Waste is a resource, and this saying is true for wastewater also. Wastewater contains municipal solid waste, household waste, agricultural waste, and industrial waste. Each year, around 359 billion cubic meters of wastewater are produced. About 48 percent of wastewater is released untreated. Wastewater itself is not a resource until it’s treated. Treatment of wastewater produces very useful products that could be used as a source of energy. This article will give you an insight into different possibilities to use wastewater. Before beginning, let’s learn the treatment processes and useful products obtained.
Each year, around 359 billion cubic meters of wastewater are produced
Composition of wastewater
Wastewater contains a variety of materials from wood, paper, clothes to pesticides, fertilizers, human waste, and many more. The purpose of treatment is to separate the material that’s not useful and could damage the treatment plant. The first step is the preliminary and primary treatment, and it’s a physical step -requiring no chemical and biological treatment. This step is employed to remove 100 percent floatable material from wastewater, around 70% suspended material, and decrease the BOD of water by 50%.
Secondary treatment is a biological treatment, and its byproduct is activated sludge – both wet and dry. European Union countries produce 10.5 million tons of dry biosolid each year.
The water obtained after secondary treatment can be used for domestic purposes, aquaculture, gardening, firefighting, and in industries. However, tertiary treatment could make water drinkable.
Wastewater as Energy source
The question that always pops up in mind when we hear the word waste-to-energy is, how will wastewater produce energy? Well, the procedure is quite simple and obvious. Carbon is extracted from wastewater, and controlled pressure is maintained in the presence of bacteria. The biogas is obtained that is burned to produce electricity.
The question of whether we can use a byproduct of wastewater treatment as a source of energy is highly dependent upon the calorific value of fuel obtained. A study conducted in Taiwan has shown that biosolid is the best available source of energy for combustion. Moreover, they have fewer environmental impacts, thus making a win-win situation for waste management and energy production.
Production of Biosludge
After secondary treatment, activated sludge is produced that is a rich source of nutrients. Hydrothermal carbonization is an innovative process to convert sludge into energy. Furthermore, gas and processed water are obtained during this process. Hydrothermal Carbonization (HTC) is a cost-effective and environmentally friendly method for the production of hydrochar. Hydrochar could be used as a substitute for sub-bituminous coal. Thus, it has wide applications in the industrial and transportation sector. It can also use for carbon sequestration and soil remediation. Processed water produced as a byproduct is rich in nutrients – both macronutrients and micronutrients – therefore could be directly applied to crops as a fertilizer.
Bio sludge can be utilized using the thermochemical process to produce biochar, bio-oil, syngas, and flue gas. Gasification of biomass produces biochar and bio-oil that have several applications in agricultural fields and MSW incineration plants, respectively. Syngas produced during the process is a mixture of different gases – hydrogen and carbon dioxide – that can be used as fuel in internal combustion engines to generate electricity.
Production of Methane Gas
Thermal hydrolysis of sludge produces a large amount of methane gas that can fulfill the energy demand of the running plant. Digestate is produced during the anaerobic digestion of sludge that increases the growth of plants.
Benefits of using wastewater for energy
Harnessing energy from sludge could help to tackle many environmental and economic issues. Here are some benefits of converting wastewater to energy.
1 – Waste Management
Developing countries have lacked the infrastructure to manage wastewater. There’s also no compliance with environmental laws and regulations; therefore, industries discharge their waste in water bodies without treatment. This leads to water pollution. Treatment of wastewater not only makes it useable but also produces valuable products from material present in water. Thus, enable countries to tackle the issue in a more sophisticated manner.
2 – Energy Production
Industrial development is the prime privilege of every country that is not possible without energy. Industries use fossil fuels that have great environmental impacts. In comparison, energy from waste is cheap and renewable. The plants that convert waste into energy could utilize the gas produced during the process itself. Waste production is unavoidable, so this is the best possible solution for waste management.
3 – Reduce Emissions
Whenever industries use methane gas for heating purposes, many pollutants are released into the environment. Methane itself is a potent greenhouse gas that is 28 times more potent than carbon dioxide. Therefore, a small amount of methane in the atmosphere accounts for HUGE impact. The anaerobic digestion of wastewater produces methane gas that can be used for industrial and commercial purposes. Hence, the generation of energy from waste can combat the issue of energy requirements.
Is it Operational?
Although the concept of conversion of waste-to-energy is old, it’s not yet commonplace. To name a few, China, US, Brazil, and Norway are the countries that turn wastewater into energy. A report in 2015 has found that one sludge-to-waste plant could produce enough energy to fulfill the gas demand of 300 cars. The figures show that the production of energy from wastewater has potential and will be widely popular in the near future.
Waste is the bigger problem of today’s world, and it’s growing each year. Management of Wastewater is one of the problems that need to be addressed. Different types of material are present in wastewater. Variation in the composition of wastewater makes it useful for different purposes. Wastewater itself cannot be used as energy. However, byproducts at each level of treatment make a good portion of resources. Biogas, Bio-oil, and fertilizers are some products that have industrial demand. The water obtained after treatment is employed in aquaculture, gardening, and firefighting. Lastly, more advanced treatment can make the water fit for drinking purposes as well. Thus, wastewater-to-energy has the potential to combat the rising issue of climate change and waste management.
- An Analysis of the Use of Biosludge as an Energy Source and Its Environmental Benefits in Taiwan by Wen-Tien Tsai