Assessment of E. coli reduction in artificially contaminated borehole water via Sand-Zero valent iron-Moringa Filtration"

The research investigates the efficacy of a novel multi-layered filtration system combining sand, zero-valent iron (ZVI), and Moringa oleifera-functionalised sand (f-sand) for improving the microbiological and physicochemical quality of borehole water used for spinach irrigation. ​ The study aims to address microbial contamination, particularly Escherichia coli, in irrigation water, soil, and spinach plants, while also evaluating the system's impact on water quality parameters. ​

Key Objectives:

1. Literature Review: Assess existing water filtration methods using sand, ZVI, and Moringa oleifera for microbial contamination mitigation. ​
2. Filtration System Development: Construct laboratory-scale filtration systems (sand-only, sand-ZVI, and sand-ZVI-Moringa) and optimize their filtration rates and contact times. ​
3. Efficacy Testing: Evaluate the ability of these systems to reduce E. coli levels in artificially inoculated borehole water, soil, and spinach plants in a greenhouse setting.
4. Physicochemical Analysis: Assess the impact of filtration treatments on water quality parameters such as pH, turbidity, nitrate levels, and dissolved oxygen.

​Research Highlights:

1. Network Analysis: A bibliometric study revealed a growing interest in plant-based coagulants like Moringa oleifera for water treatment, with significant advancements in functionalised sand filtration systems over the last two decades. ​
2. Filtration Trials: Two trials were conducted using spinach plants irrigated with filtered water. ​ Results showed that sand-ZVI-Moringa filters were the most effective in reducing E. coli levels in water, soil, and spinach leaves compared to sand-only and sand-ZVI filters. ​
3. Physicochemical Parameters: While most water quality parameters remained within acceptable limits, turbidity and nitrate levels occasionally exceeded guidelines, highlighting areas for system optimization. ​
4. Mechanisms of Action: ZVI generates reactive oxygen species (ROS) that inactivate bacteria, while Moringa oleifera's cationic proteins disrupt bacterial membranes and enhance pathogen removal.

​Findings:

• Sand-ZVI-Moringa filtration significantly reduced E. coli levels in irrigation water and minimized its transfer to soil and spinach leaves. ​
• The system demonstrated potential for improving irrigation water safety, but challenges such as turbidity and nitrate removal need further optimization. ​
• Physicochemical parameters like pH, dissolved oxygen, and iron content were generally within permissible limits, confirming the system's stability. ​

Conclusion:

The study introduces a scalable, cost-effective filtration system that integrates natural and engineered materials to address microbial contamination in irrigation water. It highlights the potential of sand-ZVI-Moringa filters to enhance water quality and food safety in resource-limited agricultural settings. ​ Further research is needed to refine the system for broader adoption and regulatory compliance. ​