The simultaneous presence of nutrients (nitrogen and phosphorus) and heavy metals in wastewater poses significant environmental challenges, including eutrophication and toxicity. Conventional treatment systems often fail to address these pollutants concurrently due to their differing chemical properties. This study presents a hybrid system integrating constructed wetlands (CWs), microbial fuel cells (MFCs), and biochar-based bio-sorption to achieve e?icient removal of nutrients and heavy metals from industrial and municipal wastewater. A pilot-scale system was tested, achieving removal e?iciencies of 87% for chemical oxygen demand (COD), 82% for total nitrogen (TN), 90% for total phosphorus (TP), and over 92% for heavy metals (Cu, Zn, Pb, Cd). Metagenomic analysis revealed mi- microbial synergistic interactions, while the MFC component generated bioelectricity, enhancing sustainability. The system’s low cost and robustness make it a promising solution for wastewater treatment in resource-constrained settings.
Introduction
1. Background
Industrial and municipal wastewater often contains high levels of:
Nutrients (e.g., nitrogen and phosphorus) – causes eutrophication,
Heavy metals (e.g., copper, zinc, lead, cadmium) – harmful to ecosystems and human health.
Conventional treatment methods (like activated sludge or chemical precipitation) are often ineffective at removing both pollutant types simultaneously due to differing chemical properties.
2. Research Objective
Develop a sustainable hybrid system integrating:
Constructed wetlands (CW)
Microbial fuel cells (MFCs)
Biochar bio-sorption
Goals:
Remove both nutrients and heavy metals,
Evaluate performance at a pilot scale,
Study microbial roles using metagenomics and analyze cost-effectiveness.
3. Methodology
A. Sample Collection
Wastewater sourced from a textile factory and treatment plant in Nagpur, India.
High initial concentrations:
TN: 50–70 mg/L
TP: 8–12 mg/L
Heavy metals: 15–25 mg/L each
COD: 300–500 mg/L
B. Microbial Consortium Development
Isolated electroactive and metal-tolerant microbes from contaminated sites.
Capacity: 1000 L/day with Hydraulic Retention Time (HRT):
CW: 48 hours
Biochar: 6 hours
D. Metagenomics and Functional Analysis
Used KEGG pathway mapping to confirm gene expression for:
Nitrogen and phosphate metabolism,
Metal-binding proteins.
MFC produced max power density of 24.35 mW/m².
4. Results
? Pollutant Removal Efficiencies
COD: 87%
TN: 82%
TP: 90%
Cu: 95%
Zn: 93%
Pb: 96%
Cd: 92%
?? System Performance
Constructed Wetland: Nutrient uptake via plants and microbes.
MFC: Enhanced nitrogen removal and generated bioelectricity.
Biochar Unit: Effective heavy metal removal through adsorption and ion exchange.
5. Cost Analysis (Indian Context)
Setup Cost: ?66,400
(vs ?1,66,000 for conventional membrane bioreactor systems – ~60% cheaper)
Operational Cost: ?5,400/month
Electricity: ?1,245
Maintenance: ?4,150
? Advantages
Economical, efficient, and suitable for rural and peri-urban decentralized wastewater treatment in India.
Conclusion
The study presents a cost-effective, high-performance hybrid system for treating wastewater contaminated with both nutrients and heavy metals. By combining constructed wetlands, MFCs, and biochar filtration, and leveraging microbial consortia, the system demonstrates strong potential for sustainable, decentralized wastewater management, particularly in resource-constrained regions.
References
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