CE 356: Fundamentals of Environmental Engineering (Microbiology and Activated Sludge Design)
CE 356: Fundamentals of Environmental Engineering (Microbiology and Activated Sludge Design)
By Ricardo B. Jacquez
Professor, CAGE Department
New Mexico State University
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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.
Enhanced Anaerobic Digestion and Hydrocarbon Precursor Production from Sewage Sludge
. Ultimate Goal: Transform negative-value or low-value biosolids into high-energy-density, fungible hydrocarbon precursors.
.Enables sustainable production of biogas that is considered as a cellulosic biofuel under new RFS2 (EPA, July 2014).
.Addresses DOE's goals of development of cost-competitive and sustainable biofuels by advancing efficient production strategies for drop-in biofuels.
Enhanced Anaerobic Digestion and Hydrocarbon Precursor Production from Sewage Sludge
. Ultimate Goal: Transform negative-value or low-value biosolids into high-energy-density, fungible hydrocarbon precursors.
.Enables sustainable production of biogas that is considered as a cellulosic biofuel under new RFS2 (EPA, July 2014).
.Addresses DOE's goals of development of cost-competitive and sustainable biofuels by advancing efficient production strategies for drop-in biofuels.
Drinking Water Treatment Plant Residuals Management Technical Report
INTRODUCTION
The U.S. Environmental Protection Agency (EPA) completed a review of discharges from water treatment plants (WTPs). The purpose of this report is to summarize the data collected during this review (principally covered in Sections 2, 3, 9, 10, and 11) and to serve as a technical resource to permit writers (primarily covered in Sections 4 through 8 and Sections 12 and 13). EPA selected the drinking water treatment (DWT) industry for a rulemaking as part of its 2004 Biennial Effluent Limitations and Guidelines Program planning process. EPA is not at this time continuing its effluent guidelines rulemaking for the DWT industry. In the 2004 Plan, EPA announced that it would begin development of a regulation to control the pollutants discharged from medium and large DWT plants. See 69 FR 53720 (September 2, 2004). Based on a preliminary study and on public comments, EPA was interested in the potential volume of discharges associated with drinking water facilities. The preliminary data were not conclusive, and the Agency proceeded with additional study and analysis of treatability, including an industry survey. After considering extensive information about the industry, its treatment residuals, wastewater treatment options, and discharge characteristics, and after considering other priorities, EPA has suspended work on this rulemaking.
Drinking Water Treatment Plant Residuals Management Technical Report
INTRODUCTION
The U.S. Environmental Protection Agency (EPA) completed a review of discharges from water treatment plants (WTPs). The purpose of this report is to summarize the data collected during this review (principally covered in Sections 2, 3, 9, 10, and 11) and to serve as a technical resource to permit writers (primarily covered in Sections 4 through 8 and Sections 12 and 13). EPA selected the drinking water treatment (DWT) industry for a rulemaking as part of its 2004 Biennial Effluent Limitations and Guidelines Program planning process. EPA is not at this time continuing its effluent guidelines rulemaking for the DWT industry. In the 2004 Plan, EPA announced that it would begin development of a regulation to control the pollutants discharged from medium and large DWT plants. See 69 FR 53720 (September 2, 2004). Based on a preliminary study and on public comments, EPA was interested in the potential volume of discharges associated with drinking water facilities. The preliminary data were not conclusive, and the Agency proceeded with additional study and analysis of treatability, including an industry survey. After considering extensive information about the industry, its treatment residuals, wastewater treatment options, and discharge characteristics, and after considering other priorities, EPA has suspended work on this rulemaking.
Sludge Dehydration Technologies
INTRODUCTION
Dewatering is a physical process integrated in the sludge line of treatment plant. It is aimed at reducing the water content and therefore the sludge volume. In this way, its transportation costs to the final destination point is reduced. On the other hand, the dewatered sludge is easier to handle and the transport process is more convenient than in the case of a sludge with higher water content.
The dewatering technique chosen must be consistent with the amount and characteristics of sludges generated and with the biosolid final destination.
Water present in the sludge exists in four forms (see figure): free, colloidal, intercellular and capillary. Free water can be separated from sludge by gravity as it is not associated with solids. Chemical conditioning prior to the use of mechanical tools is required in order to remove colloidal and capillary water. For intercellular water removal, the structure containing it must be broken and this can be done through heat treatment.
Sludge Dehydration Technologies
INTRODUCTION
Dewatering is a physical process integrated in the sludge line of treatment plant. It is aimed at reducing the water content and therefore the sludge volume. In this way, its transportation costs to the final destination point is reduced. On the other hand, the dewatered sludge is easier to handle and the transport process is more convenient than in the case of a sludge with higher water content.
The dewatering technique chosen must be consistent with the amount and characteristics of sludges generated and with the biosolid final destination.
Water present in the sludge exists in four forms (see figure): free, colloidal, intercellular and capillary. Free water can be separated from sludge by gravity as it is not associated with solids. Chemical conditioning prior to the use of mechanical tools is required in order to remove colloidal and capillary water. For intercellular water removal, the structure containing it must be broken and this can be done through heat treatment.
Sewage Sludge Management In Germany
Introduction
What is sewage sludge?
In Germany, daily water use now reaches 120 litres per person. All of this water ultimately ends up in the sewage system, and from there is channelled to sewage treatment plants. At such plants, the sewage passes through screens and sieves and undergoes mechanical and biological purification,
the goal being to remove impurities from the sewage and to then channel the resulting purified water into waterbodies. The residue of this process is known as
sewage sludge, which can occur in anhydrous, dried or other processed forms.
Sewage Sludge Management In Germany
Introduction
What is sewage sludge?
In Germany, daily water use now reaches 120 litres per person. All of this water ultimately ends up in the sewage system, and from there is channelled to sewage treatment plants. At such plants, the sewage passes through screens and sieves and undergoes mechanical and biological purification,
the goal being to remove impurities from the sewage and to then channel the resulting purified water into waterbodies. The residue of this process is known as
sewage sludge, which can occur in anhydrous, dried or other processed forms.
Feasibility Study for Production of Biogas from Wastewater and Sewage Sludge – Development of a Sustainability Assessment Framework and its Application
Abstract
Clean water and renewable energy are essential requirements to build resilience towards the adverse effects of climate change and global warming. Advanced wastewater treatment
options may provide a unique opportunity to recover various useful resources such as energy (biogas), fertilizers, minerals, and metals embedded in the wastewater stream. However,
considerable challenges remain when it comes to designing and planning sustainable wastewater treatment systems. This thesis focuses on the avenues of energy recovery from wastewater treatment plants (WWTP), by evaluating the potential for biogas recovery from wastewater and sewage sludge treatment in WWTPs. Various available technologies for biogas recovery are examined and evaluated to understand their viability in different applications and relative performance. Further, the methodologies and tools employed to assess such energy recovery systems are evaluated, covering the technical, economic, and environmental performance aspects. A sustainability assessment framework is then developed, using appropriate sustainability indicators to assess performance. The framework is applied to a case study of a WWTP in the emerging city of Tbilisi, Georgia. A spreadsheet tool is also developed to aid the sustainability (techno-economic and environmental) assessments for the case study. The case study results reveal a significant biogas recovery potential, with an annual energy generation potential of 130 GWh from combined heat and power (CHP) recovery, and a potential to avoid 28,200 tCO2eq emissions every year when biogas is recovered only from the wastewater. The recovery potential increases when biogas is recovered from both wastewater and sewage sludge. Further, the contribution of overall resource (energy and nutrient) recovery in WWTPs to the Sustainable Development Goals is examined. By studying the linkage of various benefits to the different SDGs, the multilateral and cross-cutting nature of benefits from resource recovery is clearly illustrated. The thesis concludes with a discussion of possible future technologies and perspectives that can enhance the sustainability of WWTPs and help transform them into Wastewater Resource Recovery Facilities (WRRFs).
Feasibility Study for Production of Biogas from Wastewater and Sewage Sludge – Development of a Sustainability Assessment Framework and its Application
Abstract
Clean water and renewable energy are essential requirements to build resilience towards the adverse effects of climate change and global warming. Advanced wastewater treatment
options may provide a unique opportunity to recover various useful resources such as energy (biogas), fertilizers, minerals, and metals embedded in the wastewater stream. However,
considerable challenges remain when it comes to designing and planning sustainable wastewater treatment systems. This thesis focuses on the avenues of energy recovery from wastewater treatment plants (WWTP), by evaluating the potential for biogas recovery from wastewater and sewage sludge treatment in WWTPs. Various available technologies for biogas recovery are examined and evaluated to understand their viability in different applications and relative performance. Further, the methodologies and tools employed to assess such energy recovery systems are evaluated, covering the technical, economic, and environmental performance aspects. A sustainability assessment framework is then developed, using appropriate sustainability indicators to assess performance. The framework is applied to a case study of a WWTP in the emerging city of Tbilisi, Georgia. A spreadsheet tool is also developed to aid the sustainability (techno-economic and environmental) assessments for the case study. The case study results reveal a significant biogas recovery potential, with an annual energy generation potential of 130 GWh from combined heat and power (CHP) recovery, and a potential to avoid 28,200 tCO2eq emissions every year when biogas is recovered only from the wastewater. The recovery potential increases when biogas is recovered from both wastewater and sewage sludge. Further, the contribution of overall resource (energy and nutrient) recovery in WWTPs to the Sustainable Development Goals is examined. By studying the linkage of various benefits to the different SDGs, the multilateral and cross-cutting nature of benefits from resource recovery is clearly illustrated. The thesis concludes with a discussion of possible future technologies and perspectives that can enhance the sustainability of WWTPs and help transform them into Wastewater Resource Recovery Facilities (WRRFs).
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