adjust temperature fluctuations where possible.

Implementing these strategies tailored to the specific causes of sludge bulking helps mitigate the problem, ensuring efficient settling of activated sludge and preventing the escape of solids into the effluent.

Stabilization Pond: Overview

A Stabilization Pond, also known as a lagoon or facultative pond, is a natural or man-made wastewater treatment system primarily used for biological treatment. It consists of shallow, earthen basins or ponds where wastewater undergoes various treatment processes.

Key Characteristics and Functions:

1. Treatment Mechanisms:

Stabilization Ponds operate through natural biological processes, utilizing sunlight, oxygen, and microorganisms to treat wastewater. The ponds promote the growth of algae, bacteria, and other microorganisms that help break down and stabilize organic matter in the wastewater.

2. Pond Types:

There are different types of Stabilization Ponds, including:

  • Anaerobic Ponds: Low-oxygen or oxygen-free zones for initial breakdown of organic matter.
  • Aerobic Ponds: Oxygen-rich zones where aerobic processes occur, facilitating further degradation of organic compounds.
  • Facultative Ponds: Combining both aerobic and anaerobic conditions, allowing diverse microbial activity.

3. Treatment Efficiency:

Stabilization Ponds offer moderate to high treatment efficiencies for organic matter, suspended solids, and pathogens. They're particularly effective in warm climates due to increased biological activity and sunlight exposure.

4. Simple Design and Low Operating Costs:

These systems are relatively simple in design, requiring minimal mechanical equipment. They often have lower operational costs compared to conventional treatment plants.

Advantages and Limitations:

Advantages:

  • Effective for small to medium-sized communities or in remote areas with limited resources.
  • Low energy consumption and minimal maintenance requirements.
  • Can be used for pre-treatment or as a part of a larger treatment system.

Limitations:

  • Land-intensive; requires significant space compared to some other treatment methods.
  • May be affected by temperature fluctuations or climate conditions.
  • Requires proper design, management, and periodic maintenance to ensure optimal performance.

Stabilization Ponds serve as cost-effective and environmentally friendly wastewater treatment alternatives, offering moderate to high treatment efficiency for various contaminants under suitable conditions.

Operational Problems of Anaerobic Treatment Units

Anaerobic treatment units, while effective in treating certain types of wastewater, can face several operational challenges that impact their performance:

  1. Startup Period:

    During the initial stages, anaerobic systems might face a prolonged startup period due to the slow growth of anaerobic bacteria. It can take time for the microbial community to establish and become fully functional.

  2. Sensitivity to pH Fluctuations:

    Anaerobic systems are sensitive to fluctuations in pH levels. Sudden changes can disturb the microbial balance, affecting the efficiency of the treatment process.

  3. Temperature Sensitivity:

    These systems are temperature-sensitive and operate optimally within certain temperature ranges. Extreme temperature fluctuations can negatively impact the performance of anaerobic units.

  4. Inhibition by Toxic Compounds:

    Toxic compounds in the influent, such as heavy metals, certain chemicals, or specific organic substances, can inhibit the anaerobic microbial activity, reducing treatment efficiency.

  5. Slow Response to Load Variations:

    Anaerobic systems might have a slow response to sudden changes or high fluctuations in influent characteristics, resulting in reduced treatment efficiency during these periods.

  6. Sludge Bulking and Foaming:

    In some cases, anaerobic systems might experience issues related to sludge bulking or foaming, impacting the settling characteristics and causing carryover of solids into the effluent.

Addressing these operational challenges requires careful monitoring, proper system design, regular maintenance, and, in some cases, specific pre-treatment steps to ensure optimal performance of anaerobic treatment units in wastewater treatment plants.

Working of Rotating Biological Contactor (RBC)

A Rotating Biological Contactor (RBC) is a type of biological wastewater treatment unit consisting of multiple discs or media mounted on a horizontal shaft, rotating slowly through the wastewater.

Key Components:

  • Media Discs: The RBC comprises multiple plastic or composite discs attached to a central shaft. These discs have a large surface area where biofilm, comprising microorganisms responsible for biological treatment, grows.
  • Wastewater Flow: Wastewater flows over the rotating discs, providing aeration and contact between the wastewater and the biofilm on the disc surface.
  • Rotational Motion: The discs rotate slowly, typically at speeds of 1-3 revolutions per minute (RPM), through the wastewater. This rotation allows for exposure of the biofilm to both the air (aerobic conditions) and wastewater (anaerobic conditions).
  • Treatment Mechanism: As the discs rotate, the biofilm attached to them comes in contact with the organic pollutants present in the wastewater. Microorganisms within the biofilm metabolize and degrade the organic matter, converting it into simpler, less harmful substances.
  • Gravity Settling: Treated wastewater is separated from the biofilm-treated solids through gravity settling. The treated effluent is collected and directed for further treatment or discharge, while the treated sludge settles at the bottom of the unit.

Advantages of RBC:

  • Compact design with relatively small footprint.
  • Operational simplicity and low energy consumption.
  • Effective for treating medium-strength wastewaters and handling shock loads.
  • Robust and durable system requiring minimal maintenance.

Considerations:

  • Periodic maintenance to ensure proper disc rotation and biofilm health.
  • Optimal design considerations for load variations and hydraulic conditions.
  • Regular monitoring of biofilm thickness and system performance.

RBCs play a significant role in biological treatment by providing a large surface area for microbial growth and facilitating effective contact between wastewater and the biofilm, ensuring efficient removal of organic pollutants from wastewater.

Extended Aeration: Overview

Extended Aeration is a biological treatment process utilized in wastewater treatment plants, characterized by prolonged aeration of wastewater in aeration tanks under controlled conditions.

Key Characteristics:

  • Extended Retention Time: The process involves maintaining wastewater in aeration tanks for an extended period, typically ranging from 24 to 48 hours. This extended contact time allows microorganisms to break down organic pollutants effectively.
  • Continuous Aeration: Aeration is maintained throughout the treatment process to ensure a sufficient supply of oxygen, facilitating the growth and activity of aerobic microorganisms responsible for biological treatment.
  • Mixing and Circulation: Aeration tanks are equipped with mechanical mixers or diffused aeration systems to promote mixing, circulation, and contact between microorganisms and wastewater for efficient treatment.
  • Bio-solids Separation: After the treatment process, the treated effluent is separated from the biomass (activated sludge) through settling or clarification processes, ensuring the removal of treated sludge from the effluent.

Advantages of Extended Aeration:

  • Effective for treating low-to-moderate strength wastewaters.
  • Provides stable treatment performance and reliable effluent quality.
  • Operates under relatively low hydraulic loading rates, reducing the risk of shock loads.
  • Requires minimal operator intervention and maintenance.

Considerations:

  • Requires a larger footprint compared to some other treatment methods due to extended retention times.
  • May not be suitable for treating high-strength industrial wastewaters or situations with fluctuating influent characteristics.
  • Monitoring of oxygen levels, mixing efficiency, and sludge settling is essential for optimal performance.

Extended Aeration is a widely used and effective biological treatment process in wastewater treatment plants, offering stable and reliable treatment for various types of municipal and industrial wastewaters with lower organic loads.

Comparison: Diffused Aerator vs. Surface Aerator
Aspect Diffused Aerator Surface Aerator
Aeration Method Utilizes diffusers or porous membranes to release fine air bubbles directly into wastewater. Agitates the surface of the water, introducing air into the wastewater through mechanical means (e.g., propellers or turbines).
Bubble Size Generates small and fine air bubbles, maximizing the contact area between air and wastewater for efficient oxygen transfer. Produces larger air bubbles that rise to the surface, promoting oxygen transfer through surface agitation.
Installation Installed at the bottom of aeration tanks or ponds. Mounted on the surface of aeration tanks or ponds.
Energy Consumption Typically consumes lower energy due to the efficiency of small bubble aeration. May consume relatively higher energy due to the mechanical power required for agitation.
Noise and Splashing Operates quietly and generates minimal splashing. Can be noisier due to mechanical movement and may cause more splashing on the water surface.
Application Preferred for applications requiring fine bubble aeration and in systems sensitive to high levels of turbulence. Suitable for mixing and oxygenation in various wastewater treatment processes, particularly in larger treatment plants.

Diffused aerators and surface aerators offer distinct methods of introducing oxygen into wastewater in treatment processes, each with its advantages and suitability based on specific treatment requirements and operational considerations.

Labeled Diagram and Components of UASB Reactor
UASB Reactor Diagram
Labeled diagram of UASB Reactor

The Upflow Anaerobic Sludge Blanket (UASB) reactor is a type of anaerobic digester used for wastewater treatment, primarily composed of the following components:

  • Inlet: Wastewater containing organic pollutants enters the UASB reactor from the top.
  • Gas-Solid-Separator (Gas Dome): A space located at the top of the reactor designed to separate biogas generated during the treatment process from the liquid. The gas is collected and removed through a gas outlet.
  • Sludge Blanket: A dense sludge bed forms at the bottom of the reactor, composed of anaerobic microorganisms responsible for the treatment of organic matter.
  • Three Phases: The UASB reactor operates in three distinct phases:
    1. Upflow Phase: Wastewater flows upward through the sludge bed, allowing the suspended organic matter to be trapped and retained by the biomass within the sludge blanket.
    2. Biogas Production: Anaerobic bacteria present in the sludge blanket break down organic pollutants, producing biogas (primarily methane and carbon dioxide) as a byproduct.
    3. Clarification: Treated effluent separates from the sludge blanket and exits the reactor for further treatment or discharge.
  • Outlet: Treated effluent is collected and discharged from the bottom of the UASB reactor.

The UASB reactor utilizes anaerobic microorganisms in the sludge blanket to digest organic pollutants in wastewater, converting them into biogas and treated effluent, making it an efficient and cost-effective method for treating high-strength organic wastewater.