With water scarcity and environmental sustainability at the forefront of global concerns, understanding the sewage treatment process is more important than ever. Modern sewage treatment plants (STPs) not only protect public health and the environment but also enable the safe reuse of water in residential, commercial, and industrial settings. This detailed guide explains what sewage is, the types of waste it contains, why treatment is essential, how the process works, the role of advanced technologies, and why SUSBIO ECOTREAT is the top choice for efficient, sustainable sewage treatment in 2025.
What is Sewage?
Sewage is wastewater generated from households, industries, institutions, and commercial establishments. It includes water from toilets, kitchens, bathrooms, and industrial processes. This water carries a mix of organic and inorganic impurities, nutrients, pathogens, and sometimes hazardous chemicals, making it unsafe for direct discharge into the environment
What Type of Waste Does Sewage Contain?
Sewage contains a complex mixture of:
Organic waste: Human and animal waste, food scraps, oils, fats, and plant matter.
Inorganic substances: Sand, grit, metals, detergents, and dissolved minerals.
Nutrients: Nitrogen and phosphorus compounds that can cause algal blooms if released untreated.
Pathogens: Bacteria, viruses, and parasites that can cause diseases like cholera, typhoid, and dysentery.
Industrial pollutants: Chemicals, heavy metals, and hazardous substances from industrial and commercial activities
Why is Sewage Treatment Required?
Treating sewage is critical for several reasons:
Environmental Protection: Prevents water pollution, protects aquatic ecosystems, and reduces the risk of eutrophication in water bodies.
Public Health: Eliminates disease-causing pathogens and reduces the risk of waterborne illnesses.
Resource Recovery: Enables the reuse of treated water for irrigation, landscaping, industrial processes, and even groundwater recharge.
Regulatory Compliance: Meets environmental standards and avoids legal penalties for non-compliance with pollution control norms
Odor and Aesthetic Control: Proper treatment prevents foul odors and improves the appearance of water bodies.
What is a Sewage Treatment Plant?
A sewage treatment plant (STP) is an engineered facility designed to remove contaminants from wastewater, making it safe for discharge or reuse. STPs use a combination of physical, chemical, and biological processes to treat sewage and manage byproducts like sludge. The main aim is to produce clean water (effluent) and minimize the environmental impact of waste disposal.
Process of Sewage Treatment
The sewage treatment process is typically divided into several key stages:
Preliminary/Primary Treatment
Screening & Grit Removal: Large solids, debris, and grit are removed using screens and grit chambers to protect downstream equipment
Sedimentation: Heavier solids settle as sludge, while lighter materials float and are skimmed off. This step removes 30-50% of suspended solids and organic matter
Secondary (Biological) Treatment
Biological Decomposition: Microorganisms break down organic matter in aerated tanks or biofilm reactors (such as MBBR, SBR, or activated sludge processes). This stage removes up to 80-90% of organic matter and nutrients, resulting in significantly cleaner effluent
Secondary Clarification: The treated water flows into clarifiers where remaining solids and biomass settle out, further purifying the water
Tertiary (Advanced) Treatment
Filtration & Disinfection: Advanced methods such as sand filters, activated carbon, UV disinfection, or chlorination are used to remove remaining impurities and pathogens. This ensures the treated water is safe for reuse or discharge
Polishing: Additional processes may be used to remove nutrients, trace contaminants, and improve water clarity.
Sludge Management
The sludge generated is dewatered and can be safely disposed of or used as fertilizer, supporting circular economy practices
Role of Wastewater Treatment Technologies
Modern wastewater treatment technologies have transformed the industry:
MBBR (Moving Bed Biofilm Reactor): Uses biofilm carriers to maximize biological treatment efficiency with a compact footprint.
MBR (Membrane Bio Reactor): Combines biological treatment with membrane filtration for superior effluent quality.
SBR (Sequencing Batch Reactor): Treats wastewater in batches, offering flexibility and high removal rates.
Automation & IoT: Real-time monitoring and smart controls optimize process efficiency, reduce manual intervention, and ensure compliance
Energy Recovery: Advanced systems recover energy from sludge, reducing operational costs and environmental impact
Upgrading Wastewater Treatment Plants for Reuse
As the demand for sustainable water management rises, upgrading existing wastewater treatment plants (WWTPs) for reuse has become critical. These upgrades enable facilities to meet stricter discharge standards and expand water reuse capabilities.
Modular Retrofit Technologies for Higher Reuse Potential
1. Membrane Bioreactor (MBR): Combines biological treatment with membrane filtration for superior effluent quality. 2. Moving Bed Biofilm Reactor (MBBR): Enhances biological treatment by supporting high biomass concentration in compact spaces. 3. Sequential Batch Reactor (SBR): A time-based batch treatment system that offers operational flexibility and effective nutrient removal.
Real-World Examples
Clouse Water Recycling Center, San Antonio: Underwent a $163 million upgrade, adding energy-efficient aeration and expanding secondary treatment.
Technopark STP, Kerala: Uses smart automation and MBR for efficient wastewater recycling in a tech campus setting.
STP Wastewater Recycling and Water Reuse Methods
Advanced Treatment Techniques
To achieve high-quality effluent suitable for reuse:
Ultrafiltration & Nanofiltration: For removal of bacteria, viruses, and suspended solids.
Reverse Osmosis (RO): Effective in reducing dissolved salts and heavy metals.
UV Disinfection & Ozonation: Ensures pathogen-free water.
Advanced Oxidation Processes (AOPs): Break down complex organics.
Zero Liquid Discharge (ZLD)
ZLD systems recover nearly all water from wastewater, producing minimal solid waste. They are especially valuable in:
Industrial zones
Water-scarce regions
Nature-Based Solutions
Constructed Wetlands: Eco-friendly solution ideal for decentralized reuse like agriculture or aquifer recharge.
Soil-Based Treatment: Supports low-maintenance reuse in rural or peri-urban areas.
Sludge-to-Resource & Biogas Integration
Anaerobic Digestion
Converts sludge into:
Biogas: Used for on-site energy needs.
Stabilized Biosolids: Can be processed into organic fertilizer.
Innovative Example
Omniprocessor Technology (e.g., Muttathara STP): Converts sludge into potable water and electricity.
Smart Monitoring, Safety & Regulatory Compliance
Real-Time Monitoring with IoT
pH, BOD, turbidity sensors
Integration with SCADA/Modbus for remote management
Safety & Compliance Measures
CPCB guidelines
Dual plumbing for reuse water
Signage for reuse categories
Worker safety: PPE, lockout/tagout procedures
Nutrient Removal & Green Infrastructure
Enhanced Biological Phosphorus Removal (EBPR)
Involves alternating anaerobic and aerobic conditions to enable phosphorus-accumulating organisms to remove excess nutrients.
Green Infrastructure Applications
Constructed wetlands supporting urban biodiversity
Decentralized STPs integrated with landscape irrigation
Modular & Decentralized STP Designs
Modern STPs offer compact, scalable solutions for:
Campuses
Remote areas
Housing developments
Examples:
MBR/MBBR-based STPs that fit in limited spaces and offer plug-and-play deployment.
Lifecycle of Sewage After Processing
Where does treated sewage go?
Irrigation: Parks, gardens, green belts
Toilet Flushing: In residential and commercial buildings
Industrial Use: Cooling towers, boilers
Groundwater Recharge: Via injection wells or percolation tanks
Consider adding a flow chart to illustrate this journey.
Economic & Environmental Benefits of Reuse
Economic Gains
Lower water bills for industries
Reduced reliance on tanker supply
Environmental Benefits
Conserves rivers, lakes, and aquifers
Helps companies meet ESG targets
Leading Examples
Singapore’s NEWater
Namami Gange STPs in India
Global Trends & Innovations
Direct Potable Reuse (DPR) vs. Indirect Potable Reuse (IPR)
NASA-Inspired Closed-Loop Systems
Agricultural Reuse in Israel’s Arava Valley
California’s DPR systems for drought resilience
Addressing Challenges & Misconceptions
Psychological resistance to reused water (“yuck” factor)
Education on microbiological safety of Class A+ water
ISO 30500 and CPCB reuse guidelines ensure quality
Wastewater Treatment and Reuse Explained Step by Step
| Treatment Stage | Contaminants Removed | Tech Used | Reuse Application |
|---|---|---|---|
|
Primary |
Solids |
Grit chamber, screening |
Not suitable for reuse |
|
Secondary |
Organics, BOD |
Aeration, MBBR |
Gardening, landscaping |
|
Tertiary |
Pathogens, TDS |
MBR, RO, UV, Ozone |
Industrial & toilet flushing |
Regulatory Overview & Policy Push
Key Policies
CPCB requires 20–25% reuse of treated water in urban areas
Jal Shakti Abhiyan: Promotes wastewater-to-wealth initiatives
Credible Resources
Central Pollution Control Board (CPCB)
Ministry of Environment, Forest and Climate Change (MoEFCC)
Applications and Where to Use Sewage Treatment Plants
STPs are essential in a variety of settings:
Residential Complexes & Apartments: Manage domestic wastewater and enable water reuse for landscaping and flushing.
Industrial Facilities: Treat process water and effluents to meet strict discharge norms.
Commercial Spaces: Hotels, malls, hospitals, and offices rely on STPs for hygiene and sustainability.
Municipalities: Large-scale urban and rural wastewater management.
Institutions: Schools, colleges, and hospitals for safe sanitation.
Agriculture & Landscaping: Treated water can be reused for irrigation, reducing demand on freshwater resources
Why SUSBIO and SUSBIO ECOTREAT is the Best Choice
SUSBIO ECOTREAT is recognized as the top sewage treatment solution in 2025, leading the industry with its innovative, eco-friendly, and efficient design
Here’s what sets it apart:
Prefabricated Design: Delivered ready-to-install, ensuring rapid deployment and minimal site disruption—ideal for remote, urban, or industrial locations.
Eco-Friendly Technology: Utilizes advanced biological and physical treatment methods to meet stringent environmental standards and support water reuse.
Energy Efficiency: Operates with up to 50% less electricity than traditional STPs, reducing operational costs and carbon footprint.
Durability: Constructed from premium fiber-reinforced plastic (FRP) with a 10-year warranty, ensuring long-term performance even in harsh environments.
Scalability: Easily adapts to projects of any size, from small residential blocks to large industrial complexes.
Cost-Effective: Low maintenance, reduced sludge generation, and minimal operating costs make it budget-friendly.
Advanced Performance: Excels in treating high BOD and COD loads, delivering consistently high-quality effluent.
Comprehensive Process: Integrates primary, secondary, and tertiary treatments, along with efficient sludge management, in a compact, modular system.
Trusted Brand: SUSBIO is a pioneer in wastewater treatment, trusted by leading developers, industries, and municipalities across India
Frequently Asked Questions (FAQ)
Q1: What is the main goal of sewage treatment?
The primary goal is to remove contaminants and pathogens from wastewater, making it safe for reuse or environmental discharge
Q2: Can treated sewage water be reused?
Yes, treated water can be reused for gardening, flushing, industrial processes, and even groundwater recharge, depending on the treatment level
Q3: How long does it take to install a SUSBIO ECOTREAT plant?
Thanks to its prefabricated design, installation is rapid and hassle-free, often completed within days
Q4: Is SUSBIO ECOTREAT suitable for both residential and industrial use?
Absolutely. Its scalable, modular design makes it ideal for residential complexes, commercial spaces, and large-scale industrial facilities
Q5: What maintenance does a modern STP require?
Routine inspections, periodic cleaning, and monitoring of automation systems are recommended. SUSBIO ECOTREAT is designed for minimal maintenance
Q6: How does sludge management work in an STP?
Sludge is separated, dewatered, and can be safely disposed of or repurposed as fertilizer, supporting sustainability
Conclusion
The sewage treatment process is essential for transforming polluted wastewater into a valuable resource, protecting public health, and supporting sustainable growth. By combining advanced treatment stages and innovative technologies, modern STPs like SUSBIO ECOTREAT deliver reliable, cost-effective, and eco-friendly solutions for diverse applications. Whether for residential, commercial, or industrial use, investing in a high-quality sewage treatment plant ensures compliance, sustainability, and a cleaner future for all
