Redefining applications of anaerobic, autotrophic, and phototrophic bioprocesses for energy and resource autarky in the wastewater treatment industry

Abstract

Novel applications of anaerobic, autotrophic, and phototrophic biological processes and technologies have the potential to invert the intense energy demands of municipal wastewater treatment. One of the major barriers to widespread full-scale implementation of anaerobic technologies in mainstream wastewater treatment is the need for a reliable and appropriate nutrient management process. A pilot-scale (720 L) anaerobic baffled reactor has operated for more than 6 years, demonstrating 80-90% of influent solids and 60-80% of influent biochemical oxygen demand (BOD), under a sludge bed contact time (SCT) of at least 8 hours. Mainstream anaerobic treatment demands a novel nutrient removal process for effluent that is low in organic carbon, but rich in nutrients. Nutrient removal and recovery processes were investigated in partnership with local water resource recovery facilities’ (WRRFs’) process goals. A partially aerobic, autotrophic deammonification process treating anaerobic digester centrate demonstrated resiliency to variable loads and dissolved oxygen concentrations. Operating this process at a constant volumetric airflow eliminated reliance on a complex pH and DO cascade control, yet still provided robust and dependable nitrogen elimination. The results of this work also suggested that deammonification was not exclusively partial nitritation and anammox, as previously assumed, but rather a complex network of biological nitrogen pathways. Finally, algal-based nutrient recovery was assessed for potential nitrogen, phosphorus, and carbon dioxide (CO2) recovery from low-carbon secondary clarifier effluent at a full-scale WRRF. This research showed that a native algal consortium, rather than proprietary or isolated algal cultures, was able to remove up to 90% of total inorganic nitrogen and 98% of phosphorus from secondary clarifier effluent. A biomass production rate (67 g/g biomass to phosphorus ratio) comparable to commercial designs was observed with supplementary CO2. Broader implications of these nutrient management studies propose simplifying process control in deammonification and enriching for native consortia in algal based nutrient recovery.