Overview
Urban sewage systems are no longer just about treatment and discharge. Advanced technologies like MBR, real-time monitoring, and automated control systems enable cities to achieve consistent compliance, handle variable loads, and produce reuse-quality water within limited space. When designed well, these systems shift wastewater from a burden into a reliable urban resource, supporting reuse, reducing freshwater demand, and improving overall city resilience.
Aapaavani’s intervention helped the city upgrade the existing facility into a compact 1.6 MLD Membrane Bioreactor-based treatment system with minimal civil work.
The Challenge
The challenge was not a lack of infrastructure. It was a mismatch between the plant’s design assumptions and its actual operating conditions. The site was fully congested, leaving no room for conventional expansion.
- Underperforming Design: The original plant evolved from an SBR system to a conventional Activated Sludge Process (ASP). Designed for 1.6 MLD, it effectively treated only about 600-700 KLD.
- Structural Failures: Insufficient equalization tank, deep invert level sewer entry, continuous pumping without flow balancing, and an undersized rectangular clarifier led to poor solids separation.
- Difficult Influent Quality: The plant received septic tank sludge along with regular sewage. This pushed Total Suspended Solids (TSS) to roughly 380 to 400 mg/L, despite moderate organic strength (BOD ~300 mg/L, COD ~550 mg/L).
The Solution
If the plant had to be upgraded, it had to happen within the existing space footprint, with a technology that could deliver higher treatment efficiency. That is what led Aapaavani to propose an MBR-based revamp, redesigning the plant around the infrastructure already available on site.
- Biological Zoning: One of the existing tanks was converted into an anoxic zone to support nitrogen removal. The remaining volume was used as an aeration zone, providing a hydraulic retention time of about 6.5 hours.
- MBR Integration: A 1.5 MLD Membrane Bioreactor (MBR) system was installed to ensure efficient solid-liquid separation and produce consistently clear treated water.
- Repurposed Clarifier: The old rectangular clarifier was repurposed as a chlorine contact tank, adding sodium hypochlorite dosing for effective disinfection.
- Smart Automation & Monitoring: Automated with PLC-based control and integrated with IoT for remote monitoring. Aapaavani also established an on-site laboratory to monitor BOD, COD, total nitrogen, TSS, TDS, conductivity, and pH daily.
Operational Performance & Outcomes
After commissioning, Aapaavani operated and maintained the plant for two years. Performance remained strong and stable. In roughly 95% of the operating time, treated water BOD stayed below 5 mg/L, and TSS was typically below 1 mg/L. Membrane cleaning was carried out twice a year without needing to shut down completely.
(Lab-tested operating values from post-commissioning monitoring)
| Sl No | Chemical Parameters | Units | Inlet | Result | Maximum Permissible Limits |
|---|---|---|---|---|---|
| 1 | Chemical Oxygen Demand (COD) | mg/L | 400-500 | <10 | ≤50 |
| 2 | BOD at 27 c (3 days) | mg/L | 250-300 | <2 | ≤10 |
| 3 | Oil & Grease | mg/L | 1000-1200 | <1 | ≤10 |
| 4 | Total Suspended Solids (TSS) | mg/L | 300-350 | <1 | ≤20 |
| 5 | pH @ 25 C | - | 7.63 | 7.21 | 6.5 – 9.0 |
Reuse & Impact
The vision of the Urban Local Body at Karwar was to reuse the treated water, and that is one of the most impressive parts of this story. Rather than treating sewage as a waste stream to be discharged and forgotten, the municipality built a 50 lakh litre storage reservoir near the seashore and created a toll-free system for citizens to request treated water tankers at a nominal cost.
Why This Project Mattered
Karwar was a key learning project for Aapaavani. It proved that even highly constrained large-scale municipal plants can be upgraded successfully when the design is built around real site conditions, not theoretical assumptions. More importantly, it showed that treated wastewater can become a civic asset when engineering, operations, and reuse are designed together.
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Business & Operational Impact
The upgrade turned a congested, underperforming plant into a high-efficiency municipal asset. It reduced manual intervention, improved reliability, and converted treated sewage into a usable city resource. Just as importantly, it gave the municipality a repeatable framework for water reuse instead of one more discharge problem to manage.
Process diagram + 3D layout
Client Perspective
“The revamp project helped the system move from shock-instability, sludge bulking, odour and manual operation to a compact, MBR-based design that was easier to run and more consistent in output. We thank the Aapaavani team for helping us convert a struggling old system to a compact, automated MBR layout, contributing to our larger vision of water conservation.”
— Senior Officer, Karwar City Municipal Council
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