Storm water is water that is produced from rain, and possibly melting snow and ice, which flows over solid surfaces, capturing gross pollutants, sedimentation, nutrients, heavy metals and a wide range of other pollutants. The majority of this water infiltrates into the soil, or evaporated or run off and enter nearby waterways. In natural areas, free from construction, buildings, motorways and agriculture etc. the water just soaks and absorbs into the soil or evaporates. In developed areas, not only does the range and concentrations of pollutants grow and grow, but the areas in which the water is usuall absorbed or evaporated is removed, the storm water is funneled through stormwater drainage systems and directly into our rivers, streams and waterways. The natural processes of stormwater removal such as infiltration evaporation and filtering are greatly reduced, causing the concentrations and size of pollutants entering our waterways to drastically increase.
Stormwater treatment and management is about protecting our environment. When we develop stormwater treatment systems we are designing ways in which to protect our environment, and rid our environment and ecosystems of pollution and contamination. Hence the need for these systems is vital for our environment and ecosystems health and prolonged life. From gross pollutant traps which remove larger plastics, debris and sedimentation from our waterways, keeping our oceanic and water ecosystems protected from the well-known dangers of ocean and marine life coming into contact with plastics, to our tertiary treatments to remove heavy metals, organic nutrients and colloidal fine particles from our water systems and prevent from poisoning the environment. If the management of stormwater is conducted properly, with effective and efficient technologies in place, we can improve our water ecosystems and effectively lengthen our environments life.
Not only does proper stormwater treatment and management protect our environment, it also has several other benefits that are less widely known. These management systems can reduce flooding to protect people’s lives and properties, reduce the demand on public stormwater drainage systems, support healthy streams and rivers, and create healthier, more sustainable and viable communities. Effective stormwater management provides not only vital environmental benefits, it also provides social, economic and communal benefits.
It’s important in society to maintain a clear image of the bigger picture. As our society continues to grow in population and city size, we increase the area covered by impervious and non –absorbent surfaces that do not allow infiltration and absorption and in turn increase the amount of polluted runoff. We must continue to implement these stormwater treatment technologies not for just the current benefit, but also for the future and more vital benefits.
Hydrocarbons make up a large majority of the pollutants present in water, being produced from fueling stations, cars and motor vehicles and in industrial processes. If these hydrocarbons flow into the stormwater systems through surface runoff they must be treated efficiently and completely. Large proportions of hydrocarbons and oils in water ways is extremely harmful to the ecosystem life that exists in the water systems that follow our stormwater treatment. There are several efficient processes of hydrocarbon removal:
- Gravity Separation – This principle works off a simple theorem, Stokes Law. This defines that the buoyant velocity rise of a droplet is greatest when the density of the droplet, in this case oil, is greater than the density of the continuous phase, the water. This hence means that oil particles and hydrocarbons will always rise to the surface of water. Hence this process can be used to separate the hydrocarbons from water in a non-turbulent flow, such as in a storage or retention system.
- Coalescence – In water treatment, the energy that is input into water is very low, causing the process of coalescence to occur in what small oil droplets collide and form bigger droplets, and due to the low energy these particles do not disperse. This process allows for the particles to be removed more simply.
- Adsorption – This process is the adhesion of atoms, ions or molecules (such as hydrocarbons) to a surface. This is a surface phenomenon in which the hydrocarbons will attach themselves to the surface of another system (such as the filter systems) and hence be removed from the flow of water.
In reality a combination of these processes is the best process for the removal of hydrocarbons from stormwater. Systems that encapsulate these are the greatest for hydrocarbon removal and management.