By: Javier Vélez Arocho
Wastewaters are a nonavoidable problem when it comes to industrialization processes and development operations. These types of water contain non-natural components for the environment and, in significant quantities, can affect the ecosystem around it by altering the ecosystem’s natural processes. Nonetheless, they are almost always treated and cleaned before their discharge into the natural world.
How are wastewaters treated before arriving into the natural water bodies?
Traditional cleaning of wastewaters relies on industrial components to remove the solids, aeration of the water, filtration, disinfection, and oxygen intake. This approach renders the cleaning process in various stages and requiring different mechanisms of doing so. The transportation mechanism of these waters is typically seen as specific closed sewage systems that transport the water from the source directly to the treatment plant. Almost every traditional wastewater cleaning requires building a treatment plant with concrete pools and passages where the water is stored and moved through the cleaning stages. Also, they rely on significant energy input to drive the machinery and water pumps. Contrary to this process, wetlands are nature’s wastewater cleaners.
Wetlands: natures water treatment plants
Wetlands are areas where the water covers the soil or near the soil surface, depending on the tide. They harbor both aquatic and terrestrial species and the prolonged presence of water favor conditions for plants and wetland soils. The combination of the animals and plants that live on the different wetlands allows the water to be “filtered” and remove and store naturally occurring cycles such as carbon, sulfur, nitrogen, and water. Nonetheless, this requires a delicate balance, and the slightest alteration may affect this natural ecosystem. If exogenous factors alter the delicate balance, wetlands may be rendered unusable for natural water cleaning, and the species inhabiting them would cease to exist. When scientists noticed such use, they started experimenting with constructed wetlands for wastewater treatment.
Using wetlands to clean wastewaters
The use of constructed wetlands for wastewater treatment began in the early 1950s. Classifying the wetlands was based on vegetation type, hydrology, and flow direction for subsurface wetlands. They can treat all kinds of wastewater during their evolution and implementations, such as sewage, industrial and agricultural, landfill leachate, and stormwater runoff. It can effectively remove organics and solids but not too effective in removing nitrogen, although these processes can be enhanced.
Additionally, they do not require energy input, making the operation and maintenance very low compared to conventional treatments (Constructed Wetlands for Wastewater Treatment, 2010). Making the constructed wetlands a sustainable mode of water treatment would rely on the plant and substrate selection, water depth, loading rate, hydraulic retention time, and feeding mode (A review on the sustainability of constructed wetlands for wastewater treatment: Design and operation, 2011). It’s important to note that these systems may appear natural, but they are indeed carefully designed engineered systems for a specific water intake and wastewater type. They are also made to mimic natural processes and their associated plants, microorganisms to remove contaminants from the waters (EPA,1993).
By studying the components of making the wetland a sustainable way of treating wastewater, scientists found a way of making a self-sustainable treatment plant with an added element of harboring natural life and restoring the ecosystem’s processes. Some case studies find that they are effective in removing organic matter and nutrients from the wastewater. The benefit of using wetlands as a means of cleaning water relates directly to an improvement of water quality and the landscape purposes such as recreational opportunities, flora and fauna habitat, stormwater harvesting, aquifer retention system, flood retention, and community education. Additionally, these natural water treatment areas function as healthy, productive, diverse, and resilient (A case study on using constructed wetlands to treat wastewater as an alternative for the petroleum industry, 2007).
What are the steps to build a constructed wetland for wastewater treatment?
The first step must be contacting the appropriate agency to comply with specific requirements. But other actions might include obtaining permits related to wastewater discharge or zoning approval. Also, the contractor must develop a stormwater management plan since the wetland will inevitably receive stormwater due to its open concept. Finally, the document must include a discussion of the relationship of the proposed wetland with its surrounding streams or water bodies. Remember, there will be a discharge from the constructed wetland into the surrounding water bodies (A handbook of constructed wetlands).
How long can the wetland wastewaters be viable?
Data from few case studies suggest that the lifetime could be finite. Nonetheless, they will be highly dependent on the loading capacity of the wetland. Operating systems indicate that there is little to no effectiveness loss in 20 years. Nonetheless, the retained pollutant (phosphorus and metals) capacity of the wetland will decrease over time if no periodical removal is done. Other than that, treatment performance capacity, such as biological oxygen demand, suspended solids, and nitrogen, does not decrease if the loading rate is not altered (A handbook of constructed wetlands).
