The International Water Association (IWA) is hosting its 2015 Nutrient Removal and Recovery Conference in Gdañsk, Poland, from May 18-21. CH2M staff, together with representatives from VandCenter Syd Denmark, will be presenting on best practices for achieving positive “net-energy” status and implementing deammonification technology at its wastewater treatment plant, in Odense, Denmark.

By: Dwight Houweling, CH2M Senior Wastewater Technologist

Dwight will chair a session on “Conventional biological nitrogen and phosphorus removal processes,” on Wednesday at 9:50 and present two papers including, “Low Energy and No External Carbon Nitrogen Removal Using Optimized Process Control Strategies,” co-authored by CH2M’s Tim Constantine & Julian Sandino, Columbia University’s Kartik Chandran and VCS Denmark’s Carsten Steen, Søren Eriksen, Lise Havsteen, Nerea Uri & Per Henrik Nielsen, on Tuesday, May 19, at 15:00.

Additionally, he presented “Anticipating the Impact of Mainstream Deammonification through Advanced Process Simulation”, co-authored by CH2M’s Tim Constantine & Julian Sandino; Columbia University’s Kartik Chandran, Hongkeun Park & Zheqin Li and VCS Denmark’s Carsten Steen, Søren Eriksen, Lise Havsteen, Nerea Uri & Per Henrik Nielsen, during Monday’s session.

This week, I have the good fortune of joining colleagues from Columbia University and VandCenter Syd (VCS) Denmark for the International Water Association’s (IWA) Nutrient Removal and Recovery conference, in Poland. IWA has not held this conference since 2009, so we are eager to reconnect with experts in the industry and share our knowledge and present on several topics, including how VCS Denmark has achieved a “net-positive energy” balance at its Ejby Mølle Wastewater Treatment Plant (EMWTTP) by implementing an ammonia-based “On/Off” aeration control strategy, as well as discuss VCS Denmark’s deammonification goals to maximize energy recovery and nutrient removal.

VCS Denmark embarked on a research program to better understand the performance of its existing process at EMWTTP, as well as identify further Energy Optimization Opportunities. Through a combination of tools, including activity testing, calibration of a dynamic process model and genetic testing for ammonia oxidizing bacteria (AOBs), nitrite oxidizing bacteria (NOBs) and anammox, three alternative nitrogen removal pathways have been investigated and quantified:

  • Simultaneous nitrification-denitrification
  • Nitrite-shunt
  • Deammonification

In addition to providing a better understanding of the performance of the existing system, the program is also helping VCS Denmark achieve its goal of implementing mainstream deammonification.

The goal of achieving positive “net-energy” status provides an important motivation for water resource recovery facilities (WRRF) to direct, as much as possible, the carbon contained in the raw wastewater to anaerobic treatment where it can be recovered as methane gas. This can be accomplished, for example, through chemically enhanced primary treatment (CEPT) or operation of extremely high-rate biological processes, such as A-stage. For many facilities, however, this energy driver clashes with the need to biologically remove nutrients to meet effluent nitrogen, phosphorus or pH requirements. Biological nutrient removal has traditionally been dependent on using influent carbon for heterotrophic denitrification or enhanced biological phosphorus removal.

The problem for many facilities is if they maximize the carbon directed to anaerobic treatment, then there is insufficient carbon remaining for nutrient removal and to recover the alkalinity consumption from nitrification. Because deammonification makes it possible to remove nitrogen without any organic carbon utilization, its emergence as a treatment technology for both sidestream and mainstream treatment provides a much needed opportunity to remove nitrogen independently of the influent carbon load. As such, deammonification provides the means for reconciling what would otherwise be two contradictory goals: maximizing both energy recovery and nutrient removal.

VCS Denmark’s EMWTTP employs two pairs of oxidation ditches, known as phased isolation ditches, downstream of a chemically enhanced primary treatment process that achieves approximately 70% TSS and 45% COD removal. The configuration includes four square anaerobic selectors for enhanced biological phosphorus removal, which operate upstream from the oxidation ditches. The process achieves an enhanced biological phosphorus removal and can reliability remove total nitrogen.

A dynamic process model was calibrated for the oxidation ditches at EMWTTP, which validated calculations of anammox inventory that can be achieved in a mainstream deammonification process, as compared to conventional nitrification in EMWTTP’s existing process. Additionally, the process model indicated that VCS Denmark’s mainstream deammonification strategy, combined with increased carbon removal in primary treatment through “optimized” CEPT, caused energy savings in the range of 21 to 45%.

I hope you can join us at the Nutrient Removal and Recovery conference to learn more about the innovative practices being employed by VCS Denmark to balance nitrogen removal and maximize energy recovery, but if you are not able to participate, I invite you to follow the conversation on Twitter by following @CH2M and the #NRR2015 hashtag for conference updates.

Dwight Houweling is a Senior Wastewater Technologist with CH2M, who specializes in the design and optimization of biological treatment processes, with a particular focus on anammox-based “deammonification” processes. Dwight has a strong background in process modelling, based on doctoral work and post-doctoral work on the application of metabolic models to the activated sludge process. He is currently authoring a chapter in the upcoming Water Environment Federation book, “Shortcut on Removal,” which is scheduled for publication in May of this year.