Guidelines for Using Activated Sludge Models

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.

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).

This study examines a potential membrane evaporation process to reduce brine concentrate volume at the San Antonio Water System’s (SAWS) 45.4 million liters per day (MLD) brackish water desalination facility in San Antonio, Texas, which is currently being constructed. This facility is a reverse osmosis (RO) process operating with 90% recovery by blending 37.9 MLD of permeate with 7.6 MLD of bypass water, producing 4.2 MLD of brine concentrate. The brine concentrate residuals are to be disposed of through deep-well injection. The deep-well injection process is anticipated to be expensive due to well-drilling costs and maintenance costs of operating at high injection pressures. Membrane evaporation systems are promising because they are compact systems and they can be used with low grade waste heat energy sources. This study investigates the potential of coupling membrane evaporation with waste heat generated from activated sludge aeration blowers.