Anaerobic digestion of microalgal bacterial flocs from a raceway pond treating aquaculture wastewater: need for a biorefinery

Bioresour Technol. 2015 Nov;196:184-93. doi: 10.1016/j.biortech.2015.07.058. Epub 2015 Jul 22.

Abstract

An outdoor raceway pond with microalgal bacterial flocs (MaB-flocs) is a novel sunlight-based system to treat pikeperch aquaculture wastewater while producing biomass. The harvested MaB-floc biomass (33tonTSha(-1)y(-1)) needs further valorization. Therefore, the biochemical methane yield (BMY) of MaB-floc biomass was determined in batch experiments. The results show significant differences between the BMY of MaB-flocs amongst their harvest dates (128-226NLCH4kg(-1)VS), a low anaerobic digestion conversion efficiency (25.0-36.2%), a moderate chlorophyll a removal (51.5-86.9%) and a low biogas profit (<0.01€m(-3)wastewater). None of the pretreatment methods screened (freezing, thermal, microwave, ultrasonic and chlorination, flue gas sparging, and acid) can be recommended due to a low BMY improvement and/or unfavorable energy balance. Therefore, anaerobic digestion of this MaB-floc biomass should only be granted a supporting role within a biorefinery concept.

Keywords: Algae; Biogas; MaB-floc; Pretreatment; Seasonal variability.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaerobiosis
  • Aquaculture
  • Biofuels / economics
  • Biomass
  • Bioreactors / microbiology
  • Chlorophyll / analogs & derivatives
  • Chlorophyll A
  • Methane / metabolism*
  • Microalgae / metabolism*
  • Ponds / microbiology
  • Seasons
  • Waste Management / methods*
  • Waste Water / microbiology*

Substances

  • Biofuels
  • Waste Water
  • Chlorophyll
  • chlorophyll a'
  • Methane
  • Chlorophyll A