The Vital Role of Sewage Treatment Plants in Housing Societies

In the world of sustainable living, where every drop of water counts, sewage treatment plants have emerged as unsung heroes. These unassuming facilities play a pivotal role in maintaining the ecological balance within our housing societies. In this article, we will delve into the significance of sewage treatment plants for housing societies, explore the intricacies of their operation, and shed light on the various types of sewage treatment plants that can be implemented.

Understanding Sewage Treatment Plants

What is a sewage treatment plant?

A sewage treatment plant is a fundamental necessity for any housing society. It serves as the unsung guardian of our environment, ensuring that the wastewater generated from our households, kitchens, and toilets is not recklessly discharged into natural water bodies. Such an unmitigated release of wastewater would wreak havoc on the delicate aquatic ecosystem. Therefore, sewage treatment plants are indispensable for safeguarding the environment and mitigating water scarcity by allowing the reuse of treated water.

The Sewage Treatment Process

Introduction to Sewage Treatment Plant

Sewage treatment, also known as domestic wastewater treatment or municipal wastewater treatment, is a specialized process designed to eliminate contaminants from sewage. These treatment plants produce effluents that are safe for discharge into the environment or can be reused, effectively preventing water pollution from untreated sewage discharges.

Sewage itself is a complex concoction, comprising wastewater from households and businesses, as well as potentially pre-treated industrial wastewater. Depending on specific requirements, various sewage treatment processes can be employed. These range from decentralized systems, which feature on-site treatment, to large centralized systems that utilize extensive networks of pipes and pump stations to convey sewage to treatment facilities. In cases where cities have combined sewer systems, these sewers also transport urban runoff, or stormwater, to sewage treatment plants.

A noteworthy trend in wastewater management is the separation of household waste into two categories: greywater and blackwater. Greywater consists of wastewater generated from domestic activities like laundry, dishwashing, and bathing, making it more amenable to reuse. On the other hand, blackwater primarily emanates from toilets and contains human waste.

The Sequential Steps of Sewage Treatment

Sewage Treatment Plant Processes

To grasp the intricate workings of sewage treatment plants in housing societies, let’s take a closer look at the sequential steps involved:

Step 1: Screening and Pumping

The initial stage involves passing incoming wastewater through screening equipment to remove debris such as rags, wood fragments, plastics, and grease. This material is then washed, pressed, and disposed of in a landfill. The screened wastewater is subsequently pumped to the next treatment phase.

Step 2: Grit Removal

In this step, heavy but fine materials such as sand and gravel are separated from the wastewater and similarly disposed of in a landfill.

Step 3: Primary Settling

Primary settling utilizes large circular tanks called clarifiers. They allow for the separation of material that settles, albeit at a slower rate than in the previous step. The settled material, known as primary sludge, is pumped from the bottom, while the wastewater exits from the top. Floating debris like grease is skimmed off the top and sent along with the settled material to digesters. Chemicals may also be added in this phase to remove phosphorus.

Step 4: Aeration / Activated Sludge

This phase is where the bulk of wastewater treatment occurs. Through biological degradation, microorganisms consume pollutants, transforming them into cell tissue, water, and nitrogen. The biological activity mirrors natural processes occurring at the bottom of lakes and rivers, although this step accelerates the degradation significantly.

Step 5: Secondary Settling

Large circular tanks known as secondary clarifiers allow treated wastewater to separate from the biological components. This yields an effluent that is now over 90% treated. The biological activated sludge is continuously pumped from the bottom of the clarifiers and returned to the aeration tanks.

Step 6: Filtration

In this phase, clarified effluent undergoes further purification by passing through 10-micron polyester media. Material captured on the surface of disc filters is periodically backwashed and returned to the treatment process.

Step 7: Disinfection

To ensure that the treated wastewater is virtually free of bacteria, ultraviolet disinfection is employed after the filtration step. This process effectively eliminates any remaining bacteria, ensuring compliance with discharge permits.

Step 8: Oxygen Uptake

The treated water, now of high quality and stability, may undergo aeration if necessary to meet dissolved oxygen requirements. Subsequently, the treated water is discharged into rivers or other water bodies, subject to stringent regulatory requirements that mandate pollutant removal levels of 98% or greater.

Types of Sewage Treatment Plants

Exploring Sewage Treatment Plant Types

In residential societies, four major types of sewage treatment plants are commonly used. Let’s examine these modern sewage treatment plant designs:

Activated Sludge Plant (ASP)

The activated sludge process is a biological wastewater treatment method that utilizes aeration and a biological floc composed of bacteria and protozoa. Air or oxygen, along with microorganisms, are employed to biologically oxidize organic pollutants, resulting in a waste sludge or floc containing the oxidized material.

The process involves an aeration tank where air is injected into the mixed liquor. This is followed by a settling tank, often referred to as the “final clarifier” or “secondary settling tank,” where biological flocs (sludge blanket) settle, separating them from clear treated water. Some waste sludge is recycled to the aeration tank, while the remaining waste sludge undergoes further treatment and ultimate disposal.

Trickling Filter

A trickling filter is a wastewater treatment system comprising a fixed bed of various materials over which sewage or wastewater flows downward. This flow encourages the growth of a microbial slime (biofilm) that covers the bed of media. Aerobic conditions are maintained through various mechanisms, including splashing, diffusion, and forced-air flow. This technology is one of the oldest and most well-established sewage treatment methods.

Key components of a trickling filter system include the filter medium bed, an enclosure or container housing the medium, a system for distributing wastewater over the medium, and a mechanism for removing and disposing of sludge from the treated effluent.

Membrane Bioreactor (MBR)

The membrane bioreactor (MBR) combines membrane processes like microfiltration or ultrafiltration with the activated sludge process. It has gained popularity in both municipal and industrial wastewater treatment. There are two primary MBR configurations: submerged membrane bioreactor (SMBR) and side stream membrane bioreactor. In SMBR, the membrane is located inside the biological reactor and submerged in the wastewater. In the side stream configuration, the membrane is positioned outside the reactor as an additional step after biological treatment.

Rotating Biological Contactor (RBC)

A rotating biological contactor (RBC) is a fixed-film treatment process used in the secondary treatment of wastewater, following primary treatment. In the primary treatment process, grit, sand, and coarse suspended material are removed through screening and settling. RBC allows wastewater to interact with a biological film, facilitating the removal of pollutants before the treated wastewater is discharged into the environment.

RBC consists of a series of closely spaced, parallel discs mounted on a rotating shaft, positioned just above the wastewater’s surface. Microorganisms grow on these discs, where they biologically degrade wastewater pollutants. The rotating discs, in turn, help slough off the microorganisms into the sewage, where they are eventually removed.

Components of Sewage Treatment Plants

Exploring the Key Components

The specific components of sewage treatment plants can vary based on the type of sewage they handle. However, there are common elements associated with these plants, all of which work in tandem to remove harmful contaminants from wastewater and household sewage before its release into the environment. These major components include:

• Bar screens: These screens remove large debris and objects from the incoming wastewater.
• Grit chamber: This component separates heavier materials like sand and gravel from the wastewater.
• Comminutors: These devices break down larger solid materials into smaller particles.
• Pre-aeration tank: This tank facilitates the initial aeration of wastewater, preparing it for subsequent treatment.
• Primary settling tank: Also known as clarifiers, these tanks allow for the settling of solid material.
• Aeration tank: This is where the main biological treatment process occurs.
• Secondary settling tank: Similar to primary clarifiers, these tanks further separate treated water from biological components.
• Biological filters: These filters provide additional treatment by promoting microbial activity.
• Sludge handler: Responsible for the management and disposal of sludge generated during treatment.

In conclusion, sewage treatment plants are indispensable for maintaining the ecological balance in housing societies. Their meticulous processes ensure that wastewater is treated effectively, preventing environmental harm and enabling water reuse. By understanding the significance of sewage treatment plants and the intricacies of their operation, we can pave the way for more sustainable living in our communities. For expert guidance on implementing sewage waste treatment plants in your society, consult with reliable consultants for solid waste treatment and disposal.