Purifying Water: Removing Pesticides For Safe Consumption

Pesticides are a common issue in water supplies, with nearly 90% of water samples in the US containing five or more different pesticides. With the threat of health issues such as birth defects, cancer, and neurological problems, it is important to consider how to purify water polluted with pesticides. While public water suppliers often filter out impurities, many contaminants are not regulated, and private wells are not monitored. There are several methods to purify water, including filtration, boiling, and chemical treatments, but a combination of techniques is the best approach to removing pesticides. Advanced oxidation processes (AOPs) are a recent purification technology that has been adopted for its thermodynamic viability and broad spectrum of applicability. Other methods include coagulation-flocculation, adsorption, sedimentation, and reverse osmosis, which is an affordable and effective way to remove pesticides.

Reverse osmosis

In reverse osmosis, pressure is applied to the concentrated side of the membrane (the contaminated side). This forces the osmotic process into reverse, so that, with adequate applied pressure, pure water is forced from the concentrated (contaminated) side to the dilute (treated) side. The rejected contaminants on the concentrated side of the membrane are washed away as wastewater. The amount of treated water produced depends on several factors, including membrane type and condition, flow control, pressure, contaminant concentration, temperature, and pH. Reverse osmosis can remove up to 99% of dozens of different contaminants, including pesticides.

Advanced oxidation processes

AOPs are especially effective in treating effluents containing refractory, toxic, or non-biodegradable materials. They offer several advantages over biological or physical processes, including unattended operation with a small footprint, no secondary wastes (sludge), and the ability to handle fluctuating flow rates and compositions.

The AOP procedure involves the generation of OH radicals in sufficient quantity to affect water purification. This can be achieved through various systems, including O3 at high pH, O3/H2O2, O3/UV, and H2O2/UV. The use of UV light and semiconductor composites has been explored to overcome the limitations of UV TiO2 photocatalysis, which include the requirement of UV light and low quantum yields.

The goal of wastewater purification using AOPs is to reduce chemical contaminants and toxicity to such an extent that the cleaned wastewater can be reintroduced into natural water sources. AOPs can achieve high levels of contaminant removal, with COD reduction rates ranging from 75-90% for AOP catalytic oxidation to 95-100% for AOP photo-catalytic UV or UV + Hydrogen Peroxide or Ozonation.

Filtration

Pesticides are common synthetic organic chemicals used to control weeds, insects, and other organisms. They are often applied to crops, lawns, and gardens and can be found in agricultural and industrial wastewater. Due to their widespread use, pesticides can contaminate both surface and groundwater, making their way into our drinking water supply. Even low concentrations of pesticides in water can be harmful to human health, as they can accumulate in the food chain and cause serious health effects such as birth defects, cancer, reproductive issues, and neurological problems.

• Reverse Osmosis (RO): RO is a widely recognized and effective method for removing pesticides from water. It is a water treatment process that uses pressure to force water molecules through a semipermeable membrane, trapping the contaminants and flushing them away. RO can remove up to 97-99% of pesticides and is also effective in reducing herbicides, insecticides, and other organic chemicals.
• Activated Carbon Filtration: Activated carbon, often in the form of carbon block filters, is highly effective in removing synthetic organic chemicals like pesticides. The carbon acts as a sorbent, attracting and retaining the pesticide molecules, thereby reducing their presence in the water. Activated carbon filtration can remove a wide range of contaminants, including asbestos, lead, mercury, trihalomethanes, and chlorine.
• Ultrafiltration: This filtration method uses membranes with small pore sizes to remove organic compounds, including pesticides, from water. Ultrafiltration can effectively separate and remove particles based on their size and molecular weight.
• Membrane Filtration: Membrane technologies, including membrane bioreactors, are also used to remove pesticides from water. These membranes act as a barrier, allowing water to pass through while blocking and trapping the contaminants.

It is important to note that a combination of different water treatment methods often provides the best results in removing pesticides from water. Additionally, the choice of filtration method depends on various factors, such as the type of pesticide, the concentration, and the specific requirements of the water treatment process.

Boiling

When boiling water, it is important to ensure that the water reaches a rolling boil. This is because the high temperature is essential for killing the organisms present in the water. The time required for boiling depends on the elevation. If you are at an elevation below 5,000 to 6,500 feet, boil the water for at least one minute. At elevations above 5,000 to 6,500 feet, the boiling time should be extended to three minutes.

To purify water through boiling, start by placing the water in a clean container over a heat source, such as a campfire or stove. Bring the water to a rolling boil, maintaining the heat for the recommended time based on your elevation. Once the water has boiled sufficiently, remove it from the heat source and allow it to cool naturally. Avoid rapid cooling methods, as these can create a breeding ground for bacteria.

After boiling, it is important to store the purified water properly. Use clean containers with covers, preferably made of glass or stainless steel, and avoid plastic containers that can leach chemicals. Store the water in a cool, dry place, away from direct sunlight and any potential contaminants. Regularly clean and sanitize the containers to prevent the growth of bacteria and the formation of biofilms.

While boiling is an effective method for killing pathogens, it does not remove all types of contaminants. If the water source is known to be contaminated with pesticides, it is advisable to combine boiling with other treatment methods, such as filtration using specific types of filters. Activated carbon filters, for example, are effective at removing pesticides, herbicides, and other organic compounds. Reverse osmosis systems, which use pressure and semipermeable membranes, are also highly effective at removing pesticides and other contaminants from water.

Disinfecting

Reverse Osmosis (RO)

Reverse Osmosis is a water treatment process that forces water molecules through a semipermeable membrane, filtering out contaminants. RO systems are effective in removing pesticides, herbicides, and insecticides, with "GAC" (granulated activated carbon) filters reducing these pollutants by 97%-99%. They are also capable of filtering out THMs (trihalomethanes), such as chloroform, and other organic chemicals.

Ultraviolet (UV) Light Treatment

Treating water with UV light is another effective method to disinfect water. UV "probe" purifiers can be dipped into water, killing any pathogens present. Portable UV water purifiers are available for purchase online and can be battery-powered for convenience. For a more permanent solution, household UV purification systems can be installed, providing potable water directly from your plumbing.

Water Filtration Kits

Water filtration kits, specifically those designed for camping, offer a lightweight and easy-to-use option for water disinfection. These filters can be attached to water bottles and typically have an "absolute pore size" of 1 micron or less, ensuring effective filtration. The LifeStraw line of products is recommended by survival experts.

Chlorine Bleach

Regular chlorine bleach labeled for water sanitation can be used for water purification. Look for bleach containing 6% or 8.25% of sodium hypochlorite, and ensure the product label includes instructions for water purification. This method is suitable for stored water and can help prevent the growth of harmful microorganisms.

It is important to note that while these methods can effectively remove pesticides and other contaminants, the specific treatment process should be chosen based on the type of pesticide and the desired efficacy. Combining multiple techniques may also be beneficial to achieve the best results.

Frequently asked questions