Engineer in Charge: Charles Bott, Ph.D., P.E., BCEE
Location: Seaford, Virginia
Media Contact: Nancy L. Munnikhuysen, HRSD Chief of Communications, 757.460.7058
HRSD, the regional utility whose mission is to protect public health and the waters of Hampton Roads by treating wastewater effectively, serves 17 municipalities in southeastern Virginia, an area with a population of 1.6 million. Its York River Treatment Plant, which is designed to clean up to 15 million gallons of wastewater per day (MGD), has received national awards for outstanding compliance with its environmental permits for 25 consecutive years. HRSD installed the equipment, performed minor piping modifications, provided engineering support during construction, and now operates and maintains the DEMON® sidestream deammonification process and related equipment.
World Water Works, Inc. (WWW) specializes in developing and providing highly efficient wastewater treatment solutions. The company was incorporated in 1998 recognizing the need for ethical product commitment and continual innovation in technology for the water and wastewater industry. Executing these goals has enabled WWW to establish strong meaningful relationships with its customers by delivering individualized on-going solutions creating rapid return on their investment. WWW manufactures a complete array of products addressing various problems in the wastewater industry. Combining an expert team with a strong investment in Research and Development yields some of the most robust, yet cost-effective high performance products available in the industry. WWW provided the equipment, control systems, imported seed biomass, and operational support required for the success of this project.
A public-private partnership made possible the first operating implementation of the innovative DEMON® sidestream deammonification process in North America. In fact, this is the first operating full-scale installation of any form of anammox sidestream treatment in North America. HRSD, a regional wastewater treatment utility that serves
17 localities in southeastern Virginia, and World Water Works, Inc. (WWW), which specializes in developing and providing highly efficient wastewater treatment solutions, joined forces to successfully install a centrifuge centrate treatment process previously used only in Europe.
Deammonification, partial nitritation by ammonia oxidizing bacteria (AOB) combined with anaerobic ammonium oxidation (anammox), provides up to 70-90% total nitrogen removal with a 65% reduction in aeration energy, a 100% reduction in supplemental carbon, and an approximate 50% reduction in alkalinity requirements as compared to traditional nitrification-denitrification. The DEMON® process is one of several available forms of single-step (in the same tank) partial nitritation-anammox designed for centrate treatment from anaerobically digested Biosolids and operated as a sequencing batch reactor (SBR). While this process had been applied at approximately 30 plants in Europe, it had not been implemented elsewhere in a full scale application, primarily because of the requirements for seeding this process using biomass imported from operating facilities in Europe. The stability of the DEMON® process has improved in recent years with the addition of a hydrocyclone for selective anammox bacteria retention in the process, and this improvement resulted in considerably more interest in other parts of the world. HRSD, which is committed to the use of sustainable nutrient removal practices that lower operational costs, agreed to partner with WWW in the first operating DEMON® installation in North America. At the present, several other DEMON® systems are either in construction or in design.
HRSD's York River Treatment Plant, located in Seaford, Virginia, currently includes a fully aerobic nitrifying activated sludge system with post denitrification filters. The plant was the site of another first that made it a stellar candidate for the DEMON® process. In 2002, HRSD launched at this facility Virginia's first municipal water reuse project, which required the construction of an SBR. The initiative ended when an adjacent refinery, the only reclaimed water customer, closed. Consequently, during recent plant upgrades, the SBR and equalization tanks installed to support the reuse project were retrofitted to serve for centrate equalization and full nitrification. This meant that only minor piping needed to be done to install DEMON®, making the project more affordable and sustainable.
The system was seeded with 5,000 gallons of concentrated anammox biomass by mixing the imported anammox biomass with plant effluent. The biomass had been dormant for about six weeks so there was minimal AOB activity present at startup. Centrate was fed to the system to bring the ammonia concentration to 50 mgNH4-N/L. The system is designed to treat 297 m3/day (78,500 gpd) equalized centrate flow with an anticipated ammonia load of .0.5 kg/m3/day (4.08 lb/day/1000 gal).
The DEMON® process was seeded and started in October 2012. After some minor modifications to the equalization tank were made in November/December 2012, the process achieved operating objectives for ammonia loading and total nitrogen removal in early January 2013.
Sidestream nitrogen removal using partial nitritation and anammox has been demonstrated to be an effective tool for improving nitrogen removal performance and reliability while achieving a savings in aeration energy, chemicals (alkalinity and supplemental carbon), and sludge production. This is clearly a sustainable nutrient removal technology that should be considered at any plant with nitrogen or ammonia permit limits and anaerobic digestion. Furthermore, this technology paves the way for continued research and development in the area of mainstream or main plant deammonification and mainstream nitrite shunt. HRSD is an active participate in these activities and is operating a 4-year, $1.2 million pilot system to develop and demonstrate these processes in collaboration with DC Water and the Strass plant in Austria. With the added potential of wastewater carbon redirection to energy generation processes, mainstream deammonification could revolutionize wastewater treatment as we know it, allowing cost effective nitrogen removal, while maximizing resource recovery and minimizing resource utilization (chemicals, energy, concrete tank size, and land).
It has also now been documented that one-step sidestream deammonification technologies like the DEMON® process are beneficial from the perspective of generation of gaseous nitrous oxide (N2O) as compared to the two-step partial nitritation-anammox processes.
HRSD was exceptionally pleased with the equipment, control systems, imported seed biomass, and operational support provided by WWW. HRSD installed the equipment, performed minor piping modifications, provided engineering support during construction, and now operates and maintains the DEMON® process and related equipment.
The total operational savings associated with the DEMON® process is estimated to be $192,000 per year. This savings is attributed to reductions in the usage of methanol, sodium hydroxide (caustic) and electrical power for blower operation. Total nitrogen and ammonia removal efficiencies of more than 80% and 90%, respectively, have been achieved, as expected based on a review of similar installations in Europe.
WWW provided key components of the DEMON® system to HRSD in return for access to excess biomass generated from the system. This biomass will aid in the start-up and seeding of new DEMON® systems in North America. The research conducted during this project identified the optimum operating setpoints of the DEMON® control system through parameter monitoring and activity tests of the biomass. The startup process was well documented to ensure that an accurate procedure could be developed and shared with the industry.
HRSD was also fortunate to include in the design, construction, startup, and operation of this process the assistance of Ms. Andrea Nifong, a Masters student and graduate research assistant with the Department of Civil and Environment Engineering at Old Dominion University in Norfolk, Virginia. HRSD is committed to educating the future generation of engineers and operators and providing meaningful Environmental Engineering graduate student research project assignments and tuition and stipend funding support.
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