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Digestate color and light intensity affect nutrient removal and competition phenomena in a microalgal-bacterial ecosystem

Abstract : During anaerobic digestion, nutrients are mineralized and may require post-treatment for optimum valorization. The cultivation of autotrophic microalgae using the digestate supernatant is a promising solution; however the dark color of the influent poses a serious problem. First, the color of the digestates was studied and the results obtained using three different digestates demonstrated a strong heterogeneity although their color remained rather constant over time. The digestates absorbed light over the whole visible spectrum and remained colored even after a ten-fold dilution. Secondly, the impact of light and of substrate color on the growth of Scenedesmus sp. and on nitrogen removal were assessed. These experiments led to the construction of a model for predicting the impact of influent color and light intensity on N removal. Maximum N removal (8.5mgN-NH4+L-1d-1) was observed with an initial optical density of 0.221 and 244?molEm-?s-1 light and the model allows to determine N removal between 15.9 and 22.7mgN-NH4+L-1d-1 in real conditions according to the dilution level of the influent and related color. Changes in the microalgae community were monitored and revealed the advantage of Chlorella over Scenedesmus under light-limitation. Additionally microalgae outcompeted nitrifying bacteria and experiments showed how microalgae become better competitors for nutrients when phosphorus is limiting. Furthermore, nitrification was limited by microalgae growth, even when P was not limiting. © 2014.
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https://hal.inrae.fr/hal-02600054
Contributor : Migration Irstea Publications <>
Submitted on : Saturday, May 16, 2020 - 3:57:15 AM
Last modification on : Monday, May 18, 2020 - 2:42:26 PM

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  • HAL Id : hal-02600054, version 1
  • IRSTEA : PUB00041487

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C. Marcilhac, Bruno Sialve, A.M. Pourcher, C. Ziebal, N. Bernet, et al.. Digestate color and light intensity affect nutrient removal and competition phenomena in a microalgal-bacterial ecosystem. Water Research, IWA Publishing, 2014, 64, pp.278-287. ⟨hal-02600054⟩

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