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Sewage Treatment Plant (STP): Complete Guide, Costs, Types & Safety

Sept. 28, 2025 22 Views

In today’s urban and industrial world, water management is crucial, and Sewage Treatment Plants (STPs) play a vital role in maintaining environmental health. STPs are designed to treat wastewater efficiently, turning polluted sewage into reusable or safe water for various purposes.

Understanding what a sewage treatment plant is, its cost, types, and safety aspects is essential for municipal authorities, industries, and commercial enterprises.

In this article, we’ll cover everything about STPs, including:

• What is a sewage treatment plant?

• Cost of an STP plant

• Types of sewage treatment plants

• Safety of treated sewage water

👉 For water treatment solutions and business opportunities, visit Plumint or register at Plumint Subscriber Registration.

What is a Sewage Treatment Plant?

A Sewage Treatment Plant (STP) is a facility that treats wastewater and sewage from households, industries, and commercial spaces to make it safe for discharge or reuse.

Key objectives of an STP include:

• Removing suspended solids, organic matter, and pathogens

• Reducing pollutants to meet environmental discharge standards

• Producing water suitable for irrigation, industrial use, or safe disposal

STPs use mechanical, biological, and chemical processes to purify water, ensuring that harmful contaminants are removed before water is released back into rivers, lakes, or reused within the community.

How Does a Sewage Treatment Plant Work?

STPs generally operate in several stages:

1. Preliminary Treatment

• Screening: Removes large debris like plastics, leaves, and stones.

• Grit Removal: Eliminates sand, gravel, and heavy inorganic matter.

2. Primary Treatment

• Sedimentation Tanks: Suspended solids settle at the bottom as sludge.

• Primary Clarifiers: Helps in removing 50–60% of suspended solids.

3. Secondary Treatment

• Biological Treatment: Microorganisms break down organic matter.

• Aeration Tanks: Oxygen is supplied to aid bacterial decomposition.

• Secondary Clarifiers: Settles biomass from treated water.

4. Tertiary Treatment (Advanced Treatment)

• Filtration: Removes remaining suspended particles.

• Disinfection: Chlorination, UV, or ozone treatment to kill pathogens.

• Polishing: Ensures water meets reuse or discharge standards.

5. Sludge Management

• Sludge collected from primary and secondary stages is treated separately using anaerobic digestion, dewatering, or composting.

What is the Cost of an STP Plant?

The cost of a sewage treatment plant varies depending on:

• Capacity: Measured in million liters per day (MLD) or kilo liters per day (KLD).

• Technology: Mechanical, biological, MBR (Membrane Bioreactor), SBR (Sequencing Batch Reactor), etc.

• Site Location: Urban or industrial setting impacts installation and labor costs.

• Additional Features: Automation, monitoring systems, odor control, sludge management.

Approximate cost ranges in India:

For commercial and industrial-scale water treatment solutions, Plumint provides professional consultation and installation services.

Types of Sewage Treatment Plants

There are several types of STPs based on the treatment technology and capacity:

1. Activated Sludge Process (ASP)

• Most common method using aeration tanks and microbial activity.

• Effective for organic pollutant removal.

2. Sequencing Batch Reactor (SBR)

• Time-based treatment in batch mode.

• Provides aeration and sedimentation in a single tank.

3. Membrane Bioreactor (MBR)

• Combines biological treatment with membrane filtration.

• Produces high-quality water suitable for reuse.

4. Oxidation Ponds / Lagoons

• Large, shallow ponds using natural sunlight and microbes.

• Suitable for small towns or low-cost solutions.

5. Moving Bed Biofilm Reactor (MBBR)

• Uses biofilm carriers in an aeration tank for biological treatment.

• Compact design and effective for industrial applications.

6. Package STP

• Pre-fabricated compact units suitable for residential complexes, hotels, and small industries.

Which Plant is Used for Sewage Treatment?

The choice of STP depends on:

• Volume of sewage

• Quality of influent water

• Purpose of treated water

• Available space

Commonly used STPs include:

• Activated Sludge Process (ASP) for municipal sewage

• SBR for batch treatment and medium-sized complexes

• MBR for high-quality water reuse in industries

• Package STP for residential apartments and commercial establishments

Is Treated Sewage Water Safe to Drink?

Treated sewage water, also known as recycled water, is generally not recommended for direct drinking unless it undergoes advanced tertiary treatment and strict disinfection.

• Safe Uses: Irrigation, industrial cooling, flushing, landscape maintenance.

• Direct Consumption: Only after MBR treatment, UV/ozone disinfection, and strict regulatory compliance.

Important: Even after treatment, some microorganisms and chemicals may remain, so drinking treated sewage water requires certification and monitoring.

Benefits of Sewage Treatment Plants

1. Environmental Protection – Reduces pollution in rivers, lakes, and groundwater.

2. Water Reuse – Helps in water conservation by providing treated water for industrial and agricultural use.

3. Public Health – Prevents waterborne diseases by removing pathogens.

4. Regulatory Compliance – Meets government standards for wastewater management.

5. Odor Control – Modern STPs reduce foul smells associated with untreated sewage.

Challenges in Sewage Treatment

1. High Installation Cost – Particularly for large-capacity plants.

2. Space Requirements – Some STP designs require significant land.

3. Maintenance – Requires skilled operators and periodic monitoring.

4. Sludge Disposal – Treated sludge must be handled properly to avoid environmental hazards.

👉 Businesses can reduce operational complexities by consulting water treatment experts like Plumint.

Modern Trends in STP Technology

1. Automation and IoT – Smart monitoring of flow, TDS, pH, and treatment efficiency.

2. Compact STPs – Prefabricated units for apartments, offices, and industries.

3. Energy Efficiency – Using solar power and energy-saving aerators.

4. Water Reuse and Recycling – Integration with industrial cooling, flushing, and landscaping.

5. Membrane Technology (MBR) – Produces high-quality water suitable for partial potable reuse.

Sewage Treatment Plant for Residential and Commercial Use

• Residential STPs: Typically 10–100 KLD capacity for apartment complexes.

• Commercial STPs: Hotels, malls, and hospitals often require 50–500 KLD capacity.

• Industrial STPs: Custom-designed based on type of wastewater (chemical, food processing, textile).

Proper STP implementation reduces water scarcity and ensures compliance with environmental regulations.

FAQs (People Also Ask Section)

1. What is the sewage treatment plant?

An STP treats wastewater to remove solids, organic matter, and pathogens, producing safe water for reuse or discharge.

2. What is the cost of STP plant?

Cost varies based on capacity, technology, and site: 10 KLD (~15–25 lakh INR), 1 MLD (~10–12 crore INR).

3. Which plant is used for sewage treatment?

Activated Sludge Process, SBR, MBR, MBBR, oxidation ponds, and package STPs are commonly used.

4. Is treated sewage water safe to drink?

Generally not recommended for direct drinking; safe for industrial, irrigation, and flushing purposes.

Conclusion

A Sewage Treatment Plant (STP) is critical for sustainable water management, pollution control, and public health. Whether for residential complexes, commercial establishments, or industrial operations, investing in a proper STP ensures compliance, environmental safety, and long-term water sustainability.

👉 For professional sewage treatment solutions and subscription-based business services, explore Plumint or register directly at Plumint Subscriber Registration.