A new paper titled ‘Low-strength wastewater treatment in an anammox UASB reactor: Effect of the liquid upflow velocity’ by C. Reino and J. Carrera has been published in Chemical Engineering Journal (2017), 313, 217-225.
The paper presents the feasibility of operating an UASB reactor performing the anammox process at high nitrogen removal rates and high effluent quality when a low-strength synthetic influent is treated. To the best of the author’s knowledge, this is the first time that the effect of liquid upflow velocity on anammox granulation and mass transfer transport is presented in detail in an anammox UASB reactor treating a low-strength influent.
A nitrogen loading rate of up to 1.8 ± 0.2 g N L-1 d-1 was achieved at 26 °C and the nitrogen removal rate obtained (1.7 ± 0.1 g N L-1 d-1) resulted considerably higher than most of the previously reported values for systems treating low-strength wastewater at similar temperatures. The evolution of the granule diameter was followed throughout the operation of the UASB reactor and a direct correlation of the average granule diameter with the liquid upflow velocity (Vup) was established, being the higher the Vup, the bigger the granules. A stable granule diameter of 790 ± 40 µm was achieved by maintaining a Vup of 1.0 ± 0.1 m h-1. The low VupS applied avoid the use of effluent recirculation which would present a huge inconvenient to implement UASB reactors at real scale, however these low VupS led to external mass transfer problems in the reactor. In spite of the mass transfer limitations, not only a high specific anammox activity (0.26 ± 0.02 g N g-1 VS d-1) was achieved in the UASB reactor but also a high nitrogen removal (80 ± 3%).