Sidestream Treatment Comparison of Post Aerobic Digestion and ANAMMOX
Williams, T.O., Bauer, H., Johnson, T.D., Johnson, B.R., Oerke, D., CH2M, USA
(free)
Abstract
This manuscript presents a comparison of Post Aerobic Digestion (PAD) and Anaerobic Ammonium Oxidation (Anammox) as sidestream treatment technologies.
Both technologies are excellent options for the reduction of nitrogen recycled back to the liquid stream without the need for supplemental carbon or alkalinity. However, the achievement of this goal is where the similarities between the two technologies end. PAD is a recently developed advanced digestion process where aerobic digestion is designed to follow anaerobic digestion. The most significant driver for selecting PAD is the reduction of nitrogen recycled back (>95% removal) to the liquid stream without the need for supplemental carbon or alkalinity (Bauer, et al., 2015, Johnson et al., 2013 and Menniti et al. 2010). Other significant benefits include volatile solids reduction (Bauer et al., 2014 and Parravicini et al., 2006), odor reduction (Kumar et al., 2006), and struvite formation reduction. Anammox harnesses a specific species of autotrophic bacteria that, in conjunction with ammonia oxidizing bacteria can achieve partial nitritation/deammonification (or, the conversion of nitrite to nitrogen gas). Similar to PAD, the most significant driver for selecting Anammox is the reduction of nitrogen recycled back (90% removal) to the liquid stream without the need for supplemental carbon or alkalinity (Nifong et al., 2013 and Daigger et al., 2011). In addition, the Anammox process if very energy efficient requiring about 60% less oxygen than conventional nitrification and denitrification.
The manuscript describes the unique benefits and challenges of each technology. Example installations are presented with a narrative of how and why the technology was selected. A whole plant simulator is used to compare and contrast the mass balances and net present value costs for each technology on an “apples to apples” basis. The discussion includes descriptions of conditions under which each technology would potentially be the most beneficial and cost-effective against a baseline, non-sidestream treatment equipped facility, including how best to integrate these facilities with other technologies such as thermal hydrolysis and phosphorous recovery.
Keywords: Post Aerobic Digestion, Anammox, advanced digestion, enhanced digestion, nutrient removal, sidestream, thermal hydrolysis, phosphorus recovery.
Introduction
Post Aerobic Digestion (PAD) and Anaerobic Ammonium Oxidation (Anammox) are both sidestream treatment technologies which are excellent options for the reduction of nitrogen recycled back to the liquid stream without the need for supplemental carbon or alkalinity. However, the achievement of this goal is where the similarities between the two technologies end. This paper includes a discussion of the unique benefits and challenges of each technology, including a presentation of example full-scale installations, and an “apples to apples” comparison of the mass balances and net present value costs for each technology using a whole plant simulator. The conclusions to this paper will be descriptions of conditions under which each technology would potentially be the most beneficial and cost-effective.
