Water Online

May 2017

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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Mainstream And Sidestream Anammox Deammonification is an emerging technology that uses anaerobic ammonia-oxidizing bacteria, or Anammox, to remove nitrogen. By taking a shortcut in the conventional nitrification/denitrification process, Anammox bacteria use less process air — saving energy — and also less supplemental carbon — reducing the number of chemical delivery trucks visiting the facility and decreasing greenhouse gas emissions. Deammonification also offers a way to remove nitrogen in less space without additional aeration basins. The microbial population must be carefully balanced so that Anammox bacteria can outcompete other microbes in the biomass. AlexRenew uses hydrocyclones to separate the heavier Anammox granules to keep them in the reactors while lighter biomass is removed. In March 2015, AlexRenew started up its sidestream centrate pretreatment facility. The facility uses Anammox bacteria to treat the ammonia‐rich sidestream from dewatered, anaerobically digested biosolids. The centrate holds as much as 25 percent of all nitrogen in the wastewater at AlexRenew. The centrate pretreatment facility — among the first of its kind in North America — can treat 276,000 gallons of centrate per day, removing 85 percent of the total nitrogen from this waste stream. The process was designed to use 60 percent less process air than conventional treatment, with no supplemental carbon required. In spring 2017, AlexRenew will launch mainstream deammonification in its biological reactor basins. Mainstream Anammox is expected to reduce supplemental carbon use by more than 40 percent and aeration use by 26 percent while increasing biogas production by 10 percent — all with minimal capital investment, helping AlexRenew meet is fiscal sustainability goal. AlexRenew's implementation of full-scale sidestream and mainstream deammonification is a milestone in the development of these technologies. As such, AlexRenew is collaborating with universities, research organizations, and other utilities, including its international partner, VandCenter Syd (Odense, Denmark), to monitor, refine, and quantify any improvements. Nutrient Management Facility The largest SANUP component, AlexRenew's nutrient management facility (NMF), is an 18-million-gallon structure made of more than 1,700 precast concrete panels. The NMF stores primary effluent during daily ammonia peaks to balance ammonia-nitrogen loading to AlexRenew's biological reactor basins. Maintaining a constant nitrogen load to the biological reactor basins helps AlexRenew optimize microbial chemical use and air demand, all on a very limited footprint for treatment. The facility — located on AlexRenew's South Carlyle site — is topped by Limerick Street Field, a public, multipurpose athletic field that transforms a historic city garbage dump into a community amenity. In December 2016, the Institute for Sustainable Infrastructure honored the NMF with an Envision Platinum Award — the first in Virginia and the D.C. metro area and also the first for a U.S. water resource recovery facility. Envision is a tool used for planning, designing, and rating all types of sustainable infrastructure projects, much like the LEED program is used to assess buildings. Through a public-private partnership, AlexRenew, the City of Alexandria, and developer Carlyle Partners constructed Limerick Street Field and the Environmental Center, AlexRenew's administrative headquarters. The field and building share a consistent aesthetic with the South Carlyle development, wateronline.com n Water Innovations 23 ADVANCEDTREATMENT The microbial population must be carefully balanced so that Anammox bacteria can outcompete other microbes in the biomass. AlexRenew uses hydrocy- clones to separate the heavier Anammox granules to keep them in the reactors while lighter biomass is removed. AlexRenew's implementation of full-scale sidestream and mainstream deammonification is a milestone in the development of these technologies.

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