Performance Assessment of a Subsurface Constructed Wetland for Greywater Reuse in a High-Footfall Religious Zone

Abstract

The increasing demand for water in urban and peri-urban regions, especially in high-footfall areas like religious tourism zones, necessitates innovative and sustainable wastewater management solutions. This study investigates the treatment performance, reuse feasibility, and cost-effectiveness of a horizontal subsurface flow constructed wetland system (HSSF CW) designed to treat greywater generated during the Ardh Kumbh Mela in Prayagraj, India. Greywater samples were collected across 12 events spanning pre-monsoon and winter seasons. Parameters such as BOD, COD, TSS, pH, and Total Nitrogen were monitored at both influent and effluent points. The system achieved average removal efficiencies of 76–83% for BOD, 68–74% for COD, 72–78% for TSS, and 40–50% for Total Nitrogen. Statistical analysis using paired t-tests (? = 0.05) confirmed significant seasonal differences in pollutant removal, while Pearson correlation showed mild inverse relationships between rainfall and system efficiency. The treated effluent was assessed for non-potable reuse applications including public landscaping, sanitation, and dust suppression. Stakeholder surveys revealed strong public acceptance, with 78% of sanitation staff and 64% of event participants supporting reuse. Economic analysis demonstrated a lifecycle treatment cost of ?49.85/KL—substantially lower than packaged STPs. The study concludes that decentralized nature-based systems like constructed wetlands are technically viable, socially acceptable, and economically feasible for greywater treatment in pilgrimage zones. It recommends scalable implementation under the Swachh Bharat Mission–Gramin and Jal Jeevan Mission frameworks.

Introduction

Religious tourism zones in India, such as Prayagraj during the Ganga Mahakumbh, experience severe water stress due to large temporary population surges, generating significant amounts of untreated greywater. Conventional centralized wastewater treatment is often impractical in these contexts due to cost and infrastructure demands. Constructed wetlands (CWs), especially horizontal subsurface flow (HSSF) systems, offer an effective, low-energy, nature-based decentralized treatment solution by leveraging plant-soil-microbe interactions to remove pollutants.

While CWs have been widely studied globally, there is limited field data on their performance in high-density, event-driven Indian settings. This study evaluates an HSSF constructed wetland pilot system implemented at the Ardh Kumbh Mela in Prayagraj, focusing on treatment efficiency, seasonal variations, reuse potential, and economic feasibility. The goal is to support sustainable greywater management aligned with national initiatives like Jal Jeevan Mission and Swachh Bharat Mission (Gramin).

The study area was selected based on high greywater generation and lack of existing treatment. The HSSF wetland was designed with specific vegetation and media, monitored biweekly over several months, and analyzed for pollutant removal (BOD, COD, TSS, coliforms) using standardized protocols. Removal efficiency was statistically evaluated and water reuse trials (for irrigation and dust control) were conducted against regulatory benchmarks. Limitations include exclusion of monsoon data and limited nutrient analysis. Ethical approvals and stakeholder consents were obtained.

Conclusion

A. Summary of Findings A pilot-scale HSSF-CW system was evaluated at the Ardh Kumbh Mela site, Prayagraj, to treat greywater under real-world religious tourism conditions. Key outcomes include: • Average removal efficiencies: o BOD: 76–83% o COD: 68–74% o TSS: 72–78% o TN: 40–50% o Faecal coliforms: ~81% • Effluent quality met CPCB norms for restricted reuse (BOD <30 mg/L, TSS <40 mg/L). • Seasonal analysis revealed slightly better winter performance; differences were statistically validated (p < 0.05). • Rainfall correlations showed weak inverse relationships (e.g., BOD vs rainfall: r = –0.25). • Reuse trials showed suitability for landscaping, dust suppression, and surface cleaning. • Stakeholder feedback indicated 78% support for reuse, with potential for replication at other pilgrimage sites. B. Economic Feasibility • Capital Cost: ?1.43 lakh • Annual O&M: ?13,500 • Unit treatment cost: ?49.85/kL over 10 years This is significantly lower than conventional packaged STPs, supporting economic viability for decentralized applications. C. Key Contributions • Demonstrates nature-based greywater treatment under high-footfall conditions. • Integrates field data, statistical analysis, and stakeholder perception. • Supports policy frameworks like SBM-G and Jal Jeevan Mission. • Provides an educational model for sustainable sanitation in temporary settlements. D. Limitations • Two-season monitoring only; monsoon performance unassessed. • Pathogen analysis limited to faecal coliforms. • Controlled flow conditions; peak-event surges not captured. • Lacks IoT-based automation or real-time data logging. E. Recommendations • Add post-treatment disinfection for human-contact reuse. • Extend monitoring to include helminths and AMR markers. • Launch training modules for caretakers via ITIs. • Promote public education on reuse through signage and campaigns. • Develop mobile O&M apps and include CWs in emergency water plans. F. Future Research Directions • Comparative studies across CW types (HSSF, vertical, hybrid). • Long-term performance tracking under dynamic loading. • Assess carbon sequestration and biodiversity enhancement. • Explore health impact and antimicrobial resistance reduction. • Integrate IoT and AI tools for real-time management. • Develop financing and ownership models for scaling via CSR and rural governance.

References

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Copyright

Copyright © 2025 Mr. Prince Vaseem, Dr. Bhavesh Joshi, Mr. Abhishek Upadhyay. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.