Comparison Of Sludge Treatment By Gasification Vs. Incineration
Introduction
Digested sludge is a complex mixture of primary mineral grains and fragments of biological and industrial materials. Sewage sludge refers to the residual, semi-solid material left from the treatment of wastewater. The management of sludge plays an important role in wastewater treatment works. Sludge management can be divided into sludge production, treatment, and disposal. Production comprises the quantity and quality of the sludge produced at wastewater treatment plant; treatment comprises the various processes used to change sludge into a form that is acceptable for disposal; and disposal comprises the alternatives for ultimate disposal or utilization of sludge. The application of sewage sludge to agricultural land (which is the most common method of disposal) has become a cause for concern as a threat to human health and the environment. Incineration, which is a common thermal method of disposal, has also become a cause for concern because of its emissions into the air, soil and water. Within the last years, new thermal technologies have arisen in order to get the most of the byproducts of the sludge treatment. One of the thermal technologies that has gained popularity is gasification. Gasification of sewage sludge should produce energy with low emissions, the reduction of sludge to a useable fuel gas and a nonleaching, low-volume, dry residue which is easily to dispose. Both technologies have the potential to produce electricity and/or other products. This is possible because of the sewage sludge composition and its energetic characteristics.
Comparison Of Sludge Treatment By Gasification Vs. Incineration
Introduction
Digested sludge is a complex mixture of primary mineral grains and fragments of biological and industrial materials. Sewage sludge refers to the residual, semi-solid material left from the treatment of wastewater. The management of sludge plays an important role in wastewater treatment works. Sludge management can be divided into sludge production, treatment, and disposal. Production comprises the quantity and quality of the sludge produced at wastewater treatment plant; treatment comprises the various processes used to change sludge into a form that is acceptable for disposal; and disposal comprises the alternatives for ultimate disposal or utilization of sludge. The application of sewage sludge to agricultural land (which is the most common method of disposal) has become a cause for concern as a threat to human health and the environment. Incineration, which is a common thermal method of disposal, has also become a cause for concern because of its emissions into the air, soil and water. Within the last years, new thermal technologies have arisen in order to get the most of the byproducts of the sludge treatment. One of the thermal technologies that has gained popularity is gasification. Gasification of sewage sludge should produce energy with low emissions, the reduction of sludge to a useable fuel gas and a nonleaching, low-volume, dry residue which is easily to dispose. Both technologies have the potential to produce electricity and/or other products. This is possible because of the sewage sludge composition and its energetic characteristics.
Wastewater Biogas to Energy
Overview
The organic matter in raw wastewater contains almost 10 times the energy needed to treat it. Some wastewater treatment works (WWTW) can produce up to 100% of the energy they need to operate, though more typically 60% of operational energy can be produced. Biogas is typically used to meet on site power and thermal energy needs. Export of gas to local industrial users, power producers or for use as a municipal vehicle fleet fuel is also possible. In a wastewater treatment works (WWTW) biogas is produced when sludge decomposes in the absence of oxygen, in digesters. This process is referred to as Anaerobic Digestion. South Africa was one of the first countries in the world to utilise digesters as part of sludge management at WWTW. Digesters at WWTW were, however, not built to capture and use the biogas produced, but rather to assist in sludge management. In most cases, digesters can actually be refurbished to allow for biogas collection.
Biogas (a methane-rich natural gas) derived from anaerobic digestion and captured at WWTW plants provides a renewable energy source which can be used for electricity, heat and biofuel production. At the same time the sludge is stabilized and its dry matter content is reduced. This sludge, or digestate (remaining solid matter after the gas has been removed), contains valuable chemical nutrients such as nitrogen and potassium, and can be used as an organic fertilizer.
Wastewater Biogas to Energy
Overview
The organic matter in raw wastewater contains almost 10 times the energy needed to treat it. Some wastewater treatment works (WWTW) can produce up to 100% of the energy they need to operate, though more typically 60% of operational energy can be produced. Biogas is typically used to meet on site power and thermal energy needs. Export of gas to local industrial users, power producers or for use as a municipal vehicle fleet fuel is also possible. In a wastewater treatment works (WWTW) biogas is produced when sludge decomposes in the absence of oxygen, in digesters. This process is referred to as Anaerobic Digestion. South Africa was one of the first countries in the world to utilise digesters as part of sludge management at WWTW. Digesters at WWTW were, however, not built to capture and use the biogas produced, but rather to assist in sludge management. In most cases, digesters can actually be refurbished to allow for biogas collection.
Biogas (a methane-rich natural gas) derived from anaerobic digestion and captured at WWTW plants provides a renewable energy source which can be used for electricity, heat and biofuel production. At the same time the sludge is stabilized and its dry matter content is reduced. This sludge, or digestate (remaining solid matter after the gas has been removed), contains valuable chemical nutrients such as nitrogen and potassium, and can be used as an organic fertilizer.