Sustainability of Full-Scale Nutrient Removal Technologies

Sustainability of nutrient removal technologies were investigated in this paper. The ultimate goal of the industry could be set for achieving energy independence at a treatment facility in the future. The state of sustainability are improving rapidly with development of technologies and operational improvements as the focus has been placed on energy and carbon management.The selection of technologies and their operation do impact the sustainability of the facility in two ways; energy management and carbon management. On energy management, the current energy usage ranged between 600 to 2,100 kwh/million gallons (MG) treated, when operated with internal carbon sources. When carbon was imported however, the energy usage increased by approximately 600 kwh/MG treated or more. Key factors included the flexibility of processes that allow for separate control of mixing and aeration, step feed modes of operation for activated sludge, and automation of controls with on-line sensors and potential side treatment of recycle loads or their equalization. On carbon management, key factors include in-plant generation of volatile fatty acids(VFA), ability to operate the step feed mode of activated sludge and side stream treatment of recycle loads. The carbon generated thus reduced the need to import carbon from external sources up to 35% and thus enhance sustainability in both nitrogen and phosphorus removal at significant savings in energy and costs.Energy generation on site is a positive measure for reaching sustainability and the biogas from anaerobic digestion is suggested for long term energy independence at a future target of 1000 kwh/MG treated.