Understanding the biological nitrogen and phosphorus removal interactions

Enhanced Biological Phosphorus Removal (EBPR) is considered as the most economical and environmentally sustainable alternative to prevent eutrophication from phosphorus discharges. Most of the reported WWTP configurations for simultaneous C/N/P removal have an aerobic zone before the settler which may result in some nitrate presence in the external recycle and consequently, in the anaerobic zone. This presence is one of the most reported causes of EBPR failure in real WWTP and, despite its significance, the processes involved have not been fully understood yet.

This research line aims at understanding and solving this major EBPR failure. The underlying mechanisms of EBPR failure under oxygen, nitrate and nitrite reducing conditions are studied with PAO and denitrifier populations. Moreover, the practical and microbiological consequences of the long-term nitrate presence under anaerobic conditions are studied in continuous pilot plant operation under A2O and JHB configurations. The utilisation of advanced modelling tools (development, calibration and validation) helps to understand the experimental results and to predict the success of new scenarios. The reduction of nitrate concentration in the anaerobic reactor by using an external carbon addition is a promising alternative and hence the research of reliable and economic carbon sources is a current focus of interest.

The results of this investigation is focused on the design of feasible, reliable and fail-safe WWTP configurations for systems with nitrate entering through the external recycle. Finally, new optimal control strategies are designed and experimentally assessed. A deep understanding of the underlying mechanisms of EBPR deterioration under nitrate-reducing conditions would help to improve the design of new plants and/or the retrofitting of the existing ones. Moreover, the design and assessment of new and fail-safe WWTP configurations will be a significant asset not only for water researchers but also for water practitioners in the close future.

We collaborate with municipal WWTP operators as Aigües de Manresa (www.aiguesmanresa.cat) in this field.


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