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.
Karainagar, Jaffna, faces brackish water issues due to seawater intrusion into groundwater sources. Cost-effective methods to purify slightly salted water in this region include:
1. Rainwater Harvesting (RWH)
Best for: Households, community-level water supply
Cost: Low (Rs. 50,000–150,000 for a domestic system)
Advantages: Fresh, non-saline water source, sustainable
Implementation: Install rooftop collection systems with storage tanks, first-flush diverters, and filtration (sand/charcoal filters)
2. Reverse Osmosis (RO)
Best for: Small community-scale desalination
Cost: Medium (Rs. 500,000–2 million for a small plant)
Advantages: Removes salts, impurities, and pathogens
Implementation: To reduce electricity costs, use small solar-powered RO units for remote areas.
3. Solar Desalination (Solar Stills)
Best for: Individual households, small communities
Cost: Low to medium (Rs. 30,000–100,000 per unit)
Advantages: Low maintenance, uses free solar energy
Implementation: Solar stills are used to evaporate and condense clean water, suitable for sunny climates.
Adaptability and Scalability
Household-Level Use: Individuals can set up solar stills in their homes, ensuring a personal water source.
Community-Based Installations: Multiple units can be installed in schools, community centres, or local cooperatives to provide clean drinking water for a larger population.
Customizable for Different Needs: Depending on water demand, different designs (e.g., single-basin or multi-effect stills) can be used to maximise output.
Multi-Effect Solar Still (Higher Output)
Design: Uses multiple evaporation-condensation stages to improve efficiency.
Efficiency: Produces 5–10 liters per day per square meter.
Advantages:
Higher water output compared to a single-basin still
More efficient in water-scarce areas
Best for: Small community clusters (10–20 households).
Case Studies of Successful Implementations
A. Solar Still Use in Gujarat, India
Problem: Coastal villages in Gujarat faced saline groundwater issues similar to Jaffna.
Solution: Community-based solar stills were installed, producing 5–7 liters per person per day.
Outcome:
Improved water security for over 200 families.
Reduced dependence on expensive bottled water.
Easy maintenance and community-managed operation.
B. Solar Desalination in Thar Desert, Pakistan
Problem: Limited freshwater sources due to arid climate.
Solution: Villages implemented solar stills with black-coated basins to increase efficiency.
Outcome:
Clean drinking water supply for households.
Sustainable use of abundant sunlight.
C. Solar Water Purification in Rural Africa
Problem: Contaminated and saline water sources.
Solution: Solar stills were installed in schools and health centers.
Best for: Areas with slightly saline water (low TDS)
Cost: Medium (Rs. 100,000–500,000 for small plants)
Advantages: Energy-efficient compared to RO, less waste brine
Implementation: Pilot projects in Jaffna could explore its feasibility.
Real-world examples where Capacitive Deionization (CDI) has been successfully implemented for water purification, particularly in coastal and water-scarce regions similar to Jaffna:
1. India - Rajasthan (Desert Areas)
Location: Barmer & Jodhpur districts, Rajasthan
Water Challenge: High salinity in groundwater due to arid conditions
Solution: Solar-powered CDI units installed in rural villages
Outcome: Provided safe drinking water with 80-90% recovery rate, significantly reducing brine waste compared to RO.
Relevance to Jaffna: Similar water salinity issues and potential for solar integration.
2. South Korea - Island Villages
Location: Small islands off South Korea’s coast
Water Challenge: Limited freshwater sources, high cost of water transport
Solution: Decentralized CDI units installed in community centers
Outcome: Reliable, cost-effective desalination without needing large-scale RO plants.
Relevance to Jaffna: Demonstrates CDI’s effectiveness in island environments.
3. China - Coastal Towns (Shandong Province)
Location: Shandong Province, China
Water Challenge: Seawater intrusion into groundwater supplies
Solution: Government-backed CDI plants for drinking water purification
Outcome: Large-scale CDI adoption reduced reliance on bottled water and RO desalination.
Relevance to Jaffna: Highlights potential for policy-driven CDI implementation at scale.
4. Netherlands - Agricultural Water Purification
Location: Greenhouse farms in the Netherlands
Water Challenge: High salinity affecting crop irrigation
Solution: CDI-based desalination for irrigation water
Outcome: Reduced soil salinity and improved crop yield.
Relevance to Jaffna: Can be applied for agriculture and livestock water needs.
What This Means for Jaffna
CDI has been successfully tested in coastal, arid, and island regions worldwide.
The solar-powered CDI model used in Rajasthan and South Korea is especially relevant for Jaffna.
Government-backed or community-scale CDI plants like in China and the Netherlands could be replicated in Sri Lanka.
5. Constructed Wetlands & Bio-Filters
Best for: Community-level water treatment
Cost: Low to medium (Rs. 200,000–1 million depending on scale)
Implementation: Use salt-tolerant plants (e.g., mangroves, vetiver) to filter saline water. Using salt-tolerant plants like mangroves and vetiver grass for filtering saline water is a sustainable and eco-friendly approach. Here’s how they help in managing saline water:
1. Mangroves for Saline Water Filtration
Salt Excretion & Filtration: Some mangrove species (e.g., Avicennia marina) excrete salt through their leaves, reducing salinity in the surrounding water.
Sediment Trapping: Their complex root systems trap sediments and pollutants, improving water quality.
Coastal Protection: Mangroves stabilize shorelines and prevent saltwater intrusion into freshwater sources.
2. Vetiver Grass for Salinity Control
Deep Root System: Vetiver (Chrysopogon zizanioides) has a dense root system that absorbs excess water and stabilizes soil in saline-prone areas.
Phytoremediation: It absorbs heavy metals and excess nutrients, improving water quality.
Soil Reclamation: Vetiver helps reclaim saline-affected soils, making them suitable for agriculture.
Application in Irrigation & Wastewater Management
Constructed Wetlands: These plants can be used in wetlands to treat saline wastewater from agriculture, aquaculture, and industry.
Desalination Support: Pre-treatment with vegetation can reduce the load on desalination plants by removing sediments and organic matter.
Biosaline Agriculture: These plants help in reclaiming saline lands, making them productive for other crops.
Implementation Strategies for Using Salt-Tolerant Plants in Saline Water Filtration
The selection and application of mangroves, vetiver, and other salt-tolerant plants depend on the site conditions, salinity levels, and project goals. Below are tailored strategies for different applications:
1. Coastal and Estuarine Areas – Mangrove-Based Filtration
Best for: Protecting shorelines, filtering brackish/saline water, and preventing saltwater intrusion.
Implementation Steps:
✅ Site Selection:
Identify intertidal zones where mangroves naturally thrive (salinity range: 10-35 ppt).
Avoid highly eroded areas unless supported by sediment trapping measures.
✅ Species Selection:
High Salinity:Avicennia marina (Grey mangrove) – salt-excreting species.
Use nursery-grown seedlings or direct planting methods.
Maintain buffer zones to allow natural regeneration.
Monitor for growth, survival rates, and pollution removal efficiency (e.g., heavy metals, nutrients).
✅ Expected Outcomes: ✔ Reduces salinity intrusion into groundwater. ✔ Enhances coastal water quality by filtering pollutants. ✔ Provides habitat for biodiversity and supports fisheries.
2. Inland & Agricultural Lands – Vetiver Grass for Saline Water Filtration
Best for: Treating saline wastewater, rehabilitating salt-affected soils, and stabilizing embankments.
Implementation Steps:
✅ Site Selection:
Choose areas with moderate to high salinity (EC: 4-15 dS/m).
Ideal for agricultural drainage canals, irrigation channels, and salt-affected farmlands.
✅ Planting Method:
Spacing: 10-15 cm apart in hedgerows along drainage lines or bunds.
Depth: Plant 15 cm deep to ensure strong root anchoring.
Water initially for establishment, then rely on natural moisture.
✅ Maintenance:
Trim leaves periodically (used for fodder or mulch).
Monitor soil EC levels and adjust planting density if needed.
✅ Expected Outcomes: ✔ Absorbs excess nutrients (N, P) and heavy metals. ✔ Reduces soil erosion and salinity accumulation. ✔ Enhances wastewater quality before reuse in agriculture.
3. Constructed Wetlands for Saline Wastewater Treatment
Best for: Municipal and industrial wastewater treatment with moderate salinity levels.
Implementation Steps:
✅ Design Considerations:
Use a hybrid system with mangroves, vetiver, and other halophytes (e.g., Salicornia).
Combine surface flow wetlands (mangroves) with subsurface flow (vetiver) for better filtration.
✅ Water Quality Parameters:
Target salinity: <15 ppt for optimal plant function.
Monitor for: Nitrogen, phosphorus, heavy metals, and suspended solids.
✅ Expected Outcomes: ✔ Reduces salinity, organic pollutants, and toxins in wastewater. ✔ Produces biomass for biofuel or fodder. ✔ Supports sustainable water reuse in irrigation.
Key Considerations Before Implementation
🔹 Water Salinity Testing – Determine site-specific salt tolerance levels. 🔹 Hydraulic Load & Retention Time – Optimize water flow rates in treatment systems. 🔹 Regulatory Compliance – Check environmental laws for wetland restoration or wastewater discharge. 🔹 Community Engagement – Involve local communities in mangrove conservation and wetland maintenance.
Case Study & Project Design Framework for Using Salt-Tolerant Plants in Saline Water Filtration
To develop an effective mangrove- or vetiver-based saline water filtration system, let’s look at a case study followed by a custom project design framework.
📌 Case Study: Mangrove & Vetiver-Based Filtration in Saline Water Management
🔹 Location: Coastal Bangladesh
Problem: Agricultural fields and freshwater ponds were affected by saltwater intrusion due to rising sea levels and tidal surges.
Solution: A combination of mangrove buffer zones and vetiver hedgerows was implemented.
Results: ✅ 25-30% reduction in salinity levels in groundwater after 2 years. ✅ Improved water retention and soil fertility, enabling the growth of salt-resistant crops. ✅ Increased fish productivity due to better water quality in aquaculture ponds.
📌 Project Design Framework for Saline Water Filtration
This framework outlines a step-by-step plan for implementing salt-tolerant plant-based filtration in your region.
🌿 Step 1: Site Selection & Assessment
✅ Identify areas affected by salinity intrusion (coastal, estuarine, or inland). ✅ Measure:
Soil Salinity (EC in dS/m) – Test at multiple points.
Water Salinity (ppt or TDS mg/L) – Assess seasonal variations.
Water Flow & Drainage – Determine suitable planting locations.
🔹 Example:
If EC > 10 dS/m, prioritize mangroves in tidal areas.
If EC between 4-10 dS/m, use vetiver in agricultural drainage zones.
Ensure natural tidal flushing for effective salt removal.
Avoid water stagnation by maintaining tidal creek flow.
🔹 Vetiver Wetlands:
Use a subsurface flow system to maximize water retention.
Introduce baffle structures to enhance pollutant removal.
✅ Regular Monitoring:
Monthly water salinity testing (ppt or EC values).
Soil quality assessment every 6 months.
Vegetation health & biomass measurements.
📊 Step 4: Expected Outcomes & Benefits
1️⃣ Reduction in Water Salinity (15-40%)
Improves irrigation water quality for agriculture.
2️⃣ Soil Salinity Improvement (10-30%)
Enhances land productivity for biosaline agriculture.
3️⃣ Wastewater Treatment (Nutrient & Metal Removal)
Vetiver removes nitrogen (N) by 50-70% and phosphorus (P) by 40-60%.
Mangroves capture heavy metals (Pb, Cd) in sediments.
4️⃣ Sustainable Land & Water Use
Supports aquaculture and agroforestry.
Promotes biodiversity conservation.
⚙️ Step 5: Scaling Up & Integration
✅ Pilot Project (1-2 years): Start with a 10-20 ha area to test effectiveness. ✅ Community Engagement: Train local farmers in vetiver planting and mangrove conservation. ✅ Integration with Irrigation Systems: Link with constructed wetlands for water reuse. ✅ Funding Sources: Explore government subsidies, foreign aid (e.g., ADB, World Bank), or CSR funding for environmental restoration.
6. Nanofiltration (NF)
Best for: Water with low-to-moderate salinity
Cost: Medium (Rs. 400,000–1.5 million)
Advantages: More efficient than RO for slightly saline water, requires less energy.
Implementation: NF units for household/community level.
Community-Level NF Plants (Medium Scale)
Capacity: 1,000–10,000 liters per day.
Best For: Schools, small villages, hospitals, or places with brackish groundwater.
Advantages: Provides clean water for 100+ people per day, lower operational cost than RO.
Why NF is a Game-Changer for Karainagar ✔ Energy-efficient & cost-effective solution for reducing salinity in well water. ✔ More sustainable than high-energy RO plants. ✔ Can be implemented at household, community, and municipal levels. ✔ Ensures long-term drinking water security for Karainagar’s residents. The cost of the NF unit itself varies based on capacity and manufacturer. For instance, a 100-gallon-per-minute (GPM) commercial-quality NF system can cost around $250,000.
A basic 5 to 10 gallons per minute (GPM) NF system might cost less than $60,000.
Here’s a cost-benefit comparison table for the different water purification methods suitable for slightly salted water in Karainagar, Jaffna:
Method
Initial Cost (LKR)
Operating Cost
Efficiency
Energy Requirement
Advantages
Challenges
Rainwater Harvesting (RWH)
50,000 – 150,000
Low (Only tank cleaning & minor repairs)
High (Freshwater)
None
Sustainable, low-maintenance, free water source
Seasonal dependence requires storage tanks
Reverse Osmosis (RO)
500,000 – 2 million
High (Electricity, filter replacement)
Very High (Removes 99% salts & contaminants)
High
Effective desalination, widely used
High waste brine, high energy use
Solar Desalination (Solar Stills)
30,000 – 100,000
Very Low
Medium (Removes ~98% of salts)
Low (Solar energy)
No electricity needed, low maintenance
Slow water production requires sunny conditions
Capacitive Deionization (CDI)
100,000 – 500,000
Medium (Electrode replacement, low power use)
Medium-High (Removes 60-90% salts)
Low
Energy-efficient produces less waste than RO
Still developing technology, limited availability
Constructed Wetlands & Bio-Filters
200,000 – 1 million
Low
Medium (Removes salts gradually, improves groundwater quality)
Solar-powered desalination is a sustainable method to convert seawater or brackish water into fresh, potable water using solar energy. This process is especially useful in regions with limited freshwater resources but abundant sunlight, providing a viable alternative to traditional, energy-intensive desalination methods. Here’s how it works:
Key Components and Processes in Solar-Powered Desalination
Solar Energy Collection The system starts with collecting solar energy, which can be harnessed through:
Solar Photovoltaic (PV) Panels: Convert sunlight directly into electricity, which powers a desalination unit (often using reverse osmosis).
Solar Thermal Collectors: Use sunlight to generate heat, which is then used in thermal desalination methods like multi-effect distillation or solar stills.
Desalination Methods Using Solar Power Several desalination techniques can be driven by solar energy, each suitable for different applications and scales:
Solar-Powered Reverse Osmosis (RO): Solar PV panels generate electricity that powers high-pressure pumps to push seawater through a semi-permeable membrane. The membrane filters out salts and impurities, leaving fresh water on one side and a concentrated brine on the other.
Solar Distillation: Also known as solar stills, this method mimics the natural water cycle. In a solar still, seawater is heated by solar energy, causing it to evaporate. The vapor rises, leaving salts and impurities behind, and condenses on a cooler surface, where it’s collected as fresh water.
Multi-Effect Distillation (MED) with Solar Thermal Energy: Uses solar heat to evaporate seawater in multiple stages (effects). The heat generated in one stage powers the next, maximizing energy efficiency. MED works well in large-scale plants combined with concentrated solar power (CSP).
Concentration of Salts and Brine Disposal Most desalination processes produce brine (a concentrated salt byproduct). Responsible disposal or brine management is essential to reduce environmental impacts. Some systems integrate brine management solutions or minimize brine by further utilizing it in salt extraction or other applications.
Benefits of Solar-Powered Desalination
Sustainability: Solar energy is renewable and clean, reducing greenhouse gas emissions compared to fossil-fuel-powered desalination.
Energy Efficiency: Solar desalination is cost-effective over the long term, especially in sunny regions where it can operate without ongoing fuel costs.
Scalability: Solar-powered desalination can be implemented on a small scale for rural and remote communities or expanded to larger systems for urban needs.
Applications and Challenges
Applications include remote or arid coastal areas, island communities, and disaster relief situations where conventional energy sources are limited. The primary challenges involve high initial setup costs, dependence on sunlight availability, and potential brine disposal impacts on marine ecosystems.
Solar-powered desalination is an evolving technology with promising advancements, offering a sustainable solution to the growing global water scarcity issue.
Project
Proposal: Sustainable Reverse Osmosis Water Purification System for Small
Islands in the Maldives
Project
Title:
Sustainable Water Purification for
Small Islands in the Maldives Using Renewable Tidal and Solar Energy
Project
Overview:
The project aims to provide small
islands in the Maldives (with populations under 6,000) with a sustainable and
reliable source of potable water through a reverse osmosis (RO) water
purification system powered by renewable energy sources. These systems will harness
tidal and solar energy, creating a resilient, environmentally friendly solution
to water scarcity and addressing the region's vulnerability to climate change.
Project
Objectives:
Ensure Access to Safe Drinking Water: Install RO desalination systems to convert seawater
into potable water, meeting the daily water needs of local populations.
Harness Renewable Energy: Use a hybrid system of tidal wave energy and solar
power to operate the RO plants sustainably, reducing reliance on fossil
fuels.
Promote Environmental Sustainability: Minimize environmental impacts by utilizing clean,
renewable energy, contributing to the Maldives' climate change mitigation
goals.
Create a Scalable Model: Develop a replicable model for water purification
that can be expanded to other islands across the Maldives.
Target
Population:
Small islands in the Maldives with
populations under 6,000 people, with a focus on islands with water scarcity
issues or those relying heavily on rainwater or expensive imports of bottled
water.
Project
Components:
Water Purification Technology:
Reverse Osmosis (RO) System: Desalination plants will be installed to purify
seawater and remove salts and impurities to produce safe drinking water.
The capacity will be designed based on the population size and water
demand, approximately 30-50 liters per person per day.
Energy Supply:
Tidal Energy:
Small-scale tidal turbines will be installed to harness the natural ebb
and flow of tidal currents, generating electricity to power the RO plant.
Solar Energy:
Solar photovoltaic (PV) panels will be installed to supplement energy
needs, especially during daylight hours, ensuring continuous operation.
Battery storage systems will store excess energy for use during low
energy production times.
Hybrid Integration:
A smart grid system will integrate both energy sources, automatically
switching between tidal and solar energy depending on availability.
Infrastructure:
Water Storage Tanks:
Large tanks will be constructed to store treated water, ensuring a steady
supply even during maintenance or power outages.
Distribution Network:
A local water distribution system will deliver clean water to households
and communal water stations.
Capacity Building and Maintenance:
Training for Local Operators: Technical training programs will be provided to
local operators to manage and maintain the RO system and the energy
generation units.
Community Engagement:
Awareness programs will be conducted to educate the local community on
water conservation, system maintenance, and the benefits of renewable
energy.
Renewable
Energy Feasibility:
Tidal Energy:
The Maldives is well-positioned to exploit tidal energy due to its oceanic
location and predictable tidal patterns. Low-impact turbines will be
designed to minimize environmental disruption.
Solar Energy:
With abundant sunshine throughout the year, solar PV systems are highly
viable for consistent energy production. Solar power complements tidal
energy, especially during low tidal activity.
Estimated
Timeline:
Phase 1: Feasibility Studies and Site Selection (3-6 months)
Conduct detailed assessments of water needs, tidal and
solar potential, and environmental impact on each island.
Phase 2: System Design and Procurement (4-6 months)
Design the RO system and energy components, procure
equipment, and prepare construction materials.
Phase 3: Construction and Installation (6-9 months)
Build the RO plants, install solar PV systems, tidal
turbines, storage tanks, and distribution systems.
Phase 4: Testing and Commissioning (2-3 months)
Test the system for efficiency, address any
operational issues, and train local staff.
Phase 5: Operation and Monitoring (Ongoing)
Operate the system, monitor energy efficiency, and
ensure water quality standards are met.
Estimated
Budget:
Total Estimated Budget: $2,500,000 - $4,000,000 (depending on island size and
specific energy requirements)
Key
Cost Breakdown:
Reverse Osmosis System: $500,000 - $1,000,000
Solar Power System (PV Panels + Batteries): $800,000 -
$1,200,000
Tidal Energy System: $700,000 - $1,000,000
Installation, Infrastructure, and Distribution
Network: $300,000 - $500,000
Training and Capacity Building: $200,000 - $300,000
Sustainability
and Impact:
Environmental Benefits: By using tidal and solar energy, the project will
reduce CO₂ emissions and dependence on diesel-powered generators.
Economic Benefits:
Lower long-term operational costs as renewable energy will reduce the need
for fuel imports. The system will provide consistent water access, decreasing
dependency on costly bottled water imports.
Social Impact:
Clean water availability will improve public health, reduce waterborne
diseases, and improve overall quality of life for island communities.
Potential
Funding Sources:
Government of the Maldives: National initiatives for water security and renewable
energy.
International Aid Organizations: Such as the World Bank, Asian Development Bank (ADB),
or Green Climate Fund.
Private Investors/Corporate Social Responsibility (CSR): Partnerships with renewable energy companies and
impact investors.
Grants and Development Agencies: From entities focused on climate resilience, such as
the UNDP and other NGOs.
Conclusion:
This project offers a sustainable,
scalable solution to water scarcity in the Maldives' small island communities.
By integrating tidal and solar energy into a reverse osmosis system, the
project addresses both water security and environmental sustainability, making
it a model for similar island nations facing climate challenges.
Source: https://water.usgs.gov/edu/pesticidesgw.html Pesticides are chemicals used to kill or control pests such as insects, weeds, fungus, bacteria, rodents, fish or any other type of organism that poses a problem. Pesticides are most often applied to farmland, gardens and lawns. Pesticides are also applied to water bodies (for example, rivers, canals or lakes) to control pests such as mosquitoes, weeds or invasive fish species.
Pesticides have the potential to contaminate drinking water supplies in both agricultural and urban settings. Under the Safe Drinking Water Act (1974), the U.S. EPA and other federal agencies monitor and regulate drinking water supplies. Many contaminants of drinking water occur at very low concentrations. Whether the contaminants pose health risk depends on how toxic the pesticides are, how much is in the water, and how much exposure occurs on a daily basis.
Pesticide contamination of drinking water is very common, especially in agricultural areas. Accidental or illegal spilling or dumping of pesticides can lead to contamination of drinking water, and even proper application of pesticides can lead to contamination of drinking water through leaching into groundwater or runoff into surface water bodies. Concentrations of pesticides tend to be highest in streams adjacent to agricultural areas.
Pesticides can sometimes first appear in drinking water wells decades after the pesticides were applied or spilled, depending on the chemical properties of the pesticide and the geologic conditions.”
In a study published in 2006 by the U.S. Geological Survey, atrazine (a pesticide banned in the European Union but still widely used in the U.S.) was found 90% of the time in streams in agricultural areas and 70% of the time in streams in urban areas, and it was also frequently detected in groundwater [1]. Because groundwater can move very slowly, pesticides can sometimes first appear in drinking water wells decades after the pesticides were applied or spilt, depending on the chemical properties of the pesticide and the geologic conditions. Because of this, even pesticides that are no longer in use can still contaminate water supplies.
PESTICIDE FACTS
Pesticides are potentially toxic to humans and can have both acute and chronic health effects, depending on the quantity and the ways in which a person is exposed.
Some of the older, cheaper pesticides can remain in the soil and water for years. They have been banned in developed countries for agricultural use but are still used in many developing countries.
There are more than 1,000 pesticides used around the world to ensure food is not damaged or destroyed by pests. Each pesticide has different properties and toxicological effects (and the toxicological effects of multiple pesticides can be greater than the sum of their parts).
When using pesticides that may contaminate water supplies, the risk of contamination may be minimized by 1) using short-lived pesticides that biodegrade easily, 2) using pesticides that tend to stick to soil and not move easily, and 3) avoiding disposal of pesticides where they may contaminate water resources, such as near a well or spring or down a storm sewer.
Interesting fact: The pesticide DDT is so persistent in the environment that it is still found in fish more than 40 years after it was banned in the U.S. in 1972.
Health Effects Associated with Pesticides in Drinking Water
There are many different pesticides, each with a different level of toxicity. The health risks associated with pesticides in drinking water are related to how toxic the compound is, how much is in the water, and how much exposure a human gets to the contaminated water. In large doses, which could come from direct exposure to pesticides, they can cause health problems such as cancer, organ damage, reproductive effects, birth defects, or nervous system damage. In drinking water, concentrations are usually low, but some pesticides are toxic even at very low levels.
“High levels of nitrate from chemical fertilizers in the water supply may indicate possible contamination by pesticides.”
Many pesticides are not regulated as contaminants in drinking water, but the U.S. Environmental Protection Agency (USEPA) has set maximum contaminant levels (MCLs) for several pesticides. A MCL is the maximum concentration of a contaminant that is legally allowed in public drinking water systems under the Safe Drinking Water Act. The long-term health risks associated with concentrations above the MCL are considered to be unacceptable. The MCLs for individual pesticides are based on their toxicity, with more toxic pesticides having lower MCLs. Their values range from 0.00005 to 4 milligrams per liter (mg/L or parts per million). For example, the MCL for atrazine, which is the most commonly detected pesticide in drinking water in the U.S., is 0.003 milligrams per litre.
High levels of nitrate from chemical fertilizers in the water supply may indicate possible contamination by pesticides. Because these tests are the expensive and only test for specific compounds, it is best to only test for pesticides that you think may be contaminating your water.
How to Treat Drinking Water for Pesticides
Pesticides can be removed from drinking water by reverse osmosis or granulated activated carbon (GAC) filters. Reverse osmosis works by forcing the water through a membrane that allows water molecules to pass through but blocks larger ions or molecules, such as ones associated with iron, lead or pesticides. In homes, reverse osmosis systems are usually small systems (called point-of-use systems) located near the kitchen sink.
Reverse osmosis systems are cost-effective, but low-end systems can only produce a few gallons of treated water each day. Significant recent improvements in membrane elements allow for more expensive systems to produce 100 or more gallon per day. The taste of the water may be affected by the removal of the minerals.
Granulated activated carbon (GAC) filters are relatively inexpensive and are simple to use. They remove pesticides and other contaminants that stick to small particles of material such as coal or charcoal. These filters can take the form of point-of-use systems or pitchers manually filled with water. GAC filters must be replaced or regenerated periodically to maintain their effectiveness.
FACTORS AFFECTING PESTICIDE POLLUTION OF WATER
Drainage: Farmland is often well-drained and natural drainage is often enhanced by land drains. Water from excessive rainfall and irrigation cannot always be held within the soil structure. Therefore, pesticides and residues (also nitrates and phosphates) can be quickly transported to contaminate groundwater and freshwater supplies over a large geographical area.
The pesticide: Individual pesticides have unique properties, and many variable factors (including those below) determine the specific risk in terms of water pollution.
active ingredient(s) in the pesticide formulation
contaminants that exist as impurities in the active ingredient(s)
additives that are mixed with the active ingredient(s) (wetting agents, diluents or solvents, extenders, adhesives, buffers, preservatives, and emulsifiers)
degradate that is formed during chemical, microbial, or photochemical degradation of the active ingredient
Pesticide half-life: The more stable the pesticide, the longer it takes to break down. This can be measured in terms of its half-life, the longer it takes to break down, the higher its persistence. The half-life is unique to individual products but variable depending on specific environmental and application factors.
An active substance is any chemical, plant extract, pheromone, or microorganism (including viruses), that has an action against ‘pests’ or on plants, or parts of plants or plant products.
Mobility in soil: All pesticides have unique mobility properties, both vertically and horizontally through the soil structure. Residual herbicides applied directly to the soil are designed to bond to the soil structure.
Solubility in water: Many pesticides are soluble in the water out of necessity so that they can be applied with water and be absorbed by the target. The higher the solubility of the pesticide, the higher the risk of leaching. Residual herbicides are generally of lower solubility to aid soil binding but their persistence in the soil can cause other problems.
Microbial activity: Pesticides in the soil are primarily broken down by microbial activity. The greater the microbial activity, the faster the degradation. Loss of pesticide residues can also occur by evaporation and photodecomposition.
Soil temperature: Soil microbial activity and pesticide breakdown is largely linked to soil temperature.
Application rate: The more pesticide that is applied, the longer significant concentrations remain.
Irrigation Management: Irrigation increases the chance that pesticides will migrate to ground water and surface water. Irrigating saturated soils or irrigating at a rate that exceeds the infiltration rate of soil promotes runoff that can carry pesticides with it. Irrigation that promotes the frequent downward movement of water beyond the root zone of plants also promotes the leaching of substances including pesticides to ground water. This is of particular concern in areas where frequent irrigation is necessary because of coarse-textured soils. Proper irrigation management is critical to minimize the risk of pesticides infiltrating ground water.
How to Prevent Water Contamination
There are a variety of common management practices that provide multiple benefits.
Crop and Soil Management Strategies
Crop rotation keeps pests off-balance, especially those that prefer a particular crop with its associated cultural practices.
Cover crops provide crop residues, which enhance soil organic matter.
Careful crop variety selection ensures that the crop is well-adapted to local conditions and grower needs,
and often provides valuable disease or insect resistance, or tolerance to pesticides that will be used to control pests.
Proper seedbed preparation and planting allows the crop to emerge quickly, potentially reducing early-season disease and insect damage and weed competition.
Proper drainage and irrigation management promotes optimum plant growth, inhibits various root diseases, and reduces runoff.
Proper equipment use avoids soil compaction, which can slow crop growth and promote runoff.
Conservation Buffers
Conservation buffers are areas designed to intercept and trap chemicals before they reach surface water. Often native grasses are planted alone or in combination with shrubs and trees along field borders between the crop and a waterway. Buffers trap pesticides, bacteria, fertilizers, and soil sediment, reducing the quantity of potential contaminants that move off the site. Buffers are one of the best management tools a landowner can install, as they offer multiple benefits, and often require little maintenance.
Choose these sites for more information on conservation buffers:
Conservation Buffers – Design Guidelines for Buffers, Corridors, and Greenways, National Agroforestry Center, USDA
Conservation buffers can improve water quality, University Extension, Iowa State University
Use conservation buffers to make dollars and sense, University Extension, Iowa State University
Buffer Strips: Common Sense Conservation, Natural Resources Conservation Service, USDA
For more on buffers, view or download The Value of Buffers For Pesticide Stewardship and Much More
Integrated Pest Management (IPM)
An IPM program combines the best techniques to prevent pests and to keep them below economically damaging threshold levels and ensure that pesticides are used appropriately. If a pesticide is prone to reach surface or groundwater, suitable IPM tactics can reduce or eliminate the risk of surface or groundwater contamination.
The IPM program also facilitates the selection of a pesticide to be delivered precisely on target and at the proper time. Crop scouting, or monitoring, correctly identifies the pest and collects information needed so that applications are made only when needed, and only when the pest is vulnerable, allowing for a more effective pesticide application. Reducing the need for multiple applications of pesticides reduces the chance that pesticides may reach and contaminate water. Visit the PES site Integrated Pest Management.
Best Management Practices (BMPs) are conservation practices, or systems of practices, and management measures that control soil loss and reduce water quality degradation caused by nutrients, animal wastes, toxics, and sediment. BMPs can improve the environment while also improving the farmer’s bottom line.
Visit any of these web sites to learn more about best management practices to protect water resources from agricultural pesticides:
Best Management Practices for Agricultural Pesticides to Protect Water Resources, Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska
Water Publications from Colorado State University,
Protecting water from contamination requires planning and records. Past pest scouting or monitoring records, along with past pesticide application records, help you select the best controls. Selecting the proper pesticide for the crop, the pest, and the site is important. When a site has groundwater near the surface and the soil is permeable, then the leaching potential of the pesticide must be considered during pesticide selection.
Applicators should read the label to find warnings that tell them that the pesticide may leach. Here is an example of language to look for in the Environmental Hazards section of the label: “This product has properties and characteristics associated with chemicals detected in groundwater. The use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in groundwater contamination.” There may also be a “Groundwater Advisory” statement on the label. Many new labels have this statement, which is a critical aid in selecting the right pesticide for the job.
Proper Pesticide Mixing and Loading Procedures
More pesticide spills occur while the pesticide is being measured and mixed than during any other part of a pesticide application. Locate the mixing/loading site away from wells, streams and lakes. Maintain a distance of at least 100 feet (check the pesticide label for more specifics) between the mixing and loading site and wellheads, ditches, streams or other water sources.
Measure, mix and load over an impervious surface, such as a concrete pad, which prevents spills from soaking into the ground. Measure the product carefully to avoid spills. Using a closed transfer system to mix and load pesticides also helps reduce the risk of spills. If you are not using a pad, move the mixing and loading steps from place to place to avoid chemical buildup from accidental splashes or spills (see Pesticide Spills).
Be prepared for spills and have a “spill kit” readily available near the mixing loading area. Never leave a tank while it is being filled, and pay constant attention during filling to prevent overfilling and spilling of the pesticide on the ground. Be disciplined and patient.
Applicators should read the label carefully to find warnings regarding mixing/loading pesticides. Here is a statement found in the Environmental Hazards section of many labels: “Most cases of groundwater contamination involving this pesticide have been associated with mixing/loading and disposal sites. Caution should be exercised when handling this product at such sites to prevent contamination of groundwater supplies. Use of closed systems for mixing or transferring this pesticide will reduce the probability of spills. Placement of the mixing/loading equipment on an impervious pad to contain spills will help prevent groundwater contamination.”
Backflow occurs when a water supply loses pressure and starts flowing backwards toward the water source. The backward flow creates a siphon that draws some of the contents of the sprayer tank back toward the water source if a pipe or hose is below the water surface in the tank. If backflow occurs, the water supply pipes, pumps, and well become contaminated by pesticides from the tank. An anti-siphon device (check valve) prevents backflow and the resulting contamination from occurring. Proper anti-siphoning techniques include the use of a reduced pressure zone (anti-siphon) device or an air gap between the filler pipe and the tank.
Proper Application Procedures
Proper application of pesticides starts with calibration. Calibrating application equipment is the only way to be sure that the proper amount of pesticide is applied. Application of excess pesticide increases the risk of contaminating water by overloading the protective mechanisms of degradation and adsorption, making them ineffective. Over application is not only risky for the environment but is a violation of label directions and the law.
Knowledge of the application site is very important for preventing water contamination. You should know where wells are located, the depth to groundwater, and where surface water is located before making an application. After identifying these features, make plans to protect them. Decide in advance where to turn the application equipment on and off. Using buffer zones and setback areas creates safety zones by keeping applications away from sensitive areas, particularly surface waters. Pesticide applications should hit the target precisely. Applications that move off-target can contribute to water contamination.
Preventing drift is another important task of the applicator. Drifting pesticide can contaminate water and cause other problems. Monitoring the weather conditions, setting the boom height as close as possible to the target, and selecting the proper nozzle type are important activities that help reduce the chance of pesticide drift contaminating surface waters.
Irrigation Management
Irrigation increases the chance that pesticides will
migrate to groundwater and surface water. Irrigating saturated soils or irrigating at a rate that exceeds the infiltration rate of soil promotes runoff that can carry pesticides with it. Irrigation that promotes the frequent downward movement of water beyond the root zone of plants also promotes the leaching of substances, including pesticides, to groundwater. This is of particular concern in areas where frequent irrigation is necessary because of coarse-textured soils. Proper irrigation management is critical to minimize the risk of pesticides moving to groundwater.
Proper Pesticide Storage
Proper storage of pesticides is also important to prevent water contamination. Locking pesticides inside a fire-resistant, spill-proof facility is an excellent way to prevent accidental pesticide spills. Proper storage is very cheap compared with the expensive consequences of accidents, spills, or fires. Be prepared for spills, and have a “spill kit” readily available inside or near the storage area.
Proper Disposal of Pesticides and Containers
Pesticide containers that have not been triple rinsed pose a risk to water resources. Contaminated containers left outside, and exposed to rain, can leak pesticides into the environment. Triple rinsing pesticide containers prior to disposal remove pesticide residues. Water collected from cleaning and rinsing application equipment should be applied to the original site of the application. Be careful not to exceed label rates. Re-using this pesticide-containing water is an environmentally responsible way to dispose of this material. Collect rinsed containers in a dry, secure, and protected area for disposal. Dispose of the rinsed containers following label directions and local ordinances. Use pesticide container recycling programs where available.
