Cofermenting Algal Biomass with Municipal Primary Solids to Enhance Carboxylate Production

Water Environ Res. 2018 Nov 1;90(11):1997-2007. doi: 10.2175/106143017X15131012188105.

Abstract

As water resource recovery facilities (WRRFs) implement biological nutrient removal (BNR) processes to remove excess wastewater nutrients, carboxylic acid demands increase; resource recovery processes (e.g., struvite, polyhydroxyalkanoate production) also demand carboxylates. In this regard, interest in algae to achieve tertiary treatment creates a new intraWRRF fermentation substrate. Indeed, fermentation potential tests indicated that algal augmentation could prove beneficial; carboxylate concentrations increased 31 % over primary solids. However, unexpectedly, and disproving a key research hypothesis, algal augmentation in a fed-batch fermenter decreased the production of carboxylic acids (26-34% at SRTs of 5-7 d); preliminary analyses suggest heterotrophic algae consumed carboxylates. Disproving a second research hypothesis, algal biomass did not significantly diversify carboxylate speciation. Finally, and unexpectedly, algal fermentation realized significant ammonia removal (39-96 % at SRTs of 5-7 d). Although decreased carboxylate yield is not desired, reduced ammonia load could potentially decrease WRRF energy demands and decrease carboxylic acid demands to achieve denitrification.

MeSH terms

  • Biomass*
  • Bioreactors*
  • Chlorella / metabolism*
  • Cities
  • Fermentation
  • Scenedesmus / metabolism*
  • Waste Disposal, Fluid