Kosad 220 MLD: Advanced BNR Upgrade

Pioneering Sustainable Wastewater Management with Advanced BNR and Energy Recovery
Location

Kosad, Surat, Gujarat, India

Procedure

EPC – Augmentation & Upgradation

Contract Type

Turnkey EPC Contract

Capacity

220 MLD

Kosad STP Augmentation: Scaling Sustainable Treatment for Surat's Growing Needs

The Kosad Sewage Treatment Plant, operated by Surat Municipal Corporation, underwent a landmark augmentation to increase capacity from 134 MLD to 220 MLD while staying strictly within the existing site footprint. Completed in 2024, this project integrates cutting-edge biological nutrient removal (BNR) technologies — including Integrated Fixed-Film Activated Sludge (IFAS), Moving Bed Biofilm Reactor (MBBR), and Sequencing Batch Reactor (SBR) processes — to deliver exceptional effluent quality (BOD and TSS ≤ 5 mg/L).

The upgrade also incorporates 0.6 MW (600 kWe) biogas-based power generation, transforming organic waste into renewable energy for on-site use and reducing the plant’s carbon footprint. Final treated effluent supports river recharge by discharging upstream of the weir in the Tapi River, promoting water reuse and recycling as a vital sustainable resource for Surat’s urban and industrial ecosystem. This project exemplifies efficient land use, minimal civil modifications, and forward-thinking environmental engineering in one of India’s fastest-growing cities.

Achieving High-Performance Treatment, Energy Self-Sufficiency, and Environmental Compliance

The primary objectives were to:

  • Accommodate an additional 86 MLD of hydraulic and organic load driven by Surat’s rapid urbanization and population growth in the North Drainage Zone.
  • Upgrade treatment performance to meet stringent discharge standards (BOD ≤5 mg/L, TSS ≤5 mg/L) with enhanced Biological Nutrient Removal (BNR) for nitrogen and phosphorus control.
  • Optimize the existing site by leveraging compact, high-rate technologies (IFAS, MBBR, SBR) to avoid major land acquisition or extensive civil reconstruction.
  • Integrate biogas capture and utilization for 0.6 MWe on-site power generation, promoting energy recovery and operational sustainability.
  • Enable safe, high-quality effluent discharge/reuse into the Tapi River, contributing to Surat’s circular water economy and pollution abatement goals.

Overcoming Space Constraints and Stringent Performance Demands

Key challenges included:

  • Severe site footprint limitations — the entire 86 MLD capacity increase had to be accommodated without expanding the land area, requiring highly efficient, compact treatment processes.
  • Need for ultra-low effluent parameters (BOD/TSS ≤5 mg/L) while handling variable sewage flows and loads typical of a major municipal system.
  • Integrating advanced BNR without disrupting ongoing operations of the existing 134 MLD plant.
  • Ensuring reliable biogas production and power generation (0.6 MWe) from anaerobic digestion/sludge in a fluctuating organic load environment.
  • Minimizing civil modifications to control costs, timelines, and environmental impact during construction in an active urban wastewater facility.

Innovative Hybrid Technologies for Compact, High-Efficiency Treatment

The project deployed a sophisticated hybrid treatment train combining IFAS, MBBR, and SBR configurations optimized for BNR. These attached-growth and suspended-growth systems maximize biomass retention and nutrient uptake in a smaller footprint compared to conventional activated sludge.

Key solutions:

  • Phased integration of MBBR media for enhanced BOD/COD removal and nitrification in compact reactors.
  • IFAS zones to boost biological phosphorus removal and overall process stability.
  • SBR sequencing for flexible operation, denitrification, and final polishing to achieve ≤5 mg/L BOD/TSS.
  • Advanced sludge handling with anaerobic digestion to maximize biogas yield, feeding a 0.6 MWe genset for captive power.
  • Tertiary polishing (if implied by ultra-low standards) and precise process controls to ensure consistent performance.

This approach minimized new civil structures, accelerated commissioning, and delivered energy-positive operations while meeting or exceeding CPCB/GPCB norms.

Site Assessment & Planning

Comprehensive hydraulic modeling, existing plant audit, and feasibility study to confirm augmentation within footprint. Defined BNR targets and biogas potential.

Design & Technology Selection

Engineered hybrid IFAS-MBBR-SBR system for nutrient removal. Detailed process design, biogas system sizing (0.6 MWe), and minimal-civil layout finalized.

Construction & Integration

Phased civil/electromechanical works with minimal downtime. Installation of media, reactors, blowers, digesters, and genset while maintaining 134 MLD operations.

Commissioning & Optimization

Gradual ramp-up, biological seeding, performance tuning for BNR, and biogas-to-power synchronization. Achieved design effluent quality and energy output.

Performance Validation & Handover

Rigorous testing confirmed BOD/TSS ≤5 mg/L, stable power generation, and river discharge compliance. Full handover to SMC with training and monitoring protocols.
Stage One
Stage Two
Stage Three
Stage Four
Stage Five

Project Partners

Fostering high-impact collaborations to deliver resilient environmental infrastructure and localized engineering excellence.
Surat Municipal Corporation (SMC)
Enviro Control Pvt. Ltd

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