Jun 13, 2019
Grace Richardson

What new technologies have you been evaluating or implementing?

AlexRenew is one of the first utilities in North America to implement sidestream deammonification and has been running this process for approximately one year. Our 276,000 gal/day Centrate Pretreatment (CPT) facility pre-treats the ammonia-rich recycle stream that results from centrifuge dewatering of anaerobically digested biosolids. This stream can account for as much as 25% of the total nitrogen load within the overall treatment facility. 

The centrate pretreatment process uses Anaerobic Ammonia Oxidizing (Anammox) bacteria to achieve a “shortcut” in the metabolic pathways that transform ammonia in the water into nitrogen gas that diffuses to the atmosphere. The CPT is designed to remove 90 % of ammonia and 80% of total nitrogen from the dewatering centrate. The deammonification process also uses 60% less process air than conventional treatment with no supplemental carbon required. 

AlexRenew is close to launching its mainstream deammonification process. Both the CPT and mainstream deammonification are part of a larger project, the State-of-the-Art Nitrogen Upgrade Program (SANUP). SANUP is a phased series of improvements designed and implemented to comply with the strict nutrient limits to protect the Chesapeake Bay. These limits are equivalent to 3 mg/L total nitrogen based on wasteload allocations at the permitted flow of 54M gallons per day (MGD).

To facilitate mainstream deammonification, AlexRenew added a sixth biological reactor basin. This basin creates additional reactor volume to house more biomass, enabling us to remove more nitrogen. The increased capacity of our biological system, expanded from 20M gallons to 24M gallons, also prepares us for future growth.  

CPT has already made a difference in our supplemental carbon use and in the efficiency of our main biological nutrient removal basins. Using sidestream and mainstream deammonification has the potential to result in operations and maintenance savings of $400,000 annually. As part of both of these efforts, we are controlling aeration based on ammonia concentration, enhancing our energy efficiency.  

The Nutrient Management Facility (NMF) is the largest construction project under SANUP.  The NMF balances the diurnal influent ammonia loading to the biological reactor basins. When nitrogen loading is higher, partially treated water is diverted to the NMF for storage. When nitrogen loading is lower, this water is returned from the NMF to our biological treatment system. By equalizing the ammonia load to the biological reactor basins, AlexRenew will enhance the performance of our microbes to further reduce our chemical and aeration demands. 

The NMF supports the transition to mainstream Anammox, as we now have very tight control over the nutrient load coming into the biological reactor basins, which feeds the Anammox bacteria. Now, we can ensure that they have the conditions required to facilitate removal of ammonia.

We have a long wish list of innovative technologies we’re keeping our eyes on, but our main focus recently has been around solids and energy. 

AlexRenew has consistently produced Class A biosolids for more than eight years and maintains a goal of 100% beneficial reuse of all biosolids. Through a partnership with Synagro, AlexRenew land applies biosolids at farms in more than 15 Virginia counties, and in 2015, more than 5,000 dry metric tons of biosolids were land applied. With potential changes on the horizon that could affect land application, AlexRenew is now conducting a long-range planning study considering all proven and emerging technologies to optimize biosolids production and to generate energy and other products. 

Alexandria Renew Facility

In the mid-2000s, AlexRenew embraced an ambitious goal: To be a net-zero energy user. In 2015, AlexRenew generated 157 m cubic feet of renewable methane gas and used 92% of it to operate our facilities. AlexRenew has also reduced greenhouse gas emissions by more than 20% since 2005, and since 2008, we have reduced our annual electrical consumption by 41 m BTUs or by 17.3%. We’ve continuously improved our energy efficiency as guided by a plantwide Energy Master Plan Study completed in 2014. For example, we have updated to LED lighting, installed motion-activated lighting, and used solar panels on building rooftops. The solar panels on the Environmental Center exterior, for example, will provide 40% of the building’s power. Equipment is also selected with energy conservation in mind, and sustainability is integral to the design and construction of new facilities on our campus. To further improve our energy efficiency, we are participating in the Department of Energy’s Superior Energy Performance Program with the goal of reducing our energy intensity by at least 25% over 10 years. Key to improving our energy efficiency is understanding the energy balance within our facility — being able to see energy use data at the process or equipment level. We are interested in technologies or software that aid in capturing and analyzing this type of information.

As an aspiring Utility of the Future and as a public steward, it is our goal to use resources in the most efficient way possible and to find the most beneficial use for our biosolids. Today, there are numerous technologies available to improve energy efficiency, generate energy, and beneficially reuse solids, and we are certainly interested in learning more about them. 


What are your facility drivers/needs?

Our needs are often driven by regulation. The Chesapeake Bay is one of the most ecologically significant estuaries in the U.S. Today, the bay is subject to the country’s largest total maximum daily load affecting six states and Washington, D.C. To improve the bay’s water quality, AlexRenew has invested millions of dollars into innovative technologies.  

Our needs are also driven by unique challenges. Sitting on just over 30 acres, AlexRenew operates one of the most space-constrained water resource recovery facilities in the U.S. at less than half an acre per million gallons of treatment capacity. We are an urban facility neighboring a major highway, as well as commercial and urban development. Because of these drivers, we have had to use innovation to adapt our process to our small footprint and ensure that odors do not affect our community. 

As we move into the future, we also plan for challenges such as treating more concentrated flows, preparing for wet weather associated with climate change, and an aging workforce. Additionally, we are continually looking for new opportunities, including sharing more beneficial products like reclaimed water with our community and diversifying our revenue. 

Finally, we are driven by our Board of Directors’ 2040 Vision that incorporates six strategic outcomes for our facility: Operational Excellence, Community Engagement, Watershed Partnerships that Enhance Collective Management, Organizational Competency and Structure, Diversified Revenue, and Incubating New Ideas and Innovations. Each project we consider and long-range planning effort that we undertake incorporates the six strategic outcomes.  


How has LIFT helped, or how would you like LIFT to help your facility?

Driven by the challenges mentioned above, AlexRenew has a history as an early adopter, from constructing one of the first large-scale UV disinfection systems to vertical treatment of solids to anammox and international partnerships. Through LIFT’s research efforts, AlexRenew has been able to get an early look at numerous cutting-edge technologies that could potentially be a good fit for our organization and the wastewater sector. Being part of LIFT will help AlexRenew both meet the next big challenge and meet our strategic outcome of being an incubator of new ideas and innovations.   


If there were one technology you would pilot or collaborate on tomorrow, what would it be?

Data is key to making meaningful improvements. From helping us make important process decisions on a daily basis to informing long-range planning efforts. Having quick access to data about the plant that is integrated into our business systems is extremely valuable. Additional research enabling data analytics, accurate sensor technology, robotics and automation, cyber security and business governance, as well as recovery of energy inherent in water is crucial for continued improvement in our field.   


Grace Richardson
Sustainability Coordinator
703.549.3381 ext. 2016