The ambitious plan of the Thiruvananthapuram City Corporation to install five decentralised sewage treatment plants (STPs) in Rajaji Nagar colony has encountered a significant hurdle. The project, designed to prevent untreated sewage from flowing into the heavily polluted Amayizhanjan canal, has been stalled due to a disagreement over environmental standards with the Kerala State Pollution Control Board (KSPCB).
Stricter Pollution Norms Cause Project Delay
The primary point of contention is the biochemical oxygen demand (BOD) level for the treated effluent. The KSPCB has refused to grant environmental consent unless the plants achieve a stringent BOD standard of below 10mg per litre. BOD measures the oxygen consumed by microorganisms to break down organic waste in water; a lower value indicates cleaner water.
City corporation officials had initially designed the STPs to meet the Central Pollution Control Board's norm of below 20mg/litre for decentralised plants. The KSPCB's insistence on a stricter limit has forced a complete reassessment of the project's design and cost estimates.
Jahamgeer S, the corporation secretary, confirmed the impasse. "Presently, the project has been stalled. The tender was called last year but didn't proceed due to KSPCB's stringent instructions. Achieving below-10 BOD is a challenging process that escalates cost, and the vendor also expressed dissent," he stated. The corporation is now awaiting an opinion from its technical sanction committee, which met last month to review the designs.
Technical Challenges and Cost Implications
Officials from the corporation and its Bengaluru-based consultant are exploring design modifications to meet the tough new standard without prohibitive cost increases. Solutions under consideration include adding tertiary polishing systems or advanced treatment modules like membrane bioreactors (MBRs).
Engineers and environmental consultants note that achieving a BOD below 10mg/litre typically requires additional treatment stages. These can involve extended aeration, constructed wetlands, or MBRs, each of which adds to both the capital expenditure and long-term operational costs of the project.
The Rajaji Nagar STP project was conceived to benefit approximately 900 families. It aimed to treat up to 5 million litres of sewage per day (5 MLD) through five modular units with capacities ranging from 50 to 100 kilolitres per day (KLD). Planned under a Design, Build, Operate, and Transfer (DBOT) model, it was estimated to cost around Rs 6 crore and targeted completion by late 2025. The contractor would have been responsible for operations and maintenance for a decade.
Compounding an Existing Environmental Crisis
This delay exacerbates the long-standing pollution crisis in the Amayizhanjan canal. Despite periodic desilting and the installation of trash-boom systems to trap plastic, the canal remains severely polluted. The State Human Rights Commission has previously called for intensified action, noting that dumped waste obstructs water flow and increases flood risks during rains.
In Rajaji Nagar, a densely populated settlement, residents and environmental activists have repeatedly criticised the slow pace of sanitation infrastructure development. The continued discharge of untreated household wastewater into drains feeding the canal perpetuates health hazards and foul odours in the neighbourhood.
The project's fate now hinges on finding a technically feasible and financially viable solution to meet the KSPCB's stringent discharge norms, highlighting the complex balance between environmental protection and practical infrastructure development in urban India.
