A new microalgal negative carbon technology for landfill leachate treatment: Simultaneous removal of nitrogen and phosphorus.

Replete with ammonia nitrogen and organic pollutants, landfill leachate typically undergoes treatment employing expensive and carbon-intensive integrated techniques. We propose a novel microalgae technology for efficient, low-carbon simultaneous treatment of carbon, nitrogen, and phosphorus in landfill leachate (LL). The microbial composition comprises a mixed microalgae culture with Chlorella accounting for 82.58%. After seven days, the process with an N/P ratio of approximately 14:1 removed 98.81% of NH ₄ ⁺ -N, 88.62 % of TN, and 99.55% of TP. Notably, the concentrations of NH ₄ ⁺ -N and TP met the discharge standards, while the removal rate of NH ₄ ⁺ -N was nearly three times higher than previously reported in relevant studies. The microalgae achieved a removal efficiency of 64.27% for Total Organic Carbon (TOC) and 99.26% for Inorganic Carbon (IC) under mixotrophic cultivation, yielding a biomass of 1.18 g/L. The treatment process employed in this study results in a carbon emissions equivalent of -8.25 kgCO ₂ /kgN _removed , representing a reduction of 33.56 kgCO ₂ compared to the 2AO + MBR process. In addition, shake flask experiments were conducted to evaluate the biodegradability of leachate after microalgae treatment. After microalgae treatment, the TOC _B (Biodegradable Total Organic Carbon)/TOC ratio decreased from 56.54% to 27.71%, with no significant improvement in biodegradability. It establishes a fundamental foundation for further applied research in microalgae treatment of leachate.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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