Cleaning Polluted Water: Nature's Way

Cleaning polluted water is a challenging and costly endeavour, but it is not impossible. The first step in cleaning a polluted river or lake is to stop new pollution from entering the water, allowing the ecosystem to recover naturally over time. This can involve removing garbage, demolishing abandoned structures, and eliminating sources of pollution, such as drain pipes from industrial buildings. In some cases, contaminated sediment may be dredged or covered with clean sediment. Disinfection methods, such as boiling, chemical treatments, and filtration, can also be used to purify contaminated water, but they may not be effective against all types of pollutants and parasites.

Characteristics of Polluted Water Cleaning

Stop adding new pollution to the water source

Preventing new pollution from entering a water source is critical to maintaining water quality and reducing the costly and time-consuming process of cleaning polluted water. Here are some ways to stop adding new pollution to a water source:

Land Management and Conservation

Proper land management practices are essential to preventing pollution. This includes implementing erosion control measures, such as planting buffer strips along streams to minimize soil loss and reduce sedimentation in water bodies. Additionally, creating rotational grazing systems for livestock can help reduce pasture erosion and give vegetation time to recover.

Stormwater Management

Stormwater runoff is a significant source of pollution. In urban areas, impermeable pavement increases stormwater runoff, leading to downstream flooding and stream bank erosion. To mitigate this, individuals can implement rainwater harvesting systems, such as rain gardens or connecting downspouts to rain barrels. When replacing driveways, consider using porous pavement that allows stormwater to infiltrate the ground.

Septic System Maintenance

Septic tanks play a crucial role in treating wastewater. Proper maintenance of septic systems is essential to prevent the release of bacteria, viruses, and chemicals into local water bodies. Regularly inspect and maintain your septic tank to ensure it functions properly, reducing the risk of contaminating groundwater and surface water.

Chemical and Fertilizer Use

Fertilizers, pesticides, and other chemicals can contaminate water sources if used improperly. Limit the use of these substances and always follow label directions. Avoid applying fertilizer before rainy weather, as the chemicals can wash into storm drains and waterways. Sweep or blow fertilizer back onto the grass if it lands on paved areas. Consider using fertilizers with low or no phosphorus if your lawn is already established, as established lawns typically have sufficient phosphorus levels.

Public Education and Participation

Communities, citizen groups, and individuals can play an active role in protecting water sources. Educate the public about water quality threats, such as polluted runoff, and provide clear instructions on proper waste disposal. Stenciling messages near street drains or distributing flyers can effectively remind people not to dump waste into drains, which often lead directly to local water sources. Additionally, posting signs along the borders of source water protection areas can help notify people that pollution in these areas can impact drinking water quality.

Remove garbage and abandoned structures

One of the most important steps in cleaning polluted water is removing the source of pollution to prevent further contamination. This can involve simple actions like properly disposing of hazardous household items, such as oils, anti-freeze, paint, solvents, and prescription drugs, by taking them to designated drop-off locations instead of pouring them down the drain. Additionally, individuals can reduce pollution by using less and properly disposing of harmful substances.

On a larger scale, government regulations play a crucial role in minimizing industrial and agricultural pollution practices. These regulations set limits on air and effluent emissions, determine permissible pollutant levels, and outline proper waste disposal methods. In the United States, the Clean Water Act establishes water quality standards, including antidegradation statements, designated stream uses, and water quality criteria.

To address aquatic trash, the U.S. Environmental Protection Agency (EPA) has implemented the Trash Free Waters (TFW) program, which focuses on both prevention and removal of garbage from U.S. rivers, lakes, streams, and creeks. This program also supports beach and watershed cleanups to remove marine debris, including derelict vessels and abandoned fishing gear.

One effective method to prevent stormwater pollution from entering waterways is to install hydrodynamic separators in stormwater treatment systems. These separators act as flow-through structures with settling or separation units to remove sediments, floatables, and other pollutants. They come in various sizes, with some small enough to fit in conventional manholes. Vacuum trucks are then used to clean these separators by pumping out the collected trash, sediment, and water.

Upgrading wastewater treatment facilities can also significantly reduce water pollution. While most urban centres have secondary treatment processes, investing in tertiary treatment can specifically target and remove phosphorus, which contributes to excess algae growth.

Use filtration systems

Filtration systems are an effective way to clean polluted water. Water filtration involves passing water through a permeable substrate or filter to remove impurities. This method can be applied through natural or man-made systems.

Natural filtration systems use materials like sand, gravel, and rocks to filter water. For instance, wetlands act as natural filters, helping to reduce water pollution. The erosion of rocks and sand by natural processes creates tiny spaces between the particles, which allow water to pass through slowly while trapping dirt particles. These natural filters can be further enhanced by planting reeds, which are effective at absorbing excess nutrients and toxins from the water.

Another natural filtration method involves creating shallow ponds or swales lined with gravel or wood chips. This system allows water to soak into the ground, filtering out contaminants. The filtered water then permeates through the earth for further cleaning as it moves through sand, rock, and clay.

In addition to natural systems, man-made filtration systems can also be employed. For example, researchers at MIT have developed a new filtration material made from natural substances like silk and cellulose. This material can effectively remove "forever chemicals" like PFAS and heavy metals from drinking water. The filtration system can be attached to a kitchen faucet or scaled up to provide filtration for municipal water supplies.

Overall, filtration systems offer a promising approach to cleaning polluted water, utilizing both natural and man-made processes to remove impurities and restore water quality.

Use chemical disinfectants

Chemical disinfectants are often used to clean and purify polluted water. This is a common method, especially in emergency situations where regular water services have been interrupted, such as after a hurricane, flood, or water pipe breakage. Local authorities may advise using bottled water, boiled water, or chemically disinfected water until regular water services are restored.

Chemical disinfectants are effective in killing most disease-causing microorganisms, such as pathogenic bacteria, viruses, and protozoa. However, it is important to note that boiling or disinfection may not eliminate other contaminants like heavy metals, salts, and most chemicals.

One common chemical disinfectant is household bleach. It is crucial to use only regular, unscented chlorine bleach products that are specifically intended for disinfection and sanitization. The bleach may contain 6% or 8.25% sodium hypochlorite, and the amount of bleach added to the water depends on this concentration. For instance, 8 drops of 6% bleach or 6 drops of 8.25% bleach can be added to each gallon of water. If the water is cloudy, coloured, or very cold, the amount of bleach should be doubled. After stirring, the water should be allowed to stand for 30 minutes. If the chlorine taste is too strong, pouring the water between clean containers and letting it stand for a few hours can help reduce the chlorine taste.

Another chemical disinfectant is granular calcium hypochlorite, often known as HTH. This method involves creating a chlorine solution by dissolving one heaping teaspoon (approximately 1/4 ounce) of HTH in two gallons of water. This solution yields approximately 500 milligrams of chlorine per litre. To disinfect the water, one part of this solution is added to every 100 parts of water being treated. Similar to the previous method, if the chlorine taste is too strong, pouring the water between containers and letting it stand can help reduce the taste. It is important to handle and store HTH carefully, as it is a powerful oxidant.

Water can also be disinfected using common household iodine, or "tincture of iodine". Five drops of 2% iodine should be added to each quart or litre of water being disinfected. If the water is cloudy or coloured, the number of drops should be increased to 10. After stirring, the water should be allowed to stand for at least 30 minutes before use.

Additionally, water disinfection tablets containing chlorine, iodine, chlorine dioxide, or other disinfecting agents are available online and at pharmacies and sporting goods stores. These tablets provide a convenient option for disinfecting water.

Bioremediation

Another method of bioremediation is bioventing, which involves injecting air into a saturated zone to encourage the movement of flammable organic chemicals upward to a nearby unsaturated zone. The success of this method depends on soil porosity and contaminant biodegradability. When used in conjunction with soil vapour extraction (SVE), bioventing can be even more effective. In situ air sparging (IAS) uses high airflow rates to volatilize contaminants, while biosparging encourages microbial degradation.

Microbial bioremediation is a specific type of bioremediation that uses prokaryotes (or microbial metabolism) to remove pollutants. This process has been used successfully for thousands of years in sewage treatment. Microbial bioremediation can also be used to remove certain toxic metals and oxides, such as selenium and arsenic compounds, from water. For example, bacteria can convert toxic mercury into non-toxic forms through anaerobic respiration.

Frequently asked questions