Resource recovery from waste has been advocated for decades. Intensified resource recovery is now being advocated by and within the wastewater industry; wastewater treatment plants (WWTPs) have even been re-branded as water resource recovery facilities (WRRFs) in an effort to emphasize resource value. Linked with resource recovery processes is the need to improve WRRF efficiency -- specifically in the use of energy and removal of nitrogen (N) and phosphorus (P). This project will advance a deeper understanding and knowledge of how bacteria present in WRRFs convert ammonia to nitrite; by stopping the biological reaction at nitrite (in contrast to the more conventional conversion fully to nitrate), energy savings can be realized. The PIs will investigate this process within the context of achieving maximum biological removal of wastewater N and P. Complementing the wastewater nutrient removal research, investigations will be conducted to recover wastewater carbon as a commercially viable plastic; this resource recovery alternative could enhance the overall economics of WRRFs. The research project will engage two graduate students with both an environmental engineering professor and practicing engineers; the combined experience will provide students with significant depth and breadth in the analysis and design of wastewater resource recovery systems.
This project will address the following research questions: (i) Post-anoxic biological nutrient removal (BNR) with nitritation: What operational conditions must be applied to sustain this enrichment and maintain nitritation? How robust/resilient is the nitritating post-anoxic BNR process? What is the relative speciation of Nitrobacter spp. and Nitrospira spp. under sustained nitritation, and how is mainstream nitritation sustained with nitrite oxidizing bacteria (NOB) present? (ii) Polyhydroxybutyrate-co-valerate (PHBV) synthesis: How do interactions between carbon/electron pathways (in particular the tricarboxylic acid cycle (TCA) cycle and PHBV synthesis) affect how mixed microbial consortia (MMC) maximize volatile fatty acid (VFA) conversion to PHBV? What is the relationship between these interactions and substrate addition/bulk solution VFA concentrations under maximum PHBV synthesis conditions? How can metabolomics data inform process operations? The following hypotheses address the research questions: (1) Stable and resilient mainstream nitritation can be sustained with an enrichment of Nitrobacter spp. over Nitrospira spp. The targeted enrichment and outcome (nitritation) can be achieved through the control of the aeration period. (2) By controlling bulk-solution VFA concentrations in the PHBV batch reactor, maximum conversion of VFAs to PHBV can be achieved. This study will generate knowledge to advance a new technology such that enhanced N and P removal can be more reliably accomplished through sustainable biological means with a reduced energy footprint. Collaboration with the city and an industrial partner will achieve proper vetting of the research through critical review of laboratory and pilot-scale operations.
