Mainstream Deammonification

The objective of this research was to investigate the feasibility of applying the deammonification concept, which is already highly successful and proven in sidestream configurations, in the mainstream treatment process. The deammonification process for nitrogen removal provides a more efficient biological pathway compared to traditional nitrification/ denitrification. The demonstrated advantages of applying deammonification to mainstream treatment include energy-neutral or even energy-positive wastewater treatment, reduction of aeration energy, and reduction in external carbon and alkalinity demands. Implementation of mainstream deammonification is compatible with existing wastewater infrastructure, often with minimal modifications. The successful application of full-plant deammonification could save wastewater utilities operations costs for aeration and external carbon costs in the life cycle. Through demonstration and conceptual application at collaborating utilities, this research develops an evaluation framework for implementing full-plant deammonification. Deammonification is a two-step biological process where ammonia-oxidizing bacteria (AOB) aerobically convert half of the ammonia present in the wastewater to nitrite. In the second step, anammox bacteria oxidize the ammonia using nitrite to produce nitrogen gas without the organic carbon substrate required for conventional heterotrophic denitrification. Deammonification requires significantly less oxygen and so less energy is needed for nitrogen removal. Deammonification requires no external carbon addition, eliminating chemical purchases such as methanol. Process configurations using mainstream deammonification maximize energy recovery by diverting more particulate organic carbon away from the nitrogen removal process and directing it toward anaerobic treatment from which methane can be captured. The implications of deammonification for sustainable, cost effective and energy positive wastewater treatment are extraordinary. The report discusses application of short-cut nitrogen removal which includes nitritation-denitritation, in which ammonia oxidation ends at the intermediate nitrite, with the mainstream deammonification pathway. Both short-cut nitrogen removal pathways result in savings in energy, carbon and alkalinity over conventional nitrification-dentrification. To be successful, short-cut nitrogen removal strategies require maximizing AOB activity, while preventing the establishment of the nitrite oxidizing bacteria (NOB) that oxidize nitrite to nitrate and this report introduces and develops concepts for NOB out-selection. To progress from nitritation-denitritaion to deammonification, the AOB activity must be controlled to oxidize only half of the influent ammonia to nitrite, and a method of retaining the slow-growing anammox bacteria must be implemented. The report presents a progressive pathway from conventional nitrification-dentrification to short-cut nitrogen removal and discusses a framework of conditions and drivers for implementation. The research concludes that mainstream deammonification can be achieved. It is possible for wastewater treatment plants to retrofit to short-cut nitrogen removal utilizing existing infrastructure, often with minor modifications. The research revealed key site-specific drivers for applying short-cut nitrogen removal technology.