Sidestream Management as Part of an Energy Optimization Roadmap for an Advanced BNR Facility

VCS Denmark carried out an energy optimization program in 2012 with the goal of achieving energy neutrality by the year 2014. The optimization work was a success, but the study showed that the implementation of deammonification technology could push the facility into net positive energy territory. Sidestream deammonification, utilizing suspended growth organisms in flocs and granules and the use of hydrocyclones for granule retention, was started up in December 2014. Within four months of operation, the sidestream deammonification facility was operating at full capacity, and significant improvements in the overall plant energy profile were observed. This paper also provided details on a sidstream deammonification control strategy that was developed by VCS to minimize nitrous oxide emissions, based on continous aeration (rather than the supplier provided on/off aeration strategy. Preliminary results from the continuous aeration control appears to be very promising for reducing nitrous oxide emissions, a potent greenhouse gas 300 times that of CO2, while maintaining the level of nitrogen removal in the reactors. Results to date show a decrese of approximately 50% of the nitrous oxide emissions compared to the on/off aeration provided in the control reactor while maintaining the overall nitrogen removal. Through this work, VCS found that sidestream deammonification was a successful contributor in realizing energy and effluent quality benefits to the Ejby Mølle WWTP, but without specific controls and operating schemes, one method of which is presented in this paper, it could result in a increase in GHG emissions.