Reduction of nitrogen content in landfill leachate using microalgae

Landfill leachate contains large amounts of biodegradable or refractory to biodegradation organic materials, where organic and inorganic salts, ammonia-nitrogen, heavy metals, and chlorinated consist important groups. Leachate from run out municipal landfills has a lower biochemical oxygen demand after five days but still high contents of N-NH4+. Usually, the ammonium concentration could be reduced by nitrification processes followed by biological denitrification, but for leachate from run out landfills, organic molecules (e.g., methanol or acetic acid) must be added as carbon source. To overcome this drawback, in this work, the use of microalgae to reduce the nitrogen content from leachate before and after nitrification processes was suggested. Microalgae cultures were performed with different quantities of leachate after a microfiltration pretreatment. Additional runs were performed in landfill leachate after biological nitrification pretreatment. Runs were compared with those carried out in classic Bold's Basal medium taken as a control. During the growth, the biomass was observed microscopically and the ammonium, nitrate, and nitrite contents were determined. Results showed that Chlorella vulgaris can proliferate in presence of exhausted landfill leachate and exhausted landfill leachate after nitrification pretreatment with an ammonium removal efficiency of 38.8 mg/L d. The produced microalgal biomass, rich in lipids, could be used for energetic purposes.