One of the most significant energy-consuming industries in Taiwan is wastewater treatment, which presently uses more than 3% of our annual electricity demand (Taiwan Construction and Planning Agency, Ministry of the Interior, Taiwan, 2015). This largely ignored problem stems from the unfortunate fact that aerobic waste processing (i.e., the conventional ‘gold-standard’ for wastewater treatment) requires intensive (and highly inefficient) aeration to supply aerobic bacteria with oxygen so that they might then oxidatively convert organic (i.e., fats, sugars, and protein to CO2) and inorganic (e.g., ammonia to nitrate) wastewater contaminants. Therefore, there is a need to pursue a paradigm-shifting strategy by which the energy-efficiency of wastewater treatment could be dramatically improved by advancing the roles of anaerobic and anoxic bio-based mechanisms in lieu of heavily relying on aerobic treatment. Indeed, the core idea is that switching away from predominantly aerobic wastewater treatment could transformatively reduce energy consumption while at the same time remarkably improving overall waste cleanup. 

The energy inefficiency of conventional aerobic waste treatment stems from two severe challenges: 1) that oxygen is highly insoluble in water, and 2) in spite of literally a century-plus period of intense research, the energetic efficiency of wastewater aeration is below (and often far lower than) 30%. Within our nation, there is yet another complicating factor in terms of escalating public and Taiwan EPA pressure to upgrade the ammonia removal in our roughly 60-plus municipal wastewater treatment facilities, and continuing to use aerobic technology will only further escalate our wastewater treatment energy demand. Rather understandably, therefore, pressure is mounting to improve both nation’s ammonia effluent standards and their level of applied technology to achieve these limits, but further use of conventional wastewater technology will only further exacerbate energy consumption to even higher levels. And a significant, complicating factor with ammonia removal is that this contaminant has a stoichiometric oxygen demand requirement more than four times larger in mass, such that every mg/L of ammonia-nitrogen consumes an astounding 4.5 mg/L of dissolved oxygen. Preliminary estimates, though, indicate that upgrading existing, conventional wastewater facilities with more advanced, but still aerobic, biological waste treatment systems to mitigate our current treatment inadequacies in nutrient pollution control will double current energy consumption, a politically and environmentally undesirable outcome. Simply put, our nation consequently has a compelling need to examine and adopt an advanced next-generation wastewater treatment strategy that shifts away from standard energy-consuming ‘aerobic’ dominant technology to solutions favouring energy-efficient, high-performance anaerobic and anoxic alternatives. 

This lecture will address: 1) that the wastewater industry should no longer focus on aerobic treatment processes intent on oxidatively ‘burning’ organic carbon and nutrient ammonia with aerobic bacteria (thereby gaining three positive outcomes, including reduced energy demand, reduced CO2 generation, and reduced nitrate generation), 2) that anaerobic processes be alternatively used as secondary treatment during organic carbon conversion, and that an advanced anoxic mechanism for ammonia transformation directly to nitrogen gas (i.e., deammonification process) be used as tertiary treatment (thereby further reducing oxygen consumption while at the same time eliminating the release of both ammonia and nitrate). A complete evaluation of the advanced next-generation wastewater treatment also includes microbial dynamic, fate of emerging contaminants in both anaerobic and anammox bioreactors and heavy metal removal in digested biosolids.