Abstract
This study investigated nutrient removal from anaerobic digestion effluent by cultivating mixed-culture microalgae enriched from anaerobic sludge under different pH conditions: RUC (uncontrolled), R7–8 (maintained at 7–8), and R<8 (maintained below 8). Significant amounts of NH4+-N were lost by volatilization in RUC cultures due to increased pH values (≤8.6) during the early period of cultivation. The pH control strategies significantly affected the biological NH4+-N removal (highest in R7–8), microalgal growth (highest in R7–8), biomass settleability (highest in R<8), and microalgal growth relative to bacteria (highest in R<8) in the cultures. Parachlorella completely dominated the microalgal communities in the inoculum and all of the cultures, and grew well at highly acidic pH (<3) induced by culture acidification with microalgal growth. Microalgae-associated bacterial community structure developed very differently among the cultures. The findings call for more attention to the influence and control of pH changes during cultivation in microalgal treatment of anaerobic digestion effluent.
Highlights
Received: 16 December 2021Microalgae have gained increasing attention in recent decades because of their promising potential for wastewater treatment, CO2 mitigation, as well as biofuel, biochemical, and biomaterial production [1,2]
The growing global shortage of water and resources highlights the benefits of wastewater-based microalgae cultivation for sustainability, more research is needed for practical application, especially regarding long-term stability [3]
The anaerobic digestion (AD) effluent collected from a full-scale digester treating sewage sludge and food waste was centrifuged at 3400× g for 20 min, and the supernatant was used as the medium for microalgae cultivation after dilution with distilled water to the desired NH4 + N concentrations
Summary
Microalgae have gained increasing attention in recent decades because of their promising potential for wastewater treatment, CO2 mitigation, as well as biofuel, biochemical, and biomaterial production [1,2]. Microalgae grow photosynthetically using CO2 as a carbon source while assimilating nutrients (i.e., N and P) in wastewater and accumulating organic compounds intracellularly. Cultivating microalgae with wastewater can minimize the consumption of water and nutrients (supplied as chemical salts), the high cost of which is a major challenge for large-scale microalgae cultivation [3]. The growing global shortage of water and resources highlights the benefits of wastewater-based microalgae cultivation for sustainability, more research is needed for practical application, especially regarding long-term stability [3].
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