Evaluation of Galdieria sulphuraria for nitrogen removal and biomass production from raw landfill leachate

This study evaluates the potential of thermophilic mixotrophic alga, Galdieria sulphuraria, to efficiently perform on-site treatment of landfill leachate (LL). Nutrient removal and algae growth experiments using various dilutions (20%, 40%, 60%, 80%, 100%) of actual municipal LL were carried out in a 14-day lab scale set-up. The effect of N/P mass ratio (255:1; 100:1; 50:1; 25:1; 10:1; 4.55:1) was also tested. Based on the results, it was evident that the growth reactors with 20% LL outperformed the other growth reactors. The final algal biomass density in 20% LL was 2.16 +/- 0.22 g L-1 (twice more than compare to standard media) and the observed growth rate was 159 mg L(-1)d(-1). Fourteen-day removal efficiencies were 99.9% for ammoniacal-nitrogen and 34% for phosphate, with removal rate of 22.78 mg L(-1)d(-1) and 2.91 mg L(-1)d(-1), respectively. Addition of P increased NH4-N removal rate from 16.3 to 23.6 mg L-1 day(-1) when N/P mass ratio was changed from 255:1 to 4.55:1. Furthermore, range of N/P mass ratio from 100:1 to 25: 1 has been found to achieve almost 100% removal of both NH4-N and PO4-P from 20% LL in 14 days. Overall, this study showed a promising algal-based treatment system for LL nutrient removal and producing algal-biomass for subsequent value-added product generation.

Automated summary

This study found that 20% LL performed the best for the growth of Galdieria sulphuraria, with significantly higher biomass and growth rate compared to other dilutions. Addition of phosphorus increased the removal rate of ammoniacal-nitrogen, and N/P mass ratios ranging from 25:1 to 100:1 achieved almost 100% removal efficiency.