Cleaning Polluted Water: How Long Does It Take?

Cleaning water polluted by human activity is a challenging and time-consuming task. The time it takes to restore a body of water depends on various factors, such as the type and extent of pollution, the methods employed, and the natural processes involved. Natural purification processes can take years, decades, or even centuries, while technological interventions, such as air stripping and filtration, can expedite the process but still require a significant amount of time. The cost of cleaning up water pollution can also be substantial, with estimates reaching up to one trillion dollars for existing environmental contamination in the United States alone. Despite the challenges, successful stories of water restoration, like First Fulda Lake in Minnesota, demonstrate that it is possible to reverse the effects of water pollution with dedication, patience, and collective effort.

How long does it take to clean water from pollution?

The Clean Water Act

The basis of the CWA was enacted in 1948 as the Federal Water Pollution Control Act, but it underwent significant reorganization and expansion in 1972, with subsequent major amendments in 1977 and 1987. Growing public awareness and concern for controlling water pollution led to these sweeping amendments in 1972, which gave the Environmental Protection Agency (EPA) the authority to implement pollution control programs. The EPA, in coordination with state governments, administers the laws and regulations of the CWA.

The CWA made it unlawful to discharge any pollutant from a point source into navigable waters without a permit. The EPA's National Pollutant Discharge Elimination System (NPDES) permit program controls these discharges, with new sources being subject to more rigorous effluent limits. The Act also funded the construction of sewage treatment plants and recognized the need to address critical problems posed by nonpoint source pollution.

The CWA has been amended several times to address emerging issues, such as the Oil Pollution Act of 1990, which provided new requirements for contingency planning and increased penalties for noncompliance. The Water Infrastructure Finance and Innovation Act of 2014 (WIFIA) expanded the credit program for water and wastewater infrastructure projects, and the Clean Water State Revolving Fund replaced the construction grants program to address water quality needs through EPA-state partnerships.

Despite the progress made under the CWA, challenges remain. Limited monitoring of water bodies has been noted, and the EPA's 2017 report found that only about half of U.S. waters had been assessed. Climate change is also presenting new threats, and further actions are needed to strengthen the Act and meet its goals.

Air stripping

The technology is based on Henry's Law, which states that, at a constant temperature, for a system containing a liquid phase and a gas phase, the partial pressure of the gaseous substance above the liquid is proportional to the concentration of the dissolved substance in the liquid. The Henry's Law coefficient, or the ratio of the concentration in air that is in equilibrium with its concentration in water, is higher for pollutants that can be more easily and economically stripped from water. These include BTEX compounds (benzene, toluene, ethylbenzene, and xylene found in gasoline) and solvents such as trichloroethylene and tetrachloroethylene.

There are several types of air strippers, including towers, stacked trays, and sliding trays. The two most common types of towers are packed towers and sieve tray towers. Packed towers use a distributor at the top to evenly distribute engineered plastic, ceramic, or metal packing material to maximize air-water contact. The high surface area provided by the packing material, along with the column height and diameter, and air-to-water flow rates, are critical design criteria for maximizing the efficiency of removing contaminants. Sieve tray towers, on the other hand, use a series of stacked trays with baffles and weirs to route contaminated water multiple times along the length of the tray, while air is sparged through the bottom of the tray in a countercurrent direction to strip out the contaminants.

While air stripping can be an effective method for removing volatile organic compounds (VOCs) and other contaminants, it is important to note that the process can take a significant amount of time. The rate at which air stripping can remediate a groundwater source varies, but it typically takes many years to clean up a contaminated site. Additionally, the water that reaches the bottom of the system may be considered treated, but additional testing is often necessary to determine if it is safe for consumption. Furthermore, since many of the compounds stripped are hazardous air pollutants, the air exiting the stripper may require emissions control using methods such as carbon adsorption or catalytic oxidation.

Activated carbon filters

There are two main types of activated carbon filters: granular activated carbon (GAC) and carbon block filters. GAC filters contain loose, millimeter-sized granules of activated carbon, while carbon block filters have pores measuring less than one micron, blocking the passage of contaminants like cysts. GAC filters are made from raw organic materials with high carbon content, such as coconut shells, coal, wood, or other natural materials. Coconut shell carbon is the most renewable option. Carbon block filters, on the other hand, use mechanical filtration to block contaminants, ensuring only clean water passes through.

The lifespan of an activated carbon filter depends on its level of activated carbon content and the contaminant levels in the water. Filters with higher levels of activated carbon will generally last longer and require fewer replacements. It's important to replace the filters periodically to maintain their effectiveness and prevent bacterial buildup. The frequency of replacement will depend on the specific filter and the level of contaminants in the water. Some filters may last for several years if contaminant levels are low, while others may need more frequent changes.

Bioremediation

One of the key advantages of bioremediation is its ability to minimize damage to ecosystems. It relies solely on natural processes and does not require substantial equipment or labour, making it a cost-effective solution. Additionally, it creates relatively few harmful by-products as contaminants are converted into water and harmless gases like carbon dioxide.

There are various techniques used in bioremediation to enhance the process. One technique is bioaugmentation, where bacteria are added to the surface of the affected area and allowed to grow. Another technique is intrinsic bioremediation, which utilizes the native microbiome on the affected area to convert toxic materials into inert materials. Mycoremediation is a unique form of bioremediation that relies on fungi rather than bacteria or other microbes to decontaminate an area.

Community action

Cleaning up water pollution is a challenging and time-consuming task, but it is not impossible. It requires the collective efforts of communities, organizations, and industries to implement effective solutions. Here are some ways in which communities can take action to address water pollution:

Education and Awareness:

Community members can educate themselves and others about the issues related to water pollution. Understanding the sources and impacts of pollution is crucial for devising effective solutions. Educational resources, such as the Chesapeake Bay Foundation's publications and programs, can be utilized to raise awareness, especially among younger generations.

Political Advocacy:

Informed voters can exert significant influence by supporting thoughtful and responsible land use policies and candidates who prioritize conservation and clean water initiatives. Staying updated on regional and watershed-specific news helps individuals advocate for specific environmental issues in their communities.

Local Action:

Community members can take direct action to address local water pollution. This may include participating in river or lake clean-up efforts, such as removing trash and debris from water bodies and their surrounding areas. Additionally, individuals can adopt practices that reduce pollution in their daily lives, such as properly disposing of harmful substances, minimizing the use of lawn fertilizers and chemicals, and maintaining septic systems to prevent groundwater contamination.

Collaboration and Partnerships:

Collaborating with local organizations, such as the Chesapeake Bay Foundation or similar groups, can amplify community efforts. These organizations often have the resources and expertise to facilitate effective pollution reduction initiatives.

Landscape and Gardening Practices:

Implementing Bay-friendly landscaping techniques, such as using native plants that require less watering and fertilizing, can reduce stormwater runoff and minimize the use of chemicals. Addressing both human-caused and natural erosion, as in the case of the Poplar River, can also help improve water quality.

Support for Indigenous Stewardship:

Indigenous communities have long played a vital role in land stewardship and conservation. Supporting their efforts and providing them with the necessary resources can help ensure the sustainable management of water resources.

While the Clean Water Act has made significant strides in reducing water pollution, community action remains essential to complement and enhance these regulatory efforts. By taking ownership and actively participating in pollution reduction initiatives, communities can make a lasting impact on the health of their local water bodies.

Frequently asked questions