The Greater Vancouver Regional District (GVRD) is a major regional agency managing wastewater collection and treatment for Vancouver, Canada and surrounding municipalities. As part of their $ 600 million program to upgrade 2 major plants to secondary treatment, the GVRD was faced with the requirement to produce a treated biosolids meeting the equivalent of a U.S. EPA Class A product to assure success of their new biosolids beneficial use program. Various alternatives to achieve a Class A product were evaluated in detail. The GVRD selected a new and innovative process which they termed extended thermophilic anaerobic digestion. The characteristics of this process which help achieve required pathogen kills are the thermophilic operating temperatures and the series operation of reactors, cutting the bleed-through of pathogens observed in conventional complete mix systems. The new thermophilic digesters have been in operation since 1996 and the flow-through vessels required to complete “extended” operation will be complete in late 1998.
The Western Lake Superior Sanitary District at Duluth, Minnesota is implementing major biosolids program changes involving the Temperature Phased Anaerobic Digestion (TPAD) process. The District's treatment plant has no digestion facilities currently, and, therefore, this project represents a major departure from the existing District sludge incineration system. This paper primarily describes the development of the digestion facilities design at the District's 162 megaliter/day (43 mgd) municipal wastewater plant. This development work involved a significant pilot testing program at Iowa State University to confirm performance of potential Class A sludge digestion processes. In particular, hydraulic retention times within the thermophilic and mesophilic stages of the TPAD system were varied to assess process performance. Additional evaluation and engineering work resulted in technical information used to develop the project design. Considerable input from and discussion with District staff occurred to develop the design and obtain concurrence on key issues. Facilities described are currently under construction.
The Western Lake Superior Sanitary District (WLSSD) is located on the western shore of Lake Superior in Duluth, Minnesota. The WLSSD has undertaken a major change in its biosolids program, shifting from sludge co-incineration with solid waste to temperature phased anaerobic digestion (TPAD) and land application. A majority of the loading to the plant's liquid stream treatment system, oxygen activated sludge, comes from paper mill wastewater making the waste activated sludge higher in poorly-degradable volatile solids than conventional municipal sludge for anaerobic digestion. All influent flow goes directly to the oxygen activated sludge system without primary treatment. Pilot studies conducted on the sludge at Iowa State University prior to commencing design indicated that the TPAD process could achieve significantly higher volatile solids destruction than conventional mesophilic digestion and produce a well-stabilized product suitable for land application.Following the initial positive results from the pilot work, the TPAD system was recommended. TPAD incorporates thermophilic and mesophilic digesters operated in series. The TPAD process biogas is captured and used for plant and digester heating. Biosolids are dewatered by new centrifuges, achieving greater than 27 percent solids prior to land application. Cake storage facilities have also been added as part of the project and are capable of storing up to 60 days of dewatered biosolids during adverse weather conditions and spring road restrictions.The TPAD process at WLSSD utilizes a single thermophilic digester that receives all raw waste activated sludge, thickened to 5 to 6.5 percent, followed by 3 mesophilic digesters operating in parallel. The nominal design hydraulic residence times are 5 days for the thermophilic digester and 15 days for the mesophilic digesters. The thermophilic digester is heated by the plant heating system, supplied by dual-fuel, low-pressure, steam boilers. All digester gas is used in the boiler system for plant and process heating. A heat recovery system is used to cool the thermophilic sludge prior to being fed to the mesophilic digesters. Recovered heat is used for building heating except during the few warm summer months when it is routed to a cooling tower.This paper presents the background and basic design elements of the system and focuses on the startup of the TPAD system and the initial months of operation. Startup began in May 2001 and all major facilities are now in operation. During startup, careful attention was given to the mechanics of equipment startup, operator training, safety issues, anaerobic biomass development, digester seeding, loading rate schedules, startup monitoring and process reactions, volatile acid speciation, ammonia concentrations, gas production and quality, and other basic digestion performance parameters. Information is also presented on pathogen destruction, biosolids dewaterablility, land application experiences, and energy issues.16th Annual Residuals and Biosolids Management Conference
For decades, plant operators from certain wastewater treatment plants have been plagued with anaerobic digester foaming. Foaming within an anaerobic digester can present significant problems for a utility, including: off-site odors, foam/sludge spillage from overflows, loss of digester cover buoyancy on floating cover digesters, fouling of gas lines, and over pressurization of the digester through clogged pressure relief valves (PRVs)
The Washington DC Water and Sewer Authority (DCWASA) is developing its Egg-Shaped Digesters Facility at the 1400 megaliter/day-capacity Blue Plains Advanced Wastewater Treatment Plant. Preliminary Design evaluations included analysis of several anaerobic digestion process options, sludge heating (and cooling) options, and assessments of pre-digestion and post-digestion processes. The temperature phased anaerobic digestion (TPAD) process has received major attention in the design because of its ability to destroy maximum solids and create a dewatered cake product with the lowest odor level. Additional thermophilic digestion stages or batch thermophilic vessels are being designed to add to the TPAD configuration to meet standards for Class A (pathogen-free) digestion. Class B mesophilic anaerobic digestion is also retained as a process option for the plant. About 300 dry tonnes/day (330 dry tons/day) of raw sludge will be processed in the new digestion facility on an average basis.The engineering team for this project has utilized a wide variety of evaluation techniques to assess the various alternatives and subsystems for this large, new digestion facility on a small footprint at the Blue Plains AWTP. Work included pilot testing of digestion process options, site visits and investigations of other facilities in North America and Europe, conducting new research on controlling odor levels and fecal coliform densities in centrifuge-dewatered cake, and development of economic and non-economic comparisons of alternatives and subsystems. Preliminary Design and Final Design has encompassed the period of 2002 to 2005. KEYWORDSSludge, anaerobic digestion, thermophilic, temperature phased anaerobic digestion, Class A, biosolids PROJECT BACKGROUNDThis section provides history and background for discussion of digestion process development of the Egg-Shaped Digesters Facility at the Blue Plains Advanced Wastewater Treatment Plant.
The Washington DC Water and Sewer Authority (DCWASA) is developing its Egg-Shaped Digesters Facility at the 1400 megaliter/day-capacity Blue Plains Advanced Wastewater Treatment Plant. Preliminary Design evaluations included analysis of several anaerobic digestion process options, sludge heating (and cooling) options, and assessments of pre-digestion and post-digestion processes. The temperature phased anaerobic digestion (TPAD) process has received major attention in the design because of its ability to destroy maximum solids and create a dewatered cake product with the lowest odor level. Additional thermophilic digestion stages or batch thermophilic vessels are being designed to add to the TPAD configuration to meet standards for Class A (pathogen-free) digestion. Class B mesophilic anaerobic digestion is also retained as a process option for the plant. About 300 dry tonnes/day (330 dry tons/day) of raw sludge will be processed in the new digestion facility on an average basis.The engineering team for this project has utilized a wide variety of evaluation techniques to assess the various alternatives and subsystems for this large, new digestion facility on a small footprint at the Blue Plains AWTP. Work included pilot testing of digestion process options, site visits and investigations of other facilities in North America and Europe, conducting new research on controlling odor levels and fecal coliform densities in centrifuge-dewatered cake, and development of economic and non-economic comparisons of alternatives and subsystems. Preliminary Design and Final Design has encompassed the period of 2002 to 2005. KEYWORDSSludge, biosolids, anaerobic digestion, thermophilic, temperature phased anaerobic digestion, Class A PROJECT BACKGROUNDThis section provides history and background for discussion of digestion process development of the Egg-Shaped Digesters Facility at the Blue Plains Advanced Wastewater Treatment Plant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.