1. Overview of CDI Technology
Capacitive Deionization (CDI) is an emerging water purification technology that removes salt and other charged contaminants using electrostatic adsorption. It works by applying a low voltage (1–2V) across two porous carbon electrodes, attracting dissolved ions from the water and storing them electrostatically. Once saturated, the electrodes discharge the ions, flushing them out.
2. Suitability for Jaffna Island Areas
Jaffna’s groundwater is slight to moderately saline (Total Dissolved Solids - TDS: 500–2000 mg/L) due to seawater intrusion. CDI is best suited for water with low to moderate salinity (TDS < 3000 mg/L), making it an ideal option for Jaffna’s conditions.
3. Key Advantages of CDI for Jaffna
| Feature | CDI Benefits |
|---|---|
| Energy-Efficient | Uses ~0.5–1.5 kWh/m³, which is much lower than Reverse Osmosis (RO) (~3–6 kWh/m³). |
| Lower Water Wastage | Recovers up to 80–90% of input water, compared to RO, which wastes 30–50%. |
| Lower Maintenance | No high-pressure pumps or membranes like RO; only requires periodic electrode cleaning. |
| Eco-Friendly | Produces less brine waste than RO, reducing disposal issues in Jaffna’s sensitive environment. |
| Scalability | Can be used for household units (10–100 L/day) or community systems (1,000–50,000 L/day). |
| Works with Renewable Energy | Can be powered by solar panels, reducing operational costs. |
4. Cost Analysis of CDI in Jaffna
| Component | Household Unit (100 L/day) | Community Unit (10,000 L/day) |
|---|---|---|
| Initial Cost (LKR) | 100,000 – 250,000 | 1.5M – 5M |
| Operating Cost (LKR/month) | 1,500 – 3,000 (electricity + electrode cleaning) | 15,000 – 40,000 |
| Energy Requirement | 20–100W | 500–2000W (Can be solar-powered) |
| Filter Replacement | Every 2–3 years | Every 2–3 years |
| Water Recovery Rate | 80–90% | 80–90% |
5. Challenges & Solutions
| Challenge | Solution |
|---|---|
| Higher Initial Cost Than RO | Government or NGO funding for pilot projects; local manufacturing to reduce import costs. |
| Lower Removal Rate for High Salinity Water (>3000 mg/L TDS) | Pre-treatment with ion exchange or Nanofiltration (NF) for very saline areas. |
| Technology Awareness | Conduct workshops and training for local engineers and communities. |
| Disposal of Wastewater (10–20%) | Use for non-drinking purposes like irrigation or flushing. |
6. Implementation Strategy for Jaffna
Phase 1: Pilot Project (1–2 Years)
- Install small CDI units in selected villages (household & community level).
- Monitor performance, cost-effectiveness, and social acceptance.
Phase 2: Scaling Up (3–5 Years)
- Expand CDI systems with solar power integration to reduce electricity dependency.
- Establish local manufacturing or assembly units to reduce costs.
Phase 3: Long-Term Sustainability (5+ Years)
- Government & NGO involvement for subsidized CDI installations in water-stressed areas.
- Public-private partnerships (PPPs) to maintain and operate CDI plants efficiently.
7. Conclusion & Recommendation
📌 CDI is a highly feasible, cost-effective, and eco-friendly water purification technology for Jaffna Island areas, especially for groundwater with low to moderate salinity (500–2000 mg/L TDS).
📌 It provides higher water recovery, lower energy use, and reduced maintenance compared to RO, making it ideal for decentralized household and community-scale applications.
📌 With proper funding and local implementation, CDI can be a game-changer for safe drinking water in Jaffna’s coastal and island communities.
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