Effect of long residence time and high temperature over anaerobic biodegradation of Scenedesmus microalgae grown in wastewater

J Environ Manage. 2018 Jul 15;218:425-434. doi: 10.1016/j.jenvman.2018.04.086. Epub 2018 Apr 27.

Abstract

Anaerobic digestion of indigenous Scenedesmus spp. microalgae was studied in continuous lab-scale anaerobic reactors at different temperatures (35 °C and 55 °C), and sludge retention time - SRT (50 and 70 days). Mesophilic digestion was performed in a continuous stirred-tank reactor (CSTR) and in an anaerobic membrane bioreactor (AnMBR). Mesophilic CSTR operated at 50 days SRT only achieved 11.9% of anaerobic biodegradability whereas in the AnMBR at 70 days SRT and 50 days HRT reached 39.5%, which is even higher than the biodegradability achieved in the thermophilic CSTR at 50 days SRT (30.4%). Microbial analysis revealed a high abundance of cellulose-degraders in both reactors, AnMBR (mainly composed of 9.4% Bacteroidetes, 10.1% Chloroflexi, 8.0% Firmicutes and 13.2% Thermotogae) and thermophilic CSTR (dominated by 23.8% Chloroflexi and 12.9% Firmicutes). However, higher microbial diversity was found in the AnMBR compared to the thermophilic CSTR which is related to the SRT. since high SRT promoted low growth-rate microorganisms, increasing the hydrolytic potential of the system. These results present the membrane technology as a promising approach to revalue microalgal biomass, suggesting that microalgae biodegradability and consequently the methane production could be improved operating at higher SRT.

Keywords: Anaerobic digestion; Biodegradability; Membrane technology; Microalgae; Microbial analysis; Scenedesmus spp.

MeSH terms

  • Anaerobiosis
  • Bioreactors*
  • Methane
  • Microalgae
  • Scenedesmus*
  • Sewage
  • Temperature
  • Waste Water*

Substances

  • Sewage
  • Waste Water
  • Methane