Assessment of microalgae and nitrifiers activity in a consortium in a continuous operation and the effect of oxygen depletion|
Vargas, Gustavo; Donoso-Bravo, Andrés; Vergara, Christian & Ruiz-Filippi, Gonzalo
Background: Industrial wastewaters with a high content of nitrogen are a relevant environmental problem.
Currently, treatments to remove nitrogen are not efficient, so is necessary to develop alternative methods. The
objective of this study is to investigate a consortium of microalgae — nitrifying, that due to the symbiosis
between them could be an interesting alternative.
Results: In this study, it was possible to obtain a consortium of nitrifying bacteria (NB) and microalgae (MA)
capable of operating with low requirements of dissolved oxygen, using aerobic sludge from wastewater
treatment plants. During the operation, this consortium presents removal percentages above 98% of ammonia,
even at concentrations of DO of 0.5 mg O2 L-1. It is estimated that the removal was caused both by the action
of nitrifying bacteria and microalgae. It was determined that approximately 60% of the ammonia feed was
oxidized to nitrate by nitrifying bacteria, while the algae assimilated 40% of the nitrogen feed at steady state. A
methodology for measuring the specific activities of nitrifying bacteria and microalgae by comparing the rates
in the variation inorganic nitrogen compounds was established with satisfactory results. An average specific
activity of 0.05 and 0.02 g NH4
+ gVSS-1 d-1 for nitrifying bacteria and microalgae was determined, respectively.
Conclusions: The consortium it can be obtained in a single continuous operation, and has a high capacity for
nitrogen removal with low oxygen content. The consortium could prove to be a more economical method
compared to traditional.
Ammonium; Consortium nitrifying-microalgae; Oxygen; Respirometry