Growing Fresh Water Microalgae in High Ammonium Landfill Leachate

Abstract

Municipal landfills are being employed for the disposal of communities solid waste. The compacted waste in landfills naturally generate leachate (liquid) which contain high concentrations of ammonium-nitrogen NH4+-N along with other toxic compounds. NH4+-N can be used as a cheap nitrogen source for microalgae biomass production, thereby facilitating tertiary treatment of landfill leachate. Two sets of studies, laboratory scale and pilot scale open raceway pond cultivation, were conducted to evaluate the potential of indigenous fresh water microalgal species to grow in ultra-membrane treated landfill leachate TL and simultaneously remove nutrients (NH4+-N-NO3- etc.). Microalgae growth was better in 50% diluted TL (1.5 gL-1 dry biomass) with 66.27% NH4+-N removal in the lab study. Onsite raceway pond cultivation had reduced biomass growth and nutrient removal. Nitrate-nitrogen NO3-N removal was minimum from both the setups. Microalgal assimilation and nitrification was the main cause of NH4+-N removal from both the setups. When lab study duration was extended, NH4+-N was found to be released back into the leachate medium. Batch cultures (when prolonged) were observed to be not an effective nutrient removal strategy in terms of NH4+-N removal via microalgal system. Further research is needed to optimize microalgal growth and nutrient removal from landfill leachate.