The Wastewater Treatment Process and its Benefits: A Short Overview
By Amir Dakkak
With water shortages plaguing the world, water scarcity has become one of the largest threats facing society today, making it one of the UN's main millennium development goals. Therefore governments have begun developing new projects and technologies to mitigate its effects on the world. Such projects and technologies include rain harvesting, water location transfers, desalination, and wastewater treatment. Unlike the rest, wastewater treatment presents a sustainable short-term and long-term solution to water scarcity. Wastewater is water used by residences and commercial and industrial establishments that has become too polluted for use. The combination between these different types of wastewater causes the resulting wastewater mix to contain both suspended and dissolved organic and inorganic substances such as carbohydrates, fats, soaps, synthetic detergents, as well as various natural and synthetic organic chemicals. Therefore, the treatment process must be divided into different treatment stages to ensure good water and sanitation quality.
The preliminary stage of the treatment process uses large filtering screens that remove large solid inorganic material such as paper, plastic, and metal. This is followed by the removal of the grit and silt which are abrasive to plant equipment. In the primary stage, wastewater is passed through a primary sedimentation tank where solid particles of organic material are removed by gravity settling at the bottom of the tank. The resultant primary sludge is then raked to the center of the tank where it is concentrated and pumped away for further treatment. The wastewater then undergoes a biological process known as activated sludge process, which uses natural occurring micro-organisms to break down dissolved and suspended organic solids. The settled wastewater then enters aeration tanks where air is blown into the water to provide oxygen promoting the growth of microorganisms. These microorganisms then consume the organic pollutants and nutrients in the wastewater. From the aeration tanks the mixture of wastewater and microorganisms is moved to a secondary sedimentation tank where the biomass settles to the bottom of the tank and is concentrated as sludge. The clarified wastewater is then passed into a tank where the third stage of treatment, known as the Tertiary treatment stage, takes place. In this stage Chlorine is used to remove any biological pathogens present in the clarified wastewater that could be a risk to human health. In some instances this treatment is repeated more than once if the treated wastewater is reused for purposes such as irrigation of food crops or where close human contact may result.
After all these treatment processes are complete, fresh water is produced. However, the water treatment process does not only produce clean reusable water, but also has the potential to produce various other benefits. It has the potential to reduce a country's waste production, to produce energy through methane harvesting, and the potential to produce natural fertilizer from the waste collected through the process. Below is a more detailed explanation of these benefits:
Through the treatment of wastewater, the amount of waste that is usually released into the environment is reduced thus improving environment's health. By doing so, the government in turn reduces the health risks associated with environmental pollution, and reduces the water loss induced through water pollution. Wastewater treatment also reduces the amount of money spent by a country on environmental rehabilitation projects required to battle pollution.
The Sludge collected during the treatment process is itself treated because it contains a large amount of biodegradable material. It is treated with anaerobic bacteria in special fully enclosed digesters heated to 35 degreesCelsius, an area where these anaerobic microorganisms thrive without any oxygen. The gas produced during this anaerobic process contains a large amount of methane, which is harvested and then burned to generate electricity. This energy can be used to power the wastewater treatment plants making them self-sustainable, and if there happens to be an excess of energy produced, it could be transported into a country's national grid. This helps lower the reliance on non-renewable energy sources such as fossil fuels, reducing a country's carbon footprint and a country's expenditure on energy production. An example of this system being used within the Middle East can be found in al-Samra wastewater treatment plants in Jordan. According to government officials the plant produces 40% of the energy it requires through burning the methane produced by the treatment process.
Any biodegradable material remaining is dried in "drying lagoons" and is then turned into natural fertilizer. The resulting natural fertilizer is then used in the agricultural sector, increasing crop yields. This decreases the use of chemical fertilizers that pollute the surrounding marine and surface ecosystems.
In summary, the combination of these benefits along with water production makes wastewater treatment a sustainable short and long-term solution to the world's water crisis, which will only increase as the world population increases. It is estimated that the world's population is set to increase to 9 billion people, and this would cause an increase in the amount of water that can be treated. This will cause the production of large amounts of fresh usable water, thus helping battle water scarcity.
Source: Arab Water Source